blob: 95f37cedcb8fd8f6fab0b3418d2208577cdbace5 [file] [log] [blame]
// Copyright 2018 The Chromium 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 "base/profiler/module_cache.h"
#include <dlfcn.h>
#include <elf.h>
#include "base/debug/elf_reader.h"
#include "build/build_config.h"
namespace base {
namespace {
// Returns the unique build ID for a module loaded at |module_addr|. Returns the
// empty string if the function fails to get the build ID.
//
// Build IDs follow a cross-platform format consisting of several fields
// concatenated together:
// - the module's unique ID, and
// - the age suffix for incremental builds.
//
// On POSIX, the unique ID is read from the ELF binary located at |module_addr|.
// The age field is always 0.
std::string GetUniqueBuildId(const void* module_addr) {
base::debug::ElfBuildIdBuffer build_id;
size_t build_id_length =
base::debug::ReadElfBuildId(module_addr, true, build_id);
if (!build_id_length)
return std::string();
// Append 0 for the age value.
return std::string(build_id, build_id_length) + "0";
}
// Returns the offset from |module_addr| to the first byte following the last
// executable segment from the ELF file mapped at |module_addr|.
// It's defined this way so that any executable address from this module is in
// range [addr, addr + GetLastExecutableOffset(addr)).
// If no executable segment is found, returns 0.
size_t GetLastExecutableOffset(const void* module_addr) {
size_t max_offset = 0;
for (const Phdr& header : base::debug::GetElfProgramHeaders(module_addr)) {
if (header.p_type != PT_LOAD || !(header.p_flags & PF_X))
continue;
max_offset = std::max(max_offset,
static_cast<size_t>(header.p_vaddr + header.p_memsz));
}
return max_offset;
}
class PosixModule : public ModuleCache::Module {
public:
PosixModule(const Dl_info& dl_info);
PosixModule(const PosixModule&) = delete;
PosixModule& operator=(const PosixModule&) = delete;
// ModuleCache::Module
uintptr_t GetBaseAddress() const override { return base_address_; }
std::string GetId() const override { return id_; }
FilePath GetDebugBasename() const override { return debug_basename_; }
size_t GetSize() const override { return size_; }
bool IsNative() const override { return true; }
private:
uintptr_t base_address_;
std::string id_;
FilePath debug_basename_;
size_t size_;
};
PosixModule::PosixModule(const Dl_info& dl_info)
: base_address_(reinterpret_cast<uintptr_t>(dl_info.dli_fbase)),
id_(GetUniqueBuildId(dl_info.dli_fbase)),
debug_basename_(FilePath(dl_info.dli_fname).BaseName()),
size_(GetLastExecutableOffset(dl_info.dli_fbase)) {}
} // namespace
// static
std::unique_ptr<ModuleCache::Module> ModuleCache::CreateModuleForAddress(
uintptr_t address) {
#if defined(ARCH_CPU_ARM64)
// arm64 has execute-only memory (XOM) protecting code pages from being read.
// PosixModule reads executable pages in order to extract module info. This
// may result in a crash if the module is mapped as XOM
// (https://crbug.com/957801).
return nullptr;
#else
Dl_info info;
if (!dladdr(reinterpret_cast<const void*>(address), &info))
return nullptr;
return std::make_unique<PosixModule>(info);
#endif
}
} // namespace base