chromium/base/profiler/module_cache_posix.cc

// Copyright 2018 The Chromium Authors
// 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 <optional>
#include <string_view>

#include "base/debug/elf_reader.h"
#include "build/build_config.h"

#if BUILDFLAG(IS_ANDROID)
extern "C" {
// &__executable_start is the start address of the current module.
extern const char __executable_start;
// &__etext is the end addesss of the code segment in the current module.
extern const char _etext;
}
#endif

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) { … }

// 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) { … }

FilePath GetDebugBasenameForModule(const void* base_address,
                                   std::string_view file) { … }

class PosixModule : public ModuleCache::Module { … };

PosixModule::PosixModule(uintptr_t base_address,
                         const std::string& build_id,
                         const FilePath& debug_basename,
                         size_t size)
    : … { … }

}  // namespace

// static
std::unique_ptr<const ModuleCache::Module> ModuleCache::CreateModuleForAddress(
    uintptr_t address) { … }

}  // namespace base