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Support PIE (Position Independent Executables)
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#include <stddef.h> | ||
#include "dynlink.h" | ||
#include "libc.h" | ||
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#ifndef START | ||
#define START "_dlstart" | ||
#endif | ||
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#define SHARED | ||
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#include "crt_arch.h" | ||
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#ifndef GETFUNCSYM | ||
#define GETFUNCSYM(fp, sym, got) do { \ | ||
hidden void sym(); \ | ||
static void (*static_func_ptr)() = sym; \ | ||
__asm__ __volatile__ ( "" : "+m"(static_func_ptr) : : "memory"); \ | ||
*(fp) = static_func_ptr; } while(0) | ||
#endif | ||
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hidden void _dlstart_c(size_t *sp, size_t *dynv) | ||
{ | ||
size_t i, aux[AUX_CNT], dyn[DYN_CNT]; | ||
size_t *rel, rel_size, base; | ||
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int argc = *sp; | ||
char **argv = (void *)(sp+1); | ||
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for (i=argc+1; argv[i]; i++); | ||
size_t *auxv = (void *)(argv+i+1); | ||
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for (i=0; i<AUX_CNT; i++) aux[i] = 0; | ||
for (i=0; auxv[i]; i+=2) if (auxv[i]<AUX_CNT) | ||
aux[auxv[i]] = auxv[i+1]; | ||
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#if DL_FDPIC | ||
struct fdpic_loadseg *segs, fakeseg; | ||
size_t j; | ||
if (dynv) { | ||
/* crt_arch.h entry point asm is responsible for reserving | ||
* space and moving the extra fdpic arguments to the stack | ||
* vector where they are easily accessible from C. */ | ||
segs = ((struct fdpic_loadmap *)(sp[-1] ? sp[-1] : sp[-2]))->segs; | ||
} else { | ||
/* If dynv is null, the entry point was started from loader | ||
* that is not fdpic-aware. We can assume normal fixed- | ||
* displacement ELF loading was performed, but when ldso was | ||
* run as a command, finding the Ehdr is a heursitic: we | ||
* have to assume Phdrs start in the first 4k of the file. */ | ||
base = aux[AT_BASE]; | ||
if (!base) base = aux[AT_PHDR] & -4096; | ||
segs = &fakeseg; | ||
segs[0].addr = base; | ||
segs[0].p_vaddr = 0; | ||
segs[0].p_memsz = -1; | ||
Ehdr *eh = (void *)base; | ||
Phdr *ph = (void *)(base + eh->e_phoff); | ||
size_t phnum = eh->e_phnum; | ||
size_t phent = eh->e_phentsize; | ||
while (phnum-- && ph->p_type != PT_DYNAMIC) | ||
ph = (void *)((size_t)ph + phent); | ||
dynv = (void *)(base + ph->p_vaddr); | ||
} | ||
#endif | ||
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for (i=0; i<DYN_CNT; i++) dyn[i] = 0; | ||
for (i=0; dynv[i]; i+=2) if (dynv[i]<DYN_CNT) | ||
dyn[dynv[i]] = dynv[i+1]; | ||
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#if DL_FDPIC | ||
for (i=0; i<DYN_CNT; i++) { | ||
if (i==DT_RELASZ || i==DT_RELSZ) continue; | ||
if (!dyn[i]) continue; | ||
for (j=0; dyn[i]-segs[j].p_vaddr >= segs[j].p_memsz; j++); | ||
dyn[i] += segs[j].addr - segs[j].p_vaddr; | ||
} | ||
base = 0; | ||
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const Sym *syms = (void *)dyn[DT_SYMTAB]; | ||
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rel = (void *)dyn[DT_RELA]; | ||
rel_size = dyn[DT_RELASZ]; | ||
for (; rel_size; rel+=3, rel_size-=3*sizeof(size_t)) { | ||
if (!IS_RELATIVE(rel[1], syms)) continue; | ||
for (j=0; rel[0]-segs[j].p_vaddr >= segs[j].p_memsz; j++); | ||
size_t *rel_addr = (void *) | ||
(rel[0] + segs[j].addr - segs[j].p_vaddr); | ||
if (R_TYPE(rel[1]) == REL_FUNCDESC_VAL) { | ||
*rel_addr += segs[rel_addr[1]].addr | ||
- segs[rel_addr[1]].p_vaddr | ||
+ syms[R_SYM(rel[1])].st_value; | ||
rel_addr[1] = dyn[DT_PLTGOT]; | ||
} else { | ||
size_t val = syms[R_SYM(rel[1])].st_value; | ||
for (j=0; val-segs[j].p_vaddr >= segs[j].p_memsz; j++); | ||
*rel_addr = rel[2] + segs[j].addr - segs[j].p_vaddr + val; | ||
} | ||
} | ||
#else | ||
/* If the dynamic linker is invoked as a command, its load | ||
* address is not available in the aux vector. Instead, compute | ||
* the load address as the difference between &_DYNAMIC and the | ||
* virtual address in the PT_DYNAMIC program header. */ | ||
base = aux[AT_BASE]; | ||
if (!base) { | ||
size_t phnum = aux[AT_PHNUM]; | ||
size_t phentsize = aux[AT_PHENT]; | ||
Phdr *ph = (void *)aux[AT_PHDR]; | ||
for (i=phnum; i--; ph = (void *)((char *)ph + phentsize)) { | ||
if (ph->p_type == PT_DYNAMIC) { | ||
base = (size_t)dynv - ph->p_vaddr; | ||
break; | ||
} | ||
} | ||
} | ||
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/* MIPS uses an ugly packed form for GOT relocations. Since we | ||
* can't make function calls yet and the code is tiny anyway, | ||
* it's simply inlined here. */ | ||
if (NEED_MIPS_GOT_RELOCS) { | ||
size_t local_cnt = 0; | ||
size_t *got = (void *)(base + dyn[DT_PLTGOT]); | ||
for (i=0; dynv[i]; i+=2) if (dynv[i]==DT_MIPS_LOCAL_GOTNO) | ||
local_cnt = dynv[i+1]; | ||
for (i=0; i<local_cnt; i++) got[i] += base; | ||
} | ||
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rel = (void *)(base+dyn[DT_REL]); | ||
rel_size = dyn[DT_RELSZ]; | ||
for (; rel_size; rel+=2, rel_size-=2*sizeof(size_t)) { | ||
if (!IS_RELATIVE(rel[1], 0)) continue; | ||
size_t *rel_addr = (void *)(base + rel[0]); | ||
*rel_addr += base; | ||
} | ||
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rel = (void *)(base+dyn[DT_RELA]); | ||
rel_size = dyn[DT_RELASZ]; | ||
for (; rel_size; rel+=3, rel_size-=3*sizeof(size_t)) { | ||
if (!IS_RELATIVE(rel[1], 0)) continue; | ||
size_t *rel_addr = (void *)(base + rel[0]); | ||
*rel_addr = base + rel[2]; | ||
} | ||
#endif | ||
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stage2_func dls2; | ||
GETFUNCSYM(&dls2, __dls2, base+dyn[DT_PLTGOT]); | ||
dls2((void *)base, sp); | ||
} |
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