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android_system_core/libunwindstack/tests/MapInfoGetElfTest.cpp
Christopher Ferris 5acf069a7a Be permissive about badly formed elf files. 
Here is the allowable issues with an elf file that will not result in an error:
- The program headers/section headers offset points to unreadable memory.
- Allow missing program header and/or section headers.
- Allow a symbol table section header to point to invalid symbol table values.

There is no real reason to require the elf file be perfect. Everything in
the code has sane defaults, so any missing information won't cause any
problems.

This gets rid of the warning that occurs any time an elf is loaded
from memory. In memory elf files never contain all of the section headers,
and do not contain the symbol table data.

Update tests to test these new cases.

Test: Builds and unit tests all pass.
Change-Id: Iaefe2cd6b6c965a01ed425a112d6afae339f3b78
2018-08-03 22:02:05 +00:00

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/*
* Copyright (C) 2016 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <elf.h>
#include <errno.h>
#include <signal.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/ptrace.h>
#include <sys/types.h>
#include <unistd.h>
#include <atomic>
#include <memory>
#include <thread>
#include <vector>
#include <android-base/file.h>
#include <android-base/test_utils.h>
#include <gtest/gtest.h>
#include <unwindstack/Elf.h>
#include <unwindstack/MapInfo.h>
#include <unwindstack/Maps.h>
#include <unwindstack/Memory.h>
#include "ElfTestUtils.h"
#include "MemoryFake.h"
namespace unwindstack {
class MapInfoGetElfTest : public ::testing::Test {
protected:
void SetUp() override {
memory_ = new MemoryFake;
process_memory_.reset(memory_);
}
template <typename Ehdr, typename Shdr>
static void InitElf(uint64_t sh_offset, Ehdr* ehdr, uint8_t class_type, uint8_t machine_type) {
memset(ehdr, 0, sizeof(*ehdr));
memcpy(ehdr->e_ident, ELFMAG, SELFMAG);
ehdr->e_ident[EI_CLASS] = class_type;
ehdr->e_machine = machine_type;
ehdr->e_shoff = sh_offset;
ehdr->e_shentsize = sizeof(Shdr) + 100;
ehdr->e_shnum = 4;
}
const size_t kMapSize = 4096;
std::shared_ptr<Memory> process_memory_;
MemoryFake* memory_;
TemporaryFile elf_;
};
TEST_F(MapInfoGetElfTest, invalid) {
MapInfo info(0x1000, 0x2000, 0, PROT_READ, "");
// The map is empty, but this should still create an invalid elf object.
Elf* elf = info.GetElf(process_memory_, false);
ASSERT_TRUE(elf != nullptr);
ASSERT_FALSE(elf->valid());
}
TEST_F(MapInfoGetElfTest, valid32) {
MapInfo info(0x3000, 0x4000, 0, PROT_READ, "");
Elf32_Ehdr ehdr;
TestInitEhdr<Elf32_Ehdr>(&ehdr, ELFCLASS32, EM_ARM);
memory_->SetMemory(0x3000, &ehdr, sizeof(ehdr));
Elf* elf = info.GetElf(process_memory_, false);
ASSERT_TRUE(elf != nullptr);
ASSERT_TRUE(elf->valid());
EXPECT_EQ(static_cast<uint32_t>(EM_ARM), elf->machine_type());
EXPECT_EQ(ELFCLASS32, elf->class_type());
}
TEST_F(MapInfoGetElfTest, valid64) {
MapInfo info(0x8000, 0x9000, 0, PROT_READ, "");
Elf64_Ehdr ehdr;
TestInitEhdr<Elf64_Ehdr>(&ehdr, ELFCLASS64, EM_AARCH64);
memory_->SetMemory(0x8000, &ehdr, sizeof(ehdr));
Elf* elf = info.GetElf(process_memory_, false);
ASSERT_TRUE(elf != nullptr);
ASSERT_TRUE(elf->valid());
EXPECT_EQ(static_cast<uint32_t>(EM_AARCH64), elf->machine_type());
EXPECT_EQ(ELFCLASS64, elf->class_type());
}
TEST_F(MapInfoGetElfTest, gnu_debugdata_do_not_init32) {
MapInfo info(0x4000, 0x8000, 0, PROT_READ, "");
TestInitGnuDebugdata<Elf32_Ehdr, Elf32_Shdr>(ELFCLASS32, EM_ARM, false,
[&](uint64_t offset, const void* ptr, size_t size) {
memory_->SetMemory(0x4000 + offset, ptr, size);
});
Elf* elf = info.GetElf(process_memory_, false);
ASSERT_TRUE(elf != nullptr);
ASSERT_TRUE(elf->valid());
EXPECT_EQ(static_cast<uint32_t>(EM_ARM), elf->machine_type());
EXPECT_EQ(ELFCLASS32, elf->class_type());
EXPECT_TRUE(elf->gnu_debugdata_interface() == nullptr);
}
TEST_F(MapInfoGetElfTest, gnu_debugdata_do_not_init64) {
MapInfo info(0x6000, 0x8000, 0, PROT_READ, "");
TestInitGnuDebugdata<Elf64_Ehdr, Elf64_Shdr>(ELFCLASS64, EM_AARCH64, false,
[&](uint64_t offset, const void* ptr, size_t size) {
memory_->SetMemory(0x6000 + offset, ptr, size);
});
Elf* elf = info.GetElf(process_memory_, false);
ASSERT_TRUE(elf != nullptr);
ASSERT_TRUE(elf->valid());
EXPECT_EQ(static_cast<uint32_t>(EM_AARCH64), elf->machine_type());
EXPECT_EQ(ELFCLASS64, elf->class_type());
EXPECT_TRUE(elf->gnu_debugdata_interface() == nullptr);
}
TEST_F(MapInfoGetElfTest, gnu_debugdata_init32) {
MapInfo info(0x2000, 0x3000, 0, PROT_READ, "");
TestInitGnuDebugdata<Elf32_Ehdr, Elf32_Shdr>(ELFCLASS32, EM_ARM, true,
[&](uint64_t offset, const void* ptr, size_t size) {
memory_->SetMemory(0x2000 + offset, ptr, size);
});
Elf* elf = info.GetElf(process_memory_, true);
ASSERT_TRUE(elf != nullptr);
ASSERT_TRUE(elf->valid());
EXPECT_EQ(static_cast<uint32_t>(EM_ARM), elf->machine_type());
EXPECT_EQ(ELFCLASS32, elf->class_type());
EXPECT_TRUE(elf->gnu_debugdata_interface() != nullptr);
}
TEST_F(MapInfoGetElfTest, gnu_debugdata_init64) {
MapInfo info(0x5000, 0x8000, 0, PROT_READ, "");
TestInitGnuDebugdata<Elf64_Ehdr, Elf64_Shdr>(ELFCLASS64, EM_AARCH64, true,
[&](uint64_t offset, const void* ptr, size_t size) {
memory_->SetMemory(0x5000 + offset, ptr, size);
});
Elf* elf = info.GetElf(process_memory_, true);
ASSERT_TRUE(elf != nullptr);
ASSERT_TRUE(elf->valid());
EXPECT_EQ(static_cast<uint32_t>(EM_AARCH64), elf->machine_type());
EXPECT_EQ(ELFCLASS64, elf->class_type());
EXPECT_TRUE(elf->gnu_debugdata_interface() != nullptr);
}
TEST_F(MapInfoGetElfTest, end_le_start) {
MapInfo info(0x1000, 0x1000, 0, PROT_READ, elf_.path);
Elf32_Ehdr ehdr;
TestInitEhdr<Elf32_Ehdr>(&ehdr, ELFCLASS32, EM_ARM);
ASSERT_TRUE(android::base::WriteFully(elf_.fd, &ehdr, sizeof(ehdr)));
Elf* elf = info.GetElf(process_memory_, false);
ASSERT_TRUE(elf != nullptr);
ASSERT_FALSE(elf->valid());
info.elf.reset();
info.end = 0xfff;
elf = info.GetElf(process_memory_, false);
ASSERT_TRUE(elf != nullptr);
ASSERT_FALSE(elf->valid());
// Make sure this test is valid.
info.elf.reset();
info.end = 0x2000;
elf = info.GetElf(process_memory_, false);
ASSERT_TRUE(elf != nullptr);
ASSERT_TRUE(elf->valid());
}
// Verify that if the offset is non-zero but there is no elf at the offset,
// that the full file is used.
TEST_F(MapInfoGetElfTest, file_backed_non_zero_offset_full_file) {
MapInfo info(0x1000, 0x2000, 0x100, PROT_READ, elf_.path);
std::vector<uint8_t> buffer(0x1000);
memset(buffer.data(), 0, buffer.size());
Elf32_Ehdr ehdr;
TestInitEhdr<Elf32_Ehdr>(&ehdr, ELFCLASS32, EM_ARM);
memcpy(buffer.data(), &ehdr, sizeof(ehdr));
ASSERT_TRUE(android::base::WriteFully(elf_.fd, buffer.data(), buffer.size()));
Elf* elf = info.GetElf(process_memory_, false);
ASSERT_TRUE(elf != nullptr);
ASSERT_TRUE(elf->valid());
ASSERT_TRUE(elf->memory() != nullptr);
ASSERT_EQ(0x100U, info.elf_offset);
// Read the entire file.
memset(buffer.data(), 0, buffer.size());
ASSERT_TRUE(elf->memory()->ReadFully(0, buffer.data(), buffer.size()));
ASSERT_EQ(0, memcmp(buffer.data(), &ehdr, sizeof(ehdr)));
for (size_t i = sizeof(ehdr); i < buffer.size(); i++) {
ASSERT_EQ(0, buffer[i]) << "Failed at byte " << i;
}
ASSERT_FALSE(elf->memory()->ReadFully(buffer.size(), buffer.data(), 1));
}
// Verify that if the offset is non-zero and there is an elf at that
// offset, that only part of the file is used.
TEST_F(MapInfoGetElfTest, file_backed_non_zero_offset_partial_file) {
MapInfo info(0x1000, 0x2000, 0x2000, PROT_READ, elf_.path);
std::vector<uint8_t> buffer(0x4000);
memset(buffer.data(), 0, buffer.size());
Elf32_Ehdr ehdr;
TestInitEhdr<Elf32_Ehdr>(&ehdr, ELFCLASS32, EM_ARM);
memcpy(&buffer[info.offset], &ehdr, sizeof(ehdr));
ASSERT_TRUE(android::base::WriteFully(elf_.fd, buffer.data(), buffer.size()));
Elf* elf = info.GetElf(process_memory_, false);
ASSERT_TRUE(elf != nullptr);
ASSERT_TRUE(elf->valid());
ASSERT_TRUE(elf->memory() != nullptr);
ASSERT_EQ(0U, info.elf_offset);
// Read the valid part of the file.
ASSERT_TRUE(elf->memory()->ReadFully(0, buffer.data(), 0x1000));
ASSERT_EQ(0, memcmp(buffer.data(), &ehdr, sizeof(ehdr)));
for (size_t i = sizeof(ehdr); i < 0x1000; i++) {
ASSERT_EQ(0, buffer[i]) << "Failed at byte " << i;
}
ASSERT_FALSE(elf->memory()->ReadFully(0x1000, buffer.data(), 1));
}
// Verify that if the offset is non-zero and there is an elf at that
// offset, that only part of the file is used. Further verify that if the
// embedded elf is bigger than the initial map, the new object is larger
// than the original map size. Do this for a 32 bit elf and a 64 bit elf.
TEST_F(MapInfoGetElfTest, file_backed_non_zero_offset_partial_file_whole_elf32) {
MapInfo info(0x5000, 0x6000, 0x1000, PROT_READ, elf_.path);
std::vector<uint8_t> buffer(0x4000);
memset(buffer.data(), 0, buffer.size());
Elf32_Ehdr ehdr;
TestInitEhdr<Elf32_Ehdr>(&ehdr, ELFCLASS32, EM_ARM);
ehdr.e_shoff = 0x2000;
ehdr.e_shentsize = sizeof(Elf32_Shdr) + 100;
ehdr.e_shnum = 4;
memcpy(&buffer[info.offset], &ehdr, sizeof(ehdr));
ASSERT_TRUE(android::base::WriteFully(elf_.fd, buffer.data(), buffer.size()));
Elf* elf = info.GetElf(process_memory_, false);
ASSERT_TRUE(elf != nullptr);
ASSERT_TRUE(elf->valid());
ASSERT_TRUE(elf->memory() != nullptr);
ASSERT_EQ(0U, info.elf_offset);
// Verify the memory is a valid elf.
memset(buffer.data(), 0, buffer.size());
ASSERT_TRUE(elf->memory()->ReadFully(0, buffer.data(), 0x1000));
ASSERT_EQ(0, memcmp(buffer.data(), &ehdr, sizeof(ehdr)));
// Read past the end of what would normally be the size of the map.
ASSERT_TRUE(elf->memory()->ReadFully(0x1000, buffer.data(), 1));
}
TEST_F(MapInfoGetElfTest, file_backed_non_zero_offset_partial_file_whole_elf64) {
MapInfo info(0x7000, 0x8000, 0x1000, PROT_READ, elf_.path);
std::vector<uint8_t> buffer(0x4000);
memset(buffer.data(), 0, buffer.size());
Elf64_Ehdr ehdr;
TestInitEhdr<Elf64_Ehdr>(&ehdr, ELFCLASS64, EM_AARCH64);
ehdr.e_shoff = 0x2000;
ehdr.e_shentsize = sizeof(Elf64_Shdr) + 100;
ehdr.e_shnum = 4;
memcpy(&buffer[info.offset], &ehdr, sizeof(ehdr));
ASSERT_TRUE(android::base::WriteFully(elf_.fd, buffer.data(), buffer.size()));
Elf* elf = info.GetElf(process_memory_, false);
ASSERT_TRUE(elf != nullptr);
ASSERT_TRUE(elf->valid());
ASSERT_TRUE(elf->memory() != nullptr);
ASSERT_EQ(0U, info.elf_offset);
// Verify the memory is a valid elf.
memset(buffer.data(), 0, buffer.size());
ASSERT_TRUE(elf->memory()->ReadFully(0, buffer.data(), 0x1000));
ASSERT_EQ(0, memcmp(buffer.data(), &ehdr, sizeof(ehdr)));
// Read past the end of what would normally be the size of the map.
ASSERT_TRUE(elf->memory()->ReadFully(0x1000, buffer.data(), 1));
}
TEST_F(MapInfoGetElfTest, process_memory_not_read_only) {
MapInfo info(0x9000, 0xa000, 0x1000, 0, "");
// Create valid elf data in process memory only.
Elf64_Ehdr ehdr;
TestInitEhdr<Elf64_Ehdr>(&ehdr, ELFCLASS64, EM_AARCH64);
ehdr.e_shoff = 0x2000;
ehdr.e_shentsize = sizeof(Elf64_Shdr) + 100;
ehdr.e_shnum = 0;
memory_->SetMemory(0x9000, &ehdr, sizeof(ehdr));
Elf* elf = info.GetElf(process_memory_, false);
ASSERT_TRUE(elf != nullptr);
ASSERT_FALSE(elf->valid());
info.elf.reset();
info.flags = PROT_READ;
elf = info.GetElf(process_memory_, false);
ASSERT_TRUE(elf->valid());
}
TEST_F(MapInfoGetElfTest, check_device_maps) {
MapInfo info(0x7000, 0x8000, 0x1000, PROT_READ | MAPS_FLAGS_DEVICE_MAP, "/dev/something");
// Create valid elf data in process memory for this to verify that only
// the name is causing invalid elf data.
Elf64_Ehdr ehdr;
TestInitEhdr<Elf64_Ehdr>(&ehdr, ELFCLASS64, EM_X86_64);
ehdr.e_shoff = 0x2000;
ehdr.e_shentsize = sizeof(Elf64_Shdr) + 100;
ehdr.e_shnum = 0;
memory_->SetMemory(0x7000, &ehdr, sizeof(ehdr));
Elf* elf = info.GetElf(process_memory_, false);
ASSERT_TRUE(elf != nullptr);
ASSERT_FALSE(elf->valid());
// Set the name to nothing to verify that it still fails.
info.elf.reset();
info.name = "";
elf = info.GetElf(process_memory_, false);
ASSERT_FALSE(elf->valid());
// Change the flags and verify the elf is valid now.
info.elf.reset();
info.flags = PROT_READ;
elf = info.GetElf(process_memory_, false);
ASSERT_TRUE(elf->valid());
}
TEST_F(MapInfoGetElfTest, multiple_thread_get_elf) {
static constexpr size_t kNumConcurrentThreads = 100;
Elf64_Ehdr ehdr;
TestInitEhdr<Elf64_Ehdr>(&ehdr, ELFCLASS64, EM_X86_64);
ehdr.e_shoff = 0x2000;
ehdr.e_shentsize = sizeof(Elf64_Shdr) + 100;
ehdr.e_shnum = 0;
memory_->SetMemory(0x7000, &ehdr, sizeof(ehdr));
Elf* elf_in_threads[kNumConcurrentThreads];
std::vector<std::thread*> threads;
std::atomic_bool wait;
wait = true;
// Create all of the threads and have them do the GetElf at the same time
// to make it likely that a race will occur.
MapInfo info(0x7000, 0x8000, 0x1000, PROT_READ, "");
for (size_t i = 0; i < kNumConcurrentThreads; i++) {
std::thread* thread = new std::thread([i, this, &wait, &info, &elf_in_threads]() {
while (wait)
;
Elf* elf = info.GetElf(process_memory_, false);
elf_in_threads[i] = elf;
});
threads.push_back(thread);
}
ASSERT_TRUE(info.elf == nullptr);
// Set them all going and wait for the threads to finish.
wait = false;
for (auto thread : threads) {
thread->join();
delete thread;
}
// Now verify that all of the elf files are exactly the same and valid.
Elf* elf = info.elf.get();
ASSERT_TRUE(elf != nullptr);
EXPECT_TRUE(elf->valid());
for (size_t i = 0; i < kNumConcurrentThreads; i++) {
EXPECT_EQ(elf, elf_in_threads[i]) << "Thread " << i << " mismatched.";
}
}
} // namespace unwindstack
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