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