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tccelf: some linker cleanup

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- generate and use SYM@PLT for plt addresses
- get rid of patch_dynsym_undef hack (no idea what it did on FreeBSD)
- use sym_attrs instead of symtab_to_dynsym
- special case for function pointers into .so on i386
- libtcc_test: test tcc_add_symbol with data object
- move target specicic code to *-link.c files
- add R_XXX_RELATIVE (needed for PE)
This commit is contained in:
grischka
2016-12-15 17:01:22 +01:00
parent fe6453f8f0
commit ca92bfc3c6
9 changed files with 466 additions and 441 deletions
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75
i386-link.c
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@ -14,8 +14,8 @@
#define ELF_START_ADDR 0x08048000
#define ELF_PAGE_SIZE 0x1000
#define HAVE_SECTION_RELOC
#define PCRELATIVE_DLLPLT 0
#define RELOCATE_DLLPLT 0
#else /* !TARGET_DEFS_ONLY */
@ -26,6 +26,7 @@
int code_reloc (int reloc_type)
{
switch (reloc_type) {
case R_386_RELATIVE:
case R_386_16:
case R_386_32:
case R_386_GOTPC:
@ -53,6 +54,7 @@ int code_reloc (int reloc_type)
int gotplt_entry_type (int reloc_type)
{
switch (reloc_type) {
case R_386_RELATIVE:
case R_386_16:
case R_386_32:
case R_386_GLOB_DAT:
@ -78,6 +80,73 @@ int gotplt_entry_type (int reloc_type)
return -1;
}
ST_FUNC unsigned create_plt_entry(TCCState *s1, unsigned got_offset, struct sym_attr *attr)
{
Section *plt = s1->plt;
uint8_t *p;
int modrm;
unsigned plt_offset, relofs;
/* on i386 if we build a DLL, we add a %ebx offset */
if (s1->output_type == TCC_OUTPUT_DLL)
modrm = 0xa3;
else
modrm = 0x25;
/* empty PLT: create PLT0 entry that pushes the library indentifier
(GOT + PTR_SIZE) and jumps to ld.so resolution routine
(GOT + 2 * PTR_SIZE) */
if (plt->data_offset == 0) {
p = section_ptr_add(plt, 16);
p[0] = 0xff; /* pushl got + PTR_SIZE */
p[1] = modrm + 0x10;
write32le(p + 2, PTR_SIZE);
p[6] = 0xff; /* jmp *(got + PTR_SIZE * 2) */
p[7] = modrm;
write32le(p + 8, PTR_SIZE * 2);
}
plt_offset = plt->data_offset;
/* The PLT slot refers to the relocation entry it needs via offset.
The reloc entry is created below, so its offset is the current
data_offset */
relofs = s1->got->reloc ? s1->got->reloc->data_offset : 0;
/* Jump to GOT entry where ld.so initially put the address of ip + 4 */
p = section_ptr_add(plt, 16);
p[0] = 0xff; /* jmp *(got + x) */
p[1] = modrm;
write32le(p + 2, got_offset);
p[6] = 0x68; /* push $xxx */
write32le(p + 7, relofs);
p[11] = 0xe9; /* jmp plt_start */
write32le(p + 12, -(plt->data_offset));
return plt_offset;
}
/* 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) {
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;
}
}
}
static ElfW_Rel *qrel; /* ptr to next reloc entry reused */
void relocate_init(Section *sr)
@ -94,7 +163,7 @@ void relocate(TCCState *s1, ElfW_Rel *rel, int type, char *ptr, addr_t addr, add
switch (type) {
case R_386_32:
if (s1->output_type == TCC_OUTPUT_DLL) {
esym_index = s1->symtab_to_dynsym[sym_index];
esym_index = s1->sym_attrs[sym_index].dyn_index;
qrel->r_offset = rel->r_offset;
if (esym_index) {
qrel->r_info = ELFW(R_INFO)(esym_index, R_386_32);
@ -110,7 +179,7 @@ void relocate(TCCState *s1, ElfW_Rel *rel, int type, char *ptr, addr_t addr, add
case R_386_PC32:
if (s1->output_type == TCC_OUTPUT_DLL) {
/* DLL relocation */
esym_index = s1->symtab_to_dynsym[sym_index];
esym_index = s1->sym_attrs[sym_index].dyn_index;
if (esym_index) {
qrel->r_offset = rel->r_offset;
qrel->r_info = ELFW(R_INFO)(esym_index, R_386_PC32);