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-rw-r--r--tools/objtool/elf.c1353
1 files changed, 1353 insertions, 0 deletions
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
new file mode 100644
index 0000000000..081befa467
--- /dev/null
+++ b/tools/objtool/elf.c
@@ -0,0 +1,1353 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * elf.c - ELF access library
+ *
+ * Adapted from kpatch (https://github.com/dynup/kpatch):
+ * Copyright (C) 2013-2015 Josh Poimboeuf <jpoimboe@redhat.com>
+ * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
+ */
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+#include <linux/interval_tree_generic.h>
+#include <objtool/builtin.h>
+
+#include <objtool/elf.h>
+#include <objtool/warn.h>
+
+#define MAX_NAME_LEN 128
+
+static inline u32 str_hash(const char *str)
+{
+ return jhash(str, strlen(str), 0);
+}
+
+#define __elf_table(name) (elf->name##_hash)
+#define __elf_bits(name) (elf->name##_bits)
+
+#define __elf_table_entry(name, key) \
+ __elf_table(name)[hash_min(key, __elf_bits(name))]
+
+#define elf_hash_add(name, node, key) \
+({ \
+ struct elf_hash_node *__node = node; \
+ __node->next = __elf_table_entry(name, key); \
+ __elf_table_entry(name, key) = __node; \
+})
+
+static inline void __elf_hash_del(struct elf_hash_node *node,
+ struct elf_hash_node **head)
+{
+ struct elf_hash_node *cur, *prev;
+
+ if (node == *head) {
+ *head = node->next;
+ return;
+ }
+
+ for (prev = NULL, cur = *head; cur; prev = cur, cur = cur->next) {
+ if (cur == node) {
+ prev->next = cur->next;
+ break;
+ }
+ }
+}
+
+#define elf_hash_del(name, node, key) \
+ __elf_hash_del(node, &__elf_table_entry(name, key))
+
+#define elf_list_entry(ptr, type, member) \
+({ \
+ typeof(ptr) __ptr = (ptr); \
+ __ptr ? container_of(__ptr, type, member) : NULL; \
+})
+
+#define elf_hash_for_each_possible(name, obj, member, key) \
+ for (obj = elf_list_entry(__elf_table_entry(name, key), typeof(*obj), member); \
+ obj; \
+ obj = elf_list_entry(obj->member.next, typeof(*(obj)), member))
+
+#define elf_alloc_hash(name, size) \
+({ \
+ __elf_bits(name) = max(10, ilog2(size)); \
+ __elf_table(name) = mmap(NULL, sizeof(struct elf_hash_node *) << __elf_bits(name), \
+ PROT_READ|PROT_WRITE, \
+ MAP_PRIVATE|MAP_ANON, -1, 0); \
+ if (__elf_table(name) == (void *)-1L) { \
+ WARN("mmap fail " #name); \
+ __elf_table(name) = NULL; \
+ } \
+ __elf_table(name); \
+})
+
+static inline unsigned long __sym_start(struct symbol *s)
+{
+ return s->offset;
+}
+
+static inline unsigned long __sym_last(struct symbol *s)
+{
+ return s->offset + s->len - 1;
+}
+
+INTERVAL_TREE_DEFINE(struct symbol, node, unsigned long, __subtree_last,
+ __sym_start, __sym_last, static, __sym)
+
+#define __sym_for_each(_iter, _tree, _start, _end) \
+ for (_iter = __sym_iter_first((_tree), (_start), (_end)); \
+ _iter; _iter = __sym_iter_next(_iter, (_start), (_end)))
+
+struct symbol_hole {
+ unsigned long key;
+ const struct symbol *sym;
+};
+
+/*
+ * Find !section symbol where @offset is after it.
+ */
+static int symbol_hole_by_offset(const void *key, const struct rb_node *node)
+{
+ const struct symbol *s = rb_entry(node, struct symbol, node);
+ struct symbol_hole *sh = (void *)key;
+
+ if (sh->key < s->offset)
+ return -1;
+
+ if (sh->key >= s->offset + s->len) {
+ if (s->type != STT_SECTION)
+ sh->sym = s;
+ return 1;
+ }
+
+ return 0;
+}
+
+struct section *find_section_by_name(const struct elf *elf, const char *name)
+{
+ struct section *sec;
+
+ elf_hash_for_each_possible(section_name, sec, name_hash, str_hash(name)) {
+ if (!strcmp(sec->name, name))
+ return sec;
+ }
+
+ return NULL;
+}
+
+static struct section *find_section_by_index(struct elf *elf,
+ unsigned int idx)
+{
+ struct section *sec;
+
+ elf_hash_for_each_possible(section, sec, hash, idx) {
+ if (sec->idx == idx)
+ return sec;
+ }
+
+ return NULL;
+}
+
+static struct symbol *find_symbol_by_index(struct elf *elf, unsigned int idx)
+{
+ struct symbol *sym;
+
+ elf_hash_for_each_possible(symbol, sym, hash, idx) {
+ if (sym->idx == idx)
+ return sym;
+ }
+
+ return NULL;
+}
+
+struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset)
+{
+ struct rb_root_cached *tree = (struct rb_root_cached *)&sec->symbol_tree;
+ struct symbol *iter;
+
+ __sym_for_each(iter, tree, offset, offset) {
+ if (iter->offset == offset && iter->type != STT_SECTION)
+ return iter;
+ }
+
+ return NULL;
+}
+
+struct symbol *find_func_by_offset(struct section *sec, unsigned long offset)
+{
+ struct rb_root_cached *tree = (struct rb_root_cached *)&sec->symbol_tree;
+ struct symbol *iter;
+
+ __sym_for_each(iter, tree, offset, offset) {
+ if (iter->offset == offset && iter->type == STT_FUNC)
+ return iter;
+ }
+
+ return NULL;
+}
+
+struct symbol *find_symbol_containing(const struct section *sec, unsigned long offset)
+{
+ struct rb_root_cached *tree = (struct rb_root_cached *)&sec->symbol_tree;
+ struct symbol *iter;
+
+ __sym_for_each(iter, tree, offset, offset) {
+ if (iter->type != STT_SECTION)
+ return iter;
+ }
+
+ return NULL;
+}
+
+/*
+ * Returns size of hole starting at @offset.
+ */
+int find_symbol_hole_containing(const struct section *sec, unsigned long offset)
+{
+ struct symbol_hole hole = {
+ .key = offset,
+ .sym = NULL,
+ };
+ struct rb_node *n;
+ struct symbol *s;
+
+ /*
+ * Find the rightmost symbol for which @offset is after it.
+ */
+ n = rb_find(&hole, &sec->symbol_tree.rb_root, symbol_hole_by_offset);
+
+ /* found a symbol that contains @offset */
+ if (n)
+ return 0; /* not a hole */
+
+ /* didn't find a symbol for which @offset is after it */
+ if (!hole.sym)
+ return 0; /* not a hole */
+
+ /* @offset >= sym->offset + sym->len, find symbol after it */
+ n = rb_next(&hole.sym->node);
+ if (!n)
+ return -1; /* until end of address space */
+
+ /* hole until start of next symbol */
+ s = rb_entry(n, struct symbol, node);
+ return s->offset - offset;
+}
+
+struct symbol *find_func_containing(struct section *sec, unsigned long offset)
+{
+ struct rb_root_cached *tree = (struct rb_root_cached *)&sec->symbol_tree;
+ struct symbol *iter;
+
+ __sym_for_each(iter, tree, offset, offset) {
+ if (iter->type == STT_FUNC)
+ return iter;
+ }
+
+ return NULL;
+}
+
+struct symbol *find_symbol_by_name(const struct elf *elf, const char *name)
+{
+ struct symbol *sym;
+
+ elf_hash_for_each_possible(symbol_name, sym, name_hash, str_hash(name)) {
+ if (!strcmp(sym->name, name))
+ return sym;
+ }
+
+ return NULL;
+}
+
+struct reloc *find_reloc_by_dest_range(const struct elf *elf, struct section *sec,
+ unsigned long offset, unsigned int len)
+{
+ struct reloc *reloc, *r = NULL;
+ struct section *rsec;
+ unsigned long o;
+
+ rsec = sec->rsec;
+ if (!rsec)
+ return NULL;
+
+ for_offset_range(o, offset, offset + len) {
+ elf_hash_for_each_possible(reloc, reloc, hash,
+ sec_offset_hash(rsec, o)) {
+ if (reloc->sec != rsec)
+ continue;
+
+ if (reloc_offset(reloc) >= offset &&
+ reloc_offset(reloc) < offset + len) {
+ if (!r || reloc_offset(reloc) < reloc_offset(r))
+ r = reloc;
+ }
+ }
+ if (r)
+ return r;
+ }
+
+ return NULL;
+}
+
+struct reloc *find_reloc_by_dest(const struct elf *elf, struct section *sec, unsigned long offset)
+{
+ return find_reloc_by_dest_range(elf, sec, offset, 1);
+}
+
+static bool is_dwarf_section(struct section *sec)
+{
+ return !strncmp(sec->name, ".debug_", 7);
+}
+
+static int read_sections(struct elf *elf)
+{
+ Elf_Scn *s = NULL;
+ struct section *sec;
+ size_t shstrndx, sections_nr;
+ int i;
+
+ if (elf_getshdrnum(elf->elf, &sections_nr)) {
+ WARN_ELF("elf_getshdrnum");
+ return -1;
+ }
+
+ if (elf_getshdrstrndx(elf->elf, &shstrndx)) {
+ WARN_ELF("elf_getshdrstrndx");
+ return -1;
+ }
+
+ if (!elf_alloc_hash(section, sections_nr) ||
+ !elf_alloc_hash(section_name, sections_nr))
+ return -1;
+
+ elf->section_data = calloc(sections_nr, sizeof(*sec));
+ if (!elf->section_data) {
+ perror("calloc");
+ return -1;
+ }
+ for (i = 0; i < sections_nr; i++) {
+ sec = &elf->section_data[i];
+
+ INIT_LIST_HEAD(&sec->symbol_list);
+
+ s = elf_getscn(elf->elf, i);
+ if (!s) {
+ WARN_ELF("elf_getscn");
+ return -1;
+ }
+
+ sec->idx = elf_ndxscn(s);
+
+ if (!gelf_getshdr(s, &sec->sh)) {
+ WARN_ELF("gelf_getshdr");
+ return -1;
+ }
+
+ sec->name = elf_strptr(elf->elf, shstrndx, sec->sh.sh_name);
+ if (!sec->name) {
+ WARN_ELF("elf_strptr");
+ return -1;
+ }
+
+ if (sec->sh.sh_size != 0 && !is_dwarf_section(sec)) {
+ sec->data = elf_getdata(s, NULL);
+ if (!sec->data) {
+ WARN_ELF("elf_getdata");
+ return -1;
+ }
+ if (sec->data->d_off != 0 ||
+ sec->data->d_size != sec->sh.sh_size) {
+ WARN("unexpected data attributes for %s",
+ sec->name);
+ return -1;
+ }
+ }
+
+ list_add_tail(&sec->list, &elf->sections);
+ elf_hash_add(section, &sec->hash, sec->idx);
+ elf_hash_add(section_name, &sec->name_hash, str_hash(sec->name));
+
+ if (is_reloc_sec(sec))
+ elf->num_relocs += sec_num_entries(sec);
+ }
+
+ if (opts.stats) {
+ printf("nr_sections: %lu\n", (unsigned long)sections_nr);
+ printf("section_bits: %d\n", elf->section_bits);
+ }
+
+ /* sanity check, one more call to elf_nextscn() should return NULL */
+ if (elf_nextscn(elf->elf, s)) {
+ WARN("section entry mismatch");
+ return -1;
+ }
+
+ return 0;
+}
+
+static void elf_add_symbol(struct elf *elf, struct symbol *sym)
+{
+ struct list_head *entry;
+ struct rb_node *pnode;
+ struct symbol *iter;
+
+ INIT_LIST_HEAD(&sym->pv_target);
+ sym->alias = sym;
+
+ sym->type = GELF_ST_TYPE(sym->sym.st_info);
+ sym->bind = GELF_ST_BIND(sym->sym.st_info);
+
+ if (sym->type == STT_FILE)
+ elf->num_files++;
+
+ sym->offset = sym->sym.st_value;
+ sym->len = sym->sym.st_size;
+
+ __sym_for_each(iter, &sym->sec->symbol_tree, sym->offset, sym->offset) {
+ if (iter->offset == sym->offset && iter->type == sym->type)
+ iter->alias = sym;
+ }
+
+ __sym_insert(sym, &sym->sec->symbol_tree);
+ pnode = rb_prev(&sym->node);
+ if (pnode)
+ entry = &rb_entry(pnode, struct symbol, node)->list;
+ else
+ entry = &sym->sec->symbol_list;
+ list_add(&sym->list, entry);
+ elf_hash_add(symbol, &sym->hash, sym->idx);
+ elf_hash_add(symbol_name, &sym->name_hash, str_hash(sym->name));
+
+ /*
+ * Don't store empty STT_NOTYPE symbols in the rbtree. They
+ * can exist within a function, confusing the sorting.
+ */
+ if (!sym->len)
+ __sym_remove(sym, &sym->sec->symbol_tree);
+}
+
+static int read_symbols(struct elf *elf)
+{
+ struct section *symtab, *symtab_shndx, *sec;
+ struct symbol *sym, *pfunc;
+ int symbols_nr, i;
+ char *coldstr;
+ Elf_Data *shndx_data = NULL;
+ Elf32_Word shndx;
+
+ symtab = find_section_by_name(elf, ".symtab");
+ if (symtab) {
+ symtab_shndx = find_section_by_name(elf, ".symtab_shndx");
+ if (symtab_shndx)
+ shndx_data = symtab_shndx->data;
+
+ symbols_nr = sec_num_entries(symtab);
+ } else {
+ /*
+ * A missing symbol table is actually possible if it's an empty
+ * .o file. This can happen for thunk_64.o. Make sure to at
+ * least allocate the symbol hash tables so we can do symbol
+ * lookups without crashing.
+ */
+ symbols_nr = 0;
+ }
+
+ if (!elf_alloc_hash(symbol, symbols_nr) ||
+ !elf_alloc_hash(symbol_name, symbols_nr))
+ return -1;
+
+ elf->symbol_data = calloc(symbols_nr, sizeof(*sym));
+ if (!elf->symbol_data) {
+ perror("calloc");
+ return -1;
+ }
+ for (i = 0; i < symbols_nr; i++) {
+ sym = &elf->symbol_data[i];
+
+ sym->idx = i;
+
+ if (!gelf_getsymshndx(symtab->data, shndx_data, i, &sym->sym,
+ &shndx)) {
+ WARN_ELF("gelf_getsymshndx");
+ goto err;
+ }
+
+ sym->name = elf_strptr(elf->elf, symtab->sh.sh_link,
+ sym->sym.st_name);
+ if (!sym->name) {
+ WARN_ELF("elf_strptr");
+ goto err;
+ }
+
+ if ((sym->sym.st_shndx > SHN_UNDEF &&
+ sym->sym.st_shndx < SHN_LORESERVE) ||
+ (shndx_data && sym->sym.st_shndx == SHN_XINDEX)) {
+ if (sym->sym.st_shndx != SHN_XINDEX)
+ shndx = sym->sym.st_shndx;
+
+ sym->sec = find_section_by_index(elf, shndx);
+ if (!sym->sec) {
+ WARN("couldn't find section for symbol %s",
+ sym->name);
+ goto err;
+ }
+ if (GELF_ST_TYPE(sym->sym.st_info) == STT_SECTION) {
+ sym->name = sym->sec->name;
+ sym->sec->sym = sym;
+ }
+ } else
+ sym->sec = find_section_by_index(elf, 0);
+
+ elf_add_symbol(elf, sym);
+ }
+
+ if (opts.stats) {
+ printf("nr_symbols: %lu\n", (unsigned long)symbols_nr);
+ printf("symbol_bits: %d\n", elf->symbol_bits);
+ }
+
+ /* Create parent/child links for any cold subfunctions */
+ list_for_each_entry(sec, &elf->sections, list) {
+ sec_for_each_sym(sec, sym) {
+ char pname[MAX_NAME_LEN + 1];
+ size_t pnamelen;
+ if (sym->type != STT_FUNC)
+ continue;
+
+ if (sym->pfunc == NULL)
+ sym->pfunc = sym;
+
+ if (sym->cfunc == NULL)
+ sym->cfunc = sym;
+
+ coldstr = strstr(sym->name, ".cold");
+ if (!coldstr)
+ continue;
+
+ pnamelen = coldstr - sym->name;
+ if (pnamelen > MAX_NAME_LEN) {
+ WARN("%s(): parent function name exceeds maximum length of %d characters",
+ sym->name, MAX_NAME_LEN);
+ return -1;
+ }
+
+ strncpy(pname, sym->name, pnamelen);
+ pname[pnamelen] = '\0';
+ pfunc = find_symbol_by_name(elf, pname);
+
+ if (!pfunc) {
+ WARN("%s(): can't find parent function",
+ sym->name);
+ return -1;
+ }
+
+ sym->pfunc = pfunc;
+ pfunc->cfunc = sym;
+
+ /*
+ * Unfortunately, -fnoreorder-functions puts the child
+ * inside the parent. Remove the overlap so we can
+ * have sane assumptions.
+ *
+ * Note that pfunc->len now no longer matches
+ * pfunc->sym.st_size.
+ */
+ if (sym->sec == pfunc->sec &&
+ sym->offset >= pfunc->offset &&
+ sym->offset + sym->len == pfunc->offset + pfunc->len) {
+ pfunc->len -= sym->len;
+ }
+ }
+ }
+
+ return 0;
+
+err:
+ free(sym);
+ return -1;
+}
+
+/*
+ * @sym's idx has changed. Update the relocs which reference it.
+ */
+static int elf_update_sym_relocs(struct elf *elf, struct symbol *sym)
+{
+ struct reloc *reloc;
+
+ for (reloc = sym->relocs; reloc; reloc = reloc->sym_next_reloc)
+ set_reloc_sym(elf, reloc, reloc->sym->idx);
+
+ return 0;
+}
+
+/*
+ * The libelf API is terrible; gelf_update_sym*() takes a data block relative
+ * index value, *NOT* the symbol index. As such, iterate the data blocks and
+ * adjust index until it fits.
+ *
+ * If no data block is found, allow adding a new data block provided the index
+ * is only one past the end.
+ */
+static int elf_update_symbol(struct elf *elf, struct section *symtab,
+ struct section *symtab_shndx, struct symbol *sym)
+{
+ Elf32_Word shndx = sym->sec ? sym->sec->idx : SHN_UNDEF;
+ Elf_Data *symtab_data = NULL, *shndx_data = NULL;
+ Elf64_Xword entsize = symtab->sh.sh_entsize;
+ int max_idx, idx = sym->idx;
+ Elf_Scn *s, *t = NULL;
+ bool is_special_shndx = sym->sym.st_shndx >= SHN_LORESERVE &&
+ sym->sym.st_shndx != SHN_XINDEX;
+
+ if (is_special_shndx)
+ shndx = sym->sym.st_shndx;
+
+ s = elf_getscn(elf->elf, symtab->idx);
+ if (!s) {
+ WARN_ELF("elf_getscn");
+ return -1;
+ }
+
+ if (symtab_shndx) {
+ t = elf_getscn(elf->elf, symtab_shndx->idx);
+ if (!t) {
+ WARN_ELF("elf_getscn");
+ return -1;
+ }
+ }
+
+ for (;;) {
+ /* get next data descriptor for the relevant sections */
+ symtab_data = elf_getdata(s, symtab_data);
+ if (t)
+ shndx_data = elf_getdata(t, shndx_data);
+
+ /* end-of-list */
+ if (!symtab_data) {
+ /*
+ * Over-allocate to avoid O(n^2) symbol creation
+ * behaviour. The down side is that libelf doesn't
+ * like this; see elf_truncate_section() for the fixup.
+ */
+ int num = max(1U, sym->idx/3);
+ void *buf;
+
+ if (idx) {
+ /* we don't do holes in symbol tables */
+ WARN("index out of range");
+ return -1;
+ }
+
+ /* if @idx == 0, it's the next contiguous entry, create it */
+ symtab_data = elf_newdata(s);
+ if (t)
+ shndx_data = elf_newdata(t);
+
+ buf = calloc(num, entsize);
+ if (!buf) {
+ WARN("malloc");
+ return -1;
+ }
+
+ symtab_data->d_buf = buf;
+ symtab_data->d_size = num * entsize;
+ symtab_data->d_align = 1;
+ symtab_data->d_type = ELF_T_SYM;
+
+ mark_sec_changed(elf, symtab, true);
+ symtab->truncate = true;
+
+ if (t) {
+ buf = calloc(num, sizeof(Elf32_Word));
+ if (!buf) {
+ WARN("malloc");
+ return -1;
+ }
+
+ shndx_data->d_buf = buf;
+ shndx_data->d_size = num * sizeof(Elf32_Word);
+ shndx_data->d_align = sizeof(Elf32_Word);
+ shndx_data->d_type = ELF_T_WORD;
+
+ mark_sec_changed(elf, symtab_shndx, true);
+ symtab_shndx->truncate = true;
+ }
+
+ break;
+ }
+
+ /* empty blocks should not happen */
+ if (!symtab_data->d_size) {
+ WARN("zero size data");
+ return -1;
+ }
+
+ /* is this the right block? */
+ max_idx = symtab_data->d_size / entsize;
+ if (idx < max_idx)
+ break;
+
+ /* adjust index and try again */
+ idx -= max_idx;
+ }
+
+ /* something went side-ways */
+ if (idx < 0) {
+ WARN("negative index");
+ return -1;
+ }
+
+ /* setup extended section index magic and write the symbol */
+ if ((shndx >= SHN_UNDEF && shndx < SHN_LORESERVE) || is_special_shndx) {
+ sym->sym.st_shndx = shndx;
+ if (!shndx_data)
+ shndx = 0;
+ } else {
+ sym->sym.st_shndx = SHN_XINDEX;
+ if (!shndx_data) {
+ WARN("no .symtab_shndx");
+ return -1;
+ }
+ }
+
+ if (!gelf_update_symshndx(symtab_data, shndx_data, idx, &sym->sym, shndx)) {
+ WARN_ELF("gelf_update_symshndx");
+ return -1;
+ }
+
+ return 0;
+}
+
+static struct symbol *
+__elf_create_symbol(struct elf *elf, struct symbol *sym)
+{
+ struct section *symtab, *symtab_shndx;
+ Elf32_Word first_non_local, new_idx;
+ struct symbol *old;
+
+ symtab = find_section_by_name(elf, ".symtab");
+ if (symtab) {
+ symtab_shndx = find_section_by_name(elf, ".symtab_shndx");
+ } else {
+ WARN("no .symtab");
+ return NULL;
+ }
+
+ new_idx = sec_num_entries(symtab);
+
+ if (GELF_ST_BIND(sym->sym.st_info) != STB_LOCAL)
+ goto non_local;
+
+ /*
+ * Move the first global symbol, as per sh_info, into a new, higher
+ * symbol index. This fees up a spot for a new local symbol.
+ */
+ first_non_local = symtab->sh.sh_info;
+ old = find_symbol_by_index(elf, first_non_local);
+ if (old) {
+
+ elf_hash_del(symbol, &old->hash, old->idx);
+ elf_hash_add(symbol, &old->hash, new_idx);
+ old->idx = new_idx;
+
+ if (elf_update_symbol(elf, symtab, symtab_shndx, old)) {
+ WARN("elf_update_symbol move");
+ return NULL;
+ }
+
+ if (elf_update_sym_relocs(elf, old))
+ return NULL;
+
+ new_idx = first_non_local;
+ }
+
+ /*
+ * Either way, we will add a LOCAL symbol.
+ */
+ symtab->sh.sh_info += 1;
+
+non_local:
+ sym->idx = new_idx;
+ if (elf_update_symbol(elf, symtab, symtab_shndx, sym)) {
+ WARN("elf_update_symbol");
+ return NULL;
+ }
+
+ symtab->sh.sh_size += symtab->sh.sh_entsize;
+ mark_sec_changed(elf, symtab, true);
+
+ if (symtab_shndx) {
+ symtab_shndx->sh.sh_size += sizeof(Elf32_Word);
+ mark_sec_changed(elf, symtab_shndx, true);
+ }
+
+ return sym;
+}
+
+static struct symbol *
+elf_create_section_symbol(struct elf *elf, struct section *sec)
+{
+ struct symbol *sym = calloc(1, sizeof(*sym));
+
+ if (!sym) {
+ perror("malloc");
+ return NULL;
+ }
+
+ sym->name = sec->name;
+ sym->sec = sec;
+
+ // st_name 0
+ sym->sym.st_info = GELF_ST_INFO(STB_LOCAL, STT_SECTION);
+ // st_other 0
+ // st_value 0
+ // st_size 0
+
+ sym = __elf_create_symbol(elf, sym);
+ if (sym)
+ elf_add_symbol(elf, sym);
+
+ return sym;
+}
+
+static int elf_add_string(struct elf *elf, struct section *strtab, char *str);
+
+struct symbol *
+elf_create_prefix_symbol(struct elf *elf, struct symbol *orig, long size)
+{
+ struct symbol *sym = calloc(1, sizeof(*sym));
+ size_t namelen = strlen(orig->name) + sizeof("__pfx_");
+ char *name = malloc(namelen);
+
+ if (!sym || !name) {
+ perror("malloc");
+ return NULL;
+ }
+
+ snprintf(name, namelen, "__pfx_%s", orig->name);
+
+ sym->name = name;
+ sym->sec = orig->sec;
+
+ sym->sym.st_name = elf_add_string(elf, NULL, name);
+ sym->sym.st_info = orig->sym.st_info;
+ sym->sym.st_value = orig->sym.st_value - size;
+ sym->sym.st_size = size;
+
+ sym = __elf_create_symbol(elf, sym);
+ if (sym)
+ elf_add_symbol(elf, sym);
+
+ return sym;
+}
+
+static struct reloc *elf_init_reloc(struct elf *elf, struct section *rsec,
+ unsigned int reloc_idx,
+ unsigned long offset, struct symbol *sym,
+ s64 addend, unsigned int type)
+{
+ struct reloc *reloc, empty = { 0 };
+
+ if (reloc_idx >= sec_num_entries(rsec)) {
+ WARN("%s: bad reloc_idx %u for %s with %d relocs",
+ __func__, reloc_idx, rsec->name, sec_num_entries(rsec));
+ return NULL;
+ }
+
+ reloc = &rsec->relocs[reloc_idx];
+
+ if (memcmp(reloc, &empty, sizeof(empty))) {
+ WARN("%s: %s: reloc %d already initialized!",
+ __func__, rsec->name, reloc_idx);
+ return NULL;
+ }
+
+ reloc->sec = rsec;
+ reloc->sym = sym;
+
+ set_reloc_offset(elf, reloc, offset);
+ set_reloc_sym(elf, reloc, sym->idx);
+ set_reloc_type(elf, reloc, type);
+ set_reloc_addend(elf, reloc, addend);
+
+ elf_hash_add(reloc, &reloc->hash, reloc_hash(reloc));
+ reloc->sym_next_reloc = sym->relocs;
+ sym->relocs = reloc;
+
+ return reloc;
+}
+
+struct reloc *elf_init_reloc_text_sym(struct elf *elf, struct section *sec,
+ unsigned long offset,
+ unsigned int reloc_idx,
+ struct section *insn_sec,
+ unsigned long insn_off)
+{
+ struct symbol *sym = insn_sec->sym;
+ int addend = insn_off;
+
+ if (!(insn_sec->sh.sh_flags & SHF_EXECINSTR)) {
+ WARN("bad call to %s() for data symbol %s",
+ __func__, sym->name);
+ return NULL;
+ }
+
+ if (!sym) {
+ /*
+ * Due to how weak functions work, we must use section based
+ * relocations. Symbol based relocations would result in the
+ * weak and non-weak function annotations being overlaid on the
+ * non-weak function after linking.
+ */
+ sym = elf_create_section_symbol(elf, insn_sec);
+ if (!sym)
+ return NULL;
+
+ insn_sec->sym = sym;
+ }
+
+ return elf_init_reloc(elf, sec->rsec, reloc_idx, offset, sym, addend,
+ elf_text_rela_type(elf));
+}
+
+struct reloc *elf_init_reloc_data_sym(struct elf *elf, struct section *sec,
+ unsigned long offset,
+ unsigned int reloc_idx,
+ struct symbol *sym,
+ s64 addend)
+{
+ if (sym->sec && (sec->sh.sh_flags & SHF_EXECINSTR)) {
+ WARN("bad call to %s() for text symbol %s",
+ __func__, sym->name);
+ return NULL;
+ }
+
+ return elf_init_reloc(elf, sec->rsec, reloc_idx, offset, sym, addend,
+ elf_data_rela_type(elf));
+}
+
+static int read_relocs(struct elf *elf)
+{
+ unsigned long nr_reloc, max_reloc = 0;
+ struct section *rsec;
+ struct reloc *reloc;
+ unsigned int symndx;
+ struct symbol *sym;
+ int i;
+
+ if (!elf_alloc_hash(reloc, elf->num_relocs))
+ return -1;
+
+ list_for_each_entry(rsec, &elf->sections, list) {
+ if (!is_reloc_sec(rsec))
+ continue;
+
+ rsec->base = find_section_by_index(elf, rsec->sh.sh_info);
+ if (!rsec->base) {
+ WARN("can't find base section for reloc section %s",
+ rsec->name);
+ return -1;
+ }
+
+ rsec->base->rsec = rsec;
+
+ nr_reloc = 0;
+ rsec->relocs = calloc(sec_num_entries(rsec), sizeof(*reloc));
+ if (!rsec->relocs) {
+ perror("calloc");
+ return -1;
+ }
+ for (i = 0; i < sec_num_entries(rsec); i++) {
+ reloc = &rsec->relocs[i];
+
+ reloc->sec = rsec;
+ symndx = reloc_sym(reloc);
+ reloc->sym = sym = find_symbol_by_index(elf, symndx);
+ if (!reloc->sym) {
+ WARN("can't find reloc entry symbol %d for %s",
+ symndx, rsec->name);
+ return -1;
+ }
+
+ elf_hash_add(reloc, &reloc->hash, reloc_hash(reloc));
+ reloc->sym_next_reloc = sym->relocs;
+ sym->relocs = reloc;
+
+ nr_reloc++;
+ }
+ max_reloc = max(max_reloc, nr_reloc);
+ }
+
+ if (opts.stats) {
+ printf("max_reloc: %lu\n", max_reloc);
+ printf("num_relocs: %lu\n", elf->num_relocs);
+ printf("reloc_bits: %d\n", elf->reloc_bits);
+ }
+
+ return 0;
+}
+
+struct elf *elf_open_read(const char *name, int flags)
+{
+ struct elf *elf;
+ Elf_Cmd cmd;
+
+ elf_version(EV_CURRENT);
+
+ elf = malloc(sizeof(*elf));
+ if (!elf) {
+ perror("malloc");
+ return NULL;
+ }
+ memset(elf, 0, sizeof(*elf));
+
+ INIT_LIST_HEAD(&elf->sections);
+
+ elf->fd = open(name, flags);
+ if (elf->fd == -1) {
+ fprintf(stderr, "objtool: Can't open '%s': %s\n",
+ name, strerror(errno));
+ goto err;
+ }
+
+ if ((flags & O_ACCMODE) == O_RDONLY)
+ cmd = ELF_C_READ_MMAP;
+ else if ((flags & O_ACCMODE) == O_RDWR)
+ cmd = ELF_C_RDWR;
+ else /* O_WRONLY */
+ cmd = ELF_C_WRITE;
+
+ elf->elf = elf_begin(elf->fd, cmd, NULL);
+ if (!elf->elf) {
+ WARN_ELF("elf_begin");
+ goto err;
+ }
+
+ if (!gelf_getehdr(elf->elf, &elf->ehdr)) {
+ WARN_ELF("gelf_getehdr");
+ goto err;
+ }
+
+ if (read_sections(elf))
+ goto err;
+
+ if (read_symbols(elf))
+ goto err;
+
+ if (read_relocs(elf))
+ goto err;
+
+ return elf;
+
+err:
+ elf_close(elf);
+ return NULL;
+}
+
+static int elf_add_string(struct elf *elf, struct section *strtab, char *str)
+{
+ Elf_Data *data;
+ Elf_Scn *s;
+ int len;
+
+ if (!strtab)
+ strtab = find_section_by_name(elf, ".strtab");
+ if (!strtab) {
+ WARN("can't find .strtab section");
+ return -1;
+ }
+
+ s = elf_getscn(elf->elf, strtab->idx);
+ if (!s) {
+ WARN_ELF("elf_getscn");
+ return -1;
+ }
+
+ data = elf_newdata(s);
+ if (!data) {
+ WARN_ELF("elf_newdata");
+ return -1;
+ }
+
+ data->d_buf = str;
+ data->d_size = strlen(str) + 1;
+ data->d_align = 1;
+
+ len = strtab->sh.sh_size;
+ strtab->sh.sh_size += data->d_size;
+
+ mark_sec_changed(elf, strtab, true);
+
+ return len;
+}
+
+struct section *elf_create_section(struct elf *elf, const char *name,
+ size_t entsize, unsigned int nr)
+{
+ struct section *sec, *shstrtab;
+ size_t size = entsize * nr;
+ Elf_Scn *s;
+
+ sec = malloc(sizeof(*sec));
+ if (!sec) {
+ perror("malloc");
+ return NULL;
+ }
+ memset(sec, 0, sizeof(*sec));
+
+ INIT_LIST_HEAD(&sec->symbol_list);
+
+ s = elf_newscn(elf->elf);
+ if (!s) {
+ WARN_ELF("elf_newscn");
+ return NULL;
+ }
+
+ sec->name = strdup(name);
+ if (!sec->name) {
+ perror("strdup");
+ return NULL;
+ }
+
+ sec->idx = elf_ndxscn(s);
+
+ sec->data = elf_newdata(s);
+ if (!sec->data) {
+ WARN_ELF("elf_newdata");
+ return NULL;
+ }
+
+ sec->data->d_size = size;
+ sec->data->d_align = 1;
+
+ if (size) {
+ sec->data->d_buf = malloc(size);
+ if (!sec->data->d_buf) {
+ perror("malloc");
+ return NULL;
+ }
+ memset(sec->data->d_buf, 0, size);
+ }
+
+ if (!gelf_getshdr(s, &sec->sh)) {
+ WARN_ELF("gelf_getshdr");
+ return NULL;
+ }
+
+ sec->sh.sh_size = size;
+ sec->sh.sh_entsize = entsize;
+ sec->sh.sh_type = SHT_PROGBITS;
+ sec->sh.sh_addralign = 1;
+ sec->sh.sh_flags = SHF_ALLOC;
+
+ /* Add section name to .shstrtab (or .strtab for Clang) */
+ shstrtab = find_section_by_name(elf, ".shstrtab");
+ if (!shstrtab)
+ shstrtab = find_section_by_name(elf, ".strtab");
+ if (!shstrtab) {
+ WARN("can't find .shstrtab or .strtab section");
+ return NULL;
+ }
+ sec->sh.sh_name = elf_add_string(elf, shstrtab, sec->name);
+ if (sec->sh.sh_name == -1)
+ return NULL;
+
+ list_add_tail(&sec->list, &elf->sections);
+ elf_hash_add(section, &sec->hash, sec->idx);
+ elf_hash_add(section_name, &sec->name_hash, str_hash(sec->name));
+
+ mark_sec_changed(elf, sec, true);
+
+ return sec;
+}
+
+static struct section *elf_create_rela_section(struct elf *elf,
+ struct section *sec,
+ unsigned int reloc_nr)
+{
+ struct section *rsec;
+ char *rsec_name;
+
+ rsec_name = malloc(strlen(sec->name) + strlen(".rela") + 1);
+ if (!rsec_name) {
+ perror("malloc");
+ return NULL;
+ }
+ strcpy(rsec_name, ".rela");
+ strcat(rsec_name, sec->name);
+
+ rsec = elf_create_section(elf, rsec_name, elf_rela_size(elf), reloc_nr);
+ free(rsec_name);
+ if (!rsec)
+ return NULL;
+
+ rsec->data->d_type = ELF_T_RELA;
+ rsec->sh.sh_type = SHT_RELA;
+ rsec->sh.sh_addralign = elf_addr_size(elf);
+ rsec->sh.sh_link = find_section_by_name(elf, ".symtab")->idx;
+ rsec->sh.sh_info = sec->idx;
+ rsec->sh.sh_flags = SHF_INFO_LINK;
+
+ rsec->relocs = calloc(sec_num_entries(rsec), sizeof(struct reloc));
+ if (!rsec->relocs) {
+ perror("calloc");
+ return NULL;
+ }
+
+ sec->rsec = rsec;
+ rsec->base = sec;
+
+ return rsec;
+}
+
+struct section *elf_create_section_pair(struct elf *elf, const char *name,
+ size_t entsize, unsigned int nr,
+ unsigned int reloc_nr)
+{
+ struct section *sec;
+
+ sec = elf_create_section(elf, name, entsize, nr);
+ if (!sec)
+ return NULL;
+
+ if (!elf_create_rela_section(elf, sec, reloc_nr))
+ return NULL;
+
+ return sec;
+}
+
+int elf_write_insn(struct elf *elf, struct section *sec,
+ unsigned long offset, unsigned int len,
+ const char *insn)
+{
+ Elf_Data *data = sec->data;
+
+ if (data->d_type != ELF_T_BYTE || data->d_off) {
+ WARN("write to unexpected data for section: %s", sec->name);
+ return -1;
+ }
+
+ memcpy(data->d_buf + offset, insn, len);
+
+ mark_sec_changed(elf, sec, true);
+
+ return 0;
+}
+
+/*
+ * When Elf_Scn::sh_size is smaller than the combined Elf_Data::d_size
+ * do you:
+ *
+ * A) adhere to the section header and truncate the data, or
+ * B) ignore the section header and write out all the data you've got?
+ *
+ * Yes, libelf sucks and we need to manually truncate if we over-allocate data.
+ */
+static int elf_truncate_section(struct elf *elf, struct section *sec)
+{
+ u64 size = sec->sh.sh_size;
+ bool truncated = false;
+ Elf_Data *data = NULL;
+ Elf_Scn *s;
+
+ s = elf_getscn(elf->elf, sec->idx);
+ if (!s) {
+ WARN_ELF("elf_getscn");
+ return -1;
+ }
+
+ for (;;) {
+ /* get next data descriptor for the relevant section */
+ data = elf_getdata(s, data);
+
+ if (!data) {
+ if (size) {
+ WARN("end of section data but non-zero size left\n");
+ return -1;
+ }
+ return 0;
+ }
+
+ if (truncated) {
+ /* when we remove symbols */
+ WARN("truncated; but more data\n");
+ return -1;
+ }
+
+ if (!data->d_size) {
+ WARN("zero size data");
+ return -1;
+ }
+
+ if (data->d_size > size) {
+ truncated = true;
+ data->d_size = size;
+ }
+
+ size -= data->d_size;
+ }
+}
+
+int elf_write(struct elf *elf)
+{
+ struct section *sec;
+ Elf_Scn *s;
+
+ if (opts.dryrun)
+ return 0;
+
+ /* Update changed relocation sections and section headers: */
+ list_for_each_entry(sec, &elf->sections, list) {
+ if (sec->truncate)
+ elf_truncate_section(elf, sec);
+
+ if (sec_changed(sec)) {
+ s = elf_getscn(elf->elf, sec->idx);
+ if (!s) {
+ WARN_ELF("elf_getscn");
+ return -1;
+ }
+
+ /* Note this also flags the section dirty */
+ if (!gelf_update_shdr(s, &sec->sh)) {
+ WARN_ELF("gelf_update_shdr");
+ return -1;
+ }
+
+ mark_sec_changed(elf, sec, false);
+ }
+ }
+
+ /* Make sure the new section header entries get updated properly. */
+ elf_flagelf(elf->elf, ELF_C_SET, ELF_F_DIRTY);
+
+ /* Write all changes to the file. */
+ if (elf_update(elf->elf, ELF_C_WRITE) < 0) {
+ WARN_ELF("elf_update");
+ return -1;
+ }
+
+ elf->changed = false;
+
+ return 0;
+}
+
+void elf_close(struct elf *elf)
+{
+ if (elf->elf)
+ elf_end(elf->elf);
+
+ if (elf->fd > 0)
+ close(elf->fd);
+
+ /*
+ * NOTE: All remaining allocations are leaked on purpose. Objtool is
+ * about to exit anyway.
+ */
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-17 08:14:03 +0000