1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/tools/footprint/foldelf.cpp Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,319 @@
1.4 +/* -*- Mode: C++; indent-tabs-mode: nil; c-basic-offset: 4 -*-
1.5 + *
1.6 + * This Source Code Form is subject to the terms of the Mozilla Public
1.7 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.8 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.9 +
1.10 +/* This program reads an ELF file and computes information about
1.11 + * redundancies.
1.12 + */
1.13 +
1.14 +#include <algorithm>
1.15 +#include <fstream>
1.16 +#include <string>
1.17 +#include <vector>
1.18 +#include <map>
1.19 +#include <elf.h>
1.20 +#include <sys/mman.h>
1.21 +#include <sys/stat.h>
1.22 +#include <fcntl.h>
1.23 +#include <unistd.h>
1.24 +#include <errno.h>
1.25 +#include <getopt.h>
1.26 +
1.27 +//----------------------------------------------------------------------
1.28 +
1.29 +char* opt_type = "func";
1.30 +char* opt_section = ".text";
1.31 +
1.32 +//----------------------------------------------------------------------
1.33 +
1.34 +static void
1.35 +hexdump(ostream& out, const char* bytes, size_t count)
1.36 +{
1.37 + hex(out);
1.38 +
1.39 + size_t off = 0;
1.40 + while (off < count) {
1.41 + out.form("%08lx: ", off);
1.42 +
1.43 + const char* p = bytes + off;
1.44 +
1.45 + int j = 0;
1.46 + while (j < 16) {
1.47 + out.form("%02x", p[j++] & 0xff);
1.48 + if (j + off >= count)
1.49 + break;
1.50 +
1.51 + out.form("%02x ", p[j++] & 0xff);
1.52 + if (j + off >= count)
1.53 + break;
1.54 + }
1.55 +
1.56 + // Pad
1.57 + for (; j < 16; ++j)
1.58 + out << ((j%2) ? " " : " ");
1.59 +
1.60 + for (j = 0; j < 16; ++j) {
1.61 + if (j + off < count)
1.62 + out.put(isprint(p[j]) ? p[j] : '.');
1.63 + }
1.64 +
1.65 + out << endl;
1.66 + off += 16;
1.67 + }
1.68 +}
1.69 +
1.70 +//----------------------------------------------------------------------
1.71 +
1.72 +int
1.73 +verify_elf_header(const Elf32_Ehdr* hdr)
1.74 +{
1.75 + if (hdr->e_ident[EI_MAG0] != ELFMAG0
1.76 + || hdr->e_ident[EI_MAG1] != ELFMAG1
1.77 + || hdr->e_ident[EI_MAG2] != ELFMAG2
1.78 + || hdr->e_ident[EI_MAG3] != ELFMAG3) {
1.79 + cerr << "not an elf file" << endl;
1.80 + return -1;
1.81 + }
1.82 +
1.83 + if (hdr->e_ident[EI_CLASS] != ELFCLASS32) {
1.84 + cerr << "not a 32-bit elf file" << endl;
1.85 + return -1;
1.86 + }
1.87 +
1.88 + if (hdr->e_ident[EI_DATA] != ELFDATA2LSB) {
1.89 + cerr << "not a little endian elf file" << endl;
1.90 + return -1;
1.91 + }
1.92 +
1.93 + if (hdr->e_ident[EI_VERSION] != EV_CURRENT) {
1.94 + cerr << "incompatible version" << endl;
1.95 + return -1;
1.96 + }
1.97 +
1.98 + return 0;
1.99 +}
1.100 +
1.101 +//----------------------------------------------------------------------
1.102 +
1.103 +class elf_symbol : public Elf32_Sym
1.104 +{
1.105 +public:
1.106 + elf_symbol(const Elf32_Sym& sym)
1.107 + { ::memcpy(static_cast<Elf32_Sym*>(this), &sym, sizeof(Elf32_Sym)); }
1.108 +
1.109 + friend bool operator==(const elf_symbol& lhs, const elf_symbol& rhs) {
1.110 + return 0 == ::memcmp(static_cast<const Elf32_Sym*>(&lhs),
1.111 + static_cast<const Elf32_Sym*>(&rhs),
1.112 + sizeof(Elf32_Sym)); }
1.113 +};
1.114 +
1.115 +//----------------------------------------------------------------------
1.116 +
1.117 +static const char*
1.118 +st_bind(unsigned char info)
1.119 +{
1.120 + switch (ELF32_ST_BIND(info)) {
1.121 + case STB_LOCAL: return "local";
1.122 + case STB_GLOBAL: return "global";
1.123 + case STB_WEAK: return "weak";
1.124 + default: return "unknown";
1.125 + }
1.126 +}
1.127 +
1.128 +static const char*
1.129 +st_type(unsigned char info)
1.130 +{
1.131 + switch (ELF32_ST_TYPE(info)) {
1.132 + case STT_NOTYPE: return "none";
1.133 + case STT_OBJECT: return "object";
1.134 + case STT_FUNC: return "func";
1.135 + case STT_SECTION: return "section";
1.136 + case STT_FILE: return "file";
1.137 + default: return "unknown";
1.138 + }
1.139 +}
1.140 +
1.141 +static unsigned char
1.142 +st_type(const char* type)
1.143 +{
1.144 + if (strcmp(type, "none") == 0) {
1.145 + return STT_NOTYPE;
1.146 + }
1.147 + else if (strcmp(type, "object") == 0) {
1.148 + return STT_OBJECT;
1.149 + }
1.150 + else if (strcmp(type, "func") == 0) {
1.151 + return STT_FUNC;
1.152 + }
1.153 + else {
1.154 + return 0;
1.155 + }
1.156 +}
1.157 +
1.158 +//----------------------------------------------------------------------
1.159 +
1.160 +typedef vector<elf_symbol> elf_symbol_table;
1.161 +typedef map< basic_string<char>, elf_symbol_table > elf_text_map;
1.162 +
1.163 +void
1.164 +process_mapping(char* mapping, size_t size)
1.165 +{
1.166 + const Elf32_Ehdr* ehdr = reinterpret_cast<Elf32_Ehdr*>(mapping);
1.167 + if (verify_elf_header(ehdr) < 0)
1.168 + return;
1.169 +
1.170 + // find the section headers
1.171 + const Elf32_Shdr* shdrs = reinterpret_cast<Elf32_Shdr*>(mapping + ehdr->e_shoff);
1.172 +
1.173 + // find the section header string table, .shstrtab
1.174 + const Elf32_Shdr* shstrtabsh = shdrs + ehdr->e_shstrndx;
1.175 + const char* shstrtab = mapping + shstrtabsh->sh_offset;
1.176 +
1.177 + // find the sections we care about
1.178 + const Elf32_Shdr *symtabsh, *strtabsh, *textsh;
1.179 + int textndx;
1.180 +
1.181 + for (int i = 0; i < ehdr->e_shnum; ++i) {
1.182 + basic_string<char> name(shstrtab + shdrs[i].sh_name);
1.183 + if (name == opt_section) {
1.184 + textsh = shdrs + i;
1.185 + textndx = i;
1.186 + }
1.187 + else if (name == ".symtab") {
1.188 + symtabsh = shdrs + i;
1.189 + }
1.190 + else if (name == ".strtab") {
1.191 + strtabsh = shdrs + i;
1.192 + }
1.193 + }
1.194 +
1.195 + // find the .strtab
1.196 + char* strtab = mapping + strtabsh->sh_offset;
1.197 +
1.198 + // find the .text
1.199 + char* text = mapping + textsh->sh_offset;
1.200 + int textaddr = textsh->sh_addr;
1.201 +
1.202 + // find the symbol table
1.203 + int nentries = symtabsh->sh_size / sizeof(Elf32_Sym);
1.204 + Elf32_Sym* symtab = reinterpret_cast<Elf32_Sym*>(mapping + symtabsh->sh_offset);
1.205 +
1.206 + // look for symbols in the .text section
1.207 + elf_text_map textmap;
1.208 +
1.209 + for (int i = 0; i < nentries; ++i) {
1.210 + const Elf32_Sym* sym = symtab + i;
1.211 + if (sym->st_shndx == textndx &&
1.212 + ELF32_ST_TYPE(sym->st_info) == st_type(opt_type) &&
1.213 + sym->st_size) {
1.214 + basic_string<char> functext(text + sym->st_value - textaddr, sym->st_size);
1.215 +
1.216 + elf_symbol_table& syms = textmap[functext];
1.217 + if (syms.end() == find(syms.begin(), syms.end(), elf_symbol(*sym)))
1.218 + syms.insert(syms.end(), *sym);
1.219 + }
1.220 + }
1.221 +
1.222 + int uniquebytes = 0, totalbytes = 0;
1.223 + int uniquecount = 0, totalcount = 0;
1.224 +
1.225 + for (elf_text_map::const_iterator entry = textmap.begin();
1.226 + entry != textmap.end();
1.227 + ++entry) {
1.228 + const elf_symbol_table& syms = entry->second;
1.229 +
1.230 + if (syms.size() <= 1)
1.231 + continue;
1.232 +
1.233 + int sz = syms.begin()->st_size;
1.234 + uniquebytes += sz;
1.235 + totalbytes += sz * syms.size();
1.236 + uniquecount += 1;
1.237 + totalcount += syms.size();
1.238 +
1.239 + for (elf_symbol_table::const_iterator sym = syms.begin(); sym != syms.end(); ++sym)
1.240 + cout << strtab + sym->st_name << endl;
1.241 +
1.242 + dec(cout);
1.243 + cout << syms.size() << " copies of " << sz << " bytes";
1.244 + cout << " (" << ((syms.size() - 1) * sz) << " redundant bytes)" << endl;
1.245 +
1.246 + hexdump(cout, entry->first.data(), entry->first.size());
1.247 + cout << endl;
1.248 + }
1.249 +
1.250 + dec(cout);
1.251 + cout << "bytes unique=" << uniquebytes << ", total=" << totalbytes << endl;
1.252 + cout << "entries unique=" << uniquecount << ", total=" << totalcount << endl;
1.253 +}
1.254 +
1.255 +void
1.256 +process_file(const char* name)
1.257 +{
1.258 + int fd = open(name, O_RDWR);
1.259 + if (fd >= 0) {
1.260 + struct stat statbuf;
1.261 + if (fstat(fd, &statbuf) >= 0) {
1.262 + size_t size = statbuf.st_size;
1.263 +
1.264 + void* mapping = mmap(0, size, PROT_READ, MAP_SHARED, fd, 0);
1.265 + if (mapping != MAP_FAILED) {
1.266 + process_mapping(static_cast<char*>(mapping), size);
1.267 + munmap(mapping, size);
1.268 + }
1.269 + }
1.270 + close(fd);
1.271 + }
1.272 +}
1.273 +
1.274 +static void
1.275 +usage()
1.276 +{
1.277 + cerr << "foldelf [--section=<section>] [--type=<type>] [file ...]\n\
1.278 + --section, -s the section of the ELF file to scan; defaults\n\
1.279 + to ``.text''. Valid values include any section\n\
1.280 + of the ELF file.\n\
1.281 + --type, -t the type of object to examine in the section;\n\
1.282 + defaults to ``func''. Valid values include\n\
1.283 + ``none'', ``func'', or ``object''.\n";
1.284 +
1.285 +}
1.286 +
1.287 +static struct option opts[] = {
1.288 + { "type", required_argument, 0, 't' },
1.289 + { "section", required_argument, 0, 's' },
1.290 + { "help", no_argument, 0, '?' },
1.291 + { 0, 0, 0, 0 }
1.292 +};
1.293 +
1.294 +int
1.295 +main(int argc, char* argv[])
1.296 +{
1.297 + while (1) {
1.298 + int option_index = 0;
1.299 + int c = getopt_long(argc, argv, "t:s:", opts, &option_index);
1.300 +
1.301 + if (c < 0) break;
1.302 +
1.303 + switch (c) {
1.304 + case 't':
1.305 + opt_type = optarg;
1.306 + break;
1.307 +
1.308 + case 's':
1.309 + opt_section = optarg;
1.310 + break;
1.311 +
1.312 + case '?':
1.313 + usage();
1.314 + break;
1.315 + }
1.316 + }
1.317 +
1.318 + for (int i = optind; i < argc; ++i)
1.319 + process_file(argv[i]);
1.320 +
1.321 + return 0;
1.322 +}
