1/*
2 * Copyright (c) 2022 Huawei Device Co., Ltd.
3 * Licensed under the Apache License, Version 2.0 (the "License");
4 * you may not use this file except in compliance with the License.
5 * You may obtain a copy of the License at
6 *
7 *     http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software
10 * distributed under the License is distributed on an "AS IS" BASIS,
11 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 * See the License for the specific language governing permissions and
13 * limitations under the License.
14 */
15
16#include <elf.h>
17#include <link.h>
18#include <limits.h>
19#include <stdint.h>
20#include <string.h>
21#include "libc.h"
22#include "syscall.h"
23
24#ifdef VDSO_USEFUL
25
26#if ULONG_MAX == 0xffffffff
27typedef Elf32_Ehdr Ehdr;
28typedef Elf32_Phdr Phdr;
29typedef Elf32_Sym Sym;
30typedef Elf32_Verdef Verdef;
31typedef Elf32_Verdaux Verdaux;
32#else
33typedef Elf64_Ehdr Ehdr;
34typedef Elf64_Phdr Phdr;
35typedef Elf64_Sym Sym;
36typedef Elf64_Verdef Verdef;
37typedef Elf64_Verdaux Verdaux;
38#endif
39
40static int checkver(Verdef *def, int vsym, const char *vername, char *strings)
41{
42	vsym &= 0x7fff;
43	for (;;) {
44		if (!(def->vd_flags & VER_FLG_BASE)
45		  && (def->vd_ndx & 0x7fff) == vsym)
46			break;
47		if (def->vd_next == 0)
48			return 0;
49		def = (Verdef *)((char *)def + def->vd_next);
50	}
51	Verdaux *aux = (Verdaux *)((char *)def + def->vd_aux);
52	return !strcmp(vername, strings + aux->vda_name);
53}
54
55#define OK_TYPES (1<<STT_NOTYPE | 1<<STT_OBJECT | 1<<STT_FUNC | 1<<STT_COMMON)
56#define OK_BINDS (1<<STB_GLOBAL | 1<<STB_WEAK | 1<<STB_GNU_UNIQUE)
57
58struct __vdso_info {
59	size_t base;
60	char *strings;
61	Sym *syms;
62	Elf_Symndx *hashtab;
63	uint16_t *versym;
64	Verdef *verdef;
65} vdso_info = {-1, 0, 0, 0, 0, 0};
66
67void __get_vdso_info()
68{
69	if (vdso_info.base != -1) {
70		return ;
71	}
72	size_t i;
73	for (i=0; libc.auxv[i] != AT_SYSINFO_EHDR; i+=2)
74		if (!libc.auxv[i]) return ;
75	if (!libc.auxv[i+1]) return ;
76	Ehdr *eh = (void *)libc.auxv[i+1];
77	Phdr *ph = (void *)((char *)eh + eh->e_phoff);
78	size_t *dynv=0, base=-1;
79	for (i=0; i<eh->e_phnum; i++, ph=(void *)((char *)ph+eh->e_phentsize)) {
80		if (ph->p_type == PT_LOAD)
81			base = (size_t)eh + ph->p_offset - ph->p_vaddr;
82		else if (ph->p_type == PT_DYNAMIC)
83			dynv = (void *)((char *)eh + ph->p_offset);
84	}
85	if (!dynv || base==(size_t)-1) return ;
86
87	for (i=0; dynv[i]; i+=2) {
88		void *p = (void *)(base + dynv[i+1]);
89		switch(dynv[i]) {
90		case DT_STRTAB: vdso_info.strings = p; break;
91		case DT_SYMTAB: vdso_info.syms = p; break;
92		case DT_HASH: vdso_info.hashtab = p; break;
93		case DT_VERSYM: vdso_info.versym = p; break;
94		case DT_VERDEF: vdso_info.verdef = p; break;
95		}
96	}
97    vdso_info.base = base;
98    return ;
99}
100
101void *__get_vdso_addr(const char *vername, const char *name)
102{
103	if (!vdso_info.strings || !vdso_info.syms || !vdso_info.hashtab) return 0;
104	if (!vdso_info.verdef) vdso_info.versym = 0;
105
106    size_t i;
107	for (i=0; i<vdso_info.hashtab[1]; i++) {
108		if (!(1<<(vdso_info.syms[i].st_info&0xf) & OK_TYPES)) continue;
109		if (!(1<<(vdso_info.syms[i].st_info>>4) & OK_BINDS)) continue;
110		if (!vdso_info.syms[i].st_shndx) continue;
111		if (strcmp(name, vdso_info.strings+vdso_info.syms[i].st_name)) continue;
112		if (vdso_info.versym && !checkver(vdso_info.verdef, vdso_info.versym[i], vername, vdso_info.strings))
113			continue;
114		return (void *)(vdso_info.base + vdso_info.syms[i].st_value);
115	}
116
117	return 0;
118}
119
120#endif
121