source: asp3_tinet_ecnl_arm/trunk/musl-1.1.18/src/internal/vdso.c@ 352

#include <elf.h>
#include <link.h>
#include <limits.h>
#include <stdint.h>
#include <string.h>
#include "libc.h"
#include "syscall.h"

#ifdef VDSO_USEFUL

#if ULONG_MAX == 0xffffffff
typedef Elf32_Ehdr Ehdr;
typedef Elf32_Phdr Phdr;
typedef Elf32_Sym Sym;
typedef Elf32_Verdef Verdef;
typedef Elf32_Verdaux Verdaux;
#else
typedef Elf64_Ehdr Ehdr;
typedef Elf64_Phdr Phdr;
typedef Elf64_Sym Sym;
typedef Elf64_Verdef Verdef;
typedef Elf64_Verdaux Verdaux;
#endif

static int checkver(Verdef *def, int vsym, const char *vername, char *strings)
{
        vsym &= 0x7fff;
        for (;;) {
                if (!(def->vd_flags & VER_FLG_BASE)
                  && (def->vd_ndx & 0x7fff) == vsym)
                        break;
                if (def->vd_next == 0)
                        return 0;
                def = (Verdef *)((char *)def + def->vd_next);
        }
        Verdaux *aux = (Verdaux *)((char *)def + def->vd_aux);
        return !strcmp(vername, strings + aux->vda_name);
}

#define OK_TYPES (1<<STT_NOTYPE | 1<<STT_OBJECT | 1<<STT_FUNC | 1<<STT_COMMON)
#define OK_BINDS (1<<STB_GLOBAL | 1<<STB_WEAK | 1<<STB_GNU_UNIQUE)

void *__vdsosym(const char *vername, const char *name)
{
        size_t i;
        for (i=0; libc.auxv[i] != AT_SYSINFO_EHDR; i+=2)
                if (!libc.auxv[i]) return 0;
        if (!libc.auxv[i+1]) return 0;
        Ehdr *eh = (void *)libc.auxv[i+1];
        Phdr *ph = (void *)((char *)eh + eh->e_phoff);
        size_t *dynv=0, base=-1;
        for (i=0; i<eh->e_phnum; i++, ph=(void *)((char *)ph+eh->e_phentsize)) {
                if (ph->p_type == PT_LOAD)
                        base = (size_t)eh + ph->p_offset - ph->p_vaddr;
                else if (ph->p_type == PT_DYNAMIC)
                        dynv = (void *)((char *)eh + ph->p_offset);
        }
        if (!dynv || base==(size_t)-1) return 0;

        char *strings = 0;
        Sym *syms = 0;
        Elf_Symndx *hashtab = 0;
        uint16_t *versym = 0;
        Verdef *verdef = 0;
        
        for (i=0; dynv[i]; i+=2) {
                void *p = (void *)(base + dynv[i+1]);
                switch(dynv[i]) {
                case DT_STRTAB: strings = p; break;
                case DT_SYMTAB: syms = p; break;
                case DT_HASH: hashtab = p; break;
                case DT_VERSYM: versym = p; break;
                case DT_VERDEF: verdef = p; break;
                }
        }       

        if (!strings || !syms || !hashtab) return 0;
        if (!verdef) versym = 0;

        for (i=0; i<hashtab[1]; i++) {
                if (!(1<<(syms[i].st_info&0xf) & OK_TYPES)) continue;
                if (!(1<<(syms[i].st_info>>4) & OK_BINDS)) continue;
                if (!syms[i].st_shndx) continue;
                if (strcmp(name, strings+syms[i].st_name)) continue;
                if (versym && !checkver(verdef, versym[i], vername, strings))
                        continue;
                return (void *)(base + syms[i].st_value);
        }

        return 0;
}

#endif