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// Copyright 2016 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "dso_test_utils.h"
#include <elf.h>
#include <fcntl.h>
#include <gelf.h>
#include <libelf.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <vector>
#include "base/logging.h"
#include "binary_data_utils.h"
namespace quipper {
namespace testing {
namespace {
// Example string table:
// index 0: "\0"
// index 1: "value 1" "\0"
// index 9: "value 2" "\0"
// index 17: "value 3" "\0"
class ElfStringTable {
public:
ElfStringTable() : table_("", 1) {} // index 0 is the empty string.
// Returns the index to use in place of the string.
GElf_Word Add(string value) {
GElf_Word ret = table_.size();
table_.append(value.data(), value.size() + 1); // Include the '\0'.
return ret;
}
const string &table() { return table_; }
private:
string table_;
};
// Helper to control the scope of data in Elf_Data.d_buf added to a Elf_Scn.
// Basically, makes sure that the d_buf pointer remains valid, and holds on to a
// copy of your buffer so you don't have to.
class ElfDataCache {
public:
Elf_Data *AddDataToSection(Elf_Scn *section, const string &data_str) {
Elf_Data *data = elf_newdata(section);
CHECK(data) << elf_errmsg(-1);
// avoid zero memory allocation
char *data_storage = new char[data_str.size() + 1];
cache_.emplace_back(data_storage);
memcpy(data_storage, data_str.data(), data_str.size());
data->d_buf = data_storage;
data->d_size = data_str.size();
return data;
}
~ElfDataCache() {
for (auto &s : cache_) {
delete[] s;
}
}
private:
std::vector<char *> cache_;
};
} // namespace
void WriteElfWithBuildid(string filename, string section_name, string buildid) {
std::vector<std::pair<string, string>> section_name_to_buildid{
std::make_pair(section_name, buildid)};
WriteElfWithMultipleBuildids(filename, section_name_to_buildid);
}
void WriteElfWithMultipleBuildids(
string filename,
const std::vector<std::pair<string, string>> section_buildids) {
int fd = open(filename.data(), O_WRONLY | O_CREAT | O_TRUNC, 0660);
CHECK_GE(fd, 0) << strerror(errno);
Elf *elf = elf_begin(fd, ELF_C_WRITE, nullptr);
CHECK(elf) << elf_errmsg(-1);
Elf64_Ehdr *elf_header = elf64_newehdr(elf);
CHECK(elf_header) << elf_errmsg(-1);
elf_header->e_ident[EI_DATA] = ELFDATA2LSB;
elf_header->e_machine = EM_X86_64;
elf_header->e_version = EV_CURRENT;
CHECK(elf_update(elf, ELF_C_NULL) > 0) << elf_errmsg(-1);
ElfStringTable string_table;
ElfDataCache data_cache;
// Note section(s)
for (const auto &entry : section_buildids) {
const string §ion_name = entry.first;
const string &buildid = entry.second;
Elf_Scn *section = elf_newscn(elf);
CHECK(section) << elf_errmsg(-1);
GElf_Shdr section_header;
CHECK(gelf_getshdr(section, §ion_header)) << elf_errmsg(-1);
section_header.sh_name = string_table.Add(section_name);
section_header.sh_type = SHT_NOTE;
CHECK(gelf_update_shdr(section, §ion_header)) << elf_errmsg(-1);
string note_name = ELF_NOTE_GNU;
GElf_Nhdr note_header;
note_header.n_namesz = Align<4>(note_name.size());
note_header.n_descsz = Align<4>(buildid.size());
note_header.n_type = NT_GNU_BUILD_ID;
string data_str;
data_str.append(reinterpret_cast<char *>(¬e_header),
sizeof(note_header));
data_str.append(note_name);
data_str.append(string(note_header.n_namesz - note_name.size(), '\0'));
data_str.append(buildid);
data_str.append(string(note_header.n_descsz - buildid.size(), '\0'));
Elf_Data *data = data_cache.AddDataToSection(section, data_str);
data->d_type = ELF_T_NHDR;
}
// String table section
{
Elf_Scn *section = elf_newscn(elf);
CHECK(section) << elf_errmsg(-1);
GElf_Shdr section_header;
CHECK(gelf_getshdr(section, §ion_header)) << elf_errmsg(-1);
section_header.sh_name = string_table.Add(".shstrtab");
section_header.sh_type = SHT_STRTAB;
CHECK(gelf_update_shdr(section, §ion_header)) << elf_errmsg(-1);
Elf_Data *data = data_cache.AddDataToSection(section, string_table.table());
data->d_type = ELF_T_BYTE;
elf_header->e_shstrndx = elf_ndxscn(section);
}
CHECK(elf_update(elf, ELF_C_WRITE) > 0) << elf_errmsg(-1);
elf_end(elf);
close(fd);
}
} // namespace testing
} // namespace quipper
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