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(I'm so sorry!) Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel os linux
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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 <ctype.h>#include <linux/align.h>#include <linux/kernel.h>#include <linux/interval_tree_generic.h>#include <linux/log2.h>#include <objtool/builtin.h>#include <objtool/elf.h>#include <objtool/klp.h>#include <objtool/warn.h>
static ssize_t demangled_name_len(const char *name);
u32 str_hash_demangled(const char *str){ return jhash(str, demangled_name_len(str), 0);}
#define elf_hash_add(name, node, key) \({ \ struct elf_hash_node *__node = node; \ __node->next = __elf_table_entry(elf, name, key); \ __elf_table_entry(elf, 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(elf, name, key))
#define elf_alloc_hash(name, size) \({ \ __elf_bits(elf, name) = max(10, ilog2(size)); \ __elf_table(elf, name) = mmap(NULL, \ sizeof(struct elf_hash_node *) << __elf_bits(elf, name), \ PROT_READ|PROT_WRITE, \ MAP_PRIVATE|MAP_ANON, -1, 0); \ if (__elf_table(elf, name) == (void *)-1L) { \ ERROR_GLIBC("mmap fail " #name); \ __elf_table(elf, name) = NULL; \ } \ __elf_table(elf, 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 ? s->len - 1 : 0);}
INTERVAL_TREE_DEFINE(struct symbol, node, unsigned long, __subtree_last, __sym_start, __sym_last, static inline __maybe_unused, __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 the last symbol before @offset. */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) { 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(elf, 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(elf, 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(elf, 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 *sym;
__sym_for_each(sym, tree, offset, offset) { if (sym->offset == offset && !is_sec_sym(sym)) return sym->alias; }
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 *func;
__sym_for_each(func, tree, offset, offset) { if (func->offset == offset && is_func_sym(func)) return func->alias; }
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 *sym = NULL, *tmp;
__sym_for_each(tmp, tree, offset, offset) { if (tmp->len) { if (!sym) { sym = tmp; continue; }
if (sym->offset != tmp->offset || sym->len != tmp->len) { /* * In the rare case of overlapping symbols, * pick the smaller one. * * TODO: outlaw overlapping symbols */ if (tmp->len < sym->len) sym = tmp; } } }
return sym ? sym->alias : NULL;}
/* * Also match the symbol end address which can be used for a bounds comparison. */struct symbol *find_symbol_containing_inclusive(const struct section *sec, unsigned long offset){ struct symbol *sym = find_symbol_containing(sec, offset);
if (!sym && offset) sym = find_symbol_containing(sec, offset - 1);
return sym;}
/* * 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 */
/* * @offset >= sym->offset + sym->len, find symbol after it. * When hole.sym is empty, use the first node to compute the hole. * If there is no symbol in the section, the first node will be NULL, * in which case, -1 is returned to skip the whole section. */ if (hole.sym) n = rb_next(&hole.sym->node); else n = rb_first_cached(&sec->symbol_tree);
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 *func;
__sym_for_each(func, tree, offset, offset) { if (is_func_sym(func)) return func->alias; }
return NULL;}
struct symbol *find_symbol_by_name(const struct elf *elf, const char *name){ struct symbol *sym;
elf_hash_for_each_possible(elf, symbol_name, sym, name_hash, str_hash(name)) { if (!strcmp(sym->name, name)) return sym; }
return NULL;}
/* Find local symbol with matching STT_FILE */static struct symbol *find_local_symbol_by_file_and_name(const struct elf *elf, struct symbol *file, const char *name){ struct symbol *sym;
elf_hash_for_each_possible(elf, symbol_name, sym, name_hash, str_hash_demangled(name)) { if (sym->bind == STB_LOCAL && sym->file == file && !strcmp(sym->name, name)) { return sym; } }
return NULL;}
struct symbol *find_global_symbol_by_name(const struct elf *elf, const char *name){ struct symbol *sym;
elf_hash_for_each_possible(elf, symbol_name, sym, name_hash, str_hash_demangled(name)) { if (!strcmp(sym->name, name) && !is_local_sym(sym)) return sym; }
return NULL;}
/* If there are multiple matches, return the first one in the range */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(elf, 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 && (reloc_offset(r) & OFFSET_STRIDE_MASK) == o) return r; }
return r;}
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, §ions_nr)) { ERROR_ELF("elf_getshdrnum"); return -1; }
if (elf_getshdrstrndx(elf->elf, &shstrndx)) { ERROR_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) { ERROR_GLIBC("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) { ERROR_ELF("elf_getscn"); return -1; }
sec->idx = elf_ndxscn(s);
if (!gelf_getshdr(s, &sec->sh)) { ERROR_ELF("gelf_getshdr"); return -1; }
sec->name = elf_strptr(elf->elf, shstrndx, sec->sh.sh_name); if (!sec->name) { ERROR_ELF("elf_strptr"); return -1; }
if (sec_size(sec) != 0 && !is_dwarf_section(sec)) { sec->data = elf_getdata(s, NULL); if (!sec->data) { ERROR_ELF("elf_getdata"); return -1; } if (sec->data->d_off != 0 || sec->data->d_size != sec_size(sec)) { ERROR("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)) { ERROR("section entry mismatch"); return -1; }
return 0;}
/* * Returns desired length of the demangled name. * If name doesn't need demangling, return strlen(name). */static ssize_t demangled_name_len(const char *name){ ssize_t idx; const char *p;
p = strstr(name, ".llvm."); if (p) return p - name;
if (!strstarts(name, "__UNIQUE_ID_") && !strchr(name, '.')) return strlen(name);
for (idx = strlen(name) - 1; idx >= 0; idx--) { char c = name[idx];
if (!isdigit(c) && c != '.' && c != '_') break; } if (idx <= 0) return strlen(name); return idx + 1;}
/* * Remove number suffix of a symbol. * * Specifically, remove trailing numbers for "__UNIQUE_ID_" symbols and * symbols with '.'. * * With CONFIG_LTO_CLANG_THIN, it is possible to have nested __UNIQUE_ID_, * such as * * __UNIQUE_ID_addressable___UNIQUE_ID_pci_invalid_bar_694_695 * * to remove both trailing numbers, also remove trailing '_'. * * For symbols with llvm suffix, i.e., foo.llvm.<hash>, remove the * .llvm.<hash> part. */static const char *demangle_name(struct symbol *sym){ char *str; ssize_t len;
if (!is_func_sym(sym) && !is_object_sym(sym)) return sym->name;
len = demangled_name_len(sym->name); if (len == strlen(sym->name)) return sym->name;
str = strndup(sym->name, len); if (!str) { ERROR_GLIBC("strdup"); return NULL; }
return str;}
static int 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 (is_file_sym(sym)) 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 (!is_undef_sym(iter) && iter->offset == sym->offset && iter->type == sym->type && iter->len == sym->len) 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);
sym->demangled_name = demangle_name(sym); if (!sym->demangled_name) return -1;
list_add_tail(&sym->global_list, &elf->symbols); elf_hash_add(symbol, &sym->hash, sym->idx); elf_hash_add(symbol_name, &sym->name_hash, str_hash(sym->demangled_name));
if (is_func_sym(sym) && (strstarts(sym->name, "__pfx_") || strstarts(sym->name, "__cfi_") || strstarts(sym->name, "__pi___pfx_") || strstarts(sym->name, "__pi___cfi_"))) sym->prefix = 1;
if (strstarts(sym->name, ".klp.sym")) sym->klp = 1;
if (!sym->klp && !is_sec_sym(sym) && strstr(sym->name, ".cold")) { sym->cold = 1;
/* * Clang doesn't mark cold subfunctions as STT_FUNC, which * breaks several objtool assumptions. Fake it. */ sym->type = STT_FUNC; }
sym->pfunc = sym->cfunc = sym;
return 0;}
static int read_symbols(struct elf *elf){ struct section *symtab, *symtab_shndx, *sec; struct symbol *sym, *pfunc, *file = NULL; 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) { ERROR_GLIBC("calloc"); return -1; }
INIT_LIST_HEAD(&elf->symbols);
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)) { ERROR_ELF("gelf_getsymshndx"); return -1; }
sym->name = elf_strptr(elf->elf, symtab->sh.sh_link, sym->sym.st_name); if (!sym->name) { ERROR_ELF("elf_strptr"); return -1; }
/* * "klp diff" renames the placeholder symbols of KLP relocs to * hide them from modpost. Hide the prefix from the rest of * objtool so its many name-based heuristics (noreturns, * uaccess safe list, ...) still see the original symbol name. * * st_name is left alone, so the renamed symbol is preserved in * the output file. */ if (strstarts(sym->name, KLP_TOMBSTONE_PREFIX)) sym->name += strlen(KLP_TOMBSTONE_PREFIX);
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) { ERROR("couldn't find section for symbol %s", sym->name); return -1; } 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);
if (elf_add_symbol(elf, sym)) return -1;
if (is_file_sym(sym)) file = sym; else if (sym->bind == STB_LOCAL && !is_sec_sym(sym)) sym->file = file; }
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; size_t pnamelen;
if (!sym->cold) continue;
coldstr = strstr(sym->name, ".cold"); if (!coldstr) { ERROR("%s(): cold subfunction without \".cold\"?", sym->name); return -1; }
pnamelen = coldstr - sym->name; pname = strndup(sym->name, pnamelen); if (!pname) { ERROR("%s(): failed to allocate memory", sym->name); return -1; }
pfunc = find_local_symbol_by_file_and_name(elf, sym->file, pname); if (!pfunc) pfunc = find_global_symbol_by_name(elf, pname); free(pname);
if (!pfunc) { ERROR("%s(): can't find parent function", sym->name); return -1; }
sym->pfunc = pfunc->alias; pfunc->cfunc = sym; pfunc->alias->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;}
static int mark_group_syms(struct elf *elf){ struct section *symtab, *sec; struct symbol *sym;
symtab = find_section_by_name(elf, ".symtab"); if (!symtab) { ERROR("no .symtab"); return -1; }
for_each_sec(elf, sec) { if (sec->sh.sh_type == SHT_GROUP && sec->sh.sh_link == symtab->idx) { sym = find_symbol_by_index(elf, sec->sh.sh_info); if (!sym) { ERROR("%s: can't find SHT_GROUP signature symbol", sec->name); return -1; }
sym->group_sec = sec; } }
return 0;}
/* * @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 = sym_next_reloc(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; 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;
shndx = is_special_shndx ? sym->sym.st_shndx : sym->sec->idx;
s = elf_getscn(elf->elf, symtab->idx); if (!s) { ERROR_ELF("elf_getscn"); return -1; }
if (symtab_shndx) { t = elf_getscn(elf->elf, symtab_shndx->idx); if (!t) { ERROR_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 */ ERROR("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) { ERROR_GLIBC("calloc"); 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) { ERROR_GLIBC("calloc"); 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) { ERROR("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) { ERROR("negative index"); return -1; }
/* setup extended section index magic and write the symbol */ if (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) { ERROR("no .symtab_shndx"); return -1; } }
if (!gelf_update_symshndx(symtab_data, shndx_data, idx, &sym->sym, shndx)) { ERROR_ELF("gelf_update_symshndx"); return -1; }
return 0;}
struct symbol *elf_create_symbol(struct elf *elf, const char *name, struct section *sec, unsigned int bind, unsigned int type, unsigned long offset, size_t size){ struct section *symtab, *symtab_shndx; Elf32_Word first_non_local, new_idx; struct symbol *old, *sym;
sym = calloc(1, sizeof(*sym)); if (!sym) { ERROR_GLIBC("calloc"); return NULL; }
sym->name = strdup(name); if (!sym->name) { ERROR_GLIBC("strdup"); return NULL; }
if (type != STT_SECTION) { sym->sym.st_name = elf_add_string(elf, NULL, sym->name); if (sym->sym.st_name == -1) return NULL; }
if (sec) { sym->sec = sec; } else { sym->sec = find_section_by_index(elf, 0); if (!sym->sec) { ERROR("no NULL section"); return NULL; } }
sym->sym.st_info = GELF_ST_INFO(bind, type); sym->sym.st_value = offset; sym->sym.st_size = size;
symtab = find_section_by_name(elf, ".symtab"); if (!symtab) { ERROR("no .symtab"); return NULL; }
symtab_shndx = find_section_by_name(elf, ".symtab_shndx");
new_idx = sec_num_entries(symtab);
if (bind != STB_LOCAL) goto non_local;
/* * Move the first global symbol, as per sh_info, into a new, higher * symbol index. This frees 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)) { ERROR("elf_update_symbol move"); return NULL; }
if (elf_update_sym_relocs(elf, old)) return NULL;
if (old->group_sec) { old->group_sec->sh.sh_info = new_idx; mark_sec_changed(elf, old->group_sec, true); }
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 (sym->idx && elf_update_symbol(elf, symtab, symtab_shndx, sym)) 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); }
if (elf_add_symbol(elf, sym)) return NULL;
return sym;}
int elf_write_symbol(struct elf *elf, struct symbol *sym){ struct section *symtab, *symtab_shndx;
symtab = find_section_by_name(elf, ".symtab"); if (!symtab) { ERROR("no .symtab"); return -1; }
symtab_shndx = find_section_by_name(elf, ".symtab_shndx");
if (elf_update_symbol(elf, symtab, symtab_shndx, sym)) return -1;
mark_sec_changed(elf, symtab, true);
return 0;}
struct symbol *elf_create_section_symbol(struct elf *elf, struct section *sec){ struct symbol *sym = calloc(1, sizeof(*sym));
sym = elf_create_symbol(elf, sec->name, sec, STB_LOCAL, STT_SECTION, 0, 0); if (!sym) return NULL;
sec->sym = sym;
return sym;}
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)) { ERROR("%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))) { ERROR("%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)); set_sym_next_reloc(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; s64 addend = insn_off;
if (!is_text_sec(insn_sec)) { ERROR("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; }
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 (is_text_sec(sec)) { ERROR("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) { ERROR("can't find base section for reloc section %s", rsec->name); return -1; }
rsec->base->rsec = rsec;
/* nr_alloc_relocs=0: libelf owns d_buf */ rsec->nr_alloc_relocs = 0;
rsec->relocs = calloc(sec_num_entries(rsec), sizeof(*reloc)); if (!rsec->relocs) { ERROR_GLIBC("calloc"); return -1; }
nr_reloc = 0; 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) { ERROR("can't find reloc entry symbol %d for %s", symndx, rsec->name); return -1; }
elf_hash_add(reloc, &reloc->hash, reloc_hash(reloc)); set_sym_next_reloc(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;}
static void mark_rodata(struct elf *elf){ struct section *sec;
for_each_sec(elf, sec) { if ((strstarts(sec->name, ".rodata") && !strstr(sec->name, ".str1.")) || strstarts(sec->name, ".data.rel.ro")) sec->rodata = true; }}
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) { ERROR_GLIBC("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; }
elf->name = strdup(name); if (!elf->name) { ERROR_GLIBC("strdup"); return NULL; }
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) { ERROR_ELF("elf_begin"); goto err; }
if (!gelf_getehdr(elf->elf, &elf->ehdr)) { ERROR_ELF("gelf_getehdr"); goto err; }
if (read_sections(elf)) goto err;
mark_rodata(elf);
if (read_symbols(elf)) goto err;
if (mark_group_syms(elf)) goto err;
if (read_relocs(elf)) goto err;
return elf;
err: elf_close(elf); return NULL;}
struct elf *elf_create_file(GElf_Ehdr *ehdr, const char *name){ struct section *null, *symtab, *strtab, *shstrtab; char *tmp_name; struct symbol *sym; struct elf *elf;
elf_version(EV_CURRENT);
elf = calloc(1, sizeof(*elf)); if (!elf) { ERROR_GLIBC("calloc"); return NULL; }
INIT_LIST_HEAD(&elf->sections);
tmp_name = malloc(strlen(name) + 8); if (!tmp_name) { ERROR_GLIBC("malloc"); return NULL; }
sprintf(tmp_name, "%s.XXXXXX", name);
elf->fd = mkstemp(tmp_name); if (elf->fd == -1) { ERROR_GLIBC("can't create tmp file"); exit(1); }
elf->tmp_name = tmp_name;
elf->name = strdup(name); if (!elf->name) { ERROR_GLIBC("strdup"); return NULL; }
elf->elf = elf_begin(elf->fd, ELF_C_WRITE, NULL); if (!elf->elf) { ERROR_ELF("elf_begin"); return NULL; }
if (!gelf_newehdr(elf->elf, ELFCLASS64)) { ERROR_ELF("gelf_newehdr"); return NULL; }
memcpy(&elf->ehdr, ehdr, sizeof(elf->ehdr));
if (!gelf_update_ehdr(elf->elf, &elf->ehdr)) { ERROR_ELF("gelf_update_ehdr"); return NULL; }
INIT_LIST_HEAD(&elf->symbols);
if (!elf_alloc_hash(section, 1000) || !elf_alloc_hash(section_name, 1000) || !elf_alloc_hash(symbol, 10000) || !elf_alloc_hash(symbol_name, 10000) || !elf_alloc_hash(reloc, 100000)) return NULL;
null = elf_create_section(elf, NULL, 0, 0, SHT_NULL, 0, 0); shstrtab = elf_create_section(elf, NULL, 0, 0, SHT_STRTAB, 1, 0); strtab = elf_create_section(elf, NULL, 0, 0, SHT_STRTAB, 1, 0);
if (!null || !shstrtab || !strtab) return NULL;
null->name = ""; shstrtab->name = ".shstrtab"; strtab->name = ".strtab";
null->sh.sh_name = elf_add_string(elf, shstrtab, null->name); shstrtab->sh.sh_name = elf_add_string(elf, shstrtab, shstrtab->name); strtab->sh.sh_name = elf_add_string(elf, shstrtab, strtab->name);
if (null->sh.sh_name == -1 || shstrtab->sh.sh_name == -1 || strtab->sh.sh_name == -1) return NULL;
elf_hash_add(section_name, &null->name_hash, str_hash(null->name)); elf_hash_add(section_name, &strtab->name_hash, str_hash(strtab->name)); elf_hash_add(section_name, &shstrtab->name_hash, str_hash(shstrtab->name));
if (elf_add_string(elf, strtab, "") == -1) return NULL;
symtab = elf_create_section(elf, ".symtab", 0x18, 0x18, SHT_SYMTAB, 0x8, 0); if (!symtab) return NULL;
symtab->sh.sh_link = strtab->idx; symtab->sh.sh_info = 1;
elf->ehdr.e_shstrndx = shstrtab->idx; if (!gelf_update_ehdr(elf->elf, &elf->ehdr)) { ERROR_ELF("gelf_update_ehdr"); return NULL; }
sym = calloc(1, sizeof(*sym)); if (!sym) { ERROR_GLIBC("calloc"); return NULL; }
sym->name = ""; sym->sec = null; elf_add_symbol(elf, sym);
return elf;}
unsigned int elf_add_string(struct elf *elf, struct section *strtab, const char *str){ unsigned int offset;
if (!strtab) strtab = find_section_by_name(elf, ".strtab"); if (!strtab) { ERROR("can't find .strtab section"); return -1; }
if (!strtab->sh.sh_addralign) { ERROR("'%s': invalid sh_addralign", strtab->name); return -1; }
offset = ALIGN(sec_size(strtab), strtab->sh.sh_addralign);
if (!elf_add_data(elf, strtab, str, strlen(str) + 1)) return -1;
return offset;}
void *elf_add_data(struct elf *elf, struct section *sec, const void *data, size_t size){ unsigned long offset; Elf_Scn *s;
if (!sec->sh.sh_addralign) { ERROR("'%s': invalid sh_addralign", sec->name); return NULL; }
s = elf_getscn(elf->elf, sec->idx); if (!s) { ERROR_ELF("elf_getscn"); return NULL; }
sec->data = elf_newdata(s); if (!sec->data) { ERROR_ELF("elf_newdata"); return NULL; }
sec->data->d_buf = calloc(1, size); if (!sec->data->d_buf) { ERROR_GLIBC("calloc"); return NULL; }
if (data) memcpy(sec->data->d_buf, data, size);
sec->data->d_size = size; sec->data->d_align = sec->sh.sh_addralign;
offset = ALIGN(sec_size(sec), sec->sh.sh_addralign); sec->sh.sh_size = offset + size;
mark_sec_changed(elf, sec, true);
return sec->data->d_buf;}
struct section *elf_create_section(struct elf *elf, const char *name, size_t size, size_t entsize, unsigned int type, unsigned int align, unsigned int flags){ struct section *sec, *shstrtab; Elf_Scn *s;
if (name && find_section_by_name(elf, name)) { ERROR("section '%s' already exists", name); return NULL; }
sec = calloc(1, sizeof(*sec)); if (!sec) { ERROR_GLIBC("calloc"); return NULL; }
INIT_LIST_HEAD(&sec->symbol_list);
/* don't actually create the section, just the data structures */ if (type == SHT_NULL) goto add;
s = elf_newscn(elf->elf); if (!s) { ERROR_ELF("elf_newscn"); return NULL; }
sec->idx = elf_ndxscn(s);
if (size) { sec->data = elf_newdata(s); if (!sec->data) { ERROR_ELF("elf_newdata"); return NULL; }
sec->data->d_size = size; sec->data->d_align = 1;
sec->data->d_buf = calloc(1, size); if (!sec->data->d_buf) { ERROR_GLIBC("calloc"); return NULL; } }
if (!gelf_getshdr(s, &sec->sh)) { ERROR_ELF("gelf_getshdr"); return NULL; }
sec->sh.sh_size = size; sec->sh.sh_entsize = entsize; sec->sh.sh_type = type; sec->sh.sh_addralign = align; sec->sh.sh_flags = flags;
if (name) { sec->name = strdup(name); if (!sec->name) { ERROR("strdup"); return NULL; }
/* 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) { ERROR("can't find .shstrtab or .strtab"); return NULL; } } sec->sh.sh_name = elf_add_string(elf, shstrtab, sec->name); if (sec->sh.sh_name == -1) return NULL;
elf_hash_add(section_name, &sec->name_hash, str_hash(sec->name)); }
add: list_add_tail(&sec->list, &elf->sections); elf_hash_add(section, &sec->hash, sec->idx);
mark_sec_changed(elf, sec, true);
return sec;}
static int elf_alloc_reloc(struct elf *elf, struct section *rsec){ struct reloc *old_relocs, *old_relocs_end, *new_relocs; unsigned int nr_relocs_old = sec_num_entries(rsec); unsigned int nr_relocs_new = nr_relocs_old + 1; unsigned long nr_alloc; struct symbol *sym;
if (!rsec->data) { rsec->data = elf_newdata(elf_getscn(elf->elf, rsec->idx)); if (!rsec->data) { ERROR_ELF("elf_newdata"); return -1; }
rsec->data->d_align = 1; rsec->data->d_type = ELF_T_RELA; rsec->data->d_buf = NULL; }
rsec->data->d_size = nr_relocs_new * elf_rela_size(elf); rsec->sh.sh_size = rsec->data->d_size;
nr_alloc = max(64UL, roundup_pow_of_two(nr_relocs_new)); if (nr_alloc <= rsec->nr_alloc_relocs) return 0;
if (rsec->data->d_buf && !rsec->nr_alloc_relocs) { void *orig_buf = rsec->data->d_buf;
/* * The original d_buf is owned by libelf so it can't be * realloced. */ rsec->data->d_buf = malloc(nr_alloc * elf_rela_size(elf)); if (!rsec->data->d_buf) { ERROR_GLIBC("malloc"); return -1; } memcpy(rsec->data->d_buf, orig_buf, nr_relocs_old * elf_rela_size(elf)); } else { rsec->data->d_buf = realloc(rsec->data->d_buf, nr_alloc * elf_rela_size(elf)); if (!rsec->data->d_buf) { ERROR_GLIBC("realloc"); return -1; } }
rsec->nr_alloc_relocs = nr_alloc;
old_relocs = rsec->relocs; new_relocs = calloc(nr_alloc, sizeof(struct reloc)); if (!new_relocs) { ERROR_GLIBC("calloc"); return -1; }
if (!old_relocs) goto done;
/* * The struct reloc's address has changed. Update all the symbols and * relocs which reference it. */
old_relocs_end = &old_relocs[nr_relocs_old]; for_each_sym(elf, sym) { struct reloc *reloc;
reloc = sym->relocs; if (!reloc) continue;
if (reloc >= old_relocs && reloc < old_relocs_end) sym->relocs = &new_relocs[reloc - old_relocs];
while (1) { struct reloc *next_reloc = sym_next_reloc(reloc);
if (!next_reloc) break;
if (next_reloc >= old_relocs && next_reloc < old_relocs_end) set_sym_next_reloc(reloc, &new_relocs[next_reloc - old_relocs]);
reloc = next_reloc; } }
memcpy(new_relocs, old_relocs, nr_relocs_old * sizeof(struct reloc));
for (int i = 0; i < nr_relocs_old; i++) { struct reloc *old = &old_relocs[i]; struct reloc *new = &new_relocs[i]; u32 key = reloc_hash(old);
elf_hash_del(reloc, &old->hash, key); elf_hash_add(reloc, &new->hash, key); }
free(old_relocs);done: rsec->relocs = new_relocs; return 0;}
struct section *elf_create_rela_section(struct elf *elf, struct section *sec, unsigned int nr_relocs){ struct section *rsec; char *rsec_name;
rsec_name = malloc(strlen(sec->name) + strlen(".rela") + 1); if (!rsec_name) { ERROR_GLIBC("malloc"); return NULL; } strcpy(rsec_name, ".rela"); strcat(rsec_name, sec->name);
rsec = elf_create_section(elf, rsec_name, nr_relocs * elf_rela_size(elf), elf_rela_size(elf), SHT_RELA, elf_addr_size(elf), SHF_INFO_LINK); free(rsec_name); if (!rsec) return NULL;
if (nr_relocs) { rsec->data->d_type = ELF_T_RELA;
rsec->nr_alloc_relocs = nr_relocs; rsec->relocs = calloc(nr_relocs, sizeof(struct reloc)); if (!rsec->relocs) { ERROR_GLIBC("calloc"); return NULL; } }
rsec->sh.sh_link = find_section_by_name(elf, ".symtab")->idx; rsec->sh.sh_info = sec->idx;
sec->rsec = rsec; rsec->base = sec;
return rsec;}
struct reloc *elf_create_reloc(struct elf *elf, struct section *sec, unsigned long offset, struct symbol *sym, s64 addend, unsigned int type){ struct section *rsec = sec->rsec;
if (!rsec) { rsec = elf_create_rela_section(elf, sec, 0); if (!rsec) return NULL; }
if (find_reloc_by_dest(elf, sec, offset)) { ERROR_FUNC(sec, offset, "duplicate reloc"); return NULL; }
if (elf_alloc_reloc(elf, rsec)) return NULL;
mark_sec_changed(elf, rsec, true);
return elf_init_reloc(elf, rsec, sec_num_entries(rsec) - 1, offset, sym, addend, type);}
struct section *elf_create_section_pair(struct elf *elf, const char *name, size_t entsize, unsigned int nr, unsigned int nr_relocs){ struct section *sec;
sec = elf_create_section(elf, name, nr * entsize, entsize, SHT_PROGBITS, 1, SHF_ALLOC); if (!sec) return NULL;
if (!elf_create_rela_section(elf, sec, nr_relocs)) 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) { ERROR("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_size(sec); bool truncated = false; Elf_Data *data = NULL; Elf_Scn *s;
s = elf_getscn(elf->elf, sec->idx); if (!s) { ERROR_ELF("elf_getscn"); return -1; }
for (;;) { /* get next data descriptor for the relevant section */ data = elf_getdata(s, data); if (!data) { if (size) { ERROR("end of section data but non-zero size left\n"); return -1; } return 0; }
if (truncated) { /* when we remove symbols */ ERROR("truncated; but more data\n"); return -1; }
if (!data->d_size) { ERROR("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;
/* Update changed relocation sections and section headers: */ list_for_each_entry(sec, &elf->sections, list) { if (sec->truncate && elf_truncate_section(elf, sec)) return -1;
if (sec_changed(sec)) { s = elf_getscn(elf->elf, sec->idx); if (!s) { ERROR_ELF("elf_getscn"); return -1; }
/* Note this also flags the section dirty */ if (!gelf_update_shdr(s, &sec->sh)) { ERROR_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) { ERROR_ELF("elf_update"); return -1; }
elf->changed = false;
return 0;}
int elf_close(struct elf *elf){ if (elf->elf) elf_end(elf->elf);
if (elf->fd > 0) close(elf->fd);
if (elf->tmp_name && rename(elf->tmp_name, elf->name)) return -1;
/* * NOTE: All remaining allocations are leaked on purpose. Objtool is * about to exit anyway. */ return 0;}