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106 lines
2.7 KiB
C
106 lines
2.7 KiB
C
#include <elf.h>
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#include <link.h>
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#include <limits.h>
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#include <stdint.h>
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#include <string.h>
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#include <sys/auxv.h>
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#include "syscall.h"
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#ifdef VDSO_USEFUL
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#if ULONG_MAX == 0xffffffff
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typedef Elf32_Ehdr Ehdr;
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typedef Elf32_Phdr Phdr;
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typedef Elf32_Sym Sym;
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typedef Elf32_Verdef Verdef;
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typedef Elf32_Verdaux Verdaux;
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#else
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typedef Elf64_Ehdr Ehdr;
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typedef Elf64_Phdr Phdr;
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typedef Elf64_Sym Sym;
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typedef Elf64_Verdef Verdef;
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typedef Elf64_Verdaux Verdaux;
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#endif
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static int checkver(Verdef *def, int vsym, const char *vername, char *strings)
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{
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vsym &= 0x7fff;
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for (;;) {
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if (!(def->vd_flags & VER_FLG_BASE)
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&& (def->vd_ndx & 0x7fff) == vsym)
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break;
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if (def->vd_next == 0)
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return 0;
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def = (Verdef *)((char *)def + def->vd_next);
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}
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Verdaux *aux = (Verdaux *)((char *)def + def->vd_aux);
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return !strcmp(vername, strings + aux->vda_name);
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}
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#define OK_TYPES (1<<STT_NOTYPE | 1<<STT_OBJECT | 1<<STT_FUNC | 1<<STT_COMMON)
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#define OK_BINDS (1<<STB_GLOBAL | 1<<STB_WEAK | 1<<STB_GNU_UNIQUE)
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extern char** environ;
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static Ehdr *eh = NULL;
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void *__vdsosym(const char *vername, const char *name);
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// We don't have libc struct available here. Compute aux vector manually.
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__attribute__((constructor)) static void auxv_init()
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{
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size_t i, *auxv;
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for (i=0; environ[i]; i++);
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auxv = (void *)(environ+i+1);
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for (i=0; auxv[i] != AT_SYSINFO_EHDR; i+=2)
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if (!auxv[i]) return;
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if (!auxv[i+1]) return;
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eh = (void *)auxv[i+1];
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}
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void *__vdsosym(const char *vername, const char *name)
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{
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size_t i;
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if (!eh) return 0;
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Phdr *ph = (void *)((char *)eh + eh->e_phoff);
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size_t *dynv=0, base=-1;
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for (i=0; i<eh->e_phnum; i++, ph=(void *)((char *)ph+eh->e_phentsize)) {
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if (ph->p_type == PT_LOAD)
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base = (size_t)eh + ph->p_offset - ph->p_vaddr;
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else if (ph->p_type == PT_DYNAMIC)
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dynv = (void *)((char *)eh + ph->p_offset);
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}
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if (!dynv || base==(size_t)-1) return 0;
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char *strings = 0;
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Sym *syms = 0;
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Elf_Symndx *hashtab = 0;
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uint16_t *versym = 0;
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Verdef *verdef = 0;
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for (i=0; dynv[i]; i+=2) {
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void *p = (void *)(base + dynv[i+1]);
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switch(dynv[i]) {
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case DT_STRTAB: strings = p; break;
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case DT_SYMTAB: syms = p; break;
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case DT_HASH: hashtab = p; break;
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case DT_VERSYM: versym = p; break;
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case DT_VERDEF: verdef = p; break;
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}
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}
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if (!strings || !syms || !hashtab) return 0;
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if (!verdef) versym = 0;
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for (i=0; i<hashtab[1]; i++) {
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if (!(1<<(syms[i].st_info&0xf) & OK_TYPES)) continue;
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if (!(1<<(syms[i].st_info>>4) & OK_BINDS)) continue;
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if (!syms[i].st_shndx) continue;
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if (strcmp(name, strings+syms[i].st_name)) continue;
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if (versym && !checkver(verdef, versym[i], vername, strings))
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continue;
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return (void *)(base + syms[i].st_value);
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}
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return 0;
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}
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#endif
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