339 lines
12 KiB
C++
339 lines
12 KiB
C++
// Copyright (c) 2010, Google Inc.
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following disclaimer
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// in the documentation and/or other materials provided with the
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// distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived from
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// this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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// linux_dumper.cc: Implement google_breakpad::LinuxDumper.
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// See linux_dumper.h for details.
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// This code deals with the mechanics of getting information about a crashed
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// process. Since this code may run in a compromised address space, the same
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// rules apply as detailed at the top of minidump_writer.h: no libc calls and
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// use the alternative allocator.
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#include "client/linux/minidump_writer/linux_dumper.h"
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#include <assert.h>
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#include <fcntl.h>
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#include <limits.h>
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#include <stddef.h>
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#include <string.h>
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#include "client/linux/minidump_writer/line_reader.h"
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#include "common/linux/file_id.h"
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#include "common/linux/linux_libc_support.h"
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#include "common/linux/memory_mapped_file.h"
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#include "common/linux/safe_readlink.h"
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#include "third_party/lss/linux_syscall_support.h"
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static const char kMappedFileUnsafePrefix[] = "/dev/";
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static const char kDeletedSuffix[] = " (deleted)";
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inline static bool IsMappedFileOpenUnsafe(
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const google_breakpad::MappingInfo& mapping) {
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// It is unsafe to attempt to open a mapped file that lives under /dev,
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// because the semantics of the open may be driver-specific so we'd risk
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// hanging the crash dumper. And a file in /dev/ almost certainly has no
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// ELF file identifier anyways.
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return my_strncmp(mapping.name,
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kMappedFileUnsafePrefix,
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sizeof(kMappedFileUnsafePrefix) - 1) == 0;
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}
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namespace google_breakpad {
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// All interesting auvx entry types are below AT_SYSINFO_EHDR
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#define AT_MAX AT_SYSINFO_EHDR
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LinuxDumper::LinuxDumper(pid_t pid)
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: pid_(pid),
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crash_address_(0),
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crash_signal_(0),
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crash_thread_(pid),
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threads_(&allocator_, 8),
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mappings_(&allocator_),
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auxv_(&allocator_, AT_MAX + 1) {
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// The passed-in size to the constructor (above) is only a hint.
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// Must call .resize() to do actual initialization of the elements.
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auxv_.resize(AT_MAX + 1);
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}
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LinuxDumper::~LinuxDumper() {
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}
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bool LinuxDumper::Init() {
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return ReadAuxv() && EnumerateThreads() && EnumerateMappings();
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}
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bool
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LinuxDumper::ElfFileIdentifierForMapping(const MappingInfo& mapping,
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bool member,
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unsigned int mapping_id,
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uint8_t identifier[sizeof(MDGUID)]) {
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assert(!member || mapping_id < mappings_.size());
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my_memset(identifier, 0, sizeof(MDGUID));
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if (IsMappedFileOpenUnsafe(mapping))
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return false;
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// Special-case linux-gate because it's not a real file.
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if (my_strcmp(mapping.name, kLinuxGateLibraryName) == 0) {
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void* linux_gate = NULL;
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if (pid_ == sys_getpid()) {
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linux_gate = reinterpret_cast<void*>(mapping.start_addr);
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} else {
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linux_gate = allocator_.Alloc(mapping.size);
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CopyFromProcess(linux_gate, pid_,
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reinterpret_cast<const void*>(mapping.start_addr),
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mapping.size);
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}
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return FileID::ElfFileIdentifierFromMappedFile(linux_gate, identifier);
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}
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char filename[NAME_MAX];
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size_t filename_len = my_strlen(mapping.name);
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assert(filename_len < NAME_MAX);
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if (filename_len >= NAME_MAX)
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return false;
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my_memcpy(filename, mapping.name, filename_len);
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filename[filename_len] = '\0';
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bool filename_modified = HandleDeletedFileInMapping(filename);
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MemoryMappedFile mapped_file(filename);
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if (!mapped_file.data()) // Should probably check if size >= ElfW(Ehdr)?
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return false;
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bool success =
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FileID::ElfFileIdentifierFromMappedFile(mapped_file.data(), identifier);
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if (success && member && filename_modified) {
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mappings_[mapping_id]->name[filename_len -
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sizeof(kDeletedSuffix) + 1] = '\0';
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}
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return success;
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}
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bool LinuxDumper::ReadAuxv() {
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char auxv_path[NAME_MAX];
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if (!BuildProcPath(auxv_path, pid_, "auxv")) {
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return false;
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}
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int fd = sys_open(auxv_path, O_RDONLY, 0);
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if (fd < 0) {
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return false;
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}
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elf_aux_entry one_aux_entry;
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bool res = false;
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while (sys_read(fd,
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&one_aux_entry,
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sizeof(elf_aux_entry)) == sizeof(elf_aux_entry) &&
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one_aux_entry.a_type != AT_NULL) {
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if (one_aux_entry.a_type <= AT_MAX) {
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auxv_[one_aux_entry.a_type] = one_aux_entry.a_un.a_val;
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res = true;
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}
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}
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sys_close(fd);
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return res;
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}
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bool LinuxDumper::EnumerateMappings() {
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char maps_path[NAME_MAX];
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if (!BuildProcPath(maps_path, pid_, "maps"))
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return false;
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// linux_gate_loc is the beginning of the kernel's mapping of
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// linux-gate.so in the process. It doesn't actually show up in the
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// maps list as a filename, but it can be found using the AT_SYSINFO_EHDR
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// aux vector entry, which gives the information necessary to special
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// case its entry when creating the list of mappings.
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// See http://www.trilithium.com/johan/2005/08/linux-gate/ for more
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// information.
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const void* linux_gate_loc =
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reinterpret_cast<void *>(auxv_[AT_SYSINFO_EHDR]);
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// Although the initial executable is usually the first mapping, it's not
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// guaranteed (see http://crosbug.com/25355); therefore, try to use the
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// actual entry point to find the mapping.
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const void* entry_point_loc = reinterpret_cast<void *>(auxv_[AT_ENTRY]);
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const int fd = sys_open(maps_path, O_RDONLY, 0);
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if (fd < 0)
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return false;
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LineReader* const line_reader = new(allocator_) LineReader(fd);
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const char* line;
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unsigned line_len;
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while (line_reader->GetNextLine(&line, &line_len)) {
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uintptr_t start_addr, end_addr, offset;
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const char* i1 = my_read_hex_ptr(&start_addr, line);
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if (*i1 == '-') {
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const char* i2 = my_read_hex_ptr(&end_addr, i1 + 1);
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if (*i2 == ' ') {
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const char* i3 = my_read_hex_ptr(&offset, i2 + 6 /* skip ' rwxp ' */);
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if (*i3 == ' ') {
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const char* name = NULL;
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// Only copy name if the name is a valid path name, or if
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// it's the VDSO image.
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if (((name = my_strchr(line, '/')) == NULL) &&
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linux_gate_loc &&
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reinterpret_cast<void*>(start_addr) == linux_gate_loc) {
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name = kLinuxGateLibraryName;
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offset = 0;
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}
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// Merge adjacent mappings with the same name into one module,
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// assuming they're a single library mapped by the dynamic linker
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if (name && !mappings_.empty()) {
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MappingInfo* module = mappings_.back();
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if ((start_addr == module->start_addr + module->size) &&
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(my_strlen(name) == my_strlen(module->name)) &&
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(my_strncmp(name, module->name, my_strlen(name)) == 0)) {
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module->size = end_addr - module->start_addr;
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line_reader->PopLine(line_len);
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continue;
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}
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}
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MappingInfo* const module = new(allocator_) MappingInfo;
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my_memset(module, 0, sizeof(MappingInfo));
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module->start_addr = start_addr;
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module->size = end_addr - start_addr;
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module->offset = offset;
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if (name != NULL) {
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const unsigned l = my_strlen(name);
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if (l < sizeof(module->name))
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my_memcpy(module->name, name, l);
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}
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// If this is the entry-point mapping, and it's not already the
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// first one, then we need to make it be first. This is because
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// the minidump format assumes the first module is the one that
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// corresponds to the main executable (as codified in
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// processor/minidump.cc:MinidumpModuleList::GetMainModule()).
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if (entry_point_loc &&
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(entry_point_loc >=
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reinterpret_cast<void*>(module->start_addr)) &&
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(entry_point_loc <
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reinterpret_cast<void*>(module->start_addr+module->size)) &&
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!mappings_.empty()) {
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// push the module onto the front of the list.
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mappings_.resize(mappings_.size() + 1);
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for (size_t idx = mappings_.size() - 1; idx > 0; idx--)
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mappings_[idx] = mappings_[idx - 1];
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mappings_[0] = module;
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} else {
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mappings_.push_back(module);
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}
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}
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}
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}
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line_reader->PopLine(line_len);
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}
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sys_close(fd);
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return !mappings_.empty();
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}
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// Get information about the stack, given the stack pointer. We don't try to
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// walk the stack since we might not have all the information needed to do
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// unwind. So we just grab, up to, 32k of stack.
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bool LinuxDumper::GetStackInfo(const void** stack, size_t* stack_len,
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uintptr_t int_stack_pointer) {
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// Move the stack pointer to the bottom of the page that it's in.
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const uintptr_t page_size = getpagesize();
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uint8_t* const stack_pointer =
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reinterpret_cast<uint8_t*>(int_stack_pointer & ~(page_size - 1));
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// The number of bytes of stack which we try to capture.
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static const ptrdiff_t kStackToCapture = 32 * 1024;
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const MappingInfo* mapping = FindMapping(stack_pointer);
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if (!mapping)
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return false;
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const ptrdiff_t offset = stack_pointer -
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reinterpret_cast<uint8_t*>(mapping->start_addr);
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const ptrdiff_t distance_to_end =
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static_cast<ptrdiff_t>(mapping->size) - offset;
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*stack_len = distance_to_end > kStackToCapture ?
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kStackToCapture : distance_to_end;
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*stack = stack_pointer;
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return true;
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}
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// Find the mapping which the given memory address falls in.
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const MappingInfo* LinuxDumper::FindMapping(const void* address) const {
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const uintptr_t addr = (uintptr_t) address;
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for (size_t i = 0; i < mappings_.size(); ++i) {
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const uintptr_t start = static_cast<uintptr_t>(mappings_[i]->start_addr);
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if (addr >= start && addr - start < mappings_[i]->size)
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return mappings_[i];
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}
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return NULL;
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}
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bool LinuxDumper::HandleDeletedFileInMapping(char* path) const {
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static const size_t kDeletedSuffixLen = sizeof(kDeletedSuffix) - 1;
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// Check for ' (deleted)' in |path|.
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// |path| has to be at least as long as "/x (deleted)".
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const size_t path_len = my_strlen(path);
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if (path_len < kDeletedSuffixLen + 2)
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return false;
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if (my_strncmp(path + path_len - kDeletedSuffixLen, kDeletedSuffix,
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kDeletedSuffixLen) != 0) {
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return false;
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}
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// Check |path| against the /proc/pid/exe 'symlink'.
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char exe_link[NAME_MAX];
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char new_path[NAME_MAX];
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if (!BuildProcPath(exe_link, pid_, "exe"))
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return false;
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if (!SafeReadLink(exe_link, new_path))
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return false;
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if (my_strcmp(path, new_path) != 0)
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return false;
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// Check to see if someone actually named their executable 'foo (deleted)'.
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struct kernel_stat exe_stat;
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struct kernel_stat new_path_stat;
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if (sys_stat(exe_link, &exe_stat) == 0 &&
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sys_stat(new_path, &new_path_stat) == 0 &&
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exe_stat.st_dev == new_path_stat.st_dev &&
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exe_stat.st_ino == new_path_stat.st_ino) {
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return false;
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}
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my_memcpy(path, exe_link, NAME_MAX);
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return true;
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}
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} // namespace google_breakpad
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