1 files changed, 190 insertions, 0 deletions
diff --git a/mozglue/linker/BaseElf.cpp b/mozglue/linker/BaseElf.cpp
new file mode 100644
index 0000000000..78542b3875
--- /dev/null
+++ b/mozglue/linker/BaseElf.cpp
@@ -0,0 +1,190 @@
+/* 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 "BaseElf.h"
+#include "Elfxx.h"
+#include "Logging.h"
+#include "mozilla/IntegerPrintfMacros.h"
+#include "mozilla/RefPtr.h"
+
+using namespace Elf;
+
+unsigned long BaseElf::Hash(const char* symbol) {
+  const unsigned char* sym = reinterpret_cast<const unsigned char*>(symbol);
+  unsigned long h = 0, g;
+  while (*sym) {
+    h = (h << 4) + *sym++;
+    g = h & 0xf0000000;
+    h ^= g;
+    h ^= g >> 24;
+  }
+  return h;
+}
+
+void* BaseElf::GetSymbolPtr(const char* symbol) const {
+  return GetSymbolPtr(symbol, Hash(symbol));
+}
+
+void* BaseElf::GetSymbolPtr(const char* symbol, unsigned long hash) const {
+  const Sym* sym = GetSymbol(symbol, hash);
+  void* ptr = nullptr;
+  if (sym && sym->st_shndx != SHN_UNDEF) ptr = GetPtr(sym->st_value);
+  DEBUG_LOG("BaseElf::GetSymbolPtr(%p [\"%s\"], \"%s\") = %p",
+            reinterpret_cast<const void*>(this), GetPath(), symbol, ptr);
+  return ptr;
+}
+
+const Sym* BaseElf::GetSymbol(const char* symbol, unsigned long hash) const {
+  /* Search symbol with the buckets and chains tables.
+   * The hash computed from the symbol name gives an index in the buckets
+   * table. The corresponding value in the bucket table is an index in the
+   * symbols table and in the chains table.
+   * If the corresponding symbol in the symbols table matches, we're done.
+   * Otherwise, the corresponding value in the chains table is a new index
+   * in both tables, which corresponding symbol is tested and so on and so
+   * forth */
+  size_t bucket = hash % buckets.numElements();
+  for (size_t y = buckets[bucket]; y != STN_UNDEF; y = chains[y]) {
+    if (strcmp(symbol, strtab.GetStringAt(symtab[y].st_name))) continue;
+    return &symtab[y];
+  }
+  return nullptr;
+}
+
+bool BaseElf::Contains(void* addr) const { return base.Contains(addr); }
+
+#ifdef __ARM_EABI__
+const void* BaseElf::FindExidx(int* pcount) const {
+  if (arm_exidx) {
+    *pcount = arm_exidx.numElements();
+    return arm_exidx;
+  }
+  *pcount = 0;
+  return nullptr;
+}
+#endif
+
+already_AddRefed<LibHandle> LoadedElf::Create(const char* path,
+                                              void* base_addr) {
+  DEBUG_LOG("LoadedElf::Create(\"%s\", %p) = ...", path, base_addr);
+
+  uint8_t mapped;
+  /* If the page is not mapped, mincore returns an error. If base_addr is
+   * nullptr, as would happen if the corresponding binary is prelinked with
+   * the prelink look (but not with the android apriori tool), no page being
+   * mapped there (right?), mincore returns an error, too, which makes
+   * prelinked libraries on glibc unsupported. This is not an interesting
+   * use case for now, so don't try supporting that case.
+   */
+  if (mincore(const_cast<void*>(base_addr), PageSize(), &mapped))
+    return nullptr;
+
+  RefPtr<LoadedElf> elf = new LoadedElf(path);
+
+  const Ehdr* ehdr = Ehdr::validate(base_addr);
+  if (!ehdr) return nullptr;
+
+  Addr min_vaddr = (Addr)-1;  // We want to find the lowest and biggest
+  Addr max_vaddr = 0;         // virtual address used by this Elf.
+  const Phdr* dyn = nullptr;
+#ifdef __ARM_EABI__
+  const Phdr* arm_exidx_phdr = nullptr;
+#endif
+
+  Array<Phdr> phdrs(reinterpret_cast<const char*>(ehdr) + ehdr->e_phoff,
+                    ehdr->e_phnum);
+  for (auto phdr = phdrs.begin(); phdr < phdrs.end(); ++phdr) {
+    switch (phdr->p_type) {
+      case PT_LOAD:
+        if (phdr->p_vaddr < min_vaddr) min_vaddr = phdr->p_vaddr;
+        if (max_vaddr < phdr->p_vaddr + phdr->p_memsz)
+          max_vaddr = phdr->p_vaddr + phdr->p_memsz;
+        break;
+      case PT_DYNAMIC:
+        dyn = &*phdr;
+        break;
+#ifdef __ARM_EABI__
+      case PT_ARM_EXIDX:
+        /* We cannot initialize arm_exidx here
+           because we don't have a base yet */
+        arm_exidx_phdr = &*phdr;
+        break;
+#endif
+    }
+  }
+
+  /* If the lowest PT_LOAD virtual address in headers is not 0, then the ELF
+   * is either prelinked or a non-PIE executable. The former case is not
+   * possible, because base_addr would be nullptr and the mincore test above
+   * would already have made us return.
+   * For a non-PIE executable, PT_LOADs contain absolute addresses, so in
+   * practice, this means min_vaddr should be equal to base_addr. max_vaddr
+   * can thus be adjusted accordingly.
+   */
+  if (min_vaddr != 0) {
+    void* min_vaddr_ptr =
+        reinterpret_cast<void*>(static_cast<uintptr_t>(min_vaddr));
+    if (min_vaddr_ptr != base_addr) {
+      LOG("%s: %p != %p", elf->GetPath(), min_vaddr_ptr, base_addr);
+      return nullptr;
+    }
+    max_vaddr -= min_vaddr;
+  }
+  if (!dyn) {
+    LOG("%s: No PT_DYNAMIC segment found", elf->GetPath());
+    return nullptr;
+  }
+
+  elf->base.Assign(base_addr, max_vaddr);
+
+  if (!elf->InitDyn(dyn)) return nullptr;
+
+#ifdef __ARM_EABI__
+  if (arm_exidx_phdr)
+    elf->arm_exidx.InitSize(elf->GetPtr(arm_exidx_phdr->p_vaddr),
+                            arm_exidx_phdr->p_memsz);
+#endif
+
+  DEBUG_LOG("LoadedElf::Create(\"%s\", %p) = %p", path, base_addr,
+            static_cast<void*>(elf));
+
+  ElfLoader::Singleton.Register(elf);
+  return elf.forget();
+}
+
+bool LoadedElf::InitDyn(const Phdr* pt_dyn) {
+  Array<Dyn> dyns;
+  dyns.InitSize(GetPtr<Dyn>(pt_dyn->p_vaddr), pt_dyn->p_filesz);
+
+  size_t symnum = 0;
+  for (auto dyn = dyns.begin(); dyn < dyns.end() && dyn->d_tag; ++dyn) {
+    switch (dyn->d_tag) {
+      case DT_HASH: {
+        DEBUG_LOG("%s 0x%08" PRIxPTR, "DT_HASH", uintptr_t(dyn->d_un.d_val));
+        const Elf::Word* hash_table_header = GetPtr<Elf::Word>(dyn->d_un.d_ptr);
+        symnum = hash_table_header[1];
+        buckets.Init(&hash_table_header[2], hash_table_header[0]);
+        chains.Init(&*buckets.end());
+      } break;
+      case DT_STRTAB:
+        DEBUG_LOG("%s 0x%08" PRIxPTR, "DT_STRTAB", uintptr_t(dyn->d_un.d_val));
+        strtab.Init(GetPtr(dyn->d_un.d_ptr));
+        break;
+      case DT_SYMTAB:
+        DEBUG_LOG("%s 0x%08" PRIxPTR, "DT_SYMTAB", uintptr_t(dyn->d_un.d_val));
+        symtab.Init(GetPtr(dyn->d_un.d_ptr));
+        break;
+    }
+  }
+  if (!buckets || !symnum) {
+    ERROR("%s: Missing or broken DT_HASH", GetPath());
+  } else if (!strtab) {
+    ERROR("%s: Missing DT_STRTAB", GetPath());
+  } else if (!symtab) {
+    ERROR("%s: Missing DT_SYMTAB", GetPath());
+  } else {
+    return true;
+  }
+  return false;
+}