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ebaa5c81f4
tinycc/x86_64-link.c
grischka ebaa5c81f4 dynamic executables (PIE) 
Allows to create dynamic executables, using the code path
for TCC_OUTPUT_DLL but add an .interp header (plus a FLAGS_1
entry in the dynamic section to make 'readelf' say "PIE")

Introduces TCC_OUTPUT_DYN as alias for TCC_OUTPUT_DLL.
There is no runtime option,  only one to configure:

    ./configure --config-pie

100 insertions(+), 76 deletions(-)
2022-07-24 09:44:50 +02:00

400 lines
13 KiB
C
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#ifdef TARGET_DEFS_ONLY
#define EM_TCC_TARGET EM_X86_64
/* relocation type for 32 bit data relocation */
#define R_DATA_32 R_X86_64_32S
#define R_DATA_PTR R_X86_64_64
#define R_JMP_SLOT R_X86_64_JUMP_SLOT
#define R_GLOB_DAT R_X86_64_GLOB_DAT
#define R_COPY R_X86_64_COPY
#define R_RELATIVE R_X86_64_RELATIVE
#define R_NUM R_X86_64_NUM
#define ELF_START_ADDR 0x400000
#define ELF_PAGE_SIZE 0x200000
#define PCRELATIVE_DLLPLT 1
#define RELOCATE_DLLPLT 1
#else /* !TARGET_DEFS_ONLY */
#include "tcc.h"
#ifdef NEED_RELOC_TYPE
/* Returns 1 for a code relocation, 0 for a data relocation. For unknown
relocations, returns -1. */
int code_reloc (int reloc_type)
{
switch (reloc_type) {
case R_X86_64_32:
case R_X86_64_32S:
case R_X86_64_64:
case R_X86_64_GOTPC32:
case R_X86_64_GOTPC64:
case R_X86_64_GOTPCREL:
case R_X86_64_GOTPCRELX:
case R_X86_64_REX_GOTPCRELX:
case R_X86_64_GOTTPOFF:
case R_X86_64_GOT32:
case R_X86_64_GOT64:
case R_X86_64_GLOB_DAT:
case R_X86_64_COPY:
case R_X86_64_RELATIVE:
case R_X86_64_GOTOFF64:
case R_X86_64_TLSGD:
case R_X86_64_TLSLD:
case R_X86_64_DTPOFF32:
case R_X86_64_TPOFF32:
case R_X86_64_DTPOFF64:
case R_X86_64_TPOFF64:
return 0;
case R_X86_64_PC32:
case R_X86_64_PC64:
case R_X86_64_PLT32:
case R_X86_64_PLTOFF64:
case R_X86_64_JUMP_SLOT:
return 1;
}
return -1;
}
/* Returns an enumerator to describe whether and when the relocation needs a
GOT and/or PLT entry to be created. See tcc.h for a description of the
different values. */
int gotplt_entry_type (int reloc_type)
{
switch (reloc_type) {
case R_X86_64_GLOB_DAT:
case R_X86_64_JUMP_SLOT:
case R_X86_64_COPY:
case R_X86_64_RELATIVE:
return NO_GOTPLT_ENTRY;
/* The following relocs wouldn't normally need GOT or PLT
slots, but we need them for simplicity in the link
editor part. See our caller for comments. */
case R_X86_64_32:
case R_X86_64_32S:
case R_X86_64_64:
case R_X86_64_PC32:
case R_X86_64_PC64:
return AUTO_GOTPLT_ENTRY;
case R_X86_64_GOTTPOFF:
return BUILD_GOT_ONLY;
case R_X86_64_GOT32:
case R_X86_64_GOT64:
case R_X86_64_GOTPC32:
case R_X86_64_GOTPC64:
case R_X86_64_GOTOFF64:
case R_X86_64_GOTPCREL:
case R_X86_64_GOTPCRELX:
case R_X86_64_TLSGD:
case R_X86_64_TLSLD:
case R_X86_64_DTPOFF32:
case R_X86_64_TPOFF32:
case R_X86_64_DTPOFF64:
case R_X86_64_TPOFF64:
case R_X86_64_REX_GOTPCRELX:
case R_X86_64_PLT32:
case R_X86_64_PLTOFF64:
return ALWAYS_GOTPLT_ENTRY;
}
return -1;
}
#ifdef NEED_BUILD_GOT
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;
modrm = 0x25;
/* empty PLT: create PLT0 entry that pushes the library identifier
(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->plt->reloc ? s1->plt->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 */
/* On x86-64, the relocation is referred to by _index_ */
write32le(p + 7, relofs / sizeof (ElfW_Rel) - 1);
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) {
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;
}
}
if (s1->plt->reloc) {
ElfW_Rel *rel;
int x = s1->plt->sh_addr + 16 + 6;
p = s1->got->data;
for_each_elem(s1->plt->reloc, 0, rel, ElfW_Rel) {
write64le(p + rel->r_offset, x);
x += 16;
}
}
}
#endif
#endif
void relocate(TCCState *s1, ElfW_Rel *rel, int type, unsigned char *ptr, addr_t addr, addr_t val)
{
int sym_index, esym_index;
sym_index = ELFW(R_SYM)(rel->r_info);
switch (type) {
case R_X86_64_64:
if (s1->output_type & TCC_OUTPUT_DYN) {
esym_index = get_sym_attr(s1, sym_index, 0)->dyn_index;
qrel->r_offset = rel->r_offset;
if (esym_index) {
qrel->r_info = ELFW(R_INFO)(esym_index, R_X86_64_64);
qrel->r_addend = rel->r_addend;
qrel++;
break;
} else {
qrel->r_info = ELFW(R_INFO)(0, R_X86_64_RELATIVE);
qrel->r_addend = read64le(ptr) + val;
qrel++;
}
}
add64le(ptr, val);
break;
case R_X86_64_32:
case R_X86_64_32S:
if (s1->output_type & TCC_OUTPUT_DYN) {
/* XXX: this logic may depend on TCC's codegen
now TCC uses R_X86_64_32 even for a 64bit pointer */
qrel->r_offset = rel->r_offset;
qrel->r_info = ELFW(R_INFO)(0, R_X86_64_RELATIVE);
/* Use sign extension! */
qrel->r_addend = (int)read32le(ptr) + val;
qrel++;
}
add32le(ptr, val);
break;
case R_X86_64_PC32:
if (s1->output_type == TCC_OUTPUT_DLL) {
/* DLL relocation */
esym_index = get_sym_attr(s1, sym_index, 0)->dyn_index;
if (esym_index) {
qrel->r_offset = rel->r_offset;
qrel->r_info = ELFW(R_INFO)(esym_index, R_X86_64_PC32);
/* Use sign extension! */
qrel->r_addend = (int)read32le(ptr) + rel->r_addend;
qrel++;
break;
}
}
goto plt32pc32;
case R_X86_64_PLT32:
/* fallthrough: val already holds the PLT slot address */
plt32pc32:
{
long long diff;
diff = (long long)val - addr;
if (diff < -2147483648LL || diff > 2147483647LL) {
tcc_error("internal error: relocation failed");
}
add32le(ptr, diff);
}
break;
case R_X86_64_COPY:
break;
case R_X86_64_PLTOFF64:
add64le(ptr, val - s1->got->sh_addr + rel->r_addend);
break;
case R_X86_64_PC64:
if (s1->output_type == TCC_OUTPUT_DLL) {
/* DLL relocation */
esym_index = get_sym_attr(s1, sym_index, 0)->dyn_index;
if (esym_index) {
qrel->r_offset = rel->r_offset;
qrel->r_info = ELFW(R_INFO)(esym_index, R_X86_64_PC64);
qrel->r_addend = read64le(ptr) + rel->r_addend;
qrel++;
break;
}
}
add64le(ptr, val - addr);
break;
case R_X86_64_GLOB_DAT:
case R_X86_64_JUMP_SLOT:
/* They don't need addend */
write64le(ptr, val - rel->r_addend);
break;
case R_X86_64_GOTPCREL:
case R_X86_64_GOTPCRELX:
case R_X86_64_REX_GOTPCRELX:
add32le(ptr, s1->got->sh_addr - addr +
get_sym_attr(s1, sym_index, 0)->got_offset - 4);
break;
case R_X86_64_GOTPC32:
add32le(ptr, s1->got->sh_addr - addr + rel->r_addend);
break;
case R_X86_64_GOTPC64:
add64le(ptr, s1->got->sh_addr - addr + rel->r_addend);
break;
case R_X86_64_GOTTPOFF:
add32le(ptr, val - s1->got->sh_addr);
break;
case R_X86_64_GOT32:
/* we load the got offset */
add32le(ptr, get_sym_attr(s1, sym_index, 0)->got_offset);
break;
case R_X86_64_GOT64:
/* we load the got offset */
add64le(ptr, get_sym_attr(s1, sym_index, 0)->got_offset);
break;
case R_X86_64_GOTOFF64:
add64le(ptr, val - s1->got->sh_addr);
break;
case R_X86_64_TLSGD:
{
static const unsigned char expect[] = {
/* .byte 0x66; lea 0(%rip),%rdi */
0x66, 0x48, 0x8d, 0x3d, 0x00, 0x00, 0x00, 0x00,
/* .word 0x6666; rex64; call __tls_get_addr@PLT */
0x66, 0x66, 0x48, 0xe8, 0x00, 0x00, 0x00, 0x00 };
static const unsigned char replace[] = {
/* mov %fs:0,%rax */
0x64, 0x48, 0x8b, 0x04, 0x25, 0x00, 0x00, 0x00, 0x00,
/* lea -4(%rax),%rax */
0x48, 0x8d, 0x80, 0x00, 0x00, 0x00, 0x00 };
if (memcmp (ptr-4, expect, sizeof(expect)) == 0) {
ElfW(Sym) *sym;
Section *sec;
int32_t x;
memcpy(ptr-4, replace, sizeof(replace));
rel[1].r_info = ELFW(R_INFO)(0, R_X86_64_NONE);
sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
sec = s1->sections[sym->st_shndx];
x = sym->st_value - sec->sh_addr - sec->data_offset;
add32le(ptr + 8, x);
}
else
tcc_error("unexpected R_X86_64_TLSGD pattern");
}
break;
case R_X86_64_TLSLD:
{
static const unsigned char expect[] = {
/* lea 0(%rip),%rdi */
0x48, 0x8d, 0x3d, 0x00, 0x00, 0x00, 0x00,
/* call __tls_get_addr@PLT */
0xe8, 0x00, 0x00, 0x00, 0x00 };
static const unsigned char replace[] = {
/* data16 data16 data16 mov %fs:0,%rax */
0x66, 0x66, 0x66, 0x64, 0x48, 0x8b, 0x04, 0x25,
0x00, 0x00, 0x00, 0x00 };
if (memcmp (ptr-3, expect, sizeof(expect)) == 0) {
memcpy(ptr-3, replace, sizeof(replace));
rel[1].r_info = ELFW(R_INFO)(0, R_X86_64_NONE);
}
else
tcc_error("unexpected R_X86_64_TLSLD pattern");
}
break;
case R_X86_64_DTPOFF32:
case R_X86_64_TPOFF32:
{
ElfW(Sym) *sym;
Section *sec;
int32_t x;
sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
sec = s1->sections[sym->st_shndx];
x = val - sec->sh_addr - sec->data_offset;
add32le(ptr, x);
}
break;
case R_X86_64_DTPOFF64:
case R_X86_64_TPOFF64:
{
ElfW(Sym) *sym;
Section *sec;
int32_t x;
sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
sec = s1->sections[sym->st_shndx];
x = val - sec->sh_addr - sec->data_offset;
add64le(ptr, x);
}
break;
case R_X86_64_NONE:
break;
case R_X86_64_RELATIVE:
#ifdef TCC_TARGET_PE
add32le(ptr, val - s1->pe_imagebase);
#endif
/* do nothing */
break;
default:
fprintf(stderr,"FIXME: handle reloc type %d at %x [%p] to %x\n",
type, (unsigned)addr, ptr, (unsigned)val);
break;
}
}
#endif /* !TARGET_DEFS_ONLY */
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