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tccelf.c
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/*
* ELF file handling for TCC
*
* Copyright (c) 2001-2004 Fabrice Bellard
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include "tcc.h"
/* Define this to get some debug output during relocation processing. */
#undef DEBUG_RELOC
/********************************************************/
/* global variables */
/* elf version information */
struct sym_version {
char *lib;
char *version;
int out_index;
int prev_same_lib;
};
#define nb_sym_versions s1->nb_sym_versions
#define sym_versions s1->sym_versions
#define nb_sym_to_version s1->nb_sym_to_version
#define sym_to_version s1->sym_to_version
#define dt_verneednum s1->dt_verneednum
#define versym_section s1->versym_section
#define verneed_section s1->verneed_section
/* special flag to indicate that the section should not be linked to the other ones */
#define SHF_PRIVATE 0x80000000
/* section is dynsymtab_section */
#define SHF_DYNSYM 0x40000000
#ifdef TCC_TARGET_PE
#define shf_RELRO SHF_ALLOC
static const char rdata[] = ".rdata";
#else
#define shf_RELRO SHF_ALLOC /* eventually made SHF_WRITE in sort_sections() */
static const char rdata[] = ".data.ro";
#endif
/* ------------------------------------------------------------------------- */
ST_FUNC void tccelf_new(TCCState *s)
{
TCCState *s1 = s;
/* no section zero */
dynarray_add(&s->sections, &s->nb_sections, NULL);
/* create standard sections */
text_section = new_section(s, ".text", SHT_PROGBITS, SHF_ALLOC | SHF_EXECINSTR);
data_section = new_section(s, ".data", SHT_PROGBITS, SHF_ALLOC | SHF_WRITE);
/* create ro data section (make ro after relocation done with GNU_RELRO) */
rodata_section = new_section(s, rdata, SHT_PROGBITS, shf_RELRO);
bss_section = new_section(s, ".bss", SHT_NOBITS, SHF_ALLOC | SHF_WRITE);
common_section = new_section(s, ".common", SHT_NOBITS, SHF_PRIVATE);
common_section->sh_num = SHN_COMMON;
/* symbols are always generated for linking stage */
symtab_section = new_symtab(s, ".symtab", SHT_SYMTAB, 0,
".strtab",
".hashtab", SHF_PRIVATE);
/* private symbol table for dynamic symbols */
s->dynsymtab_section = new_symtab(s, ".dynsymtab", SHT_SYMTAB, SHF_PRIVATE|SHF_DYNSYM,
".dynstrtab",
".dynhashtab", SHF_PRIVATE);
get_sym_attr(s, 0, 1);
if (s->do_debug) {
/* add debug sections */
tcc_debug_new(s);
}
#if TCC_EH_FRAME
if (s->output_format != TCC_OUTPUT_FORMAT_ELF)
s->unwind_tables = 0;
tcc_eh_frame_start(s);
#endif
#ifdef CONFIG_TCC_BCHECK
if (s->do_bounds_check) {
/* if bound checking, then add corresponding sections */
/* (make ro after relocation done with GNU_RELRO) */
bounds_section = new_section(s, ".bounds", SHT_PROGBITS, shf_RELRO);
lbounds_section = new_section(s, ".lbounds", SHT_PROGBITS, shf_RELRO);
}
#endif
#ifdef TCC_TARGET_PE
/* to make sure that -ltcc1 -Wl,-e,_start will grab the startup code
from libtcc1.a (unless _start defined) */
if (s->elf_entryname)
set_global_sym(s, s->elf_entryname, NULL, 0); /* SHN_UNDEF */
#endif
}
ST_FUNC void free_section(Section *s)
{
if (!s)
return;
tcc_free(s->data);
s->data = NULL;
s->data_allocated = s->data_offset = 0;
}
ST_FUNC void tccelf_delete(TCCState *s1)
{
int i;
#ifndef ELF_OBJ_ONLY
/* free symbol versions */
for (i = 0; i < nb_sym_versions; i++) {
tcc_free(sym_versions[i].version);
tcc_free(sym_versions[i].lib);
}
tcc_free(sym_versions);
tcc_free(sym_to_version);
#endif
/* free all sections */
for(i = 1; i < s1->nb_sections; i++)
free_section(s1->sections[i]);
dynarray_reset(&s1->sections, &s1->nb_sections);
for(i = 0; i < s1->nb_priv_sections; i++)
free_section(s1->priv_sections[i]);
dynarray_reset(&s1->priv_sections, &s1->nb_priv_sections);
tcc_free(s1->sym_attrs);
symtab_section = NULL; /* for tccrun.c:rt_printline() */
}
/* save section data state */
ST_FUNC void tccelf_begin_file(TCCState *s1)
{
Section *s; int i;
for (i = 1; i < s1->nb_sections; i++) {
s = s1->sections[i];
s->sh_offset = s->data_offset;
}
/* disable symbol hashing during compilation */
s = s1->symtab, s->reloc = s->hash, s->hash = NULL;
#if defined TCC_TARGET_X86_64 && defined TCC_TARGET_PE
s1->uw_sym = 0;
s1->uw_offs = 0;
#endif
}
static void update_relocs(TCCState *s1, Section *s, int *old_to_new_syms, int first_sym);
/* At the end of compilation, convert any UNDEF syms to global, and merge
with previously existing symbols */
ST_FUNC void tccelf_end_file(TCCState *s1)
{
Section *s = s1->symtab;
int first_sym, nb_syms, *tr, i;
first_sym = s->sh_offset / sizeof (ElfSym);
nb_syms = s->data_offset / sizeof (ElfSym) - first_sym;
s->data_offset = s->sh_offset;
s->link->data_offset = s->link->sh_offset;
s->hash = s->reloc, s->reloc = NULL;
tr = tcc_mallocz(nb_syms * sizeof *tr);
for (i = 0; i < nb_syms; ++i) {
ElfSym *sym = (ElfSym*)s->data + first_sym + i;
if (sym->st_shndx == SHN_UNDEF) {
int sym_bind = ELFW(ST_BIND)(sym->st_info);
int sym_type = ELFW(ST_TYPE)(sym->st_info);
if (sym_bind == STB_LOCAL)
sym_bind = STB_GLOBAL;
#ifndef TCC_TARGET_PE
if (sym_bind == STB_GLOBAL && s1->output_type == TCC_OUTPUT_OBJ) {
/* undefined symbols with STT_FUNC are confusing gnu ld when
linking statically to STT_GNU_IFUNC */
sym_type = STT_NOTYPE;
}
#endif
sym->st_info = ELFW(ST_INFO)(sym_bind, sym_type);
}
tr[i] = set_elf_sym(s, sym->st_value, sym->st_size, sym->st_info,
sym->st_other, sym->st_shndx, (char*)s->link->data + sym->st_name);
}
/* now update relocations */
update_relocs(s1, s, tr, first_sym);
tcc_free(tr);
/* record text/data/bss output for -bench info */
for (i = 0; i < 4; ++i) {
s = s1->sections[i + 1];
s1->total_output[i] += s->data_offset - s->sh_offset;
}
}
ST_FUNC Section *new_section(TCCState *s1, const char *name, int sh_type, int sh_flags)
{
Section *sec;
sec = tcc_mallocz(sizeof(Section) + strlen(name));
sec->s1 = s1;
strcpy(sec->name, name);
sec->sh_type = sh_type;
sec->sh_flags = sh_flags;
switch(sh_type) {
case SHT_GNU_versym:
sec->sh_addralign = 2;
break;
case SHT_HASH:
case SHT_GNU_HASH:
case SHT_REL:
case SHT_RELA:
case SHT_DYNSYM:
case SHT_SYMTAB:
case SHT_DYNAMIC:
case SHT_GNU_verneed:
case SHT_GNU_verdef:
sec->sh_addralign = PTR_SIZE;
break;
case SHT_STRTAB:
sec->sh_addralign = 1;
break;
default:
sec->sh_addralign = PTR_SIZE; /* gcc/pcc default alignment */
break;
}
if (sh_flags & SHF_PRIVATE) {
dynarray_add(&s1->priv_sections, &s1->nb_priv_sections, sec);
} else {
sec->sh_num = s1->nb_sections;
dynarray_add(&s1->sections, &s1->nb_sections, sec);
}
return sec;
}
ST_FUNC void init_symtab(Section *s)
{
int *ptr, nb_buckets = 1;
put_elf_str(s->link, "");
section_ptr_add(s, sizeof (ElfW(Sym)));
ptr = section_ptr_add(s->hash, (2 + nb_buckets + 1) * sizeof(int));
ptr[0] = nb_buckets;
ptr[1] = 1;
memset(ptr + 2, 0, (nb_buckets + 1) * sizeof(int));
}
ST_FUNC Section *new_symtab(TCCState *s1,
const char *symtab_name, int sh_type, int sh_flags,
const char *strtab_name,
const char *hash_name, int hash_sh_flags)
{
Section *symtab, *strtab, *hash;
symtab = new_section(s1, symtab_name, sh_type, sh_flags);
symtab->sh_entsize = sizeof(ElfW(Sym));
strtab = new_section(s1, strtab_name, SHT_STRTAB, sh_flags);
symtab->link = strtab;
hash = new_section(s1, hash_name, SHT_HASH, hash_sh_flags);
hash->sh_entsize = sizeof(int);
symtab->hash = hash;
hash->link = symtab;
init_symtab(symtab);
return symtab;
}
/* realloc section and set its content to zero */
ST_FUNC void section_realloc(Section *sec, unsigned long new_size)
{
unsigned long size;
unsigned char *data;
size = sec->data_allocated;
if (size == 0)
size = 1;
while (size < new_size)
size = size * 2;
data = tcc_realloc(sec->data, size);
memset(data + sec->data_allocated, 0, size - sec->data_allocated);
sec->data = data;
sec->data_allocated = size;
}
/* reserve at least 'size' bytes aligned per 'align' in section
'sec' from current offset, and return the aligned offset */
ST_FUNC size_t section_add(Section *sec, addr_t size, int align)
{
size_t offset, offset1;
offset = (sec->data_offset + align - 1) & -align;
offset1 = offset + size;
if (sec->sh_type != SHT_NOBITS && offset1 > sec->data_allocated)
section_realloc(sec, offset1);
sec->data_offset = offset1;
if (align > sec->sh_addralign)
sec->sh_addralign = align;
return offset;
}
/* reserve at least 'size' bytes in section 'sec' from
sec->data_offset. */
ST_FUNC void *section_ptr_add(Section *sec, addr_t size)
{
size_t offset = section_add(sec, size, 1);
return sec->data + offset;
}
#ifndef ELF_OBJ_ONLY
/* reserve at least 'size' bytes from section start */
static void section_reserve(Section *sec, unsigned long size)
{
if (size > sec->data_allocated)
section_realloc(sec, size);
if (size > sec->data_offset)
sec->data_offset = size;
}
#endif
static Section *have_section(TCCState *s1, const char *name)
{
Section *sec;
int i;
for(i = 1; i < s1->nb_sections; i++) {
sec = s1->sections[i];
if (!strcmp(name, sec->name))
return sec;
}
return NULL;
}
/* return a reference to a section, and create it if it does not
exists */
ST_FUNC Section *find_section(TCCState *s1, const char *name)
{
Section *sec = have_section(s1, name);
if (sec)
return sec;
/* sections are created as PROGBITS */
return new_section(s1, name, SHT_PROGBITS, SHF_ALLOC);
}
/* ------------------------------------------------------------------------- */
ST_FUNC int put_elf_str(Section *s, const char *sym)
{
int offset, len;
char *ptr;
len = strlen(sym) + 1;
offset = s->data_offset;
ptr = section_ptr_add(s, len);
memmove(ptr, sym, len);
return offset;
}
/* elf symbol hashing function */
static ElfW(Word) elf_hash(const unsigned char *name)
{
ElfW(Word) h = 0, g;
while (*name) {
h = (h << 4) + *name++;
g = h & 0xf0000000;
if (g)
h ^= g >> 24;
h &= ~g;
}
return h;
}
/* rebuild hash table of section s */
/* NOTE: we do factorize the hash table code to go faster */
static void rebuild_hash(Section *s, unsigned int nb_buckets)
{
ElfW(Sym) *sym;
int *ptr, *hash, nb_syms, sym_index, h;
unsigned char *strtab;
strtab = s->link->data;
nb_syms = s->data_offset / sizeof(ElfW(Sym));
if (!nb_buckets)
nb_buckets = ((int*)s->hash->data)[0];
s->hash->data_offset = 0;
ptr = section_ptr_add(s->hash, (2 + nb_buckets + nb_syms) * sizeof(int));
ptr[0] = nb_buckets;
ptr[1] = nb_syms;
ptr += 2;
hash = ptr;
memset(hash, 0, (nb_buckets + 1) * sizeof(int));
ptr += nb_buckets + 1;
sym = (ElfW(Sym) *)s->data + 1;
for(sym_index = 1; sym_index < nb_syms; sym_index++) {
if (ELFW(ST_BIND)(sym->st_info) != STB_LOCAL) {
h = elf_hash(strtab + sym->st_name) % nb_buckets;
*ptr = hash[h];
hash[h] = sym_index;
} else {
*ptr = 0;
}
ptr++;
sym++;
}
}
/* return the symbol number */
ST_FUNC int put_elf_sym(Section *s, addr_t value, unsigned long size,
int info, int other, int shndx, const char *name)
{
int name_offset, sym_index;
int nbuckets, h;
ElfW(Sym) *sym;
Section *hs;
sym = section_ptr_add(s, sizeof(ElfW(Sym)));
if (name && name[0])
name_offset = put_elf_str(s->link, name);
else
name_offset = 0;
/* XXX: endianness */
sym->st_name = name_offset;
sym->st_value = value;
sym->st_size = size;
sym->st_info = info;
sym->st_other = other;
sym->st_shndx = shndx;
sym_index = sym - (ElfW(Sym) *)s->data;
hs = s->hash;
if (hs) {
int *ptr, *base;
ptr = section_ptr_add(hs, sizeof(int));
base = (int *)hs->data;
/* only add global or weak symbols. */
if (ELFW(ST_BIND)(info) != STB_LOCAL) {
/* add another hashing entry */
nbuckets = base[0];
h = elf_hash((unsigned char *)s->link->data + name_offset) % nbuckets;
*ptr = base[2 + h];
base[2 + h] = sym_index;
base[1]++;
/* we resize the hash table */
hs->nb_hashed_syms++;
if (hs->nb_hashed_syms > 2 * nbuckets) {
rebuild_hash(s, 2 * nbuckets);
}
} else {
*ptr = 0;
base[1]++;
}
}
return sym_index;
}
ST_FUNC int find_elf_sym(Section *s, const char *name)
{
ElfW(Sym) *sym;
Section *hs;
int nbuckets, sym_index, h;
const char *name1;
hs = s->hash;
if (!hs)
return 0;
nbuckets = ((int *)hs->data)[0];
h = elf_hash((unsigned char *) name) % nbuckets;
sym_index = ((int *)hs->data)[2 + h];
while (sym_index != 0) {
sym = &((ElfW(Sym) *)s->data)[sym_index];
name1 = (char *) s->link->data + sym->st_name;
if (!strcmp(name, name1))
return sym_index;
sym_index = ((int *)hs->data)[2 + nbuckets + sym_index];
}
return 0;
}
/* return elf symbol value, signal error if 'err' is nonzero, decorate
name if FORC */
ST_FUNC addr_t get_sym_addr(TCCState *s1, const char *name, int err, int forc)
{
int sym_index;
ElfW(Sym) *sym;
char buf[256];
if (forc && s1->leading_underscore
#ifdef TCC_TARGET_PE
/* win32-32bit stdcall symbols always have _ already */
&& !strchr(name, '@')
#endif
) {
buf[0] = '_';
pstrcpy(buf + 1, sizeof(buf) - 1, name);
name = buf;
}
sym_index = find_elf_sym(s1->symtab, name);
sym = &((ElfW(Sym) *)s1->symtab->data)[sym_index];
if (!sym_index || sym->st_shndx == SHN_UNDEF) {
if (err)
tcc_error_noabort("%s not defined", name);
return (addr_t)-1;
}
return sym->st_value;
}
/* return elf symbol value */
LIBTCCAPI void *tcc_get_symbol(TCCState *s, const char *name)
{
addr_t addr = get_sym_addr(s, name, 0, 1);
return addr == -1 ? NULL : (void*)(uintptr_t)addr;
}
/* list elf symbol names and values */
ST_FUNC void list_elf_symbols(TCCState *s, void *ctx,
void (*symbol_cb)(void *ctx, const char *name, const void *val))
{
ElfW(Sym) *sym;
Section *symtab;
int sym_index, end_sym;
const char *name;
unsigned char sym_vis, sym_bind;
symtab = s->symtab;
end_sym = symtab->data_offset / sizeof (ElfSym);
for (sym_index = 0; sym_index < end_sym; ++sym_index) {
sym = &((ElfW(Sym) *)symtab->data)[sym_index];
if (sym->st_value) {
name = (char *) symtab->link->data + sym->st_name;
sym_bind = ELFW(ST_BIND)(sym->st_info);
sym_vis = ELFW(ST_VISIBILITY)(sym->st_other);
if (sym_bind == STB_GLOBAL && sym_vis == STV_DEFAULT)
symbol_cb(ctx, name, (void*)(uintptr_t)sym->st_value);
}
}
}
/* list elf symbol names and values */
LIBTCCAPI void tcc_list_symbols(TCCState *s, void *ctx,
void (*symbol_cb)(void *ctx, const char *name, const void *val))
{
list_elf_symbols(s, ctx, symbol_cb);
}
#ifndef ELF_OBJ_ONLY
static void
version_add (TCCState *s1)
{
int i;
ElfW(Sym) *sym;
ElfW(Verneed) *vn = NULL;
Section *symtab;
int sym_index, end_sym, nb_versions = 2, nb_entries = 0;
ElfW(Half) *versym;
const char *name;
if (0 == nb_sym_versions)
return;
versym_section = new_section(s1, ".gnu.version", SHT_GNU_versym, SHF_ALLOC);
versym_section->sh_entsize = sizeof(ElfW(Half));
versym_section->link = s1->dynsym;
/* add needed symbols */
symtab = s1->dynsym;
end_sym = symtab->data_offset / sizeof (ElfSym);
versym = section_ptr_add(versym_section, end_sym * sizeof(ElfW(Half)));
for (sym_index = 1; sym_index < end_sym; ++sym_index) {
int dllindex, verndx;
sym = &((ElfW(Sym) *)symtab->data)[sym_index];
name = (char *) symtab->link->data + sym->st_name;
dllindex = find_elf_sym(s1->dynsymtab_section, name);
verndx = (dllindex && dllindex < nb_sym_to_version)
? sym_to_version[dllindex] : -1;
if (verndx >= 0
/* XXX: on android, clang refuses to link with a libtcc.so made by tcc
when defined symbols have a version > 1 or when the version is '0'.
Whereas version '1' for example for 'signal' in an exe defeats
bcheck's signal_redir. */
&& (sym->st_shndx == SHN_UNDEF || (s1->output_type & TCC_OUTPUT_EXE))
) {
if (!sym_versions[verndx].out_index)
sym_versions[verndx].out_index = nb_versions++;
versym[sym_index] = sym_versions[verndx].out_index;
} else {
versym[sym_index] = 1; /* (*global*) */
}
//printf("SYM %d %s\n", versym[sym_index], name);
}
/* generate verneed section, but not when it will be empty. Some
dynamic linkers look at their contents even when DTVERNEEDNUM and
section size is zero. */
if (nb_versions > 2) {
verneed_section = new_section(s1, ".gnu.version_r",
SHT_GNU_verneed, SHF_ALLOC);
verneed_section->link = s1->dynsym->link;
for (i = nb_sym_versions; i-- > 0;) {
struct sym_version *sv = &sym_versions[i];
int n_same_libs = 0, prev;
size_t vnofs;
ElfW(Vernaux) *vna = 0;
if (sv->out_index < 1)
continue;
/* make sure that a DT_NEEDED tag is put */
/* abitest-tcc fails on older i386-linux with "ld-linux.so.2" DT_NEEDED
ret_int_test... Inconsistency detected by ld.so: dl-minimal.c: 148:
realloc: Assertion `ptr == alloc_last_block' failed! */
if (strcmp(sv->lib, "ld-linux.so.2"))
tcc_add_dllref(s1, sv->lib, 0);
vnofs = section_add(verneed_section, sizeof(*vn), 1);
vn = (ElfW(Verneed)*)(verneed_section->data + vnofs);
vn->vn_version = 1;
vn->vn_file = put_elf_str(verneed_section->link, sv->lib);
vn->vn_aux = sizeof (*vn);
do {
prev = sv->prev_same_lib;
if (sv->out_index > 0) {
vna = section_ptr_add(verneed_section, sizeof(*vna));
vna->vna_hash = elf_hash ((const unsigned char *)sv->version);
vna->vna_flags = 0;
vna->vna_other = sv->out_index;
sv->out_index = -2;
vna->vna_name = put_elf_str(verneed_section->link, sv->version);
vna->vna_next = sizeof (*vna);
//printf("LIB %d %s %s\n", vna->vna_other, sv->lib, verneed_section->link->data + vna->vna_name);
n_same_libs++;
}
if (prev >= 0)
sv = &sym_versions[prev];
} while(prev >= 0);
vna->vna_next = 0;
vn = (ElfW(Verneed)*)(verneed_section->data + vnofs);
vn->vn_cnt = n_same_libs;
vn->vn_next = sizeof(*vn) + n_same_libs * sizeof(*vna);
nb_entries++;
}
if (vn)
vn->vn_next = 0;
verneed_section->sh_info = nb_entries;
}
dt_verneednum = nb_entries;
}
#endif /* ndef ELF_OBJ_ONLY */
/* add an elf symbol : check if it is already defined and patch
it. Return symbol index. NOTE that sh_num can be SHN_UNDEF. */
ST_FUNC int set_elf_sym(Section *s, addr_t value, unsigned long size,
int info, int other, int shndx, const char *name)
{
TCCState *s1 = s->s1;
ElfW(Sym) *esym;
int sym_bind, sym_index, sym_type, esym_bind;
unsigned char sym_vis, esym_vis, new_vis;
sym_bind = ELFW(ST_BIND)(info);
sym_type = ELFW(ST_TYPE)(info);
sym_vis = ELFW(ST_VISIBILITY)(other);
if (sym_bind != STB_LOCAL) {
/* we search global or weak symbols */
sym_index = find_elf_sym(s, name);
if (!sym_index)
goto do_def;
esym = &((ElfW(Sym) *)s->data)[sym_index];
if (esym->st_value == value && esym->st_size == size && esym->st_info == info
&& esym->st_other == other && esym->st_shndx == shndx)
return sym_index;
if (esym->st_shndx != SHN_UNDEF) {
esym_bind = ELFW(ST_BIND)(esym->st_info);
/* propagate the most constraining visibility */
/* STV_DEFAULT(0)<STV_PROTECTED(3)<STV_HIDDEN(2)<STV_INTERNAL(1) */
esym_vis = ELFW(ST_VISIBILITY)(esym->st_other);
if (esym_vis == STV_DEFAULT) {
new_vis = sym_vis;
} else if (sym_vis == STV_DEFAULT) {
new_vis = esym_vis;
} else {
new_vis = (esym_vis < sym_vis) ? esym_vis : sym_vis;
}
esym->st_other = (esym->st_other & ~ELFW(ST_VISIBILITY)(-1))
| new_vis;
if (shndx == SHN_UNDEF) {
/* ignore adding of undefined symbol if the
corresponding symbol is already defined */
} else if (sym_bind == STB_GLOBAL && esym_bind == STB_WEAK) {
/* global overrides weak, so patch */
goto do_patch;
} else if (sym_bind == STB_WEAK && esym_bind == STB_GLOBAL) {
/* weak is ignored if already global */
} else if (sym_bind == STB_WEAK && esym_bind == STB_WEAK) {
/* keep first-found weak definition, ignore subsequents */
} else if (sym_vis == STV_HIDDEN || sym_vis == STV_INTERNAL) {
/* ignore hidden symbols after */
} else if ((esym->st_shndx == SHN_COMMON
|| esym->st_shndx == bss_section->sh_num)
&& (shndx < SHN_LORESERVE
&& shndx != bss_section->sh_num)) {
/* data symbol gets precedence over common/bss */
goto do_patch;
} else if (shndx == SHN_COMMON || shndx == bss_section->sh_num) {
/* data symbol keeps precedence over common/bss */
} else if (s->sh_flags & SHF_DYNSYM) {
/* we accept that two DLL define the same symbol */
} else if (esym->st_other & ST_ASM_SET) {
/* If the existing symbol came from an asm .set
we can override. */
goto do_patch;
} else {
#if 0
printf("new_bind=%x new_shndx=%x new_vis=%x old_bind=%x old_shndx=%x old_vis=%x\n",
sym_bind, shndx, new_vis, esym_bind, esym->st_shndx, esym_vis);
#endif
tcc_error_noabort("'%s' defined twice", name);
}
} else {
esym->st_other = other;
do_patch:
esym->st_info = ELFW(ST_INFO)(sym_bind, sym_type);
esym->st_shndx = shndx;
s1->new_undef_sym = 1;
esym->st_value = value;
esym->st_size = size;
}
} else {
do_def:
sym_index = put_elf_sym(s, value, size,
ELFW(ST_INFO)(sym_bind, sym_type), other,
shndx, name);
}
return sym_index;
}
/* put relocation */
ST_FUNC void put_elf_reloca(Section *symtab, Section *s, unsigned long offset,
int type, int symbol, addr_t addend)
{
TCCState *s1 = s->s1;
char buf[256];
Section *sr;
ElfW_Rel *rel;
sr = s->reloc;
if (!sr) {
/* if no relocation section, create it */
snprintf(buf, sizeof(buf), REL_SECTION_FMT, s->name);
/* if the symtab is allocated, then we consider the relocation
are also */
sr = new_section(s->s1, buf, SHT_RELX, symtab->sh_flags);
sr->sh_entsize = sizeof(ElfW_Rel);
sr->link = symtab;
sr->sh_info = s->sh_num;
s->reloc = sr;
}
rel = section_ptr_add(sr, sizeof(ElfW_Rel));
rel->r_offset = offset;
rel->r_info = ELFW(R_INFO)(symbol, type);
#if SHT_RELX == SHT_RELA
rel->r_addend = addend;
#endif
if (SHT_RELX != SHT_RELA && addend)
tcc_error_noabort("non-zero addend on REL architecture");
}
ST_FUNC void put_elf_reloc(Section *symtab, Section *s, unsigned long offset,
int type, int symbol)
{
put_elf_reloca(symtab, s, offset, type, symbol, 0);
}
ST_FUNC struct sym_attr *get_sym_attr(TCCState *s1, int index, int alloc)
{
int n;
struct sym_attr *tab;
if (index >= s1->nb_sym_attrs) {
if (!alloc)
return s1->sym_attrs;
/* find immediately bigger power of 2 and reallocate array */
n = 1;
while (index >= n)
n *= 2;
tab = tcc_realloc(s1->sym_attrs, n * sizeof(*s1->sym_attrs));
s1->sym_attrs = tab;
memset(s1->sym_attrs + s1->nb_sym_attrs, 0,
(n - s1->nb_sym_attrs) * sizeof(*s1->sym_attrs));
s1->nb_sym_attrs = n;
}
return &s1->sym_attrs[index];
}
static void update_relocs(TCCState *s1, Section *s, int *old_to_new_syms, int first_sym)
{
int i, type, sym_index;
Section *sr;
ElfW_Rel *rel;
for(i = 1; i < s1->nb_sections; i++) {
sr = s1->sections[i];
if (sr->sh_type == SHT_RELX && sr->link == s) {
for_each_elem(sr, 0, rel, ElfW_Rel) {
sym_index = ELFW(R_SYM)(rel->r_info);
type = ELFW(R_TYPE)(rel->r_info);
if ((sym_index -= first_sym) < 0)
continue; /* zero sym_index in reloc (can happen with asm) */
sym_index = old_to_new_syms[sym_index];
rel->r_info = ELFW(R_INFO)(sym_index, type);
}
}
}
}
/* In an ELF file symbol table, the local symbols must appear below
the global and weak ones. Since TCC cannot sort it while generating
the code, we must do it after. All the relocation tables are also
modified to take into account the symbol table sorting */
static void sort_syms(TCCState *s1, Section *s)
{
int *old_to_new_syms;
ElfW(Sym) *new_syms;
int nb_syms, i;
ElfW(Sym) *p, *q;
nb_syms = s->data_offset / sizeof(ElfW(Sym));
new_syms = tcc_malloc(nb_syms * sizeof(ElfW(Sym)));
old_to_new_syms = tcc_malloc(nb_syms * sizeof(int));
/* first pass for local symbols */
p = (ElfW(Sym) *)s->data;
q = new_syms;
for(i = 0; i < nb_syms; i++) {
if (ELFW(ST_BIND)(p->st_info) == STB_LOCAL) {
old_to_new_syms[i] = q - new_syms;
*q++ = *p;
}
p++;
}
/* save the number of local symbols in section header */
if( s->sh_size ) /* this 'if' makes IDA happy */
s->sh_info = q - new_syms;
/* then second pass for non local symbols */
p = (ElfW(Sym) *)s->data;
for(i = 0; i < nb_syms; i++) {
if (ELFW(ST_BIND)(p->st_info) != STB_LOCAL) {
old_to_new_syms[i] = q - new_syms;
*q++ = *p;
}
p++;
}
/* we copy the new symbols to the old */
memcpy(s->data, new_syms, nb_syms * sizeof(ElfW(Sym)));
tcc_free(new_syms);
update_relocs(s1, s, old_to_new_syms, 0);
tcc_free(old_to_new_syms);
}
#ifndef ELF_OBJ_ONLY
/* See: https://flapenguin.me/elf-dt-gnu-hash */
#define ELFCLASS_BITS (PTR_SIZE * 8)
static Section *create_gnu_hash(TCCState *s1)
{
int nb_syms, i, ndef, nbuckets, symoffset, bloom_size, bloom_shift;
ElfW(Sym) *p;
Section *gnu_hash;
Section *dynsym = s1->dynsym;
Elf32_Word *ptr;
gnu_hash = new_section(s1, ".gnu.hash", SHT_GNU_HASH, SHF_ALLOC);
gnu_hash->link = dynsym->hash->link;
nb_syms = dynsym->data_offset / sizeof(ElfW(Sym));
/* count def symbols */
ndef = 0;
p = (ElfW(Sym) *)dynsym->data;
for(i = 0; i < nb_syms; i++, p++)
ndef += p->st_shndx != SHN_UNDEF;
/* calculate gnu hash sizes and fill header */
nbuckets = ndef / 4 + 1;
symoffset = nb_syms - ndef;
bloom_shift = PTR_SIZE == 8 ? 6 : 5;
bloom_size = 1; /* must be power of two */
while (ndef >= bloom_size * (1 << (bloom_shift - 3)))
bloom_size *= 2;
ptr = section_ptr_add(gnu_hash, 4 * 4 +
PTR_SIZE * bloom_size +
nbuckets * 4 +
ndef * 4);
ptr[0] = nbuckets;
ptr[1] = symoffset;
ptr[2] = bloom_size;
ptr[3] = bloom_shift;
return gnu_hash;
}
static Elf32_Word elf_gnu_hash (const unsigned char *name)
{
Elf32_Word h = 5381;
unsigned char c;
while ((c = *name++))
h = h * 33 + c;
return h;
}
static void update_gnu_hash(TCCState *s1, Section *gnu_hash)
{
int *old_to_new_syms;
ElfW(Sym) *new_syms;
int nb_syms, i, nbuckets, bloom_size, bloom_shift;
ElfW(Sym) *p, *q;
Section *vs;
Section *dynsym = s1->dynsym;
Elf32_Word *ptr, *buckets, *chain, *hash;
unsigned int *nextbuck;
addr_t *bloom;
unsigned char *strtab;
struct { int first, last; } *buck;
strtab = dynsym->link->data;
nb_syms = dynsym->data_offset / sizeof(ElfW(Sym));
new_syms = tcc_malloc(nb_syms * sizeof(ElfW(Sym)));
old_to_new_syms = tcc_malloc(nb_syms * sizeof(int));
hash = tcc_malloc(nb_syms * sizeof(Elf32_Word));
nextbuck = tcc_malloc(nb_syms * sizeof(int));
/* calculate hashes and copy undefs */
p = (ElfW(Sym) *)dynsym->data;
q = new_syms;
for(i = 0; i < nb_syms; i++, p++) {
if (p->st_shndx == SHN_UNDEF) {
old_to_new_syms[i] = q - new_syms;
*q++ = *p;
}
else
hash[i] = elf_gnu_hash(strtab + p->st_name);
}
ptr = (Elf32_Word *) gnu_hash->data;
nbuckets = ptr[0];
bloom_size = ptr[2];
bloom_shift = ptr[3];
bloom = (addr_t *) (void *) &ptr[4];
buckets = (Elf32_Word*) (void *) &bloom[bloom_size];
chain = &buckets[nbuckets];
buck = tcc_malloc(nbuckets * sizeof(*buck));
if (gnu_hash->data_offset != 4 * 4 +
PTR_SIZE * bloom_size +
nbuckets * 4 +
(nb_syms - (q - new_syms)) * 4)
tcc_error_noabort ("gnu_hash size incorrect");
/* find buckets */
for(i = 0; i < nbuckets; i++)
buck[i].first = -1;
p = (ElfW(Sym) *)dynsym->data;
for(i = 0; i < nb_syms; i++, p++)
if (p->st_shndx != SHN_UNDEF) {
int bucket = hash[i] % nbuckets;
if (buck[bucket].first == -1)
buck[bucket].first = buck[bucket].last = i;
else {
nextbuck[buck[bucket].last] = i;
buck[bucket].last = i;
}
}
/* fill buckets/chains/bloom and sort symbols */
p = (ElfW(Sym) *)dynsym->data;
for(i = 0; i < nbuckets; i++) {
int cur = buck[i].first;
if (cur != -1) {
buckets[i] = q - new_syms;
for (;;) {
old_to_new_syms[cur] = q - new_syms;
*q++ = p[cur];