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
checkver(Verdef * def,int vsym,const char * vername,char * strings)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
__vdsosym(const char * vername,const char * name)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
92