tools/reorder/elf_symbol_table.cpp@97036ab72558
tools/reorder/elf_symbol_table.cpp
Tue, 06 Jan 2015 21:39:09 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Tue, 06 Jan 2015 21:39:09 +0100
- branch
- TOR_BUG_9701
- changeset 8
- 97036ab72558
- permissions
- -rw-r--r--
Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.
1 /* This Source Code Form is subject to the terms of the Mozilla Public
2 * License, v. 2.0. If a copy of the MPL was not distributed with this
3 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
5 #include <string>
6 #include <fstream>
7 #include <errno.h>
8 #include <fcntl.h>
9 #include <stdlib.h>
10 #include <stdio.h>
11 #include <unistd.h>
12 #include <sys/stat.h>
14 #include "elf_symbol_table.h"
15 #include "elf_utils.h"
17 int
18 elf_symbol_table::init(const char *name)
19 {
20 // Open the file readonly.
21 m_fd = open(name, O_RDONLY);
22 if (m_fd < 0) {
23 perror(name);
24 return m_fd;
25 }
27 // Get its size.
28 struct stat statbuf;
29 if (fstat(m_fd, &statbuf) < 0) {
30 perror(name);
31 return -1;
32 }
34 m_size = statbuf.st_size;
36 // Memory map it.
37 m_mapping = mmap(0, m_size, PROT_READ, MAP_SHARED, m_fd, 0);
38 if (m_mapping == MAP_FAILED) {
39 perror(name);
40 return -1;
41 }
43 // Make sure it's an ELF header.
44 const Elf32_Ehdr *ehdr = reinterpret_cast<const Elf32_Ehdr *>(m_mapping);
45 if (elf_verify_header(ehdr) < 0)
46 return -1;
48 const char *mapping = reinterpret_cast<const char *>(m_mapping);
50 // Find the section headers
51 const Elf32_Shdr *shdrs
52 = reinterpret_cast<const Elf32_Shdr *>(mapping + ehdr->e_shoff);
54 // find the section header string table, .shstrtab
55 const Elf32_Shdr *shstrtabsh = shdrs + ehdr->e_shstrndx;
56 const char *shstrtab = mapping + shstrtabsh->sh_offset;
58 // parse the sections we care about
59 int shndx = 0;
60 const Elf32_Shdr *shlimit = shdrs + ehdr->e_shnum;
61 for (const Elf32_Shdr *shdr = shdrs; shdr < shlimit; ++shdr, ++shndx) {
62 basic_string<char> name(shstrtab + shdr->sh_name);
63 if (name == ".symtab") {
64 m_symbols = reinterpret_cast<const Elf32_Sym *>(mapping + shdr->sh_offset);
65 m_nsymbols = shdr->sh_size / sizeof(Elf32_Sym);
66 }
67 else if (name == ".strtab") {
68 m_strtab = mapping + shdr->sh_offset;
69 }
70 else if (name == ".text") {
71 m_text_shndx = shndx;
72 }
73 }
75 // Parse the symbol table
76 const Elf32_Sym *limit = m_symbols + m_nsymbols;
77 for (const Elf32_Sym *sym = m_symbols; sym < limit; ++sym) {
78 if (is_function(sym)) {
79 #ifdef DEBUG
80 hex(cout);
81 cout << sym->st_value << endl;
82 #endif
83 m_rsymtab.put(sym->st_value, sym->st_value + sym->st_size, sym);
84 }
85 }
87 return 0;
88 }
90 int
91 elf_symbol_table::finish()
92 {
93 if (m_mapping != MAP_FAILED) {
94 munmap(m_mapping, m_size);
95 m_mapping = MAP_FAILED;
96 }
98 if (m_fd >= 0) {
99 close(m_fd);
100 m_fd = -1;
101 }
103 return 0;
104 }
106 const Elf32_Sym *
107 elf_symbol_table::lookup(unsigned int addr) const
108 {
109 rsymtab_t::const_iterator result = m_rsymtab.get(addr);
110 return result != m_rsymtab.end() ? reinterpret_cast<const Elf32_Sym *>(*result) : 0;
111 }
113 const char *
114 elf_symbol_table::get_symbol_name(const Elf32_Sym *sym) const
115 {
116 return m_strtab + sym->st_name;
117 }
