Alien-TinyCCx
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src/tccelf.c view on Meta::CPAN
/*
* 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 */
ST_DATA Section *text_section, *data_section, *bss_section; /* predefined sections */
ST_DATA Section *cur_text_section; /* current section where function code is generated */
#ifdef CONFIG_TCC_ASM
ST_DATA Section *last_text_section; /* to handle .previous asm directive */
#endif
#ifdef CONFIG_TCC_BCHECK
/* bound check related sections */
ST_DATA Section *bounds_section; /* contains global data bound description */
ST_DATA Section *lbounds_section; /* contains local data bound description */
#endif
/* symbol sections */
ST_DATA Section *symtab_section, *strtab_section;
/* debug sections */
ST_DATA Section *stab_section, *stabstr_section;
/* XXX: avoid static variable */
static int new_undef_sym = 0; /* Is there a new undefined sym since last new_undef_sym() */
/* ------------------------------------------------------------------------- */
ST_FUNC void tccelf_new(TCCState *s)
{
/* no section zero */
dynarray_add((void ***)&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);
bss_section = new_section(s, ".bss", SHT_NOBITS, SHF_ALLOC | SHF_WRITE);
/* symbols are always generated for linking stage */
symtab_section = new_symtab(s, ".symtab", SHT_SYMTAB, 0,
".strtab",
".hashtab", SHF_PRIVATE);
strtab_section = symtab_section->link;
s->symtab = symtab_section;
/* private symbol table for dynamic symbols */
s->dynsymtab_section = new_symtab(s, ".dynsymtab", SHT_SYMTAB, SHF_PRIVATE,
".dynstrtab",
".dynhashtab", SHF_PRIVATE);
}
#ifdef CONFIG_TCC_BCHECK
ST_FUNC void tccelf_bounds_new(TCCState *s)
{
/* create bounds sections */
bounds_section = new_section(s, ".bounds",
SHT_PROGBITS, SHF_ALLOC);
lbounds_section = new_section(s, ".lbounds",
SHT_PROGBITS, SHF_ALLOC);
}
#endif
ST_FUNC void tccelf_stab_new(TCCState *s)
{
stab_section = new_section(s, ".stab", SHT_PROGBITS, 0);
stab_section->sh_entsize = sizeof(Stab_Sym);
stabstr_section = new_section(s, ".stabstr", SHT_STRTAB, 0);
put_elf_str(stabstr_section, "");
stab_section->link = stabstr_section;
/* put first entry */
put_stabs("", 0, 0, 0, 0);
}
static void free_section(Section *s)
{
tcc_free(s->data);
src/tccelf.c view on Meta::CPAN
/* 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));
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_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 *) name) % 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;
}
/* find global ELF symbol 'name' and return its index. Return 0 if not
found. */
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 */
ST_FUNC addr_t get_elf_sym_addr(TCCState *s, const char *name, int err)
{
int sym_index;
ElfW(Sym) *sym;
sym_index = find_elf_sym(s->symtab, name);
sym = &((ElfW(Sym) *)s->symtab->data)[sym_index];
if (!sym_index || sym->st_shndx == SHN_UNDEF) {
if (err)
tcc_error("%s not defined", name);
return 0;
}
return sym->st_value;
}
/* return elf symbol value */
LIBTCCAPI void *tcc_get_symbol(TCCState *s, const char *name)
{
return (void*)(uintptr_t)get_elf_sym_addr(s, name, 0);
}
#if defined TCC_IS_NATIVE || defined TCC_TARGET_PE
/* return elf symbol value or error */
ST_FUNC void* tcc_get_symbol_err(TCCState *s, const char *name)
{
return (void*)(uintptr_t)get_elf_sym_addr(s, name, 1);
}
#endif
/* 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 add_elf_sym(Section *s, addr_t value, unsigned long size,
int info, int other, int sh_num, const char *name)
{
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_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;
other = esym->st_other; /* in case we have to patch esym */
if (sh_num == 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)
&& (sh_num < SHN_LORESERVE
&& sh_num != bss_section->sh_num)) {
/* data symbol gets precedence over common/bss */
goto do_patch;
} else if (sh_num == SHN_COMMON || sh_num == bss_section->sh_num) {
/* data symbol keeps precedence over common/bss */
} else if (s == tcc_state->dynsymtab_section) {
/* we accept that two DLL define the same symbol */
} 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, sh_num, new_vis, esym_bind, esym->st_shndx, esym_vis);
#endif
tcc_error_noabort("'%s' defined twice", name);
}
} else {
do_patch:
esym->st_info = ELFW(ST_INFO)(sym_bind, sym_type);
esym->st_shndx = sh_num;
new_undef_sym = 1;
esym->st_value = value;
esym->st_size = size;
esym->st_other = other;
}
} else {
do_def:
sym_index = put_elf_sym(s, value, size,
ELFW(ST_INFO)(sym_bind, sym_type), other,
sh_num, 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)
{
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(tcc_state, 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));
src/tccelf.c view on Meta::CPAN
rel->r_info = ELFW(R_INFO)(symbol, type);
#if defined(TCC_TARGET_ARM64) || defined(TCC_TARGET_X86_64)
rel->r_addend = addend;
#else
if (addend)
tcc_error("non-zero addend on REL architecture");
#endif
}
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);
}
/* put stab debug information */
ST_FUNC void put_stabs(const char *str, int type, int other, int desc,
unsigned long value)
{
Stab_Sym *sym;
sym = section_ptr_add(stab_section, sizeof(Stab_Sym));
if (str) {
sym->n_strx = put_elf_str(stabstr_section, str);
} else {
sym->n_strx = 0;
}
sym->n_type = type;
sym->n_other = other;
sym->n_desc = desc;
sym->n_value = value;
}
ST_FUNC void put_stabs_r(const char *str, int type, int other, int desc,
unsigned long value, Section *sec, int sym_index)
{
put_stabs(str, type, other, desc, value);
put_elf_reloc(symtab_section, stab_section,
stab_section->data_offset - sizeof(unsigned int),
R_DATA_32, sym_index);
}
ST_FUNC void put_stabn(int type, int other, int desc, int value)
{
put_stabs(NULL, type, other, desc, value);
}
ST_FUNC void put_stabd(int type, int other, int desc)
{
put_stabs(NULL, type, other, desc, 0);
}
/* Browse each elem of type <type> in section <sec> starting at elem <startoff>
using variable <elem> */
#define for_each_elem(sec, startoff, elem, type) \
for (elem = (type *) sec->data + startoff; \
elem < (type *) (sec->data + sec->data_offset); elem++)
/* 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;
ElfW_Rel *rel;
Section *sr;
int type, sym_index;
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 */
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);
/* now we modify all the relocations */
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);
sym_index = old_to_new_syms[sym_index];
rel->r_info = ELFW(R_INFO)(sym_index, type);
}
}
}
tcc_free(old_to_new_syms);
}
/* relocate common symbols in the .bss section */
src/tccelf.c view on Meta::CPAN
+ dynsym->st_name;
put_elf_sym(s1->dynsym, offset, dynsym->st_size,
dynsym->st_info, 0,
bss_section->sh_num, dynname);
break;
}
}
}
put_elf_reloc(s1->dynsym, bss_section,
offset, R_COPY, index);
offset += esym->st_size;
bss_section->data_offset = offset;
}
} else {
/* STB_WEAK undefined symbols are accepted */
/* XXX: _fp_hw seems to be part of the ABI, so we ignore it */
if (ELFW(ST_BIND)(sym->st_info) == STB_WEAK ||
!strcmp(name, "_fp_hw")) {
} else {
tcc_error_noabort("undefined symbol '%s'", name);
}
}
} else if (s1->rdynamic && ELFW(ST_BIND)(sym->st_info) != STB_LOCAL) {
/* if -rdynamic option, then export all non local symbols */
name = (char *) symtab_section->link->data + sym->st_name;
put_elf_sym(s1->dynsym, sym->st_value, sym->st_size, sym->st_info,
0, sym->st_shndx, name);
}
}
}
/* Bind symbols of libraries: export non local symbols of executable that
resolve undefined symbols of shared libraries */
static void bind_libs_dynsyms(TCCState *s1)
{
const char *name;
int sym_index;
ElfW(Sym) *sym, *esym;
/* now look at unresolved dynamic symbols and export
corresponding symbol */
for_each_elem(s1->dynsymtab_section, 1, esym, ElfW(Sym)) {
name = (char *) s1->dynsymtab_section->link->data + esym->st_name;
sym_index = find_elf_sym(symtab_section, name);
if (sym_index) {
/* XXX: avoid adding a symbol if already present because of
-rdynamic ? */
sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
if (sym->st_shndx != SHN_UNDEF)
put_elf_sym(s1->dynsym, sym->st_value, sym->st_size,
sym->st_info, 0, sym->st_shndx, name);
} else if (esym->st_shndx == SHN_UNDEF) {
/* weak symbols can stay undefined */
if (ELFW(ST_BIND)(esym->st_info) != STB_WEAK)
tcc_warning("undefined dynamic symbol '%s'", name);
}
}
}
/* Export all non local symbols (for shared libraries) */
static void export_global_syms(TCCState *s1)
{
int nb_syms, dynindex, index;
const char *name;
ElfW(Sym) *sym;
nb_syms = symtab_section->data_offset / sizeof(ElfW(Sym));
s1->symtab_to_dynsym = tcc_mallocz(sizeof(int) * nb_syms);
for_each_elem(symtab_section, 1, sym, ElfW(Sym)) {
if (ELFW(ST_BIND)(sym->st_info) != STB_LOCAL) {
name = (char *) symtab_section->link->data + sym->st_name;
dynindex = put_elf_sym(s1->dynsym, sym->st_value, sym->st_size,
sym->st_info, 0, sym->st_shndx, name);
index = sym - (ElfW(Sym) *) symtab_section->data;
s1->symtab_to_dynsym[index] = dynindex;
}
}
}
/* relocate the PLT: compute addresses and offsets in the PLT now that final
address for PLT and GOT are known (see fill_program_header) */
ST_FUNC void relocate_plt(TCCState *s1)
{
uint8_t *p, *p_end;
if (!s1->plt)
return;
p = s1->plt->data;
p_end = p + s1->plt->data_offset;
if (p < p_end) {
#if defined(TCC_TARGET_I386)
add32le(p + 2, s1->got->sh_addr);
add32le(p + 8, s1->got->sh_addr);
p += 16;
while (p < p_end) {
add32le(p + 2, s1->got->sh_addr);
p += 16;
}
#elif defined(TCC_TARGET_X86_64)
int x = s1->got->sh_addr - s1->plt->sh_addr - 6;
add32le(p + 2, x);
add32le(p + 8, x - 6);
p += 16;
while (p < p_end) {
add32le(p + 2, x + s1->plt->data - p);
p += 16;
}
#elif defined(TCC_TARGET_ARM)
int x = s1->got->sh_addr - s1->plt->sh_addr - 12;
p += 16;
while (p < p_end) {
if (read32le(p) == 0x46c04778) /* PLT Thumb stub present */
p += 4;
add32le(p + 12, x + s1->plt->data - p);
p += 16;
}
#elif defined(TCC_TARGET_ARM64)
uint64_t plt = s1->plt->sh_addr;
uint64_t got = s1->got->sh_addr;
uint64_t off = (got >> 12) - (plt >> 12);
src/tccelf.c view on Meta::CPAN
struct dyn_inf dyninf;
ElfW(Phdr) *phdr;
ElfW(Sym) *sym;
Section *strsec, *interp, *dynamic, *dynstr;
file_type = s1->output_type;
s1->nb_errors = 0;
/* if linking, also link in runtime libraries (libc, libgcc, etc.) */
if (file_type != TCC_OUTPUT_OBJ) {
tcc_add_runtime(s1);
}
phdr = NULL;
sec_order = NULL;
interp = dynamic = dynstr = NULL; /* avoid warning */
dyninf.dyn_rel_off = 0; /* avoid warning */
if (file_type != TCC_OUTPUT_OBJ) {
relocate_common_syms();
tcc_add_linker_symbols(s1);
if (!s1->static_link) {
if (file_type == TCC_OUTPUT_EXE) {
char *ptr;
/* allow override the dynamic loader */
const char *elfint = getenv("LD_SO");
if (elfint == NULL)
elfint = DEFAULT_ELFINTERP(s1);
/* add interpreter section only if executable */
interp = new_section(s1, ".interp", SHT_PROGBITS, SHF_ALLOC);
interp->sh_addralign = 1;
ptr = section_ptr_add(interp, 1 + strlen(elfint));
strcpy(ptr, elfint);
}
/* add dynamic symbol table */
s1->dynsym = new_symtab(s1, ".dynsym", SHT_DYNSYM, SHF_ALLOC,
".dynstr",
".hash", SHF_ALLOC);
dynstr = s1->dynsym->link;
/* add dynamic section */
dynamic = new_section(s1, ".dynamic", SHT_DYNAMIC,
SHF_ALLOC | SHF_WRITE);
dynamic->link = dynstr;
dynamic->sh_entsize = sizeof(ElfW(Dyn));
build_got(s1);
if (file_type == TCC_OUTPUT_EXE) {
bind_exe_dynsyms(s1);
if (s1->nb_errors) {
ret = -1;
goto the_end;
}
bind_libs_dynsyms(s1);
} else /* shared library case: simply export all global symbols */
export_global_syms(s1);
build_got_entries(s1);
/* add a list of needed dlls */
for(i = 0; i < s1->nb_loaded_dlls; i++) {
DLLReference *dllref = s1->loaded_dlls[i];
if (dllref->level == 0)
put_dt(dynamic, DT_NEEDED, put_elf_str(dynstr, dllref->name));
}
if (s1->rpath)
put_dt(dynamic, DT_RPATH, put_elf_str(dynstr, s1->rpath));
/* XXX: currently, since we do not handle PIC code, we
must relocate the readonly segments */
if (file_type == TCC_OUTPUT_DLL) {
if (s1->soname)
put_dt(dynamic, DT_SONAME, put_elf_str(dynstr, s1->soname));
put_dt(dynamic, DT_TEXTREL, 0);
}
if (s1->symbolic)
put_dt(dynamic, DT_SYMBOLIC, 0);
/* add necessary space for other entries */
dyninf.dyn_rel_off = dynamic->data_offset;
dynamic->data_offset += sizeof(ElfW(Dyn)) * EXTRA_RELITEMS;
} else {
/* still need to build got entries in case of static link */
build_got_entries(s1);
}
}
/* we add a section for symbols */
strsec = new_section(s1, ".shstrtab", SHT_STRTAB, 0);
put_elf_str(strsec, "");
/* compute number of sections */
shnum = s1->nb_sections;
/* this array is used to reorder sections in the output file */
sec_order = tcc_malloc(sizeof(int) * shnum);
sec_order[0] = 0;
/* compute number of program headers */
switch(file_type) {
default:
case TCC_OUTPUT_OBJ:
phnum = 0;
break;
case TCC_OUTPUT_EXE:
if (!s1->static_link)
phnum = 4 + HAVE_PHDR;
else
phnum = 2;
break;
case TCC_OUTPUT_DLL:
phnum = 3;
break;
}
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