src/internal/vdso.c

   1 #include <elf.h>
   2 #include <limits.h>
   3 #include <stdint.h>
   4 #include <string.h>
   5 #include "libc.h"
   6 #include "syscall.h"
   7
   8 #ifdef VDSO_USEFUL
   9
  10 #if ULONG_MAX == 0xffffffff
  11 typedef Elf32_Ehdr Ehdr;
  12 typedef Elf32_Phdr Phdr;
  13 typedef Elf32_Sym Sym;
  14 typedef Elf32_Verdef Verdef;
  15 typedef Elf32_Verdaux Verdaux;
  16 #else
  17 typedef Elf64_Ehdr Ehdr;
  18 typedef Elf64_Phdr Phdr;
  19 typedef Elf64_Sym Sym;
  20 typedef Elf64_Verdef Verdef;
  21 typedef Elf64_Verdaux Verdaux;
  22 #endif
  23
  24 static int checkver(Verdef *def, int vsym, const char *vername, char *strings)
  25 {
  26         vsym &= 0x7fff;
  27         for (;;) {
  28                 if (!(def->vd_flags & VER_FLG_BASE)
  29                   && (def->vd_ndx & 0x7fff) == vsym)
  30                         break;
  31                 if (def->vd_next == 0)
  32                         return 0;
  33                 def = (Verdef *)((char *)def + def->vd_next);
  34         }
  35         Verdaux *aux = (Verdaux *)((char *)def + def->vd_aux);
  36         return !strcmp(vername, strings + aux->vda_name);
  37 }
  38
  39 #define OK_TYPES (1<<STT_NOTYPE | 1<<STT_OBJECT | 1<<STT_FUNC | 1<<STT_COMMON)
  40 #define OK_BINDS (1<<STB_GLOBAL | 1<<STB_WEAK | 1<<STB_GNU_UNIQUE)
  41
  42 void *__vdsosym(const char *vername, const char *name)
  43 {
  44         size_t i;
  45         for (i=0; libc.auxv[i] != AT_SYSINFO_EHDR; i+=2)
  46                 if (!libc.auxv[i]) return 0;
  47         Ehdr *eh = (void *)libc.auxv[i+1];
  48         Phdr *ph = (void *)((char *)eh + eh->e_phoff);
  49         size_t *dynv=0, base=-1;
  50         for (i=0; i<eh->e_phnum; i++, ph=(void *)((char *)ph+eh->e_phentsize)) {
  51                 if (ph->p_type == PT_LOAD)
  52                         base = (size_t)eh + ph->p_offset - ph->p_vaddr;
  53                 else if (ph->p_type == PT_DYNAMIC)
  54                         dynv = (void *)((char *)eh + ph->p_offset);
  55         }
  56         if (!dynv || base==(size_t)-1) return 0;
  57
  58         char *strings = 0;
  59         Sym *syms = 0;
  60         uint32_t *hashtab = 0;
  61         uint16_t *versym = 0;
  62         Verdef *verdef = 0;
  63
  64         for (i=0; dynv[i]; i+=2) {
  65                 void *p = (void *)(base + dynv[i+1]);
  66                 switch(dynv[i]) {
  67                 case DT_STRTAB: strings = p; break;
  68                 case DT_SYMTAB: syms = p; break;
  69                 case DT_HASH: hashtab = p; break;
  70                 case DT_VERSYM: versym = p; break;
  71                 case DT_VERDEF: verdef = p; break;
  72                 }
  73         }
  74
  75         if (!strings || !syms || !hashtab) return 0;
  76         if (!verdef) versym = 0;
  77
  78         for (i=0; i<hashtab[1]; i++) {
  79                 if (!(1<<(syms[i].st_info&0xf) & OK_TYPES)) continue;
  80                 if (!(1<<(syms[i].st_info>>4) & OK_BINDS)) continue;
  81                 if (!syms[i].st_shndx) continue;
  82                 if (strcmp(name, strings+syms[i].st_name)) continue;
  83                 if (versym && !checkver(verdef, versym[i], vername, strings))
  84                         continue;
  85                 return (void *)(base + syms[i].st_value);
  86         }
  87
  88         return 0;
  89 }
  90
  91 #endif