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-rw-r--r--build/unix/elfhack/Makefile.in44
-rw-r--r--build/unix/elfhack/README28
-rw-r--r--build/unix/elfhack/dummy.c7
-rw-r--r--build/unix/elfhack/elf.cpp934
-rw-r--r--build/unix/elfhack/elfhack.cpp1325
-rw-r--r--build/unix/elfhack/elfxx.h691
-rw-r--r--build/unix/elfhack/inject.c124
-rw-r--r--build/unix/elfhack/inject/copy_source.py10
-rw-r--r--build/unix/elfhack/inject/moz.build40
-rw-r--r--build/unix/elfhack/moz.build32
-rw-r--r--build/unix/elfhack/test-array.c8
-rw-r--r--build/unix/elfhack/test-ctors.c16
-rw-r--r--build/unix/elfhack/test.c170
13 files changed, 3429 insertions, 0 deletions
diff --git a/build/unix/elfhack/Makefile.in b/build/unix/elfhack/Makefile.in
new file mode 100644
index 0000000000..08cc3d6852
--- /dev/null
+++ b/build/unix/elfhack/Makefile.in
@@ -0,0 +1,44 @@
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+include $(topsrcdir)/config/rules.mk
+
+test-array$(DLL_SUFFIX) test-ctors$(DLL_SUFFIX): %$(DLL_SUFFIX): %.$(OBJ_SUFFIX) elfhack
+ $(MKSHLIB) $(LDFLAGS) $< -nostartfiles
+ @echo ===
+ @echo === If you get failures below, please file a bug describing the error
+ @echo === and your environment \(compiler and linker versions\), and
+ @echo === provide the pre-elfhacked library as an attachment.
+ @echo === Use --disable-elf-hack until this is fixed.
+ @echo ===
+ # Fail if the library doesn't have $(DT_TYPE) .dynamic info
+ $(TOOLCHAIN_PREFIX)readelf -d $@ | grep '($(DT_TYPE))'
+ @rm -f $@.bak
+ $(CURDIR)/elfhack -b -f $@
+ # Fail if the backup file doesn't exist
+ [ -f '$@.bak' ]
+ # Fail if the new library doesn't contain less relocations
+ [ $$($(TOOLCHAIN_PREFIX)objdump -R $@.bak | wc -l) -gt $$(objdump -R $@ | wc -l) ]
+
+test-array$(DLL_SUFFIX) test-ctors$(DLL_SUFFIX): DSO_SONAME=$@
+test-array$(DLL_SUFFIX): DT_TYPE=INIT_ARRAY
+test-ctors$(DLL_SUFFIX): DT_TYPE=INIT
+
+.PRECIOUS: test-array$(DLL_SUFFIX) test-ctors$(DLL_SUFFIX)
+
+ifndef CROSS_COMPILE
+ifdef COMPILE_ENVIRONMENT
+libs:: test-array$(DLL_SUFFIX) test-ctors$(DLL_SUFFIX)
+
+dummy: dummy.$(OBJ_SUFFIX)
+ $(CC) -o $@ $^ $(LDFLAGS)
+
+libs:: dummy
+ # Will either crash or return exit code 1 if elfhack is broken
+ LD_PRELOAD=$(CURDIR)/test-array$(DLL_SUFFIX) $(CURDIR)/dummy
+ LD_PRELOAD=$(CURDIR)/test-ctors$(DLL_SUFFIX) $(CURDIR)/dummy
+
+endif
+endif
diff --git a/build/unix/elfhack/README b/build/unix/elfhack/README
new file mode 100644
index 0000000000..8c68031e33
--- /dev/null
+++ b/build/unix/elfhack/README
@@ -0,0 +1,28 @@
+Elfhack is a program to optimize ELF binaries for size and cold startup
+speed.
+
+Presently, it is quite experimental, though it works well for the target
+it was created for: Firefox's libxul.so.
+
+Elfhack currently only does one thing: packing dynamic relocations ;
+which ends up being a quite complex task, that can be summarized this
+way:
+- Remove RELATIVE relocations from the .rel.dyn/.rela.dyn section.
+- Inject a small code able to apply relative relocations "by hand"
+ after the .rel.dyn/.rela.dyn section.
+- Inject a section containing relocative relocations in a different
+ and more packed format, after the small code.
+- Register the small code as DT_INIT function. Make the small code call
+ what was initially the DT_INIT function, if there was one.
+- Remove the hole between the new section containing relative
+ relocations and the following sections, adjusting offsets and base
+ addresses accordingly.
+- Adjust PT_LOAD entries to fit new offsets, and add an additional
+ PT_LOAD entry when that is necessary to handle the discrepancy between
+ offsets and base addresses, meaning the section offsets may yet again
+ need adjustments.
+- Adjust various DT_* dynamic tags to fit the new ELF layout.
+- Adjust section headers.
+- Adjust ELF headers.
+
+See http://glandium.org/blog/?p=1177#relocations for some figures.
diff --git a/build/unix/elfhack/dummy.c b/build/unix/elfhack/dummy.c
new file mode 100644
index 0000000000..2cde16102e
--- /dev/null
+++ b/build/unix/elfhack/dummy.c
@@ -0,0 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+extern __attribute__((visibility("default"), weak)) int print_status();
+
+int main() { return print_status(); }
diff --git a/build/unix/elfhack/elf.cpp b/build/unix/elfhack/elf.cpp
new file mode 100644
index 0000000000..679770fcba
--- /dev/null
+++ b/build/unix/elfhack/elf.cpp
@@ -0,0 +1,934 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#undef NDEBUG
+#include <cstring>
+#include <assert.h>
+#include "elfxx.h"
+
+template <class endian, typename R, typename T>
+void Elf_Ehdr_Traits::swap(T& t, R& r) {
+ memcpy(r.e_ident, t.e_ident, sizeof(r.e_ident));
+ r.e_type = endian::swap(t.e_type);
+ r.e_machine = endian::swap(t.e_machine);
+ r.e_version = endian::swap(t.e_version);
+ r.e_entry = endian::swap(t.e_entry);
+ r.e_phoff = endian::swap(t.e_phoff);
+ r.e_shoff = endian::swap(t.e_shoff);
+ r.e_flags = endian::swap(t.e_flags);
+ r.e_ehsize = endian::swap(t.e_ehsize);
+ r.e_phentsize = endian::swap(t.e_phentsize);
+ r.e_phnum = endian::swap(t.e_phnum);
+ r.e_shentsize = endian::swap(t.e_shentsize);
+ r.e_shnum = endian::swap(t.e_shnum);
+ r.e_shstrndx = endian::swap(t.e_shstrndx);
+}
+
+template <class endian, typename R, typename T>
+void Elf_Phdr_Traits::swap(T& t, R& r) {
+ r.p_type = endian::swap(t.p_type);
+ r.p_offset = endian::swap(t.p_offset);
+ r.p_vaddr = endian::swap(t.p_vaddr);
+ r.p_paddr = endian::swap(t.p_paddr);
+ r.p_filesz = endian::swap(t.p_filesz);
+ r.p_memsz = endian::swap(t.p_memsz);
+ r.p_flags = endian::swap(t.p_flags);
+ r.p_align = endian::swap(t.p_align);
+}
+
+template <class endian, typename R, typename T>
+void Elf_Shdr_Traits::swap(T& t, R& r) {
+ r.sh_name = endian::swap(t.sh_name);
+ r.sh_type = endian::swap(t.sh_type);
+ r.sh_flags = endian::swap(t.sh_flags);
+ r.sh_addr = endian::swap(t.sh_addr);
+ r.sh_offset = endian::swap(t.sh_offset);
+ r.sh_size = endian::swap(t.sh_size);
+ r.sh_link = endian::swap(t.sh_link);
+ r.sh_info = endian::swap(t.sh_info);
+ r.sh_addralign = endian::swap(t.sh_addralign);
+ r.sh_entsize = endian::swap(t.sh_entsize);
+}
+
+template <class endian, typename R, typename T>
+void Elf_Dyn_Traits::swap(T& t, R& r) {
+ r.d_tag = endian::swap(t.d_tag);
+ r.d_un.d_val = endian::swap(t.d_un.d_val);
+}
+
+template <class endian, typename R, typename T>
+void Elf_Sym_Traits::swap(T& t, R& r) {
+ r.st_name = endian::swap(t.st_name);
+ r.st_value = endian::swap(t.st_value);
+ r.st_size = endian::swap(t.st_size);
+ r.st_info = t.st_info;
+ r.st_other = t.st_other;
+ r.st_shndx = endian::swap(t.st_shndx);
+}
+
+template <class endian>
+struct _Rel_info {
+ static inline void swap(Elf32_Word& t, Elf32_Word& r) { r = endian::swap(t); }
+ static inline void swap(Elf64_Xword& t, Elf64_Xword& r) {
+ r = endian::swap(t);
+ }
+ static inline void swap(Elf64_Xword& t, Elf32_Word& r) {
+ r = endian::swap(ELF32_R_INFO(ELF64_R_SYM(t), ELF64_R_TYPE(t)));
+ }
+ static inline void swap(Elf32_Word& t, Elf64_Xword& r) {
+ r = endian::swap(ELF64_R_INFO(ELF32_R_SYM(t), ELF32_R_TYPE(t)));
+ }
+};
+
+template <class endian, typename R, typename T>
+void Elf_Rel_Traits::swap(T& t, R& r) {
+ r.r_offset = endian::swap(t.r_offset);
+ _Rel_info<endian>::swap(t.r_info, r.r_info);
+}
+
+template <class endian, typename R, typename T>
+void Elf_Rela_Traits::swap(T& t, R& r) {
+ r.r_offset = endian::swap(t.r_offset);
+ _Rel_info<endian>::swap(t.r_info, r.r_info);
+ r.r_addend = endian::swap(t.r_addend);
+}
+
+static const Elf32_Shdr null32_section = {0, SHT_NULL, 0, 0, 0,
+ 0, SHN_UNDEF, 0, 0, 0};
+
+Elf_Shdr null_section(null32_section);
+
+Elf_Ehdr::Elf_Ehdr(std::ifstream& file, char ei_class, char ei_data)
+ : serializable<Elf_Ehdr_Traits>(file, ei_class, ei_data),
+ ElfSection(null_section, nullptr, nullptr) {
+ shdr.sh_size = Elf_Ehdr::size(ei_class);
+}
+
+Elf::Elf(std::ifstream& file) {
+ if (!file.is_open()) throw std::runtime_error("Error opening file");
+
+ file.exceptions(std::ifstream::eofbit | std::ifstream::failbit |
+ std::ifstream::badbit);
+ // Read ELF magic number and identification information
+ char e_ident[EI_VERSION];
+ file.seekg(0);
+ file.read(e_ident, sizeof(e_ident));
+ file.seekg(0);
+ ehdr = new Elf_Ehdr(file, e_ident[EI_CLASS], e_ident[EI_DATA]);
+
+ // ELFOSABI_LINUX is kept unsupported because I haven't looked whether
+ // STB_GNU_UNIQUE or STT_GNU_IFUNC would need special casing.
+ if ((ehdr->e_ident[EI_OSABI] != ELFOSABI_NONE) &&
+ (ehdr->e_ident[EI_ABIVERSION] != 0))
+ throw std::runtime_error("unsupported ELF ABI");
+
+ if (ehdr->e_version != 1) throw std::runtime_error("unsupported ELF version");
+
+ // Sanity checks
+ if (ehdr->e_shnum == 0)
+ throw std::runtime_error("sstripped ELF files aren't supported");
+
+ if (ehdr->e_ehsize != Elf_Ehdr::size(e_ident[EI_CLASS]))
+ throw std::runtime_error(
+ "unsupported ELF inconsistency: ehdr.e_ehsize != sizeof(ehdr)");
+
+ if (ehdr->e_shentsize != Elf_Shdr::size(e_ident[EI_CLASS]))
+ throw std::runtime_error(
+ "unsupported ELF inconsistency: ehdr.e_shentsize != sizeof(shdr)");
+
+ if (ehdr->e_phnum == 0) {
+ if (ehdr->e_phoff != 0)
+ throw std::runtime_error(
+ "unsupported ELF inconsistency: e_phnum == 0 && e_phoff != 0");
+ if (ehdr->e_phentsize != 0)
+ throw std::runtime_error(
+ "unsupported ELF inconsistency: e_phnum == 0 && e_phentsize != 0");
+ } else if (ehdr->e_phoff != ehdr->e_ehsize)
+ throw std::runtime_error(
+ "unsupported ELF inconsistency: ehdr->e_phoff != ehdr->e_ehsize");
+ else if (ehdr->e_phentsize != Elf_Phdr::size(e_ident[EI_CLASS]))
+ throw std::runtime_error(
+ "unsupported ELF inconsistency: ehdr->e_phentsize != sizeof(phdr)");
+
+ // Read section headers
+ Elf_Shdr** shdr = new Elf_Shdr*[ehdr->e_shnum];
+ file.seekg(ehdr->e_shoff);
+ for (int i = 0; i < ehdr->e_shnum; i++)
+ shdr[i] = new Elf_Shdr(file, e_ident[EI_CLASS], e_ident[EI_DATA]);
+
+ // Sanity check in section header for index 0
+ if ((shdr[0]->sh_name != 0) || (shdr[0]->sh_type != SHT_NULL) ||
+ (shdr[0]->sh_flags != 0) || (shdr[0]->sh_addr != 0) ||
+ (shdr[0]->sh_offset != 0) || (shdr[0]->sh_size != 0) ||
+ (shdr[0]->sh_link != SHN_UNDEF) || (shdr[0]->sh_info != 0) ||
+ (shdr[0]->sh_addralign != 0) || (shdr[0]->sh_entsize != 0))
+ throw std::runtime_error(
+ "Section header for index 0 contains unsupported values");
+
+ if ((shdr[ehdr->e_shstrndx]->sh_link != 0) ||
+ (shdr[ehdr->e_shstrndx]->sh_info != 0))
+ throw std::runtime_error(
+ "unsupported ELF content: string table with sh_link != 0 || sh_info != "
+ "0");
+
+ // Store these temporarily
+ tmp_shdr = shdr;
+ tmp_file = &file;
+
+ // Fill sections list
+ sections = new ElfSection*[ehdr->e_shnum];
+ for (int i = 0; i < ehdr->e_shnum; i++) sections[i] = nullptr;
+ for (int i = 1; i < ehdr->e_shnum; i++) {
+ // The .dynamic section is going to have references to other sections,
+ // so it's better to start with that one and recursively initialize those
+ // other sections first, to avoid possible infinite recursion (bug 1606739).
+ if (tmp_shdr[i]->sh_type == SHT_DYNAMIC) {
+ getSection(i);
+ }
+ }
+ for (int i = 1; i < ehdr->e_shnum; i++) {
+ if (sections[i] != nullptr) continue;
+ getSection(i);
+ }
+ Elf_Shdr s;
+ s.sh_name = 0;
+ s.sh_type = SHT_NULL;
+ s.sh_flags = 0;
+ s.sh_addr = 0;
+ s.sh_offset = ehdr->e_shoff;
+ s.sh_entsize = Elf_Shdr::size(e_ident[EI_CLASS]);
+ s.sh_size = s.sh_entsize * ehdr->e_shnum;
+ s.sh_link = 0;
+ s.sh_info = 0;
+ s.sh_addralign = (e_ident[EI_CLASS] == ELFCLASS32) ? 4 : 8;
+ shdr_section = new ElfSection(s, nullptr, nullptr);
+
+ // Fake section for program headers
+ s.sh_offset = ehdr->e_phoff;
+ s.sh_addr = ehdr->e_phoff;
+ s.sh_entsize = Elf_Phdr::size(e_ident[EI_CLASS]);
+ s.sh_size = s.sh_entsize * ehdr->e_phnum;
+ phdr_section = new ElfSection(s, nullptr, nullptr);
+
+ phdr_section->insertAfter(ehdr, false);
+
+ sections[1]->insertAfter(phdr_section, false);
+ for (int i = 2; i < ehdr->e_shnum; i++) {
+ // TODO: this should be done in a better way
+ if ((shdr_section->getPrevious() == nullptr) &&
+ (shdr[i]->sh_offset > ehdr->e_shoff)) {
+ shdr_section->insertAfter(sections[i - 1], false);
+ sections[i]->insertAfter(shdr_section, false);
+ } else
+ sections[i]->insertAfter(sections[i - 1], false);
+ }
+ if (shdr_section->getPrevious() == nullptr)
+ shdr_section->insertAfter(sections[ehdr->e_shnum - 1], false);
+
+ tmp_file = nullptr;
+ tmp_shdr = nullptr;
+ for (int i = 0; i < ehdr->e_shnum; i++) delete shdr[i];
+ delete[] shdr;
+
+ eh_shstrndx = (ElfStrtab_Section*)sections[ehdr->e_shstrndx];
+
+ // Skip reading program headers if there aren't any
+ if (ehdr->e_phnum == 0) return;
+
+ bool adjusted_phdr_section = false;
+ // Read program headers
+ file.seekg(ehdr->e_phoff);
+ for (int i = 0; i < ehdr->e_phnum; i++) {
+ Elf_Phdr phdr(file, e_ident[EI_CLASS], e_ident[EI_DATA]);
+ if (phdr.p_type == PT_LOAD) {
+ // Default alignment for PT_LOAD on x86-64 prevents elfhack from
+ // doing anything useful. However, the system doesn't actually
+ // require such a big alignment, so in order for elfhack to work
+ // efficiently, reduce alignment when it's originally the default
+ // one.
+ if ((ehdr->e_machine == EM_X86_64) && (phdr.p_align == 0x200000))
+ phdr.p_align = 0x1000;
+ }
+ ElfSegment* segment = new ElfSegment(&phdr);
+ // Some segments aren't entirely filled (if at all) by sections
+ // For those, we use fake sections
+ if ((phdr.p_type == PT_LOAD) && (phdr.p_offset == 0)) {
+ // Use a fake section for ehdr and phdr
+ ehdr->getShdr().sh_addr = phdr.p_vaddr;
+ if (!adjusted_phdr_section) {
+ phdr_section->getShdr().sh_addr += phdr.p_vaddr;
+ adjusted_phdr_section = true;
+ }
+ segment->addSection(ehdr);
+ segment->addSection(phdr_section);
+ }
+ if (phdr.p_type == PT_PHDR) {
+ if (!adjusted_phdr_section) {
+ phdr_section->getShdr().sh_addr = phdr.p_vaddr;
+ adjusted_phdr_section = true;
+ }
+ segment->addSection(phdr_section);
+ }
+ for (int j = 1; j < ehdr->e_shnum; j++)
+ if (phdr.contains(sections[j])) segment->addSection(sections[j]);
+ // Make sure that our view of segments corresponds to the original
+ // ELF file.
+ // GNU gold likes to start some segments before the first section
+ // they contain. https://sourceware.org/bugzilla/show_bug.cgi?id=19392
+ unsigned int gold_adjustment = segment->getAddr() - phdr.p_vaddr;
+ assert(segment->getFileSize() == phdr.p_filesz - gold_adjustment);
+ // gold makes TLS segments end on an aligned virtual address, even
+ // when the underlying section ends before that, while bfd ld
+ // doesn't. It's fine if we don't keep that alignment.
+ unsigned int memsize = segment->getMemSize();
+ if (phdr.p_type == PT_TLS && memsize != phdr.p_memsz) {
+ unsigned int align = segment->getAlign();
+ memsize = (memsize + align - 1) & ~(align - 1);
+ }
+ assert(memsize == phdr.p_memsz - gold_adjustment);
+ segments.push_back(segment);
+ }
+
+ new (&eh_entry) ElfLocation(ehdr->e_entry, this);
+}
+
+Elf::~Elf() {
+ for (std::vector<ElfSegment*>::iterator seg = segments.begin();
+ seg != segments.end(); seg++)
+ delete *seg;
+ delete[] sections;
+ ElfSection* section = ehdr;
+ while (section != nullptr) {
+ ElfSection* next = section->getNext();
+ delete section;
+ section = next;
+ }
+}
+
+// TODO: This shouldn't fail after inserting sections
+ElfSection* Elf::getSection(int index) {
+ if ((index < -1) || (index >= ehdr->e_shnum))
+ throw std::runtime_error("Section index out of bounds");
+ if (index == -1)
+ index = ehdr->e_shstrndx; // TODO: should be fixed to use the actual
+ // current number
+ // Special case: the section at index 0 is void
+ if (index == 0) return nullptr;
+ // Infinite recursion guard
+ if (sections[index] == (ElfSection*)this) return nullptr;
+ if (sections[index] == nullptr) {
+ sections[index] = (ElfSection*)this;
+ switch (tmp_shdr[index]->sh_type) {
+ case SHT_DYNAMIC:
+ sections[index] =
+ new ElfDynamic_Section(*tmp_shdr[index], tmp_file, this);
+ break;
+ case SHT_REL:
+ sections[index] =
+ new ElfRel_Section<Elf_Rel>(*tmp_shdr[index], tmp_file, this);
+ break;
+ case SHT_RELA:
+ sections[index] =
+ new ElfRel_Section<Elf_Rela>(*tmp_shdr[index], tmp_file, this);
+ break;
+ case SHT_DYNSYM:
+ case SHT_SYMTAB:
+ sections[index] =
+ new ElfSymtab_Section(*tmp_shdr[index], tmp_file, this);
+ break;
+ case SHT_STRTAB:
+ sections[index] =
+ new ElfStrtab_Section(*tmp_shdr[index], tmp_file, this);
+ break;
+ default:
+ sections[index] = new ElfSection(*tmp_shdr[index], tmp_file, this);
+ }
+ }
+ return sections[index];
+}
+
+ElfSection* Elf::getSectionAt(unsigned int offset) {
+ for (int i = 1; i < ehdr->e_shnum; i++) {
+ ElfSection* section = getSection(i);
+ if ((section != nullptr) && (section->getFlags() & SHF_ALLOC) &&
+ !(section->getFlags() & SHF_TLS) && (offset >= section->getAddr()) &&
+ (offset < section->getAddr() + section->getSize()))
+ return section;
+ }
+ return nullptr;
+}
+
+ElfSegment* Elf::getSegmentByType(unsigned int type, ElfSegment* last) {
+ std::vector<ElfSegment*>::iterator seg;
+ if (last) {
+ seg = std::find(segments.begin(), segments.end(), last);
+ ++seg;
+ } else
+ seg = segments.begin();
+ for (; seg != segments.end(); seg++)
+ if ((*seg)->getType() == type) return *seg;
+ return nullptr;
+}
+
+void Elf::removeSegment(ElfSegment* segment) {
+ if (!segment) return;
+ std::vector<ElfSegment*>::iterator seg;
+ seg = std::find(segments.begin(), segments.end(), segment);
+ if (seg == segments.end()) return;
+ segment->clear();
+ segments.erase(seg);
+}
+
+ElfDynamic_Section* Elf::getDynSection() {
+ for (std::vector<ElfSegment*>::iterator seg = segments.begin();
+ seg != segments.end(); seg++)
+ if (((*seg)->getType() == PT_DYNAMIC) &&
+ ((*seg)->getFirstSection() != nullptr) &&
+ (*seg)->getFirstSection()->getType() == SHT_DYNAMIC)
+ return (ElfDynamic_Section*)(*seg)->getFirstSection();
+
+ return nullptr;
+}
+
+void Elf::normalize() {
+ // fixup section headers sh_name; TODO: that should be done by sections
+ // themselves
+ for (ElfSection* section = ehdr; section != nullptr;
+ section = section->getNext()) {
+ if (section->getIndex() == 0)
+ continue;
+ else
+ ehdr->e_shnum = section->getIndex() + 1;
+ section->getShdr().sh_name = eh_shstrndx->getStrIndex(section->getName());
+ }
+ ehdr->markDirty();
+ // Check segments consistency
+ int i = 0;
+ for (std::vector<ElfSegment*>::iterator seg = segments.begin();
+ seg != segments.end(); seg++, i++) {
+ std::list<ElfSection*>::iterator it = (*seg)->begin();
+ for (ElfSection* last = *(it++); it != (*seg)->end(); last = *(it++)) {
+ if (((*it)->getType() != SHT_NOBITS) &&
+ ((*it)->getAddr() - last->getAddr()) !=
+ ((*it)->getOffset() - last->getOffset())) {
+ throw std::runtime_error("Segments inconsistency");
+ }
+ }
+ }
+
+ ElfSegment* prevLoad = nullptr;
+ for (auto& it : segments) {
+ if (it->getType() == PT_LOAD) {
+ if (prevLoad) {
+ size_t alignedPrevEnd = (prevLoad->getAddr() + prevLoad->getMemSize() +
+ prevLoad->getAlign() - 1) &
+ ~(prevLoad->getAlign() - 1);
+ size_t alignedStart = it->getAddr() & ~(it->getAlign() - 1);
+ if (alignedPrevEnd > alignedStart) {
+ throw std::runtime_error("Segments overlap");
+ }
+ }
+ prevLoad = it;
+ }
+ }
+
+ // fixup ehdr before writing
+ if (ehdr->e_phnum != segments.size()) {
+ ehdr->e_phnum = segments.size();
+ phdr_section->getShdr().sh_size =
+ segments.size() * Elf_Phdr::size(ehdr->e_ident[EI_CLASS]);
+ phdr_section->getNext()->markDirty();
+ }
+ // fixup shdr before writing
+ if (ehdr->e_shnum != shdr_section->getSize() / shdr_section->getEntSize())
+ shdr_section->getShdr().sh_size =
+ ehdr->e_shnum * Elf_Shdr::size(ehdr->e_ident[EI_CLASS]);
+ ehdr->e_shoff = shdr_section->getOffset();
+ ehdr->e_entry = eh_entry.getValue();
+ ehdr->e_shstrndx = eh_shstrndx->getIndex();
+
+ // Check sections consistency
+ unsigned int minOffset = 0;
+ for (ElfSection* section = ehdr; section != nullptr;
+ section = section->getNext()) {
+ unsigned int offset = section->getOffset();
+ if (offset < minOffset) {
+ throw std::runtime_error("Sections overlap");
+ }
+ if (section->getType() != SHT_NOBITS) {
+ minOffset = offset + section->getSize();
+ }
+ }
+}
+
+void Elf::write(std::ofstream& file) {
+ normalize();
+ for (ElfSection* section = ehdr; section != nullptr;
+ section = section->getNext()) {
+ file.seekp(section->getOffset());
+ if (section == phdr_section) {
+ for (std::vector<ElfSegment*>::iterator seg = segments.begin();
+ seg != segments.end(); seg++) {
+ Elf_Phdr phdr;
+ phdr.p_type = (*seg)->getType();
+ phdr.p_flags = (*seg)->getFlags();
+ phdr.p_offset = (*seg)->getOffset();
+ phdr.p_vaddr = (*seg)->getAddr();
+ phdr.p_paddr = phdr.p_vaddr + (*seg)->getVPDiff();
+ phdr.p_filesz = (*seg)->getFileSize();
+ phdr.p_memsz = (*seg)->getMemSize();
+ phdr.p_align = (*seg)->getAlign();
+ phdr.serialize(file, ehdr->e_ident[EI_CLASS], ehdr->e_ident[EI_DATA]);
+ }
+ } else if (section == shdr_section) {
+ null_section.serialize(file, ehdr->e_ident[EI_CLASS],
+ ehdr->e_ident[EI_DATA]);
+ for (ElfSection* sec = ehdr; sec != nullptr; sec = sec->getNext()) {
+ if (sec->getType() != SHT_NULL)
+ sec->getShdr().serialize(file, ehdr->e_ident[EI_CLASS],
+ ehdr->e_ident[EI_DATA]);
+ }
+ } else
+ section->serialize(file, ehdr->e_ident[EI_CLASS], ehdr->e_ident[EI_DATA]);
+ }
+}
+
+ElfSection::ElfSection(Elf_Shdr& s, std::ifstream* file, Elf* parent)
+ : shdr(s),
+ link(shdr.sh_link == SHN_UNDEF ? nullptr
+ : parent->getSection(shdr.sh_link)),
+ next(nullptr),
+ previous(nullptr),
+ index(-1) {
+ if ((file == nullptr) || (shdr.sh_type == SHT_NULL) ||
+ (shdr.sh_type == SHT_NOBITS))
+ data = nullptr;
+ else {
+ data = static_cast<char*>(malloc(shdr.sh_size));
+ if (!data) {
+ throw std::runtime_error("Could not malloc ElfSection data");
+ }
+ auto pos = file->tellg();
+ file->seekg(shdr.sh_offset);
+ file->read(data, shdr.sh_size);
+ file->seekg(pos);
+ }
+ if (shdr.sh_name == 0)
+ name = nullptr;
+ else {
+ ElfStrtab_Section* strtab = (ElfStrtab_Section*)parent->getSection(-1);
+ // Special case (see elfgeneric.cpp): if strtab is nullptr, the
+ // section being created is the strtab.
+ if (strtab == nullptr)
+ name = &data[shdr.sh_name];
+ else
+ name = strtab->getStr(shdr.sh_name);
+ }
+ // Only SHT_REL/SHT_RELA sections use sh_info to store a section
+ // number.
+ if ((shdr.sh_type == SHT_REL) || (shdr.sh_type == SHT_RELA))
+ info.section = shdr.sh_info ? parent->getSection(shdr.sh_info) : nullptr;
+ else
+ info.index = shdr.sh_info;
+}
+
+unsigned int ElfSection::getAddr() {
+ if (shdr.sh_addr != (Elf32_Word)-1) return shdr.sh_addr;
+
+ // It should be safe to adjust sh_addr for all allocated sections that
+ // are neither SHT_NOBITS nor SHT_PROGBITS
+ if ((previous != nullptr) && isRelocatable()) {
+ unsigned int addr = previous->getAddr();
+ if (previous->getType() != SHT_NOBITS) addr += previous->getSize();
+
+ if (addr & (getAddrAlign() - 1)) addr = (addr | (getAddrAlign() - 1)) + 1;
+
+ return (shdr.sh_addr = addr);
+ }
+ return shdr.sh_addr;
+}
+
+unsigned int ElfSection::getOffset() {
+ if (shdr.sh_offset != (Elf32_Word)-1) return shdr.sh_offset;
+
+ if (previous == nullptr) return (shdr.sh_offset = 0);
+
+ unsigned int offset = previous->getOffset();
+
+ ElfSegment* ptload = getSegmentByType(PT_LOAD);
+ ElfSegment* prev_ptload = previous->getSegmentByType(PT_LOAD);
+
+ if (ptload && (ptload == prev_ptload)) {
+ offset += getAddr() - previous->getAddr();
+ return (shdr.sh_offset = offset);
+ }
+
+ if (previous->getType() != SHT_NOBITS) offset += previous->getSize();
+
+ Elf32_Word align = 0x1000;
+ for (std::vector<ElfSegment*>::iterator seg = segments.begin();
+ seg != segments.end(); seg++)
+ align = std::max(align, (*seg)->getAlign());
+
+ Elf32_Word mask = align - 1;
+ // SHF_TLS is used for .tbss which is some kind of special case.
+ if (((getType() != SHT_NOBITS) || (getFlags() & SHF_TLS)) &&
+ (getFlags() & SHF_ALLOC)) {
+ if ((getAddr() & mask) < (offset & mask))
+ offset = (offset | mask) + (getAddr() & mask) + 1;
+ else
+ offset = (offset & ~mask) + (getAddr() & mask);
+ }
+ if ((getType() != SHT_NOBITS) && (offset & (getAddrAlign() - 1)))
+ offset = (offset | (getAddrAlign() - 1)) + 1;
+
+ return (shdr.sh_offset = offset);
+}
+
+int ElfSection::getIndex() {
+ if (index != -1) return index;
+ if (getType() == SHT_NULL) return (index = 0);
+ ElfSection* reference;
+ for (reference = previous;
+ (reference != nullptr) && (reference->getType() == SHT_NULL);
+ reference = reference->getPrevious())
+ ;
+ if (reference == nullptr) return (index = 1);
+ return (index = reference->getIndex() + 1);
+}
+
+Elf_Shdr& ElfSection::getShdr() {
+ getOffset();
+ if (shdr.sh_link == (Elf32_Word)-1)
+ shdr.sh_link = getLink() ? getLink()->getIndex() : 0;
+ if (shdr.sh_info == (Elf32_Word)-1)
+ shdr.sh_info = ((getType() == SHT_REL) || (getType() == SHT_RELA))
+ ? (getInfo().section ? getInfo().section->getIndex() : 0)
+ : getInfo().index;
+
+ return shdr;
+}
+
+ElfSegment::ElfSegment(Elf_Phdr* phdr)
+ : type(phdr->p_type),
+ v_p_diff(phdr->p_paddr - phdr->p_vaddr),
+ flags(phdr->p_flags),
+ align(phdr->p_align),
+ vaddr(phdr->p_vaddr),
+ filesz(phdr->p_filesz),
+ memsz(phdr->p_memsz) {}
+
+void ElfSegment::addSection(ElfSection* section) {
+ // Make sure all sections in PT_GNU_RELRO won't be moved by elfhack
+ assert(!((type == PT_GNU_RELRO) && (section->isRelocatable())));
+
+ // TODO: Check overlapping sections
+ std::list<ElfSection*>::iterator i;
+ for (i = sections.begin(); i != sections.end(); ++i)
+ if ((*i)->getAddr() > section->getAddr()) break;
+ sections.insert(i, section);
+ section->addToSegment(this);
+}
+
+void ElfSegment::removeSection(ElfSection* section) {
+ sections.remove(section);
+ section->removeFromSegment(this);
+}
+
+unsigned int ElfSegment::getFileSize() {
+ if (type == PT_GNU_RELRO) return filesz;
+
+ if (sections.empty()) return 0;
+ // Search the last section that is not SHT_NOBITS
+ std::list<ElfSection*>::reverse_iterator i;
+ for (i = sections.rbegin();
+ (i != sections.rend()) && ((*i)->getType() == SHT_NOBITS); ++i)
+ ;
+ // All sections are SHT_NOBITS
+ if (i == sections.rend()) return 0;
+
+ unsigned int end = (*i)->getAddr() + (*i)->getSize();
+
+ return end - sections.front()->getAddr();
+}
+
+unsigned int ElfSegment::getMemSize() {
+ if (type == PT_GNU_RELRO) return memsz;
+
+ if (sections.empty()) return 0;
+
+ unsigned int end = sections.back()->getAddr() + sections.back()->getSize();
+
+ return end - sections.front()->getAddr();
+}
+
+unsigned int ElfSegment::getOffset() {
+ if ((type == PT_GNU_RELRO) && !sections.empty() &&
+ (sections.front()->getAddr() != vaddr))
+ throw std::runtime_error(
+ "PT_GNU_RELRO segment doesn't start on a section start");
+
+ return sections.empty() ? 0 : sections.front()->getOffset();
+}
+
+unsigned int ElfSegment::getAddr() {
+ if ((type == PT_GNU_RELRO) && !sections.empty() &&
+ (sections.front()->getAddr() != vaddr))
+ throw std::runtime_error(
+ "PT_GNU_RELRO segment doesn't start on a section start");
+
+ return sections.empty() ? 0 : sections.front()->getAddr();
+}
+
+void ElfSegment::clear() {
+ for (std::list<ElfSection*>::iterator i = sections.begin();
+ i != sections.end(); ++i)
+ (*i)->removeFromSegment(this);
+ sections.clear();
+}
+
+ElfValue* ElfDynamic_Section::getValueForType(unsigned int tag) {
+ for (unsigned int i = 0; i < shdr.sh_size / shdr.sh_entsize; i++)
+ if (dyns[i].tag == tag) return dyns[i].value;
+
+ return nullptr;
+}
+
+ElfSection* ElfDynamic_Section::getSectionForType(unsigned int tag) {
+ ElfValue* value = getValueForType(tag);
+ return value ? value->getSection() : nullptr;
+}
+
+bool ElfDynamic_Section::setValueForType(unsigned int tag, ElfValue* val) {
+ unsigned int i;
+ unsigned int shnum = shdr.sh_size / shdr.sh_entsize;
+ for (i = 0; (i < shnum) && (dyns[i].tag != DT_NULL); i++)
+ if (dyns[i].tag == tag) {
+ delete dyns[i].value;
+ dyns[i].value = val;
+ return true;
+ }
+ // If we get here, this means we didn't match for the given tag
+ // Most of the time, there are a few DT_NULL entries, that we can
+ // use to add our value, but if we are on the last entry, we can't.
+ if (i >= shnum - 1) return false;
+
+ dyns[i].tag = tag;
+ dyns[i].value = val;
+ return true;
+}
+
+ElfDynamic_Section::ElfDynamic_Section(Elf_Shdr& s, std::ifstream* file,
+ Elf* parent)
+ : ElfSection(s, file, parent) {
+ auto pos = file->tellg();
+ dyns.resize(s.sh_size / s.sh_entsize);
+ file->seekg(shdr.sh_offset);
+ // Here we assume tags refer to only one section (e.g. DT_RELSZ accounts
+ // for .rel.dyn size)
+ for (unsigned int i = 0; i < s.sh_size / s.sh_entsize; i++) {
+ Elf_Dyn dyn(*file, parent->getClass(), parent->getData());
+ dyns[i].tag = dyn.d_tag;
+ switch (dyn.d_tag) {
+ case DT_NULL:
+ case DT_SYMBOLIC:
+ case DT_TEXTREL:
+ case DT_BIND_NOW:
+ dyns[i].value = new ElfValue();
+ break;
+ case DT_NEEDED:
+ case DT_SONAME:
+ case DT_RPATH:
+ case DT_PLTREL:
+ case DT_RUNPATH:
+ case DT_FLAGS:
+ case DT_RELACOUNT:
+ case DT_RELCOUNT:
+ case DT_VERDEFNUM:
+ case DT_VERNEEDNUM:
+ dyns[i].value = new ElfPlainValue(dyn.d_un.d_val);
+ break;
+ case DT_PLTGOT:
+ case DT_HASH:
+ case DT_STRTAB:
+ case DT_SYMTAB:
+ case DT_RELA:
+ case DT_INIT:
+ case DT_FINI:
+ case DT_REL:
+ case DT_JMPREL:
+ case DT_INIT_ARRAY:
+ case DT_FINI_ARRAY:
+ case DT_GNU_HASH:
+ case DT_VERSYM:
+ case DT_VERNEED:
+ case DT_VERDEF:
+ dyns[i].value = new ElfLocation(dyn.d_un.d_ptr, parent);
+ break;
+ default:
+ dyns[i].value = nullptr;
+ }
+ }
+ // Another loop to get the section sizes
+ for (unsigned int i = 0; i < s.sh_size / s.sh_entsize; i++)
+ switch (dyns[i].tag) {
+ case DT_PLTRELSZ:
+ dyns[i].value = new ElfSize(getSectionForType(DT_JMPREL));
+ break;
+ case DT_RELASZ:
+ dyns[i].value = new ElfSize(getSectionForType(DT_RELA));
+ break;
+ case DT_STRSZ:
+ dyns[i].value = new ElfSize(getSectionForType(DT_STRTAB));
+ break;
+ case DT_RELSZ:
+ dyns[i].value = new ElfSize(getSectionForType(DT_REL));
+ break;
+ case DT_INIT_ARRAYSZ:
+ dyns[i].value = new ElfSize(getSectionForType(DT_INIT_ARRAY));
+ break;
+ case DT_FINI_ARRAYSZ:
+ dyns[i].value = new ElfSize(getSectionForType(DT_FINI_ARRAY));
+ break;
+ case DT_RELAENT:
+ dyns[i].value = new ElfEntSize(getSectionForType(DT_RELA));
+ break;
+ case DT_SYMENT:
+ dyns[i].value = new ElfEntSize(getSectionForType(DT_SYMTAB));
+ break;
+ case DT_RELENT:
+ dyns[i].value = new ElfEntSize(getSectionForType(DT_REL));
+ break;
+ }
+
+ file->seekg(pos);
+}
+
+ElfDynamic_Section::~ElfDynamic_Section() {
+ for (unsigned int i = 0; i < shdr.sh_size / shdr.sh_entsize; i++)
+ delete dyns[i].value;
+}
+
+void ElfDynamic_Section::serialize(std::ofstream& file, char ei_class,
+ char ei_data) {
+ for (unsigned int i = 0; i < shdr.sh_size / shdr.sh_entsize; i++) {
+ Elf_Dyn dyn;
+ dyn.d_tag = dyns[i].tag;
+ dyn.d_un.d_val = (dyns[i].value != nullptr) ? dyns[i].value->getValue() : 0;
+ dyn.serialize(file, ei_class, ei_data);
+ }
+}
+
+ElfSymtab_Section::ElfSymtab_Section(Elf_Shdr& s, std::ifstream* file,
+ Elf* parent)
+ : ElfSection(s, file, parent) {
+ auto pos = file->tellg();
+ syms.resize(s.sh_size / s.sh_entsize);
+ ElfStrtab_Section* strtab = (ElfStrtab_Section*)getLink();
+ file->seekg(shdr.sh_offset);
+ for (unsigned int i = 0; i < shdr.sh_size / shdr.sh_entsize; i++) {
+ Elf_Sym sym(*file, parent->getClass(), parent->getData());
+ syms[i].name = strtab->getStr(sym.st_name);
+ syms[i].info = sym.st_info;
+ syms[i].other = sym.st_other;
+ ElfSection* section =
+ (sym.st_shndx == SHN_ABS) ? nullptr : parent->getSection(sym.st_shndx);
+ new (&syms[i].value)
+ ElfLocation(section, sym.st_value, ElfLocation::ABSOLUTE);
+ syms[i].size = sym.st_size;
+ syms[i].defined = (sym.st_shndx != SHN_UNDEF);
+ }
+ file->seekg(pos);
+}
+
+void ElfSymtab_Section::serialize(std::ofstream& file, char ei_class,
+ char ei_data) {
+ ElfStrtab_Section* strtab = (ElfStrtab_Section*)getLink();
+ for (unsigned int i = 0; i < shdr.sh_size / shdr.sh_entsize; i++) {
+ Elf_Sym sym;
+ sym.st_name = strtab->getStrIndex(syms[i].name);
+ sym.st_info = syms[i].info;
+ sym.st_other = syms[i].other;
+ sym.st_value = syms[i].value.getValue();
+ ElfSection* section = syms[i].value.getSection();
+ if (syms[i].defined)
+ sym.st_shndx = section ? section->getIndex() : SHN_ABS;
+ else
+ sym.st_shndx = SHN_UNDEF;
+ sym.st_size = syms[i].size;
+ sym.serialize(file, ei_class, ei_data);
+ }
+}
+
+Elf_SymValue* ElfSymtab_Section::lookup(const char* name,
+ unsigned int type_filter) {
+ for (std::vector<Elf_SymValue>::iterator sym = syms.begin();
+ sym != syms.end(); sym++) {
+ if ((type_filter & (1 << ELF32_ST_TYPE(sym->info))) &&
+ (strcmp(sym->name, name) == 0)) {
+ return &*sym;
+ }
+ }
+ return nullptr;
+}
+
+const char* ElfStrtab_Section::getStr(unsigned int index) {
+ for (std::vector<table_storage>::iterator t = table.begin(); t != table.end();
+ t++) {
+ if (index < t->used) return t->buf + index;
+ index -= t->used;
+ }
+ assert(1 == 0);
+ return nullptr;
+}
+
+const char* ElfStrtab_Section::getStr(const char* string) {
+ if (string == nullptr) return nullptr;
+
+ // If the given string is within the section, return it
+ for (std::vector<table_storage>::iterator t = table.begin(); t != table.end();
+ t++)
+ if ((string >= t->buf) && (string < t->buf + t->used)) return string;
+
+ // TODO: should scan in the section to find an existing string
+
+ // If not, we need to allocate the string in the section
+ size_t len = strlen(string) + 1;
+
+ if (table.back().size - table.back().used < len)
+ table.resize(table.size() + 1);
+
+ char* alloc_str = table.back().buf + table.back().used;
+ memcpy(alloc_str, string, len);
+ table.back().used += len;
+
+ shdr.sh_size += len;
+ markDirty();
+
+ return alloc_str;
+}
+
+unsigned int ElfStrtab_Section::getStrIndex(const char* string) {
+ if (string == nullptr) return 0;
+
+ unsigned int index = 0;
+ string = getStr(string);
+ for (std::vector<table_storage>::iterator t = table.begin(); t != table.end();
+ t++) {
+ if ((string >= t->buf) && (string < t->buf + t->used))
+ return index + (string - t->buf);
+ index += t->used;
+ }
+
+ assert(1 == 0);
+ return 0;
+}
+
+void ElfStrtab_Section::serialize(std::ofstream& file, char ei_class,
+ char ei_data) {
+ file.seekp(getOffset());
+ for (std::vector<table_storage>::iterator t = table.begin(); t != table.end();
+ t++)
+ file.write(t->buf, t->used);
+}
diff --git a/build/unix/elfhack/elfhack.cpp b/build/unix/elfhack/elfhack.cpp
new file mode 100644
index 0000000000..ec01e54674
--- /dev/null
+++ b/build/unix/elfhack/elfhack.cpp
@@ -0,0 +1,1325 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#undef NDEBUG
+#include <assert.h>
+#include <cstring>
+#include <cstdlib>
+#include <cstdio>
+#include "elfxx.h"
+#include "mozilla/CheckedInt.h"
+
+#define ver "0"
+#define elfhack_data ".elfhack.data.v" ver
+#define elfhack_text ".elfhack.text.v" ver
+
+#ifndef R_ARM_V4BX
+# define R_ARM_V4BX 0x28
+#endif
+#ifndef R_ARM_CALL
+# define R_ARM_CALL 0x1c
+#endif
+#ifndef R_ARM_JUMP24
+# define R_ARM_JUMP24 0x1d
+#endif
+#ifndef R_ARM_THM_JUMP24
+# define R_ARM_THM_JUMP24 0x1e
+#endif
+
+char* rundir = nullptr;
+
+template <typename T>
+struct wrapped {
+ T value;
+};
+
+class Elf_Addr_Traits {
+ public:
+ typedef wrapped<Elf32_Addr> Type32;
+ typedef wrapped<Elf64_Addr> Type64;
+
+ template <class endian, typename R, typename T>
+ static inline void swap(T& t, R& r) {
+ r.value = endian::swap(t.value);
+ }
+};
+
+typedef serializable<Elf_Addr_Traits> Elf_Addr;
+
+class Elf_RelHack_Traits {
+ public:
+ typedef Elf32_Rel Type32;
+ typedef Elf32_Rel Type64;
+
+ template <class endian, typename R, typename T>
+ static inline void swap(T& t, R& r) {
+ r.r_offset = endian::swap(t.r_offset);
+ r.r_info = endian::swap(t.r_info);
+ }
+};
+
+typedef serializable<Elf_RelHack_Traits> Elf_RelHack;
+
+class ElfRelHack_Section : public ElfSection {
+ public:
+ ElfRelHack_Section(Elf_Shdr& s) : ElfSection(s, nullptr, nullptr) {
+ name = elfhack_data;
+ };
+
+ void serialize(std::ofstream& file, char ei_class, char ei_data) {
+ for (std::vector<Elf_RelHack>::iterator i = rels.begin(); i != rels.end();
+ ++i)
+ (*i).serialize(file, ei_class, ei_data);
+ }
+
+ bool isRelocatable() { return true; }
+
+ void push_back(Elf_RelHack& r) {
+ rels.push_back(r);
+ shdr.sh_size = rels.size() * shdr.sh_entsize;
+ }
+
+ private:
+ std::vector<Elf_RelHack> rels;
+};
+
+class ElfRelHackCode_Section : public ElfSection {
+ public:
+ ElfRelHackCode_Section(Elf_Shdr& s, Elf& e,
+ ElfRelHack_Section& relhack_section, unsigned int init,
+ unsigned int mprotect_cb, unsigned int sysconf_cb)
+ : ElfSection(s, nullptr, nullptr),
+ parent(e),
+ relhack_section(relhack_section),
+ init(init),
+ init_trampoline(nullptr),
+ mprotect_cb(mprotect_cb),
+ sysconf_cb(sysconf_cb) {
+ std::string file(rundir);
+ file += "/inject/";
+ switch (parent.getMachine()) {
+ case EM_386:
+ file += "x86";
+ break;
+ case EM_X86_64:
+ file += "x86_64";
+ break;
+ case EM_ARM:
+ file += "arm";
+ break;
+ default:
+ throw std::runtime_error("unsupported architecture");
+ }
+ file += ".o";
+ std::ifstream inject(file.c_str(), std::ios::in | std::ios::binary);
+ elf = new Elf(inject);
+ if (elf->getType() != ET_REL)
+ throw std::runtime_error("object for injected code is not ET_REL");
+ if (elf->getMachine() != parent.getMachine())
+ throw std::runtime_error(
+ "architecture of object for injected code doesn't match");
+
+ ElfSymtab_Section* symtab = nullptr;
+
+ // Find the symbol table.
+ for (ElfSection* section = elf->getSection(1); section != nullptr;
+ section = section->getNext()) {
+ if (section->getType() == SHT_SYMTAB)
+ symtab = (ElfSymtab_Section*)section;
+ }
+ if (symtab == nullptr)
+ throw std::runtime_error(
+ "Couldn't find a symbol table for the injected code");
+
+ relro = parent.getSegmentByType(PT_GNU_RELRO);
+
+ // Find the init symbol
+ entry_point = -1;
+ std::string symbol = "init";
+ if (!init) symbol += "_noinit";
+ if (relro) symbol += "_relro";
+ Elf_SymValue* sym = symtab->lookup(symbol.c_str());
+ if (!sym)
+ throw std::runtime_error(
+ "Couldn't find an 'init' symbol in the injected code");
+
+ entry_point = sym->value.getValue();
+
+ // Get all relevant sections from the injected code object.
+ add_code_section(sym->value.getSection());
+
+ // If the original init function is located too far away, we're going to
+ // need to use a trampoline. See comment in inject.c.
+ // Theoretically, we should check for (init - instr) > 0xffffff, where instr
+ // is the virtual address of the instruction that calls the original init,
+ // but we don't have it at this point, so punt to just init.
+ if (init > 0xffffff && parent.getMachine() == EM_ARM) {
+ Elf_SymValue* trampoline = symtab->lookup("init_trampoline");
+ if (!trampoline) {
+ throw std::runtime_error(
+ "Couldn't find an 'init_trampoline' symbol in the injected code");
+ }
+
+ init_trampoline = trampoline->value.getSection();
+ add_code_section(init_trampoline);
+ }
+
+ // Adjust code sections offsets according to their size
+ std::vector<ElfSection*>::iterator c = code.begin();
+ (*c)->getShdr().sh_addr = 0;
+ for (ElfSection* last = *(c++); c != code.end(); ++c) {
+ unsigned int addr = last->getShdr().sh_addr + last->getSize();
+ if (addr & ((*c)->getAddrAlign() - 1))
+ addr = (addr | ((*c)->getAddrAlign() - 1)) + 1;
+ (*c)->getShdr().sh_addr = addr;
+ // We need to align this section depending on the greater
+ // alignment required by code sections.
+ if (shdr.sh_addralign < (*c)->getAddrAlign())
+ shdr.sh_addralign = (*c)->getAddrAlign();
+ last = *c;
+ }
+ shdr.sh_size = code.back()->getAddr() + code.back()->getSize();
+ data = static_cast<char*>(malloc(shdr.sh_size));
+ if (!data) {
+ throw std::runtime_error("Could not malloc ElfSection data");
+ }
+ char* buf = data;
+ for (c = code.begin(); c != code.end(); ++c) {
+ memcpy(buf, (*c)->getData(), (*c)->getSize());
+ buf += (*c)->getSize();
+ }
+ name = elfhack_text;
+ }
+
+ ~ElfRelHackCode_Section() { delete elf; }
+
+ void serialize(std::ofstream& file, char ei_class, char ei_data) override {
+ // Readjust code offsets
+ for (std::vector<ElfSection*>::iterator c = code.begin(); c != code.end();
+ ++c)
+ (*c)->getShdr().sh_addr += getAddr();
+
+ // Apply relocations
+ for (std::vector<ElfSection*>::iterator c = code.begin(); c != code.end();
+ ++c) {
+ for (ElfSection* rel = elf->getSection(1); rel != nullptr;
+ rel = rel->getNext())
+ if (((rel->getType() == SHT_REL) || (rel->getType() == SHT_RELA)) &&
+ (rel->getInfo().section == *c)) {
+ if (rel->getType() == SHT_REL)
+ apply_relocations((ElfRel_Section<Elf_Rel>*)rel, *c);
+ else
+ apply_relocations((ElfRel_Section<Elf_Rela>*)rel, *c);
+ }
+ }
+
+ ElfSection::serialize(file, ei_class, ei_data);
+ }
+
+ bool isRelocatable() override { return false; }
+
+ unsigned int getEntryPoint() { return entry_point; }
+
+ void insertBefore(ElfSection* section, bool dirty = true) override {
+ // Adjust the address so that this section is adjacent to the one it's
+ // being inserted before. This avoids creating holes which subsequently
+ // might lead the PHDR-adjusting code to create unnecessary additional
+ // PT_LOADs.
+ shdr.sh_addr =
+ (section->getAddr() - shdr.sh_size) & ~(shdr.sh_addralign - 1);
+ ElfSection::insertBefore(section, dirty);
+ }
+
+ private:
+ void add_code_section(ElfSection* section) {
+ if (section) {
+ /* Don't add section if it's already been added in the past */
+ for (auto s = code.begin(); s != code.end(); ++s) {
+ if (section == *s) return;
+ }
+ code.push_back(section);
+ find_code(section);
+ }
+ }
+
+ /* Look at the relocations associated to the given section to find other
+ * sections that it requires */
+ void find_code(ElfSection* section) {
+ for (ElfSection* s = elf->getSection(1); s != nullptr; s = s->getNext()) {
+ if (((s->getType() == SHT_REL) || (s->getType() == SHT_RELA)) &&
+ (s->getInfo().section == section)) {
+ if (s->getType() == SHT_REL)
+ scan_relocs_for_code((ElfRel_Section<Elf_Rel>*)s);
+ else
+ scan_relocs_for_code((ElfRel_Section<Elf_Rela>*)s);
+ }
+ }
+ }
+
+ template <typename Rel_Type>
+ void scan_relocs_for_code(ElfRel_Section<Rel_Type>* rel) {
+ ElfSymtab_Section* symtab = (ElfSymtab_Section*)rel->getLink();
+ for (auto r = rel->rels.begin(); r != rel->rels.end(); ++r) {
+ ElfSection* section =
+ symtab->syms[ELF32_R_SYM(r->r_info)].value.getSection();
+ add_code_section(section);
+ }
+ }
+
+ class pc32_relocation {
+ public:
+ Elf32_Addr operator()(unsigned int base_addr, Elf32_Off offset,
+ Elf32_Word addend, unsigned int addr) {
+ return addr + addend - offset - base_addr;
+ }
+ };
+
+ class arm_plt32_relocation {
+ public:
+ Elf32_Addr operator()(unsigned int base_addr, Elf32_Off offset,
+ Elf32_Word addend, unsigned int addr) {
+ // We don't care about sign_extend because the only case where this is
+ // going to be used only jumps forward.
+ Elf32_Addr tmp = (Elf32_Addr)(addr - offset - base_addr) >> 2;
+ tmp = (addend + tmp) & 0x00ffffff;
+ return (addend & 0xff000000) | tmp;
+ }
+ };
+
+ class arm_thm_jump24_relocation {
+ public:
+ Elf32_Addr operator()(unsigned int base_addr, Elf32_Off offset,
+ Elf32_Word addend, unsigned int addr) {
+ /* Follows description of b.w and bl instructions as per
+ ARM Architecture Reference Manual ARM® v7-A and ARM® v7-R edition,
+ A8.6.16 We limit ourselves to Encoding T4 of b.w and Encoding T1 of bl.
+ We don't care about sign_extend because the only case where this is
+ going to be used only jumps forward. */
+ Elf32_Addr tmp = (Elf32_Addr)(addr - offset - base_addr);
+ unsigned int word0 = addend & 0xffff, word1 = addend >> 16;
+
+ /* Encoding T4 of B.W is 10x1 ; Encoding T1 of BL is 11x1. */
+ unsigned int type = (word1 & 0xd000) >> 12;
+ if (((word0 & 0xf800) != 0xf000) || ((type & 0x9) != 0x9))
+ throw std::runtime_error(
+ "R_ARM_THM_JUMP24/R_ARM_THM_CALL relocation only supported for B.W "
+ "<label> and BL <label>");
+
+ /* When the target address points to ARM code, switch a BL to a
+ * BLX. This however can't be done with a B.W without adding a
+ * trampoline, which is not supported as of now. */
+ if ((addr & 0x1) == 0) {
+ if (type == 0x9)
+ throw std::runtime_error(
+ "R_ARM_THM_JUMP24/R_ARM_THM_CALL relocation only supported for "
+ "BL <label> when label points to ARM code");
+ /* The address of the target is always relative to a 4-bytes
+ * aligned address, so if the address of the BL instruction is
+ * not 4-bytes aligned, adjust for it. */
+ if ((base_addr + offset) & 0x2) tmp += 2;
+ /* Encoding T2 of BLX is 11x0. */
+ type = 0xc;
+ }
+
+ unsigned int s = (word0 & (1 << 10)) >> 10;
+ unsigned int j1 = (word1 & (1 << 13)) >> 13;
+ unsigned int j2 = (word1 & (1 << 11)) >> 11;
+ unsigned int i1 = j1 ^ s ? 0 : 1;
+ unsigned int i2 = j2 ^ s ? 0 : 1;
+
+ tmp += ((s << 24) | (i1 << 23) | (i2 << 22) | ((word0 & 0x3ff) << 12) |
+ ((word1 & 0x7ff) << 1));
+
+ s = (tmp & (1 << 24)) >> 24;
+ j1 = ((tmp & (1 << 23)) >> 23) ^ !s;
+ j2 = ((tmp & (1 << 22)) >> 22) ^ !s;
+
+ return 0xf000 | (s << 10) | ((tmp & (0x3ff << 12)) >> 12) | (type << 28) |
+ (j1 << 29) | (j2 << 27) | ((tmp & 0xffe) << 15);
+ }
+ };
+
+ class gotoff_relocation {
+ public:
+ Elf32_Addr operator()(unsigned int base_addr, Elf32_Off offset,
+ Elf32_Word addend, unsigned int addr) {
+ return addr + addend;
+ }
+ };
+
+ template <class relocation_type>
+ void apply_relocation(ElfSection* the_code, char* base, Elf_Rel* r,
+ unsigned int addr) {
+ relocation_type relocation;
+ Elf32_Addr value;
+ memcpy(&value, base + r->r_offset, 4);
+ value = relocation(the_code->getAddr(), r->r_offset, value, addr);
+ memcpy(base + r->r_offset, &value, 4);
+ }
+
+ template <class relocation_type>
+ void apply_relocation(ElfSection* the_code, char* base, Elf_Rela* r,
+ unsigned int addr) {
+ relocation_type relocation;
+ Elf32_Addr value =
+ relocation(the_code->getAddr(), r->r_offset, r->r_addend, addr);
+ memcpy(base + r->r_offset, &value, 4);
+ }
+
+ template <typename Rel_Type>
+ void apply_relocations(ElfRel_Section<Rel_Type>* rel, ElfSection* the_code) {
+ assert(rel->getType() == Rel_Type::sh_type);
+ char* buf = data + (the_code->getAddr() - code.front()->getAddr());
+ // TODO: various checks on the sections
+ ElfSymtab_Section* symtab = (ElfSymtab_Section*)rel->getLink();
+ for (typename std::vector<Rel_Type>::iterator r = rel->rels.begin();
+ r != rel->rels.end(); ++r) {
+ // TODO: various checks on the symbol
+ const char* name = symtab->syms[ELF32_R_SYM(r->r_info)].name;
+ unsigned int addr;
+ if (symtab->syms[ELF32_R_SYM(r->r_info)].value.getSection() == nullptr) {
+ if (strcmp(name, "relhack") == 0) {
+ addr = relhack_section.getAddr();
+ } else if (strcmp(name, "elf_header") == 0) {
+ // TODO: change this ungly hack to something better
+ ElfSection* ehdr = parent.getSection(1)->getPrevious()->getPrevious();
+ addr = ehdr->getAddr();
+ } else if (strcmp(name, "original_init") == 0) {
+ if (init_trampoline) {
+ addr = init_trampoline->getAddr();
+ } else {
+ addr = init;
+ }
+ } else if (strcmp(name, "real_original_init") == 0) {
+ addr = init;
+ } else if (relro && strcmp(name, "mprotect_cb") == 0) {
+ addr = mprotect_cb;
+ } else if (relro && strcmp(name, "sysconf_cb") == 0) {
+ addr = sysconf_cb;
+ } else if (relro && strcmp(name, "relro_start") == 0) {
+ addr = relro->getAddr();
+ } else if (relro && strcmp(name, "relro_end") == 0) {
+ addr = (relro->getAddr() + relro->getMemSize());
+ } else if (strcmp(name, "_GLOBAL_OFFSET_TABLE_") == 0) {
+ // We actually don't need a GOT, but need it as a reference for
+ // GOTOFF relocations. We'll just use the start of the ELF file
+ addr = 0;
+ } else if (strcmp(name, "") == 0) {
+ // This is for R_ARM_V4BX, until we find something better
+ addr = -1;
+ } else {
+ throw std::runtime_error("Unsupported symbol in relocation");
+ }
+ } else {
+ ElfSection* section =
+ symtab->syms[ELF32_R_SYM(r->r_info)].value.getSection();
+ assert((section->getType() == SHT_PROGBITS) &&
+ (section->getFlags() & SHF_EXECINSTR));
+ addr = symtab->syms[ELF32_R_SYM(r->r_info)].value.getValue();
+ }
+ // Do the relocation
+#define REL(machine, type) (EM_##machine | (R_##machine##_##type << 8))
+ switch (elf->getMachine() | (ELF32_R_TYPE(r->r_info) << 8)) {
+ case REL(X86_64, PC32):
+ case REL(X86_64, PLT32):
+ case REL(386, PC32):
+ case REL(386, GOTPC):
+ case REL(ARM, GOTPC):
+ case REL(ARM, REL32):
+ apply_relocation<pc32_relocation>(the_code, buf, &*r, addr);
+ break;
+ case REL(ARM, CALL):
+ case REL(ARM, JUMP24):
+ case REL(ARM, PLT32):
+ apply_relocation<arm_plt32_relocation>(the_code, buf, &*r, addr);
+ break;
+ case REL(ARM, THM_PC22 /* THM_CALL */):
+ case REL(ARM, THM_JUMP24):
+ apply_relocation<arm_thm_jump24_relocation>(the_code, buf, &*r, addr);
+ break;
+ case REL(386, GOTOFF):
+ case REL(ARM, GOTOFF):
+ apply_relocation<gotoff_relocation>(the_code, buf, &*r, addr);
+ break;
+ case REL(ARM, V4BX):
+ // Ignore R_ARM_V4BX relocations
+ break;
+ default:
+ throw std::runtime_error("Unsupported relocation type");
+ }
+ }
+ }
+
+ Elf *elf, &parent;
+ ElfRelHack_Section& relhack_section;
+ std::vector<ElfSection*> code;
+ unsigned int init;
+ ElfSection* init_trampoline;
+ unsigned int mprotect_cb;
+ unsigned int sysconf_cb;
+ int entry_point;
+ ElfSegment* relro;
+};
+
+unsigned int get_addend(Elf_Rel* rel, Elf* elf) {
+ ElfLocation loc(rel->r_offset, elf);
+ Elf_Addr addr(loc.getBuffer(), Elf_Addr::size(elf->getClass()),
+ elf->getClass(), elf->getData());
+ return addr.value;
+}
+
+unsigned int get_addend(Elf_Rela* rel, Elf* elf) { return rel->r_addend; }
+
+void set_relative_reloc(Elf_Rel* rel, Elf* elf, unsigned int value) {
+ ElfLocation loc(rel->r_offset, elf);
+ Elf_Addr addr;
+ addr.value = value;
+ addr.serialize(const_cast<char*>(loc.getBuffer()),
+ Elf_Addr::size(elf->getClass()), elf->getClass(),
+ elf->getData());
+}
+
+void set_relative_reloc(Elf_Rela* rel, Elf* elf, unsigned int value) {
+ // ld puts the value of relocated relocations both in the addend and
+ // at r_offset. For consistency, keep it that way.
+ set_relative_reloc((Elf_Rel*)rel, elf, value);
+ rel->r_addend = value;
+}
+
+void maybe_split_segment(Elf* elf, ElfSegment* segment) {
+ std::list<ElfSection*>::iterator it = segment->begin();
+ for (ElfSection* last = *(it++); it != segment->end(); last = *(it++)) {
+ // When two consecutive non-SHT_NOBITS sections are apart by more
+ // than the alignment of the section, the second can be moved closer
+ // to the first, but this requires the segment to be split.
+ if (((*it)->getType() != SHT_NOBITS) && (last->getType() != SHT_NOBITS) &&
+ ((*it)->getOffset() - last->getOffset() - last->getSize() >
+ segment->getAlign())) {
+ // Probably very wrong.
+ Elf_Phdr phdr;
+ phdr.p_type = PT_LOAD;
+ phdr.p_vaddr = 0;
+ phdr.p_paddr = phdr.p_vaddr + segment->getVPDiff();
+ phdr.p_flags = segment->getFlags();
+ phdr.p_align = segment->getAlign();
+ phdr.p_filesz = (unsigned int)-1;
+ phdr.p_memsz = (unsigned int)-1;
+ ElfSegment* newSegment = new ElfSegment(&phdr);
+ elf->insertSegmentAfter(segment, newSegment);
+ for (; it != segment->end(); ++it) {
+ newSegment->addSection(*it);
+ }
+ for (it = newSegment->begin(); it != newSegment->end(); ++it) {
+ segment->removeSection(*it);
+ }
+ break;
+ }
+ }
+}
+
+// EH_FRAME constants
+static const char DW_EH_PE_absptr = 0x00;
+static const char DW_EH_PE_omit = 0xff;
+
+// Data size
+static const char DW_EH_PE_LEB128 = 0x01;
+static const char DW_EH_PE_data2 = 0x02;
+static const char DW_EH_PE_data4 = 0x03;
+static const char DW_EH_PE_data8 = 0x04;
+
+// Data signedness
+static const char DW_EH_PE_signed = 0x08;
+
+// Modifiers
+static const char DW_EH_PE_pcrel = 0x10;
+
+// Return the data size part of the encoding value
+static char encoding_data_size(char encoding) { return encoding & 0x07; }
+
+// Advance `step` bytes in the buffer at `data` with size `size`, returning
+// the advanced buffer pointer and remaining size.
+// Returns true if step <= size.
+static bool advance_buffer(char** data, size_t* size, size_t step) {
+ if (step > *size) return false;
+
+ *data += step;
+ *size -= step;
+ return true;
+}
+
+// Advance in the given buffer, skipping the full length of the variable-length
+// encoded LEB128 type in CIE/FDE data.
+static bool skip_LEB128(char** data, size_t* size) {
+ if (!*size) return false;
+
+ while (*size && (*(*data)++ & (char)0x80)) {
+ (*size)--;
+ }
+ return true;
+}
+
+// Advance in the given buffer, skipping the full length of a pointer encoded
+// with the given encoding.
+static bool skip_eh_frame_pointer(char** data, size_t* size, char encoding) {
+ switch (encoding_data_size(encoding)) {
+ case DW_EH_PE_data2:
+ return advance_buffer(data, size, 2);
+ case DW_EH_PE_data4:
+ return advance_buffer(data, size, 4);
+ case DW_EH_PE_data8:
+ return advance_buffer(data, size, 8);
+ case DW_EH_PE_LEB128:
+ return skip_LEB128(data, size);
+ }
+ throw std::runtime_error("unreachable");
+}
+
+// Specialized implementations for adjust_eh_frame_pointer().
+template <typename T>
+static bool adjust_eh_frame_sized_pointer(char** data, size_t* size,
+ ElfSection* eh_frame,
+ unsigned int origAddr, Elf* elf) {
+ if (*size < sizeof(T)) return false;
+
+ serializable<FixedSizeData<T>> pointer(*data, *size, elf->getClass(),
+ elf->getData());
+ mozilla::CheckedInt<T> value = pointer.value;
+ if (origAddr < eh_frame->getAddr()) {
+ unsigned int diff = eh_frame->getAddr() - origAddr;
+ value -= diff;
+ } else {
+ unsigned int diff = origAddr - eh_frame->getAddr();
+ value += diff;
+ }
+ if (!value.isValid())
+ throw std::runtime_error("Overflow while adjusting eh_frame");
+ pointer.value = value.value();
+ pointer.serialize(*data, *size, elf->getClass(), elf->getData());
+ return advance_buffer(data, size, sizeof(T));
+}
+
+// In the given eh_frame section, adjust the pointer with the given encoding,
+// pointed to by the given buffer (`data`, `size`), considering the eh_frame
+// section was originally at `origAddr`. Also advances in the buffer.
+static bool adjust_eh_frame_pointer(char** data, size_t* size, char encoding,
+ ElfSection* eh_frame, unsigned int origAddr,
+ Elf* elf) {
+ if ((encoding & 0x70) != DW_EH_PE_pcrel)
+ return skip_eh_frame_pointer(data, size, encoding);
+
+ if (encoding & DW_EH_PE_signed) {
+ switch (encoding_data_size(encoding)) {
+ case DW_EH_PE_data2:
+ return adjust_eh_frame_sized_pointer<int16_t>(data, size, eh_frame,
+ origAddr, elf);
+ case DW_EH_PE_data4:
+ return adjust_eh_frame_sized_pointer<int32_t>(data, size, eh_frame,
+ origAddr, elf);
+ case DW_EH_PE_data8:
+ return adjust_eh_frame_sized_pointer<int64_t>(data, size, eh_frame,
+ origAddr, elf);
+ }
+ } else {
+ switch (encoding_data_size(encoding)) {
+ case DW_EH_PE_data2:
+ return adjust_eh_frame_sized_pointer<uint16_t>(data, size, eh_frame,
+ origAddr, elf);
+ case DW_EH_PE_data4:
+ return adjust_eh_frame_sized_pointer<uint32_t>(data, size, eh_frame,
+ origAddr, elf);
+ case DW_EH_PE_data8:
+ return adjust_eh_frame_sized_pointer<uint64_t>(data, size, eh_frame,
+ origAddr, elf);
+ }
+ }
+
+ throw std::runtime_error("Unsupported eh_frame pointer encoding");
+}
+
+// The eh_frame section may contain "PC"-relative pointers. If we move the
+// section, those need to be adjusted. Other type of pointers are relative to
+// sections we don't touch.
+static void adjust_eh_frame(ElfSection* eh_frame, unsigned int origAddr,
+ Elf* elf) {
+ if (eh_frame->getAddr() == origAddr) // nothing to do;
+ return;
+
+ char* data = const_cast<char*>(eh_frame->getData());
+ size_t size = eh_frame->getSize();
+ char LSDAencoding = DW_EH_PE_omit;
+ char FDEencoding = DW_EH_PE_absptr;
+ bool hasZ = false;
+
+ // Decoding of eh_frame based on https://www.airs.com/blog/archives/460
+ while (size) {
+ if (size < sizeof(uint32_t)) goto malformed;
+
+ serializable<FixedSizeData<uint32_t>> entryLength(
+ data, size, elf->getClass(), elf->getData());
+ if (!advance_buffer(&data, &size, sizeof(uint32_t))) goto malformed;
+
+ char* cursor = data;
+ size_t length = entryLength.value;
+
+ if (length == 0) {
+ continue;
+ }
+
+ if (size < sizeof(uint32_t)) goto malformed;
+
+ serializable<FixedSizeData<uint32_t>> id(data, size, elf->getClass(),
+ elf->getData());
+ if (!advance_buffer(&cursor, &length, sizeof(uint32_t))) goto malformed;
+
+ if (id.value == 0) {
+ // This is a Common Information Entry
+ if (length < 2) goto malformed;
+ // Reset LSDA and FDE encodings, and hasZ for subsequent FDEs.
+ LSDAencoding = DW_EH_PE_omit;
+ FDEencoding = DW_EH_PE_absptr;
+ hasZ = false;
+ // CIE version. Should only be 1 or 3.
+ char version = *cursor++;
+ length--;
+ if (version != 1 && version != 3) {
+ throw std::runtime_error("Unsupported eh_frame version");
+ }
+ // NUL terminated string.
+ const char* augmentationString = cursor;
+ size_t l = strnlen(augmentationString, length - 1);
+ if (l == length - 1) goto malformed;
+ if (!advance_buffer(&cursor, &length, l + 1)) goto malformed;
+ // Skip code alignment factor (LEB128)
+ if (!skip_LEB128(&cursor, &length)) goto malformed;
+ // Skip data alignment factor (LEB128)
+ if (!skip_LEB128(&cursor, &length)) goto malformed;
+ // Skip return address register (single byte in CIE version 1, LEB128
+ // in CIE version 3)
+ if (version == 1) {
+ if (!advance_buffer(&cursor, &length, 1)) goto malformed;
+ } else {
+ if (!skip_LEB128(&cursor, &length)) goto malformed;
+ }
+ // Past this, it's data driven by the contents of the augmentation string.
+ for (size_t i = 0; i < l; i++) {
+ if (!length) goto malformed;
+ switch (augmentationString[i]) {
+ case 'z':
+ if (!skip_LEB128(&cursor, &length)) goto malformed;
+ hasZ = true;
+ break;
+ case 'L':
+ LSDAencoding = *cursor++;
+ length--;
+ break;
+ case 'R':
+ FDEencoding = *cursor++;
+ length--;
+ break;
+ case 'P': {
+ char encoding = *cursor++;
+ length--;
+ if (!adjust_eh_frame_pointer(&cursor, &length, encoding, eh_frame,
+ origAddr, elf))
+ goto malformed;
+ } break;
+ default:
+ goto malformed;
+ }
+ }
+ } else {
+ // This is a Frame Description Entry
+ // Starting address
+ if (!adjust_eh_frame_pointer(&cursor, &length, FDEencoding, eh_frame,
+ origAddr, elf))
+ goto malformed;
+
+ if (LSDAencoding != DW_EH_PE_omit) {
+ // Skip number of bytes, same size as the starting address.
+ if (!skip_eh_frame_pointer(&cursor, &length, FDEencoding))
+ goto malformed;
+ if (hasZ) {
+ if (!skip_LEB128(&cursor, &length)) goto malformed;
+ }
+ // pointer to the LSDA.
+ if (!adjust_eh_frame_pointer(&cursor, &length, LSDAencoding, eh_frame,
+ origAddr, elf))
+ goto malformed;
+ }
+ }
+
+ data += entryLength.value;
+ size -= entryLength.value;
+ }
+ return;
+
+malformed:
+ throw std::runtime_error("malformed .eh_frame");
+}
+
+template <typename Rel_Type>
+int do_relocation_section(Elf* elf, unsigned int rel_type,
+ unsigned int rel_type2, bool force) {
+ ElfDynamic_Section* dyn = elf->getDynSection();
+ if (dyn == nullptr) {
+ fprintf(stderr, "Couldn't find SHT_DYNAMIC section\n");
+ return -1;
+ }
+
+ ElfRel_Section<Rel_Type>* section =
+ (ElfRel_Section<Rel_Type>*)dyn->getSectionForType(Rel_Type::d_tag);
+ if (section == nullptr) {
+ fprintf(stderr, "No relocations\n");
+ return -1;
+ }
+ assert(section->getType() == Rel_Type::sh_type);
+
+ Elf32_Shdr relhack32_section = {
+ 0,
+ SHT_PROGBITS,
+ SHF_ALLOC,
+ 0,
+ (Elf32_Off)-1,
+ 0,
+ SHN_UNDEF,
+ 0,
+ Elf_RelHack::size(elf->getClass()),
+ Elf_RelHack::size(elf->getClass())}; // TODO: sh_addralign should be an
+ // alignment, not size
+ Elf32_Shdr relhackcode32_section = {0,
+ SHT_PROGBITS,
+ SHF_ALLOC | SHF_EXECINSTR,
+ 0,
+ (Elf32_Off)-1,
+ 0,
+ SHN_UNDEF,
+ 0,
+ 1,
+ 0};
+
+ unsigned int entry_sz = Elf_Addr::size(elf->getClass());
+
+ // The injected code needs to be executed before any init code in the
+ // binary. There are three possible cases:
+ // - The binary has no init code at all. In this case, we will add a
+ // DT_INIT entry pointing to the injected code.
+ // - The binary has a DT_INIT entry. In this case, we will interpose:
+ // we change DT_INIT to point to the injected code, and have the
+ // injected code call the original DT_INIT entry point.
+ // - The binary has no DT_INIT entry, but has a DT_INIT_ARRAY. In this
+ // case, we interpose as well, by replacing the first entry in the
+ // array to point to the injected code, and have the injected code
+ // call the original first entry.
+ // The binary may have .ctors instead of DT_INIT_ARRAY, for its init
+ // functions, but this falls into the second case above, since .ctors
+ // are actually run by DT_INIT code.
+ ElfValue* value = dyn->getValueForType(DT_INIT);
+ unsigned int original_init = value ? value->getValue() : 0;
+ ElfSection* init_array = nullptr;
+ if (!value || !value->getValue()) {
+ value = dyn->getValueForType(DT_INIT_ARRAYSZ);
+ if (value && value->getValue() >= entry_sz)
+ init_array = dyn->getSectionForType(DT_INIT_ARRAY);
+ }
+
+ Elf_Shdr relhack_section(relhack32_section);
+ Elf_Shdr relhackcode_section(relhackcode32_section);
+ ElfRelHack_Section* relhack = new ElfRelHack_Section(relhack_section);
+
+ ElfSymtab_Section* symtab = (ElfSymtab_Section*)section->getLink();
+ Elf_SymValue* sym = symtab->lookup("__cxa_pure_virtual");
+
+ std::vector<Rel_Type> new_rels;
+ Elf_RelHack relhack_entry;
+ relhack_entry.r_offset = relhack_entry.r_info = 0;
+ std::vector<Rel_Type> init_array_relocs;
+ size_t init_array_insert = 0;
+ for (typename std::vector<Rel_Type>::iterator i = section->rels.begin();
+ i != section->rels.end(); ++i) {
+ // We don't need to keep R_*_NONE relocations
+ if (!ELF32_R_TYPE(i->r_info)) continue;
+ ElfLocation loc(i->r_offset, elf);
+ // __cxa_pure_virtual is a function used in vtables to point at pure
+ // virtual methods. The __cxa_pure_virtual function usually abort()s.
+ // These functions are however normally never called. In the case
+ // where they would, jumping to the null address instead of calling
+ // __cxa_pure_virtual is going to work just as well. So we can remove
+ // relocations for the __cxa_pure_virtual symbol and null out the
+ // content at the offset pointed by the relocation.
+ if (sym) {
+ if (sym->defined) {
+ // If we are statically linked to libstdc++, the
+ // __cxa_pure_virtual symbol is defined in our lib, and we
+ // have relative relocations (rel_type) for it.
+ if (ELF32_R_TYPE(i->r_info) == rel_type) {
+ Elf_Addr addr(loc.getBuffer(), entry_sz, elf->getClass(),
+ elf->getData());
+ if (addr.value == sym->value.getValue()) {
+ memset((char*)loc.getBuffer(), 0, entry_sz);
+ continue;
+ }
+ }
+ } else {
+ // If we are dynamically linked to libstdc++, the
+ // __cxa_pure_virtual symbol is undefined in our lib, and we
+ // have absolute relocations (rel_type2) for it.
+ if ((ELF32_R_TYPE(i->r_info) == rel_type2) &&
+ (sym == &symtab->syms[ELF32_R_SYM(i->r_info)])) {
+ memset((char*)loc.getBuffer(), 0, entry_sz);
+ continue;
+ }
+ }
+ }
+ // Keep track of the relocations associated with the init_array section.
+ if (init_array && i->r_offset >= init_array->getAddr() &&
+ i->r_offset < init_array->getAddr() + init_array->getSize()) {
+ init_array_relocs.push_back(*i);
+ init_array_insert = new_rels.size();
+ } else if (!(loc.getSection()->getFlags() & SHF_WRITE) ||
+ (ELF32_R_TYPE(i->r_info) != rel_type)) {
+ // Don't pack relocations happening in non writable sections.
+ // Our injected code is likely not to be allowed to write there.
+ new_rels.push_back(*i);
+ } else {
+ // With Elf_Rel, the value pointed by the relocation offset is the addend.
+ // With Elf_Rela, the addend is in the relocation entry, but the elfhacked
+ // relocation info doesn't contain it. Elfhack relies on the value pointed
+ // by the relocation offset to also contain the addend. Which is true with
+ // BFD ld and gold, but not lld, which leaves that nulled out. So if that
+ // value is nulled out, we update it to the addend.
+ Elf_Addr addr(loc.getBuffer(), entry_sz, elf->getClass(), elf->getData());
+ unsigned int addend = get_addend(&*i, elf);
+ if (addr.value == 0) {
+ addr.value = addend;
+ addr.serialize(const_cast<char*>(loc.getBuffer()), entry_sz,
+ elf->getClass(), elf->getData());
+ } else if (addr.value != addend) {
+ fprintf(stderr,
+ "Relocation addend inconsistent with content. Skipping\n");
+ return -1;
+ }
+ if (i->r_offset ==
+ relhack_entry.r_offset + relhack_entry.r_info * entry_sz) {
+ relhack_entry.r_info++;
+ } else {
+ if (relhack_entry.r_offset) relhack->push_back(relhack_entry);
+ relhack_entry.r_offset = i->r_offset;
+ relhack_entry.r_info = 1;
+ }
+ }
+ }
+ if (relhack_entry.r_offset) relhack->push_back(relhack_entry);
+ // Last entry must be nullptr
+ relhack_entry.r_offset = relhack_entry.r_info = 0;
+ relhack->push_back(relhack_entry);
+
+ if (init_array) {
+ // Some linkers create a DT_INIT_ARRAY section that, for all purposes,
+ // is empty: it only contains 0x0 or 0xffffffff pointers with no
+ // relocations. In some other cases, there can be null pointers with no
+ // relocations in the middle of the section. Example: crtend_so.o in the
+ // Android NDK contains a sized .init_array with a null pointer and no
+ // relocation, which ends up in all Android libraries, and in some cases it
+ // ends up in the middle of the final .init_array section. If we have such a
+ // reusable slot at the beginning of .init_array, we just use it. It we have
+ // one in the middle of .init_array, we slide its content to move the "hole"
+ // at the beginning and use it there (we need our injected code to run
+ // before any other). Otherwise, replace the first entry and keep the
+ // original pointer.
+ std::sort(init_array_relocs.begin(), init_array_relocs.end(),
+ [](Rel_Type& a, Rel_Type& b) { return a.r_offset < b.r_offset; });
+ size_t expected = init_array->getAddr();
+ const size_t zero = 0;
+ const size_t all = SIZE_MAX;
+ const char* data = init_array->getData();
+ size_t length = Elf_Addr::size(elf->getClass());
+ size_t off = 0;
+ for (; off < init_array_relocs.size(); off++) {
+ auto& r = init_array_relocs[off];
+ if (r.r_offset >= expected + length &&
+ (memcmp(data + off * length, &zero, length) == 0 ||
+ memcmp(data + off * length, &all, length) == 0)) {
+ // We found a hole, move the preceding entries.
+ while (off) {
+ auto& p = init_array_relocs[--off];
+ if (ELF32_R_TYPE(p.r_info) == rel_type) {
+ unsigned int addend = get_addend(&p, elf);
+ p.r_offset += length;
+ set_relative_reloc(&p, elf, addend);
+ } else {
+ fprintf(stderr,
+ "Unsupported relocation type in DT_INIT_ARRAY. Skipping\n");
+ return -1;
+ }
+ }
+ break;
+ }
+ expected = r.r_offset + length;
+ }
+
+ if (off == 0) {
+ // We either found a hole above, and can now use the first entry,
+ // or the init_array section is effectively empty (see further above)
+ // and we also can use the first entry.
+ // Either way, code further below will take care of actually setting
+ // the right r_info and r_added for the relocation.
+ Rel_Type rel;
+ rel.r_offset = init_array->getAddr();
+ init_array_relocs.insert(init_array_relocs.begin(), rel);
+ } else {
+ // Use relocated value of DT_INIT_ARRAY's first entry for the
+ // function to be called by the injected code.
+ auto& rel = init_array_relocs[0];
+ unsigned int addend = get_addend(&rel, elf);
+ if (ELF32_R_TYPE(rel.r_info) == rel_type) {
+ original_init = addend;
+ } else if (ELF32_R_TYPE(rel.r_info) == rel_type2) {
+ ElfSymtab_Section* symtab = (ElfSymtab_Section*)section->getLink();
+ original_init =
+ symtab->syms[ELF32_R_SYM(rel.r_info)].value.getValue() + addend;
+ } else {
+ fprintf(stderr,
+ "Unsupported relocation type for DT_INIT_ARRAY's first entry. "
+ "Skipping\n");
+ return -1;
+ }
+ }
+
+ new_rels.insert(std::next(new_rels.begin(), init_array_insert),
+ init_array_relocs.begin(), init_array_relocs.end());
+ }
+
+ unsigned int mprotect_cb = 0;
+ unsigned int sysconf_cb = 0;
+ // If there is a relro segment, our injected code will run after the linker
+ // sets the corresponding pages read-only. We need to make our code change
+ // that to read-write before applying relocations, which means it needs to
+ // call mprotect. To do that, we need to find a reference to the mprotect
+ // symbol. In case the library already has one, we use that, but otherwise, we
+ // add the symbol. Then the injected code needs to be able to call the
+ // corresponding function, which means it needs access to a pointer to it. We
+ // get such a pointer by making the linker apply a relocation for the symbol
+ // at an address our code can read. The problem here is that there is not much
+ // relocated space where we can put such a pointer, so we abuse the bss
+ // section temporarily (it will be restored to a null value before any code
+ // can actually use it)
+ if (elf->getSegmentByType(PT_GNU_RELRO)) {
+ ElfSection* gnu_versym = dyn->getSectionForType(DT_VERSYM);
+ auto lookup = [&symtab, &gnu_versym](const char* symbol) {
+ Elf_SymValue* sym_value = symtab->lookup(symbol, STT(FUNC));
+ if (!sym_value) {
+ symtab->syms.emplace_back();
+ sym_value = &symtab->syms.back();
+ symtab->grow(symtab->syms.size() * symtab->getEntSize());
+ sym_value->name =
+ ((ElfStrtab_Section*)symtab->getLink())->getStr(symbol);
+ sym_value->info = ELF32_ST_INFO(STB_GLOBAL, STT_FUNC);
+ sym_value->other = STV_DEFAULT;
+ new (&sym_value->value) ElfLocation(nullptr, 0, ElfLocation::ABSOLUTE);
+ sym_value->size = 0;
+ sym_value->defined = false;
+
+ // The DT_VERSYM data (in the .gnu.version section) has the same number
+ // of entries as the symbols table. Since we added one entry there, we
+ // need to add one entry here. Zeroes in the extra data means no version
+ // for that symbol, which is the simplest thing to do.
+ if (gnu_versym) {
+ gnu_versym->grow(gnu_versym->getSize() + gnu_versym->getEntSize());
+ }
+ }
+ return sym_value;
+ };
+
+ Elf_SymValue* mprotect = lookup("mprotect");
+ Elf_SymValue* sysconf = lookup("sysconf");
+
+ // Add relocations for the mprotect and sysconf symbols.
+ auto add_relocation_to = [&new_rels, &symtab, rel_type2](
+ Elf_SymValue* symbol, unsigned int location) {
+ new_rels.emplace_back();
+ Rel_Type& rel = new_rels.back();
+ memset(&rel, 0, sizeof(rel));
+ rel.r_info = ELF32_R_INFO(
+ std::distance(symtab->syms.begin(),
+ std::vector<Elf_SymValue>::iterator(symbol)),
+ rel_type2);
+ rel.r_offset = location;
+ return location;
+ };
+
+ // Find the beginning of the bss section, and use an aligned location in
+ // there for the relocation.
+ for (ElfSection* s = elf->getSection(1); s != nullptr; s = s->getNext()) {
+ if (s->getType() != SHT_NOBITS ||
+ (s->getFlags() & (SHF_TLS | SHF_WRITE)) != SHF_WRITE) {
+ continue;
+ }
+ size_t ptr_size = Elf_Addr::size(elf->getClass());
+ size_t usable_start = (s->getAddr() + ptr_size - 1) & ~(ptr_size - 1);
+ size_t usable_end = (s->getAddr() + s->getSize()) & ~(ptr_size - 1);
+ if (usable_end - usable_start >= 2 * ptr_size) {
+ mprotect_cb = add_relocation_to(mprotect, usable_start);
+ sysconf_cb = add_relocation_to(sysconf, usable_start + ptr_size);
+ break;
+ }
+ }
+
+ if (mprotect_cb == 0 || sysconf_cb == 0) {
+ fprintf(stderr, "Couldn't find .bss. Skipping\n");
+ return -1;
+ }
+ }
+
+ size_t old_size = section->getSize();
+
+ section->rels.assign(new_rels.begin(), new_rels.end());
+ section->shrink(new_rels.size() * section->getEntSize());
+
+ ElfRelHackCode_Section* relhackcode =
+ new ElfRelHackCode_Section(relhackcode_section, *elf, *relhack,
+ original_init, mprotect_cb, sysconf_cb);
+ // Find the first executable section, and insert the relhack code before
+ // that. The relhack data is inserted between .rel.dyn and .rel.plt.
+ ElfSection* first_executable = nullptr;
+ for (ElfSection* s = elf->getSection(1); s != nullptr; s = s->getNext()) {
+ if (s->getFlags() & SHF_EXECINSTR) {
+ first_executable = s;
+ break;
+ }
+ }
+
+ if (!first_executable) {
+ fprintf(stderr, "Couldn't find executable section. Skipping\n");
+ return -1;
+ }
+
+ relhack->insertBefore(section);
+ relhackcode->insertBefore(first_executable);
+
+ // Don't try further if we can't gain from the relocation section size change.
+ // We account for the fact we're going to split the PT_LOAD before the
+ // injected code section, so the overhead of the page alignment for section
+ // needs to be accounted for.
+ size_t align = first_executable->getSegmentByType(PT_LOAD)->getAlign();
+ size_t new_size = relhack->getSize() + section->getSize() +
+ relhackcode->getSize() +
+ (relhackcode->getAddr() & (align - 1));
+ if (!force && (new_size >= old_size || old_size - new_size < align)) {
+ fprintf(stderr, "No gain. Skipping\n");
+ return -1;
+ }
+
+ // .eh_frame/.eh_frame_hdr may be between the relocation sections and the
+ // executable sections. When that happens, we may end up creating a separate
+ // PT_LOAD for just both of them because they are not considered relocatable.
+ // But they are, in fact, kind of relocatable, albeit with some manual work.
+ // Which we'll do here.
+ ElfSegment* eh_frame_segment = elf->getSegmentByType(PT_GNU_EH_FRAME);
+ ElfSection* eh_frame_hdr =
+ eh_frame_segment ? eh_frame_segment->getFirstSection() : nullptr;
+ // The .eh_frame section usually follows the eh_frame_hdr section.
+ ElfSection* eh_frame = eh_frame_hdr ? eh_frame_hdr->getNext() : nullptr;
+ ElfSection* first = eh_frame_hdr;
+ ElfSection* second = eh_frame;
+ if (eh_frame && strcmp(eh_frame->getName(), ".eh_frame")) {
+ // But sometimes it appears *before* the eh_frame_hdr section.
+ eh_frame = eh_frame_hdr->getPrevious();
+ first = eh_frame;
+ second = eh_frame_hdr;
+ }
+ if (eh_frame_hdr && (!eh_frame || strcmp(eh_frame->getName(), ".eh_frame"))) {
+ throw std::runtime_error(
+ "Expected to find an .eh_frame section adjacent to .eh_frame_hdr");
+ }
+ if (eh_frame && first->getAddr() > relhack->getAddr() &&
+ second->getAddr() < first_executable->getAddr()) {
+ // The distance between both sections needs to be preserved because
+ // eh_frame_hdr contains relative offsets to eh_frame. Well, they could be
+ // relocated too, but it's not worth the effort for the few number of bytes
+ // this would save.
+ unsigned int distance = second->getAddr() - first->getAddr();
+ unsigned int origAddr = eh_frame->getAddr();
+ ElfSection* previous = first->getPrevious();
+ first->getShdr().sh_addr = (previous->getAddr() + previous->getSize() +
+ first->getAddrAlign() - 1) &
+ ~(first->getAddrAlign() - 1);
+ second->getShdr().sh_addr =
+ (first->getAddr() + std::min(first->getSize(), distance) +
+ second->getAddrAlign() - 1) &
+ ~(second->getAddrAlign() - 1);
+ // Re-adjust to keep the original distance.
+ // If the first section has a smaller alignment requirement than the second,
+ // the second will be farther away, so we need to adjust the first.
+ // If the second section has a smaller alignment requirement than the first,
+ // it will already be at the right distance.
+ first->getShdr().sh_addr = second->getAddr() - distance;
+ assert(distance == second->getAddr() - first->getAddr());
+ first->markDirty();
+ adjust_eh_frame(eh_frame, origAddr, elf);
+ }
+
+ // Adjust PT_LOAD segments
+ for (ElfSegment* segment = elf->getSegmentByType(PT_LOAD); segment;
+ segment = elf->getSegmentByType(PT_LOAD, segment)) {
+ maybe_split_segment(elf, segment);
+ }
+
+ // Ensure Elf sections will be at their final location.
+ elf->normalize();
+ ElfLocation* init =
+ new ElfLocation(relhackcode, relhackcode->getEntryPoint());
+ if (init_array) {
+ // Adjust the first DT_INIT_ARRAY entry to point at the injected code
+ // by transforming its relocation into a relative one pointing to the
+ // address of the injected code.
+ Rel_Type* rel = &section->rels[init_array_insert];
+ rel->r_info = ELF32_R_INFO(0, rel_type); // Set as a relative relocation
+ set_relative_reloc(rel, elf, init->getValue());
+ } else if (!dyn->setValueForType(DT_INIT, init)) {
+ fprintf(stderr, "Can't grow .dynamic section to set DT_INIT. Skipping\n");
+ return -1;
+ }
+ // TODO: adjust the value according to the remaining number of relative
+ // relocations
+ if (dyn->getValueForType(Rel_Type::d_tag_count))
+ dyn->setValueForType(Rel_Type::d_tag_count, new ElfPlainValue(0));
+
+ return 0;
+}
+
+static inline int backup_file(const char* name) {
+ std::string fname(name);
+ fname += ".bak";
+ return rename(name, fname.c_str());
+}
+
+void do_file(const char* name, bool backup = false, bool force = false) {
+ std::ifstream file(name, std::ios::in | std::ios::binary);
+ Elf elf(file);
+ unsigned int size = elf.getSize();
+ fprintf(stderr, "%s: ", name);
+ if (elf.getType() != ET_DYN) {
+ fprintf(stderr, "Not a shared object. Skipping\n");
+ return;
+ }
+
+ for (ElfSection* section = elf.getSection(1); section != nullptr;
+ section = section->getNext()) {
+ if (section->getName() &&
+ (strncmp(section->getName(), ".elfhack.", 9) == 0)) {
+ fprintf(stderr, "Already elfhacked. Skipping\n");
+ return;
+ }
+ }
+
+ int exit = -1;
+ switch (elf.getMachine()) {
+ case EM_386:
+ exit =
+ do_relocation_section<Elf_Rel>(&elf, R_386_RELATIVE, R_386_32, force);
+ break;
+ case EM_X86_64:
+ exit = do_relocation_section<Elf_Rela>(&elf, R_X86_64_RELATIVE,
+ R_X86_64_64, force);
+ break;
+ case EM_ARM:
+ exit = do_relocation_section<Elf_Rel>(&elf, R_ARM_RELATIVE, R_ARM_ABS32,
+ force);
+ break;
+ }
+ if (exit == 0) {
+ if (!force && (elf.getSize() >= size)) {
+ fprintf(stderr, "No gain. Skipping\n");
+ } else if (backup && backup_file(name) != 0) {
+ fprintf(stderr, "Couln't create backup file\n");
+ } else {
+ std::ofstream ofile(name,
+ std::ios::out | std::ios::binary | std::ios::trunc);
+ elf.write(ofile);
+ fprintf(stderr, "Reduced by %d bytes\n", size - elf.getSize());
+ }
+ }
+}
+
+void undo_file(const char* name, bool backup = false) {
+ std::ifstream file(name, std::ios::in | std::ios::binary);
+ Elf elf(file);
+ unsigned int size = elf.getSize();
+ fprintf(stderr, "%s: ", name);
+ if (elf.getType() != ET_DYN) {
+ fprintf(stderr, "Not a shared object. Skipping\n");
+ return;
+ }
+
+ ElfSection *data = nullptr, *text = nullptr;
+ for (ElfSection* section = elf.getSection(1); section != nullptr;
+ section = section->getNext()) {
+ if (section->getName() && (strcmp(section->getName(), elfhack_data) == 0))
+ data = section;
+ if (section->getName() && (strcmp(section->getName(), elfhack_text) == 0))
+ text = section;
+ }
+
+ if (!data || !text) {
+ fprintf(stderr, "Not elfhacked. Skipping\n");
+ return;
+ }
+
+ // When both elfhack sections are in the same segment, try to merge
+ // the segment that contains them both and the following segment.
+ // When the elfhack sections are in separate segments, try to merge
+ // those segments.
+ ElfSegment* first = data->getSegmentByType(PT_LOAD);
+ ElfSegment* second = text->getSegmentByType(PT_LOAD);
+ if (first == second) {
+ second = elf.getSegmentByType(PT_LOAD, first);
+ }
+
+ // Only merge the segments when their flags match.
+ if (second->getFlags() != first->getFlags()) {
+ fprintf(stderr, "Couldn't merge PT_LOAD segments. Skipping\n");
+ return;
+ }
+ // Move sections from the second PT_LOAD to the first, and remove the
+ // second PT_LOAD segment.
+ for (std::list<ElfSection*>::iterator section = second->begin();
+ section != second->end(); ++section)
+ first->addSection(*section);
+
+ elf.removeSegment(second);
+ elf.normalize();
+
+ if (backup && backup_file(name) != 0) {
+ fprintf(stderr, "Couln't create backup file\n");
+ } else {
+ std::ofstream ofile(name,
+ std::ios::out | std::ios::binary | std::ios::trunc);
+ elf.write(ofile);
+ fprintf(stderr, "Grown by %d bytes\n", elf.getSize() - size);
+ }
+}
+
+int main(int argc, char* argv[]) {
+ int arg;
+ bool backup = false;
+ bool force = false;
+ bool revert = false;
+ char* lastSlash = rindex(argv[0], '/');
+ if (lastSlash != nullptr) rundir = strndup(argv[0], lastSlash - argv[0]);
+ for (arg = 1; arg < argc; arg++) {
+ if (strcmp(argv[arg], "-f") == 0)
+ force = true;
+ else if (strcmp(argv[arg], "-b") == 0)
+ backup = true;
+ else if (strcmp(argv[arg], "-r") == 0)
+ revert = true;
+ else if (revert) {
+ undo_file(argv[arg], backup);
+ } else
+ do_file(argv[arg], backup, force);
+ }
+
+ free(rundir);
+ return 0;
+}
diff --git a/build/unix/elfhack/elfxx.h b/build/unix/elfhack/elfxx.h
new file mode 100644
index 0000000000..c309e88c72
--- /dev/null
+++ b/build/unix/elfhack/elfxx.h
@@ -0,0 +1,691 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <stdexcept>
+#include <list>
+#include <vector>
+#include <cstring>
+#include <iostream>
+#include <fstream>
+#include <algorithm>
+#include <elf.h>
+#include <asm/byteorder.h>
+
+// Technically, __*_to_cpu and __cpu_to* function are equivalent,
+// so swap can use either of both.
+#define def_swap(endian, type, bits) \
+ static inline type##bits##_t swap(type##bits##_t i) { \
+ return __##endian##bits##_to_cpu(i); \
+ }
+
+class little_endian {
+ public:
+ def_swap(le, uint, 16);
+ def_swap(le, uint, 32);
+ def_swap(le, uint, 64);
+ def_swap(le, int, 16);
+ def_swap(le, int, 32);
+ def_swap(le, int, 64);
+};
+
+class big_endian {
+ public:
+ def_swap(be, uint, 16);
+ def_swap(be, uint, 32);
+ def_swap(be, uint, 64);
+ def_swap(be, int, 16);
+ def_swap(be, int, 32);
+ def_swap(be, int, 64);
+};
+
+// forward declaration
+class ElfSection;
+class ElfSegment;
+// TODO: Rename Elf_* types
+class Elf_Ehdr;
+class Elf_Phdr;
+class Elf;
+class ElfDynamic_Section;
+class ElfStrtab_Section;
+
+template <typename X>
+class FixedSizeData {
+ public:
+ struct Wrapper {
+ X value;
+ };
+ typedef Wrapper Type32;
+ typedef Wrapper Type64;
+
+ template <class endian, typename R, typename T>
+ static void swap(T& t, R& r) {
+ r.value = endian::swap(t.value);
+ }
+};
+
+class Elf_Ehdr_Traits {
+ public:
+ typedef Elf32_Ehdr Type32;
+ typedef Elf64_Ehdr Type64;
+
+ template <class endian, typename R, typename T>
+ static void swap(T& t, R& r);
+};
+
+class Elf_Phdr_Traits {
+ public:
+ typedef Elf32_Phdr Type32;
+ typedef Elf64_Phdr Type64;
+
+ template <class endian, typename R, typename T>
+ static void swap(T& t, R& r);
+};
+
+class Elf_Shdr_Traits {
+ public:
+ typedef Elf32_Shdr Type32;
+ typedef Elf64_Shdr Type64;
+
+ template <class endian, typename R, typename T>
+ static void swap(T& t, R& r);
+};
+
+class Elf_Dyn_Traits {
+ public:
+ typedef Elf32_Dyn Type32;
+ typedef Elf64_Dyn Type64;
+
+ template <class endian, typename R, typename T>
+ static void swap(T& t, R& r);
+};
+
+class Elf_Sym_Traits {
+ public:
+ typedef Elf32_Sym Type32;
+ typedef Elf64_Sym Type64;
+
+ template <class endian, typename R, typename T>
+ static void swap(T& t, R& r);
+};
+
+class Elf_Rel_Traits {
+ public:
+ typedef Elf32_Rel Type32;
+ typedef Elf64_Rel Type64;
+
+ template <class endian, typename R, typename T>
+ static void swap(T& t, R& r);
+};
+
+class Elf_Rela_Traits {
+ public:
+ typedef Elf32_Rela Type32;
+ typedef Elf64_Rela Type64;
+
+ template <class endian, typename R, typename T>
+ static void swap(T& t, R& r);
+};
+
+class ElfValue {
+ public:
+ virtual unsigned int getValue() { return 0; }
+ virtual ElfSection* getSection() { return nullptr; }
+};
+
+class ElfPlainValue : public ElfValue {
+ unsigned int value;
+
+ public:
+ ElfPlainValue(unsigned int val) : value(val){};
+ unsigned int getValue() { return value; }
+};
+
+class ElfLocation : public ElfValue {
+ ElfSection* section;
+ unsigned int offset;
+
+ public:
+ enum position { ABSOLUTE, RELATIVE };
+ ElfLocation() : section(nullptr), offset(0){};
+ ElfLocation(ElfSection* section, unsigned int off,
+ enum position pos = RELATIVE);
+ ElfLocation(unsigned int location, Elf* elf);
+ unsigned int getValue();
+ ElfSection* getSection() { return section; }
+ const char* getBuffer();
+};
+
+class ElfSize : public ElfValue {
+ ElfSection* section;
+
+ public:
+ ElfSize(ElfSection* s) : section(s){};
+ unsigned int getValue();
+ ElfSection* getSection() { return section; }
+};
+
+class ElfEntSize : public ElfValue {
+ ElfSection* section;
+
+ public:
+ ElfEntSize(ElfSection* s) : section(s){};
+ unsigned int getValue();
+ ElfSection* getSection() { return section; }
+};
+
+template <typename T>
+class serializable : public T::Type32 {
+ public:
+ serializable(){};
+ serializable(const typename T::Type32& p) : T::Type32(p){};
+
+ private:
+ template <typename R>
+ void init(const char* buf, size_t len, char ei_data) {
+ R e;
+ assert(len >= sizeof(e));
+ memcpy(&e, buf, sizeof(e));
+ if (ei_data == ELFDATA2LSB) {
+ T::template swap<little_endian>(e, *this);
+ return;
+ } else if (ei_data == ELFDATA2MSB) {
+ T::template swap<big_endian>(e, *this);
+ return;
+ }
+ throw std::runtime_error("Unsupported ELF data encoding");
+ }
+
+ template <typename R>
+ void serialize(const char* buf, size_t len, char ei_data) {
+ assert(len >= sizeof(R));
+ if (ei_data == ELFDATA2LSB) {
+ T::template swap<little_endian>(*this, *(R*)buf);
+ return;
+ } else if (ei_data == ELFDATA2MSB) {
+ T::template swap<big_endian>(*this, *(R*)buf);
+ return;
+ }
+ throw std::runtime_error("Unsupported ELF data encoding");
+ }
+
+ public:
+ serializable(const char* buf, size_t len, char ei_class, char ei_data) {
+ if (ei_class == ELFCLASS32) {
+ init<typename T::Type32>(buf, len, ei_data);
+ return;
+ } else if (ei_class == ELFCLASS64) {
+ init<typename T::Type64>(buf, len, ei_data);
+ return;
+ }
+ throw std::runtime_error("Unsupported ELF class");
+ }
+
+ serializable(std::ifstream& file, char ei_class, char ei_data) {
+ if (ei_class == ELFCLASS32) {
+ typename T::Type32 e;
+ file.read((char*)&e, sizeof(e));
+ init<typename T::Type32>((char*)&e, sizeof(e), ei_data);
+ return;
+ } else if (ei_class == ELFCLASS64) {
+ typename T::Type64 e;
+ file.read((char*)&e, sizeof(e));
+ init<typename T::Type64>((char*)&e, sizeof(e), ei_data);
+ return;
+ }
+ throw std::runtime_error("Unsupported ELF class or data encoding");
+ }
+
+ void serialize(std::ofstream& file, char ei_class, char ei_data) {
+ if (ei_class == ELFCLASS32) {
+ typename T::Type32 e;
+ serialize<typename T::Type32>((char*)&e, sizeof(e), ei_data);
+ file.write((char*)&e, sizeof(e));
+ return;
+ } else if (ei_class == ELFCLASS64) {
+ typename T::Type64 e;
+ serialize<typename T::Type64>((char*)&e, sizeof(e), ei_data);
+ file.write((char*)&e, sizeof(e));
+ return;
+ }
+ throw std::runtime_error("Unsupported ELF class or data encoding");
+ }
+
+ void serialize(char* buf, size_t len, char ei_class, char ei_data) {
+ if (ei_class == ELFCLASS32) {
+ serialize<typename T::Type32>(buf, len, ei_data);
+ return;
+ } else if (ei_class == ELFCLASS64) {
+ serialize<typename T::Type64>(buf, len, ei_data);
+ return;
+ }
+ throw std::runtime_error("Unsupported ELF class");
+ }
+
+ static inline unsigned int size(char ei_class) {
+ if (ei_class == ELFCLASS32)
+ return sizeof(typename T::Type32);
+ else if (ei_class == ELFCLASS64)
+ return sizeof(typename T::Type64);
+ return 0;
+ }
+};
+
+typedef serializable<Elf_Shdr_Traits> Elf_Shdr;
+
+class Elf {
+ public:
+ Elf(std::ifstream& file);
+ ~Elf();
+
+ /* index == -1 is treated as index == ehdr.e_shstrndx */
+ ElfSection* getSection(int index);
+
+ ElfSection* getSectionAt(unsigned int offset);
+
+ ElfSegment* getSegmentByType(unsigned int type, ElfSegment* last = nullptr);
+
+ ElfDynamic_Section* getDynSection();
+
+ void normalize();
+ void write(std::ofstream& file);
+
+ char getClass();
+ char getData();
+ char getType();
+ char getMachine();
+ unsigned int getSize();
+
+ void insertSegmentAfter(ElfSegment* previous, ElfSegment* segment) {
+ std::vector<ElfSegment*>::iterator prev =
+ std::find(segments.begin(), segments.end(), previous);
+ segments.insert(prev + 1, segment);
+ }
+
+ void removeSegment(ElfSegment* segment);
+
+ private:
+ Elf_Ehdr* ehdr;
+ ElfLocation eh_entry;
+ ElfStrtab_Section* eh_shstrndx;
+ ElfSection** sections;
+ std::vector<ElfSegment*> segments;
+ ElfSection *shdr_section, *phdr_section;
+ /* Values used only during initialization */
+ Elf_Shdr** tmp_shdr;
+ std::ifstream* tmp_file;
+};
+
+class ElfSection {
+ public:
+ typedef union {
+ ElfSection* section;
+ int index;
+ } SectionInfo;
+
+ ElfSection(Elf_Shdr& s, std::ifstream* file, Elf* parent);
+
+ virtual ~ElfSection() { free(data); }
+
+ const char* getName() { return name; }
+ unsigned int getType() { return shdr.sh_type; }
+ unsigned int getFlags() { return shdr.sh_flags; }
+ unsigned int getAddr();
+ unsigned int getSize() { return shdr.sh_size; }
+ unsigned int getAddrAlign() { return shdr.sh_addralign; }
+ unsigned int getEntSize() { return shdr.sh_entsize; }
+ const char* getData() { return data; }
+ ElfSection* getLink() { return link; }
+ SectionInfo getInfo() { return info; }
+
+ void shrink(unsigned int newsize) {
+ if (newsize < shdr.sh_size) {
+ shdr.sh_size = newsize;
+ markDirty();
+ }
+ }
+
+ void grow(unsigned int newsize) {
+ if (newsize > shdr.sh_size) {
+ data = static_cast<char*>(realloc(data, newsize));
+ memset(data + shdr.sh_size, 0, newsize - shdr.sh_size);
+ shdr.sh_size = newsize;
+ markDirty();
+ }
+ }
+
+ unsigned int getOffset();
+ int getIndex();
+ Elf_Shdr& getShdr();
+
+ ElfSection* getNext() { return next; }
+ ElfSection* getPrevious() { return previous; }
+
+ virtual bool isRelocatable() {
+ return ((getType() == SHT_SYMTAB) || (getType() == SHT_STRTAB) ||
+ (getType() == SHT_RELA) || (getType() == SHT_HASH) ||
+ (getType() == SHT_NOTE) || (getType() == SHT_REL) ||
+ (getType() == SHT_DYNSYM) || (getType() == SHT_GNU_HASH) ||
+ (getType() == SHT_GNU_verdef) || (getType() == SHT_GNU_verneed) ||
+ (getType() == SHT_GNU_versym) || getSegmentByType(PT_INTERP)) &&
+ (getFlags() & SHF_ALLOC);
+ }
+
+ void insertAfter(ElfSection* section, bool dirty = true) {
+ if (previous != nullptr) previous->next = next;
+ if (next != nullptr) next->previous = previous;
+ previous = section;
+ if (section != nullptr) {
+ next = section->next;
+ section->next = this;
+ } else
+ next = nullptr;
+ if (next != nullptr) next->previous = this;
+ if (dirty) markDirty();
+ insertInSegments(section->segments);
+ }
+
+ virtual void insertBefore(ElfSection* section, bool dirty = true) {
+ if (previous != nullptr) previous->next = next;
+ if (next != nullptr) next->previous = previous;
+ next = section;
+ if (section != nullptr) {
+ previous = section->previous;
+ section->previous = this;
+ } else
+ previous = nullptr;
+ if (previous != nullptr) previous->next = this;
+ if (dirty) markDirty();
+ insertInSegments(section->segments);
+ }
+
+ void markDirty() {
+ if (link != nullptr) shdr.sh_link = -1;
+ if (info.index) shdr.sh_info = -1;
+ shdr.sh_offset = -1;
+ if (isRelocatable()) shdr.sh_addr = -1;
+ if (next) next->markDirty();
+ }
+
+ virtual void serialize(std::ofstream& file, char ei_class, char ei_data) {
+ if (getType() == SHT_NOBITS) return;
+ file.seekp(getOffset());
+ file.write(data, getSize());
+ }
+
+ ElfSegment* getSegmentByType(unsigned int type);
+
+ private:
+ friend class ElfSegment;
+
+ void addToSegment(ElfSegment* segment) { segments.push_back(segment); }
+
+ void removeFromSegment(ElfSegment* segment) {
+ std::vector<ElfSegment*>::iterator i =
+ std::find(segments.begin(), segments.end(), segment);
+ segments.erase(i, i + 1);
+ }
+
+ void insertInSegments(std::vector<ElfSegment*>& segs);
+
+ protected:
+ Elf_Shdr shdr;
+ char* data;
+ const char* name;
+
+ private:
+ ElfSection* link;
+ SectionInfo info;
+ ElfSection *next, *previous;
+ int index;
+ std::vector<ElfSegment*> segments;
+};
+
+class ElfSegment {
+ public:
+ ElfSegment(Elf_Phdr* phdr);
+
+ unsigned int getType() { return type; }
+ unsigned int getFlags() { return flags; }
+ unsigned int getAlign() { return align; }
+
+ ElfSection* getFirstSection() {
+ return sections.empty() ? nullptr : sections.front();
+ }
+ int getVPDiff() { return v_p_diff; }
+ unsigned int getFileSize();
+ unsigned int getMemSize();
+ unsigned int getOffset();
+ unsigned int getAddr();
+
+ void addSection(ElfSection* section);
+ void removeSection(ElfSection* section);
+
+ std::list<ElfSection*>::iterator begin() { return sections.begin(); }
+ std::list<ElfSection*>::iterator end() { return sections.end(); }
+
+ void clear();
+
+ private:
+ unsigned int type;
+ int v_p_diff; // Difference between physical and virtual address
+ unsigned int flags;
+ unsigned int align;
+ std::list<ElfSection*> sections;
+ // The following are only really used for PT_GNU_RELRO until something
+ // better is found.
+ unsigned int vaddr;
+ unsigned int filesz, memsz;
+};
+
+class Elf_Ehdr : public serializable<Elf_Ehdr_Traits>, public ElfSection {
+ public:
+ Elf_Ehdr(std::ifstream& file, char ei_class, char ei_data);
+ void serialize(std::ofstream& file, char ei_class, char ei_data) {
+ serializable<Elf_Ehdr_Traits>::serialize(file, ei_class, ei_data);
+ }
+};
+
+class Elf_Phdr : public serializable<Elf_Phdr_Traits> {
+ public:
+ Elf_Phdr(){};
+ Elf_Phdr(std::ifstream& file, char ei_class, char ei_data)
+ : serializable<Elf_Phdr_Traits>(file, ei_class, ei_data){};
+ bool contains(ElfSection* section) {
+ unsigned int size = section->getSize();
+ unsigned int addr = section->getAddr();
+ // This may be biased, but should work in most cases
+ if ((section->getFlags() & SHF_ALLOC) == 0) return false;
+ // Special case for PT_DYNAMIC. Eventually, this should
+ // be better handled than special cases
+ if ((p_type == PT_DYNAMIC) && (section->getType() != SHT_DYNAMIC))
+ return false;
+ // Special case for PT_TLS.
+ if ((p_type == PT_TLS) && !(section->getFlags() & SHF_TLS)) return false;
+ return (addr >= p_vaddr) && (addr + size <= p_vaddr + p_memsz);
+ }
+};
+
+typedef serializable<Elf_Dyn_Traits> Elf_Dyn;
+
+struct Elf_DynValue {
+ unsigned int tag;
+ ElfValue* value;
+};
+
+class ElfDynamic_Section : public ElfSection {
+ public:
+ ElfDynamic_Section(Elf_Shdr& s, std::ifstream* file, Elf* parent);
+ ~ElfDynamic_Section();
+
+ void serialize(std::ofstream& file, char ei_class, char ei_data);
+
+ ElfValue* getValueForType(unsigned int tag);
+ ElfSection* getSectionForType(unsigned int tag);
+ bool setValueForType(unsigned int tag, ElfValue* val);
+
+ private:
+ std::vector<Elf_DynValue> dyns;
+};
+
+typedef serializable<Elf_Sym_Traits> Elf_Sym;
+
+struct Elf_SymValue {
+ const char* name;
+ unsigned char info;
+ unsigned char other;
+ ElfLocation value;
+ unsigned int size;
+ bool defined;
+};
+
+#define STT(type) (1 << STT_##type)
+
+class ElfSymtab_Section : public ElfSection {
+ public:
+ ElfSymtab_Section(Elf_Shdr& s, std::ifstream* file, Elf* parent);
+
+ void serialize(std::ofstream& file, char ei_class, char ei_data);
+
+ Elf_SymValue* lookup(const char* name,
+ unsigned int type_filter = STT(OBJECT) | STT(FUNC));
+
+ // private: // Until we have a real API
+ std::vector<Elf_SymValue> syms;
+};
+
+class Elf_Rel : public serializable<Elf_Rel_Traits> {
+ public:
+ Elf_Rel() : serializable<Elf_Rel_Traits>(){};
+
+ Elf_Rel(std::ifstream& file, char ei_class, char ei_data)
+ : serializable<Elf_Rel_Traits>(file, ei_class, ei_data){};
+
+ static const unsigned int sh_type = SHT_REL;
+ static const unsigned int d_tag = DT_REL;
+ static const unsigned int d_tag_count = DT_RELCOUNT;
+};
+
+class Elf_Rela : public serializable<Elf_Rela_Traits> {
+ public:
+ Elf_Rela() : serializable<Elf_Rela_Traits>(){};
+
+ Elf_Rela(std::ifstream& file, char ei_class, char ei_data)
+ : serializable<Elf_Rela_Traits>(file, ei_class, ei_data){};
+
+ static const unsigned int sh_type = SHT_RELA;
+ static const unsigned int d_tag = DT_RELA;
+ static const unsigned int d_tag_count = DT_RELACOUNT;
+};
+
+template <class Rel>
+class ElfRel_Section : public ElfSection {
+ public:
+ ElfRel_Section(Elf_Shdr& s, std::ifstream* file, Elf* parent)
+ : ElfSection(s, file, parent) {
+ auto pos = file->tellg();
+ file->seekg(shdr.sh_offset);
+ for (unsigned int i = 0; i < s.sh_size / s.sh_entsize; i++) {
+ Rel r(*file, parent->getClass(), parent->getData());
+ rels.push_back(r);
+ }
+ file->seekg(pos);
+ }
+
+ void serialize(std::ofstream& file, char ei_class, char ei_data) {
+ for (typename std::vector<Rel>::iterator i = rels.begin(); i != rels.end();
+ ++i)
+ (*i).serialize(file, ei_class, ei_data);
+ }
+ // private: // Until we have a real API
+ std::vector<Rel> rels;
+};
+
+class ElfStrtab_Section : public ElfSection {
+ public:
+ ElfStrtab_Section(Elf_Shdr& s, std::ifstream* file, Elf* parent)
+ : ElfSection(s, file, parent) {
+ table.push_back(table_storage(data, shdr.sh_size));
+ }
+
+ ~ElfStrtab_Section() {
+ for (std::vector<table_storage>::iterator t = table.begin() + 1;
+ t != table.end(); ++t)
+ delete[] t->buf;
+ }
+
+ const char* getStr(unsigned int index);
+
+ const char* getStr(const char* string);
+
+ unsigned int getStrIndex(const char* string);
+
+ void serialize(std::ofstream& file, char ei_class, char ei_data);
+
+ private:
+ struct table_storage {
+ unsigned int size, used;
+ char* buf;
+
+ table_storage() : size(4096), used(0), buf(new char[4096]) {}
+ table_storage(const char* data, unsigned int sz)
+ : size(sz), used(sz), buf(const_cast<char*>(data)) {}
+ };
+ std::vector<table_storage> table;
+};
+
+inline char Elf::getClass() { return ehdr->e_ident[EI_CLASS]; }
+
+inline char Elf::getData() { return ehdr->e_ident[EI_DATA]; }
+
+inline char Elf::getType() { return ehdr->e_type; }
+
+inline char Elf::getMachine() { return ehdr->e_machine; }
+
+inline unsigned int Elf::getSize() {
+ ElfSection* section;
+ for (section = shdr_section /* It's usually not far from the end */;
+ section->getNext() != nullptr; section = section->getNext())
+ ;
+ return section->getOffset() + section->getSize();
+}
+
+inline ElfSegment* ElfSection::getSegmentByType(unsigned int type) {
+ for (std::vector<ElfSegment*>::iterator seg = segments.begin();
+ seg != segments.end(); ++seg)
+ if ((*seg)->getType() == type) return *seg;
+ return nullptr;
+}
+
+inline void ElfSection::insertInSegments(std::vector<ElfSegment*>& segs) {
+ for (std::vector<ElfSegment*>::iterator it = segs.begin(); it != segs.end();
+ ++it) {
+ (*it)->addSection(this);
+ }
+}
+
+inline ElfLocation::ElfLocation(ElfSection* section, unsigned int off,
+ enum position pos)
+ : section(section) {
+ if ((pos == ABSOLUTE) && section)
+ offset = off - section->getAddr();
+ else
+ offset = off;
+}
+
+inline ElfLocation::ElfLocation(unsigned int location, Elf* elf) {
+ section = elf->getSectionAt(location);
+ offset = location - (section ? section->getAddr() : 0);
+}
+
+inline unsigned int ElfLocation::getValue() {
+ return (section ? section->getAddr() : 0) + offset;
+}
+
+inline const char* ElfLocation::getBuffer() {
+ return section ? section->getData() + offset : nullptr;
+}
+
+inline unsigned int ElfSize::getValue() { return section->getSize(); }
+
+inline unsigned int ElfEntSize::getValue() { return section->getEntSize(); }
diff --git a/build/unix/elfhack/inject.c b/build/unix/elfhack/inject.c
new file mode 100644
index 0000000000..54049fb268
--- /dev/null
+++ b/build/unix/elfhack/inject.c
@@ -0,0 +1,124 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <elf.h>
+
+/* The Android NDK headers define those */
+#undef Elf_Ehdr
+#undef Elf_Addr
+
+#if defined(__LP64__)
+# define Elf_Ehdr Elf64_Ehdr
+# define Elf_Addr Elf64_Addr
+#else
+# define Elf_Ehdr Elf32_Ehdr
+# define Elf_Addr Elf32_Addr
+#endif
+
+// On ARM, PC-relative function calls have a limit in how far they can jump,
+// which might not be enough for e.g. libxul.so. The easy way out would be
+// to use the long_call attribute, which forces the compiler to generate code
+// that can call anywhere, but clang doesn't support the attribute yet
+// (https://bugs.llvm.org/show_bug.cgi?id=40623), and while the command-line
+// equivalent does exist, it's currently broken
+// (https://bugs.llvm.org/show_bug.cgi?id=40624). So we create a manual
+// trampoline, corresponding to the code GCC generates with long_call.
+#ifdef __arm__
+__attribute__((section(".text._init_trampoline"), naked)) int init_trampoline(
+ int argc, char** argv, char** env) {
+ __asm__ __volatile__(
+ // thumb doesn't allow to use r12/ip with ldr, and thus would require an
+ // additional push/pop to save/restore the modified register, which would
+ // also change the call into a blx. It's simpler to switch to arm.
+ ".arm\n"
+ " ldr ip, .LADDR\n"
+ ".LAFTER:\n"
+ " add ip, pc, ip\n"
+ " bx ip\n"
+ ".LADDR:\n"
+ " .word real_original_init-(.LAFTER+8)\n");
+}
+#endif
+
+extern __attribute__((visibility("hidden"))) void original_init(int argc,
+ char** argv,
+ char** env);
+
+extern __attribute__((visibility("hidden"))) Elf32_Rel relhack[];
+extern __attribute__((visibility("hidden"))) Elf_Ehdr elf_header;
+
+extern __attribute__((visibility("hidden"))) int (*mprotect_cb)(void* addr,
+ size_t len,
+ int prot);
+extern __attribute__((visibility("hidden"))) long (*sysconf_cb)(int name);
+extern __attribute__((visibility("hidden"))) char relro_start[];
+extern __attribute__((visibility("hidden"))) char relro_end[];
+
+static inline __attribute__((always_inline)) void do_relocations(void) {
+ Elf32_Rel* rel;
+ Elf_Addr *ptr, *start;
+ for (rel = relhack; rel->r_offset; rel++) {
+ start = (Elf_Addr*)((intptr_t)&elf_header + rel->r_offset);
+ for (ptr = start; ptr < &start[rel->r_info]; ptr++)
+ *ptr += (intptr_t)&elf_header;
+ }
+}
+
+__attribute__((section(".text._init_noinit"))) int init_noinit(int argc,
+ char** argv,
+ char** env) {
+ do_relocations();
+ return 0;
+}
+
+__attribute__((section(".text._init"))) int init(int argc, char** argv,
+ char** env) {
+ do_relocations();
+ original_init(argc, argv, env);
+ // Ensure there is no tail-call optimization, avoiding the use of the
+ // B.W instruction in Thumb for the call above.
+ return 0;
+}
+
+static inline __attribute__((always_inline)) void do_relocations_with_relro(
+ void) {
+ long page_size = sysconf_cb(_SC_PAGESIZE);
+ uintptr_t aligned_relro_start = ((uintptr_t)relro_start) & ~(page_size - 1);
+ // The relro segment may not end at a page boundary. If that's the case, the
+ // remainder of the page needs to stay read-write, so the last page is never
+ // set read-only. Thus the aligned relro end is page-rounded down.
+ uintptr_t aligned_relro_end = ((uintptr_t)relro_end) & ~(page_size - 1);
+ // By the time the injected code runs, the relro segment is read-only. But
+ // we want to apply relocations in it, so we set it r/w first. We'll restore
+ // it to read-only in relro_post.
+ mprotect_cb((void*)aligned_relro_start,
+ aligned_relro_end - aligned_relro_start, PROT_READ | PROT_WRITE);
+
+ do_relocations();
+
+ mprotect_cb((void*)aligned_relro_start,
+ aligned_relro_end - aligned_relro_start, PROT_READ);
+ // mprotect_cb and sysconf_cb are allocated in .bss, so we need to restore
+ // them to a NULL value.
+ mprotect_cb = NULL;
+ sysconf_cb = NULL;
+}
+
+__attribute__((section(".text._init_noinit_relro"))) int init_noinit_relro(
+ int argc, char** argv, char** env) {
+ do_relocations_with_relro();
+ return 0;
+}
+
+__attribute__((section(".text._init_relro"))) int init_relro(int argc,
+ char** argv,
+ char** env) {
+ do_relocations_with_relro();
+ original_init(argc, argv, env);
+ return 0;
+}
diff --git a/build/unix/elfhack/inject/copy_source.py b/build/unix/elfhack/inject/copy_source.py
new file mode 100644
index 0000000000..02b4f6237e
--- /dev/null
+++ b/build/unix/elfhack/inject/copy_source.py
@@ -0,0 +1,10 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+
+def copy(out_file, in_path):
+ with open(in_path, "r") as fh:
+ out_file.write(fh.read())
diff --git a/build/unix/elfhack/inject/moz.build b/build/unix/elfhack/inject/moz.build
new file mode 100644
index 0000000000..5b717a49cf
--- /dev/null
+++ b/build/unix/elfhack/inject/moz.build
@@ -0,0 +1,40 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# dummy library name to avoid skipping building the source here, which
+# we only need the object for.
+Library("elfhack_inject")
+
+DIST_INSTALL = False
+
+cpu = CONFIG["CPU_ARCH"]
+
+gen_src = "%s.c" % cpu
+GeneratedFile(
+ gen_src, script="copy_source.py", entry_point="copy", inputs=["../inject.c"]
+)
+
+SOURCES += [
+ "!%s" % gen_src,
+]
+
+NO_PGO = True
+
+for v in ("OS_CPPFLAGS", "OS_CFLAGS", "DEBUG", "CLANG_PLUGIN", "OPTIMIZE", "FRAMEPTR"):
+ flags = []
+ idx = 0
+ for flag in COMPILE_FLAGS[v]:
+ if flag == "-isystem":
+ flags.append("".join(COMPILE_FLAGS[v][idx : idx + 2]))
+ elif flag.startswith(("-m", "-I", "-isystem")):
+ flags.append(flag)
+ idx += 1
+ COMPILE_FLAGS[v] = flags
+
+COMPILE_FLAGS["OS_CFLAGS"] += ["-O2", "-fno-stack-protector", "-fno-lto"]
+
+AllowCompilerWarnings()
+NoVisibilityFlags()
diff --git a/build/unix/elfhack/moz.build b/build/unix/elfhack/moz.build
new file mode 100644
index 0000000000..bb68b3aa4e
--- /dev/null
+++ b/build/unix/elfhack/moz.build
@@ -0,0 +1,32 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DIST_INSTALL = False
+DIRS += ["inject"]
+
+if not CONFIG["CROSS_COMPILE"]:
+ SOURCES += [
+ "dummy.c",
+ "test-array.c",
+ "test-ctors.c",
+ ]
+
+ SOURCES["dummy.c"].flags += ["-fno-lto"]
+ SOURCES["test-array.c"].flags += ["-fno-lto"]
+ SOURCES["test-ctors.c"].flags += ["-fno-lto"]
+
+HOST_SOURCES += [
+ "elf.cpp",
+ "elfhack.cpp",
+]
+
+HostProgram("elfhack")
+
+NO_PGO = True
+
+COMPILE_FLAGS["OS_CXXFLAGS"] = [
+ f for f in COMPILE_FLAGS["OS_CXXFLAGS"] if f != "-fno-exceptions"
+] + ["-fexceptions"]
diff --git a/build/unix/elfhack/test-array.c b/build/unix/elfhack/test-array.c
new file mode 100644
index 0000000000..21aec3d360
--- /dev/null
+++ b/build/unix/elfhack/test-array.c
@@ -0,0 +1,8 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "test.c"
+
+__attribute__((section(".init_array"), used)) static void (*init_array[])() = {
+ end_test, test};
diff --git a/build/unix/elfhack/test-ctors.c b/build/unix/elfhack/test-ctors.c
new file mode 100644
index 0000000000..d082411e3d
--- /dev/null
+++ b/build/unix/elfhack/test-ctors.c
@@ -0,0 +1,16 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "test.c"
+
+/* Recent binutils would put .ctors content into a .init_array section */
+__attribute__((section(".manual_ctors"), used)) static void (*ctors[])() = {
+ (void (*)()) - 1, end_test, test, NULL};
+
+__attribute__((section(".init"))) void _init() {
+ void (**func)() = &ctors[sizeof(ctors) / sizeof(void (*)()) - 1];
+ while (*(--func) != (void (*)()) - 1) {
+ (*func)();
+ }
+}
diff --git a/build/unix/elfhack/test.c b/build/unix/elfhack/test.c
new file mode 100644
index 0000000000..11e06bd024
--- /dev/null
+++ b/build/unix/elfhack/test.c
@@ -0,0 +1,170 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifdef DEF
+DEF(This)
+DEF(is)
+DEF(a)
+DEF(test)
+DEF(of)
+DEF(string)
+DEF(array)
+DEF(for)
+DEF(use)
+DEF(with)
+DEF(elfhack)
+DEF(to)
+DEF(see)
+DEF(whether)
+DEF(it)
+DEF(breaks)
+DEF(anything)
+DEF(but)
+DEF(one)
+DEF(needs)
+DEF(quite)
+DEF(some)
+DEF(strings)
+DEF(before)
+DEF(the)
+DEF(program)
+DEF(can)
+DEF(do)
+DEF(its)
+DEF(work)
+DEF(efficiently)
+DEF(Without)
+DEF(enough)
+DEF(data)
+DEF(relocation)
+DEF(sections)
+DEF(are)
+// clang-format off
+DEF(not)
+// clang-format on
+DEF(sufficiently)
+DEF(large)
+DEF(and)
+DEF(injected)
+DEF(code)
+DEF(wouldnt)
+DEF(fit)
+DEF(Said)
+DEF(otherwise)
+DEF(we)
+DEF(need)
+DEF(more)
+DEF(words)
+DEF(than)
+DEF(up)
+DEF(here)
+DEF(so)
+DEF(that)
+DEF(relocations)
+DEF(take)
+DEF(significant)
+DEF(bytes)
+DEF(amounts)
+DEF(which)
+DEF(isnt)
+DEF(exactly)
+DEF(easily)
+DEF(achieved)
+DEF(like)
+DEF(this)
+DEF(Actually)
+DEF(I)
+DEF(must)
+DEF(cheat)
+DEF(by)
+DEF(including)
+DEF(these)
+DEF(phrases)
+DEF(several)
+DEF(times)
+
+#else
+# pragma GCC visibility push(default)
+# include <stdlib.h>
+# include <stdio.h>
+
+# define DEF(w) static const char str_##w[] = # w;
+# include "test.c"
+# undef DEF
+
+const char* strings[] = {
+# define DEF(w) str_##w,
+# include "test.c"
+# include "test.c"
+# include "test.c"
+};
+
+/* Create a hole between two zones of relative relocations */
+const int hole[] = {42, 42, 42, 42};
+
+const char* strings2[] = {
+# include "test.c"
+# include "test.c"
+# include "test.c"
+# include "test.c"
+# include "test.c"
+# undef DEF
+};
+
+static int ret = 1;
+
+int print_status() {
+ fprintf(stderr, "%s\n", ret ? "FAIL" : "PASS");
+ return ret;
+}
+
+/* On ARM, this creates a .tbss section before .init_array, which
+ * elfhack could then pick instead of .init_array.
+ * Also, when .tbss is big enough, elfhack may wrongfully consider
+ * following sections as part of the PT_TLS segment.
+ * Finally, gold makes TLS segments end on an aligned virtual address,
+ * even when the underlying section ends before that, and elfhack
+ * sanity checks may yield an error. */
+__thread int foo;
+__thread long long int bar[512];
+
+/* We need a .bss that can hold at least 2 pointers. The static in
+ * end_test() plus this variable should do. */
+size_t dummy;
+
+void end_test() {
+ static size_t count = 0;
+ /* Only exit when both constructors have been called */
+ if (++count == 2) {
+ ret = 0;
+ // Avoid the dummy variable being stripped out at link time because
+ // it's unused.
+ dummy = 1;
+ }
+}
+
+void test() {
+ int i = 0, j = 0;
+# define DEF_(a, i, w) \
+ if (a[i++] != str_##w) return;
+# define DEF(w) DEF_(strings, i, w)
+# include "test.c"
+# include "test.c"
+# include "test.c"
+# undef DEF
+# define DEF(w) DEF_(strings2, j, w)
+# include "test.c"
+# include "test.c"
+# include "test.c"
+# include "test.c"
+# include "test.c"
+# undef DEF
+ if (i != sizeof(strings) / sizeof(strings[0]) &&
+ j != sizeof(strings2) / sizeof(strings2[0]))
+ fprintf(stderr, "WARNING: Test doesn't cover the whole array\n");
+ end_test();
+}
+
+# pragma GCC visibility pop
+#endif
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-19 13:46:25 +0000