Abseil Common Libraries (C++) (grcp 依赖)
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1613 lines
54 KiB
1613 lines
54 KiB
// Copyright 2018 The Abseil Authors. |
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// |
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// Licensed under the Apache License, Version 2.0 (the "License"); |
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// you may not use this file except in compliance with the License. |
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// You may obtain a copy of the License at |
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// |
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// https://www.apache.org/licenses/LICENSE-2.0 |
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// |
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// Unless required by applicable law or agreed to in writing, software |
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// distributed under the License is distributed on an "AS IS" BASIS, |
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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// See the License for the specific language governing permissions and |
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// limitations under the License. |
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// This library provides Symbolize() function that symbolizes program |
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// counters to their corresponding symbol names on linux platforms. |
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// This library has a minimal implementation of an ELF symbol table |
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// reader (i.e. it doesn't depend on libelf, etc.). |
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// |
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// The algorithm used in Symbolize() is as follows. |
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// |
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// 1. Go through a list of maps in /proc/self/maps and find the map |
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// containing the program counter. |
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// |
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// 2. Open the mapped file and find a regular symbol table inside. |
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// Iterate over symbols in the symbol table and look for the symbol |
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// containing the program counter. If such a symbol is found, |
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// obtain the symbol name, and demangle the symbol if possible. |
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// If the symbol isn't found in the regular symbol table (binary is |
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// stripped), try the same thing with a dynamic symbol table. |
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// |
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// Note that Symbolize() is originally implemented to be used in |
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// signal handlers, hence it doesn't use malloc() and other unsafe |
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// operations. It should be both thread-safe and async-signal-safe. |
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// |
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// Implementation note: |
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// |
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// We don't use heaps but only use stacks. We want to reduce the |
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// stack consumption so that the symbolizer can run on small stacks. |
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// |
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// Here are some numbers collected with GCC 4.1.0 on x86: |
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// - sizeof(Elf32_Sym) = 16 |
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// - sizeof(Elf32_Shdr) = 40 |
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// - sizeof(Elf64_Sym) = 24 |
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// - sizeof(Elf64_Shdr) = 64 |
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// |
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// This implementation is intended to be async-signal-safe but uses some |
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// functions which are not guaranteed to be so, such as memchr() and |
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// memmove(). We assume they are async-signal-safe. |
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#include <dlfcn.h> |
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#include <elf.h> |
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#include <fcntl.h> |
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#include <link.h> // For ElfW() macro. |
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#include <sys/stat.h> |
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#include <sys/types.h> |
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#include <unistd.h> |
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#include <algorithm> |
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#include <array> |
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#include <atomic> |
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#include <cerrno> |
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#include <cinttypes> |
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#include <climits> |
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#include <cstdint> |
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#include <cstdio> |
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#include <cstdlib> |
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#include <cstring> |
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#include "absl/base/casts.h" |
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#include "absl/base/dynamic_annotations.h" |
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#include "absl/base/internal/low_level_alloc.h" |
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#include "absl/base/internal/raw_logging.h" |
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#include "absl/base/internal/spinlock.h" |
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#include "absl/base/port.h" |
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#include "absl/debugging/internal/demangle.h" |
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#include "absl/debugging/internal/vdso_support.h" |
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#include "absl/strings/string_view.h" |
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#if defined(__FreeBSD__) && !defined(ElfW) |
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#define ElfW(x) __ElfN(x) |
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#endif |
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namespace absl { |
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ABSL_NAMESPACE_BEGIN |
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// Value of argv[0]. Used by MaybeInitializeObjFile(). |
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static char *argv0_value = nullptr; |
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void InitializeSymbolizer(const char *argv0) { |
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#ifdef ABSL_HAVE_VDSO_SUPPORT |
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// We need to make sure VDSOSupport::Init() is called before any setuid or |
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// chroot calls, so InitializeSymbolizer() should be called very early in the |
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// life of a program. |
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absl::debugging_internal::VDSOSupport::Init(); |
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#endif |
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if (argv0_value != nullptr) { |
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free(argv0_value); |
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argv0_value = nullptr; |
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} |
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if (argv0 != nullptr && argv0[0] != '\0') { |
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argv0_value = strdup(argv0); |
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} |
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} |
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namespace debugging_internal { |
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namespace { |
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// Re-runs fn until it doesn't cause EINTR. |
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#define NO_INTR(fn) \ |
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do { \ |
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} while ((fn) < 0 && errno == EINTR) |
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// On Linux, ELF_ST_* are defined in <linux/elf.h>. To make this portable |
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// we define our own ELF_ST_BIND and ELF_ST_TYPE if not available. |
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#ifndef ELF_ST_BIND |
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#define ELF_ST_BIND(info) (((unsigned char)(info)) >> 4) |
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#endif |
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#ifndef ELF_ST_TYPE |
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#define ELF_ST_TYPE(info) (((unsigned char)(info)) & 0xF) |
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#endif |
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// Some platforms use a special .opd section to store function pointers. |
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const char kOpdSectionName[] = ".opd"; |
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#if (defined(__powerpc__) && !(_CALL_ELF > 1)) || defined(__ia64) |
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// Use opd section for function descriptors on these platforms, the function |
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// address is the first word of the descriptor. |
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enum { kPlatformUsesOPDSections = 1 }; |
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#else // not PPC or IA64 |
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enum { kPlatformUsesOPDSections = 0 }; |
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#endif |
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// This works for PowerPC & IA64 only. A function descriptor consist of two |
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// pointers and the first one is the function's entry. |
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const size_t kFunctionDescriptorSize = sizeof(void *) * 2; |
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const int kMaxDecorators = 10; // Seems like a reasonable upper limit. |
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struct InstalledSymbolDecorator { |
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SymbolDecorator fn; |
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void *arg; |
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int ticket; |
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}; |
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int g_num_decorators; |
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InstalledSymbolDecorator g_decorators[kMaxDecorators]; |
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struct FileMappingHint { |
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const void *start; |
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const void *end; |
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uint64_t offset; |
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const char *filename; |
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}; |
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// Protects g_decorators. |
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// We are using SpinLock and not a Mutex here, because we may be called |
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// from inside Mutex::Lock itself, and it prohibits recursive calls. |
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// This happens in e.g. base/stacktrace_syscall_unittest. |
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// Moreover, we are using only TryLock(), if the decorator list |
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// is being modified (is busy), we skip all decorators, and possibly |
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// loose some info. Sorry, that's the best we could do. |
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ABSL_CONST_INIT absl::base_internal::SpinLock g_decorators_mu( |
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absl::kConstInit, absl::base_internal::SCHEDULE_KERNEL_ONLY); |
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const int kMaxFileMappingHints = 8; |
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int g_num_file_mapping_hints; |
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FileMappingHint g_file_mapping_hints[kMaxFileMappingHints]; |
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// Protects g_file_mapping_hints. |
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ABSL_CONST_INIT absl::base_internal::SpinLock g_file_mapping_mu( |
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absl::kConstInit, absl::base_internal::SCHEDULE_KERNEL_ONLY); |
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// Async-signal-safe function to zero a buffer. |
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// memset() is not guaranteed to be async-signal-safe. |
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static void SafeMemZero(void* p, size_t size) { |
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unsigned char *c = static_cast<unsigned char *>(p); |
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while (size--) { |
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*c++ = 0; |
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} |
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} |
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struct ObjFile { |
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ObjFile() |
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: filename(nullptr), |
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start_addr(nullptr), |
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end_addr(nullptr), |
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offset(0), |
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fd(-1), |
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elf_type(-1) { |
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SafeMemZero(&elf_header, sizeof(elf_header)); |
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SafeMemZero(&phdr[0], sizeof(phdr)); |
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} |
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char *filename; |
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const void *start_addr; |
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const void *end_addr; |
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uint64_t offset; |
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// The following fields are initialized on the first access to the |
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// object file. |
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int fd; |
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int elf_type; |
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ElfW(Ehdr) elf_header; |
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// PT_LOAD program header describing executable code. |
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// Normally we expect just one, but SWIFT binaries have two. |
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std::array<ElfW(Phdr), 2> phdr; |
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}; |
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// Build 4-way associative cache for symbols. Within each cache line, symbols |
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// are replaced in LRU order. |
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enum { |
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ASSOCIATIVITY = 4, |
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}; |
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struct SymbolCacheLine { |
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const void *pc[ASSOCIATIVITY]; |
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char *name[ASSOCIATIVITY]; |
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// age[i] is incremented when a line is accessed. it's reset to zero if the |
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// i'th entry is read. |
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uint32_t age[ASSOCIATIVITY]; |
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}; |
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// --------------------------------------------------------------- |
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// An async-signal-safe arena for LowLevelAlloc |
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static std::atomic<base_internal::LowLevelAlloc::Arena *> g_sig_safe_arena; |
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static base_internal::LowLevelAlloc::Arena *SigSafeArena() { |
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return g_sig_safe_arena.load(std::memory_order_acquire); |
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} |
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static void InitSigSafeArena() { |
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if (SigSafeArena() == nullptr) { |
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base_internal::LowLevelAlloc::Arena *new_arena = |
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base_internal::LowLevelAlloc::NewArena( |
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base_internal::LowLevelAlloc::kAsyncSignalSafe); |
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base_internal::LowLevelAlloc::Arena *old_value = nullptr; |
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if (!g_sig_safe_arena.compare_exchange_strong(old_value, new_arena, |
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std::memory_order_release, |
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std::memory_order_relaxed)) { |
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// We lost a race to allocate an arena; deallocate. |
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base_internal::LowLevelAlloc::DeleteArena(new_arena); |
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} |
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} |
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} |
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// --------------------------------------------------------------- |
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// An AddrMap is a vector of ObjFile, using SigSafeArena() for allocation. |
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class AddrMap { |
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public: |
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AddrMap() : size_(0), allocated_(0), obj_(nullptr) {} |
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~AddrMap() { base_internal::LowLevelAlloc::Free(obj_); } |
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int Size() const { return size_; } |
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ObjFile *At(int i) { return &obj_[i]; } |
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ObjFile *Add(); |
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void Clear(); |
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private: |
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int size_; // count of valid elements (<= allocated_) |
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int allocated_; // count of allocated elements |
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ObjFile *obj_; // array of allocated_ elements |
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AddrMap(const AddrMap &) = delete; |
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AddrMap &operator=(const AddrMap &) = delete; |
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}; |
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void AddrMap::Clear() { |
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for (int i = 0; i != size_; i++) { |
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At(i)->~ObjFile(); |
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} |
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size_ = 0; |
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} |
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ObjFile *AddrMap::Add() { |
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if (size_ == allocated_) { |
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int new_allocated = allocated_ * 2 + 50; |
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ObjFile *new_obj_ = |
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static_cast<ObjFile *>(base_internal::LowLevelAlloc::AllocWithArena( |
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new_allocated * sizeof(*new_obj_), SigSafeArena())); |
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if (obj_) { |
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memcpy(new_obj_, obj_, allocated_ * sizeof(*new_obj_)); |
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base_internal::LowLevelAlloc::Free(obj_); |
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} |
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obj_ = new_obj_; |
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allocated_ = new_allocated; |
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} |
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return new (&obj_[size_++]) ObjFile; |
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} |
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// --------------------------------------------------------------- |
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enum FindSymbolResult { SYMBOL_NOT_FOUND = 1, SYMBOL_TRUNCATED, SYMBOL_FOUND }; |
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class Symbolizer { |
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public: |
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Symbolizer(); |
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~Symbolizer(); |
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const char *GetSymbol(const void *const pc); |
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private: |
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char *CopyString(const char *s) { |
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int len = strlen(s); |
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char *dst = static_cast<char *>( |
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base_internal::LowLevelAlloc::AllocWithArena(len + 1, SigSafeArena())); |
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ABSL_RAW_CHECK(dst != nullptr, "out of memory"); |
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memcpy(dst, s, len + 1); |
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return dst; |
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} |
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ObjFile *FindObjFile(const void *const start, |
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size_t size) ABSL_ATTRIBUTE_NOINLINE; |
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static bool RegisterObjFile(const char *filename, |
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const void *const start_addr, |
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const void *const end_addr, uint64_t offset, |
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void *arg); |
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SymbolCacheLine *GetCacheLine(const void *const pc); |
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const char *FindSymbolInCache(const void *const pc); |
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const char *InsertSymbolInCache(const void *const pc, const char *name); |
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void AgeSymbols(SymbolCacheLine *line); |
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void ClearAddrMap(); |
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FindSymbolResult GetSymbolFromObjectFile(const ObjFile &obj, |
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const void *const pc, |
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const ptrdiff_t relocation, |
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char *out, int out_size, |
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char *tmp_buf, int tmp_buf_size); |
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const char *GetUncachedSymbol(const void *pc); |
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enum { |
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SYMBOL_BUF_SIZE = 3072, |
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TMP_BUF_SIZE = 1024, |
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SYMBOL_CACHE_LINES = 128, |
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}; |
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AddrMap addr_map_; |
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bool ok_; |
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bool addr_map_read_; |
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char symbol_buf_[SYMBOL_BUF_SIZE]; |
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// tmp_buf_ will be used to store arrays of ElfW(Shdr) and ElfW(Sym) |
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// so we ensure that tmp_buf_ is properly aligned to store either. |
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alignas(16) char tmp_buf_[TMP_BUF_SIZE]; |
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static_assert(alignof(ElfW(Shdr)) <= 16, |
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"alignment of tmp buf too small for Shdr"); |
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static_assert(alignof(ElfW(Sym)) <= 16, |
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"alignment of tmp buf too small for Sym"); |
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SymbolCacheLine symbol_cache_[SYMBOL_CACHE_LINES]; |
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}; |
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static std::atomic<Symbolizer *> g_cached_symbolizer; |
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} // namespace |
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static int SymbolizerSize() { |
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#if defined(__wasm__) || defined(__asmjs__) |
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int pagesize = getpagesize(); |
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#else |
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int pagesize = sysconf(_SC_PAGESIZE); |
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#endif |
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return ((sizeof(Symbolizer) - 1) / pagesize + 1) * pagesize; |
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} |
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// Return (and set null) g_cached_symbolized_state if it is not null. |
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// Otherwise return a new symbolizer. |
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static Symbolizer *AllocateSymbolizer() { |
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InitSigSafeArena(); |
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Symbolizer *symbolizer = |
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g_cached_symbolizer.exchange(nullptr, std::memory_order_acquire); |
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if (symbolizer != nullptr) { |
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return symbolizer; |
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} |
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return new (base_internal::LowLevelAlloc::AllocWithArena( |
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SymbolizerSize(), SigSafeArena())) Symbolizer(); |
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} |
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// Set g_cached_symbolize_state to s if it is null, otherwise |
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// delete s. |
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static void FreeSymbolizer(Symbolizer *s) { |
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Symbolizer *old_cached_symbolizer = nullptr; |
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if (!g_cached_symbolizer.compare_exchange_strong(old_cached_symbolizer, s, |
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std::memory_order_release, |
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std::memory_order_relaxed)) { |
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s->~Symbolizer(); |
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base_internal::LowLevelAlloc::Free(s); |
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} |
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} |
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Symbolizer::Symbolizer() : ok_(true), addr_map_read_(false) { |
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for (SymbolCacheLine &symbol_cache_line : symbol_cache_) { |
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for (size_t j = 0; j < ABSL_ARRAYSIZE(symbol_cache_line.name); ++j) { |
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symbol_cache_line.pc[j] = nullptr; |
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symbol_cache_line.name[j] = nullptr; |
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symbol_cache_line.age[j] = 0; |
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} |
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} |
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} |
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Symbolizer::~Symbolizer() { |
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for (SymbolCacheLine &symbol_cache_line : symbol_cache_) { |
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for (char *s : symbol_cache_line.name) { |
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base_internal::LowLevelAlloc::Free(s); |
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} |
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} |
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ClearAddrMap(); |
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} |
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// We don't use assert() since it's not guaranteed to be |
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// async-signal-safe. Instead we define a minimal assertion |
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// macro. So far, we don't need pretty printing for __FILE__, etc. |
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#define SAFE_ASSERT(expr) ((expr) ? static_cast<void>(0) : abort()) |
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// Read up to "count" bytes from file descriptor "fd" into the buffer |
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// starting at "buf" while handling short reads and EINTR. On |
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// success, return the number of bytes read. Otherwise, return -1. |
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static ssize_t ReadPersistent(int fd, void *buf, size_t count) { |
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SAFE_ASSERT(fd >= 0); |
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SAFE_ASSERT(count <= SSIZE_MAX); |
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char *buf0 = reinterpret_cast<char *>(buf); |
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size_t num_bytes = 0; |
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while (num_bytes < count) { |
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ssize_t len; |
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NO_INTR(len = read(fd, buf0 + num_bytes, count - num_bytes)); |
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if (len < 0) { // There was an error other than EINTR. |
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ABSL_RAW_LOG(WARNING, "read failed: errno=%d", errno); |
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return -1; |
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} |
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if (len == 0) { // Reached EOF. |
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break; |
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} |
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num_bytes += len; |
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} |
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SAFE_ASSERT(num_bytes <= count); |
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return static_cast<ssize_t>(num_bytes); |
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} |
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// Read up to "count" bytes from "offset" in the file pointed by file |
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// descriptor "fd" into the buffer starting at "buf". On success, |
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// return the number of bytes read. Otherwise, return -1. |
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static ssize_t ReadFromOffset(const int fd, void *buf, const size_t count, |
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const off_t offset) { |
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off_t off = lseek(fd, offset, SEEK_SET); |
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if (off == (off_t)-1) { |
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ABSL_RAW_LOG(WARNING, "lseek(%d, %ju, SEEK_SET) failed: errno=%d", fd, |
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static_cast<uintmax_t>(offset), errno); |
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return -1; |
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} |
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return ReadPersistent(fd, buf, count); |
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} |
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// Try reading exactly "count" bytes from "offset" bytes in a file |
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// pointed by "fd" into the buffer starting at "buf" while handling |
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// short reads and EINTR. On success, return true. Otherwise, return |
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// false. |
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static bool ReadFromOffsetExact(const int fd, void *buf, const size_t count, |
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const off_t offset) { |
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ssize_t len = ReadFromOffset(fd, buf, count, offset); |
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return len >= 0 && static_cast<size_t>(len) == count; |
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} |
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// Returns elf_header.e_type if the file pointed by fd is an ELF binary. |
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static int FileGetElfType(const int fd) { |
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ElfW(Ehdr) elf_header; |
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if (!ReadFromOffsetExact(fd, &elf_header, sizeof(elf_header), 0)) { |
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return -1; |
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} |
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if (memcmp(elf_header.e_ident, ELFMAG, SELFMAG) != 0) { |
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return -1; |
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} |
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return elf_header.e_type; |
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} |
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// Read the section headers in the given ELF binary, and if a section |
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// of the specified type is found, set the output to this section header |
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// and return true. Otherwise, return false. |
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// To keep stack consumption low, we would like this function to not get |
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// inlined. |
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static ABSL_ATTRIBUTE_NOINLINE bool GetSectionHeaderByType( |
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const int fd, ElfW(Half) sh_num, const off_t sh_offset, ElfW(Word) type, |
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ElfW(Shdr) * out, char *tmp_buf, int tmp_buf_size) { |
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ElfW(Shdr) *buf = reinterpret_cast<ElfW(Shdr) *>(tmp_buf); |
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const int buf_entries = tmp_buf_size / sizeof(buf[0]); |
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const int buf_bytes = buf_entries * sizeof(buf[0]); |
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for (int i = 0; i < sh_num;) { |
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const ssize_t num_bytes_left = (sh_num - i) * sizeof(buf[0]); |
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const ssize_t num_bytes_to_read = |
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(buf_bytes > num_bytes_left) ? num_bytes_left : buf_bytes; |
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const off_t offset = sh_offset + i * sizeof(buf[0]); |
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const ssize_t len = ReadFromOffset(fd, buf, num_bytes_to_read, offset); |
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if (len % sizeof(buf[0]) != 0) { |
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ABSL_RAW_LOG( |
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WARNING, |
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"Reading %zd bytes from offset %ju returned %zd which is not a " |
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"multiple of %zu.", |
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num_bytes_to_read, static_cast<uintmax_t>(offset), len, |
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sizeof(buf[0])); |
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return false; |
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} |
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const ssize_t num_headers_in_buf = len / sizeof(buf[0]); |
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SAFE_ASSERT(num_headers_in_buf <= buf_entries); |
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for (int j = 0; j < num_headers_in_buf; ++j) { |
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if (buf[j].sh_type == type) { |
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*out = buf[j]; |
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return true; |
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} |
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} |
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i += num_headers_in_buf; |
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} |
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return false; |
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} |
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// There is no particular reason to limit section name to 63 characters, |
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// but there has (as yet) been no need for anything longer either. |
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const int kMaxSectionNameLen = 64; |
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bool ForEachSection(int fd, |
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const std::function<bool(absl::string_view name, |
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const ElfW(Shdr) &)> &callback) { |
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ElfW(Ehdr) elf_header; |
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if (!ReadFromOffsetExact(fd, &elf_header, sizeof(elf_header), 0)) { |
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return false; |
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} |
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ElfW(Shdr) shstrtab; |
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off_t shstrtab_offset = |
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(elf_header.e_shoff + elf_header.e_shentsize * elf_header.e_shstrndx); |
|
if (!ReadFromOffsetExact(fd, &shstrtab, sizeof(shstrtab), shstrtab_offset)) { |
|
return false; |
|
} |
|
|
|
for (int i = 0; i < elf_header.e_shnum; ++i) { |
|
ElfW(Shdr) out; |
|
off_t section_header_offset = |
|
(elf_header.e_shoff + elf_header.e_shentsize * i); |
|
if (!ReadFromOffsetExact(fd, &out, sizeof(out), section_header_offset)) { |
|
return false; |
|
} |
|
off_t name_offset = shstrtab.sh_offset + out.sh_name; |
|
char header_name[kMaxSectionNameLen]; |
|
ssize_t n_read = |
|
ReadFromOffset(fd, &header_name, kMaxSectionNameLen, name_offset); |
|
if (n_read == -1) { |
|
return false; |
|
} else if (n_read > kMaxSectionNameLen) { |
|
// Long read? |
|
return false; |
|
} |
|
|
|
absl::string_view name(header_name, strnlen(header_name, n_read)); |
|
if (!callback(name, out)) { |
|
break; |
|
} |
|
} |
|
return true; |
|
} |
|
|
|
// name_len should include terminating '\0'. |
|
bool GetSectionHeaderByName(int fd, const char *name, size_t name_len, |
|
ElfW(Shdr) * out) { |
|
char header_name[kMaxSectionNameLen]; |
|
if (sizeof(header_name) < name_len) { |
|
ABSL_RAW_LOG(WARNING, |
|
"Section name '%s' is too long (%zu); " |
|
"section will not be found (even if present).", |
|
name, name_len); |
|
// No point in even trying. |
|
return false; |
|
} |
|
|
|
ElfW(Ehdr) elf_header; |
|
if (!ReadFromOffsetExact(fd, &elf_header, sizeof(elf_header), 0)) { |
|
return false; |
|
} |
|
|
|
ElfW(Shdr) shstrtab; |
|
off_t shstrtab_offset = |
|
(elf_header.e_shoff + elf_header.e_shentsize * elf_header.e_shstrndx); |
|
if (!ReadFromOffsetExact(fd, &shstrtab, sizeof(shstrtab), shstrtab_offset)) { |
|
return false; |
|
} |
|
|
|
for (int i = 0; i < elf_header.e_shnum; ++i) { |
|
off_t section_header_offset = |
|
(elf_header.e_shoff + elf_header.e_shentsize * i); |
|
if (!ReadFromOffsetExact(fd, out, sizeof(*out), section_header_offset)) { |
|
return false; |
|
} |
|
off_t name_offset = shstrtab.sh_offset + out->sh_name; |
|
ssize_t n_read = ReadFromOffset(fd, &header_name, name_len, name_offset); |
|
if (n_read < 0) { |
|
return false; |
|
} else if (static_cast<size_t>(n_read) != name_len) { |
|
// Short read -- name could be at end of file. |
|
continue; |
|
} |
|
if (memcmp(header_name, name, name_len) == 0) { |
|
return true; |
|
} |
|
} |
|
return false; |
|
} |
|
|
|
// Compare symbols at in the same address. |
|
// Return true if we should pick symbol1. |
|
static bool ShouldPickFirstSymbol(const ElfW(Sym) & symbol1, |
|
const ElfW(Sym) & symbol2) { |
|
// If one of the symbols is weak and the other is not, pick the one |
|
// this is not a weak symbol. |
|
char bind1 = ELF_ST_BIND(symbol1.st_info); |
|
char bind2 = ELF_ST_BIND(symbol1.st_info); |
|
if (bind1 == STB_WEAK && bind2 != STB_WEAK) return false; |
|
if (bind2 == STB_WEAK && bind1 != STB_WEAK) return true; |
|
|
|
// If one of the symbols has zero size and the other is not, pick the |
|
// one that has non-zero size. |
|
if (symbol1.st_size != 0 && symbol2.st_size == 0) { |
|
return true; |
|
} |
|
if (symbol1.st_size == 0 && symbol2.st_size != 0) { |
|
return false; |
|
} |
|
|
|
// If one of the symbols has no type and the other is not, pick the |
|
// one that has a type. |
|
char type1 = ELF_ST_TYPE(symbol1.st_info); |
|
char type2 = ELF_ST_TYPE(symbol1.st_info); |
|
if (type1 != STT_NOTYPE && type2 == STT_NOTYPE) { |
|
return true; |
|
} |
|
if (type1 == STT_NOTYPE && type2 != STT_NOTYPE) { |
|
return false; |
|
} |
|
|
|
// Pick the first one, if we still cannot decide. |
|
return true; |
|
} |
|
|
|
// Return true if an address is inside a section. |
|
static bool InSection(const void *address, const ElfW(Shdr) * section) { |
|
const char *start = reinterpret_cast<const char *>(section->sh_addr); |
|
size_t size = static_cast<size_t>(section->sh_size); |
|
return start <= address && address < (start + size); |
|
} |
|
|
|
static const char *ComputeOffset(const char *base, ptrdiff_t offset) { |
|
// Note: cast to uintptr_t to avoid undefined behavior when base evaluates to |
|
// zero and offset is non-zero. |
|
return reinterpret_cast<const char *>( |
|
reinterpret_cast<uintptr_t>(base) + offset); |
|
} |
|
|
|
// Read a symbol table and look for the symbol containing the |
|
// pc. Iterate over symbols in a symbol table and look for the symbol |
|
// containing "pc". If the symbol is found, and its name fits in |
|
// out_size, the name is written into out and SYMBOL_FOUND is returned. |
|
// If the name does not fit, truncated name is written into out, |
|
// and SYMBOL_TRUNCATED is returned. Out is NUL-terminated. |
|
// If the symbol is not found, SYMBOL_NOT_FOUND is returned; |
|
// To keep stack consumption low, we would like this function to not get |
|
// inlined. |
|
static ABSL_ATTRIBUTE_NOINLINE FindSymbolResult FindSymbol( |
|
const void *const pc, const int fd, char *out, int out_size, |
|
ptrdiff_t relocation, const ElfW(Shdr) * strtab, const ElfW(Shdr) * symtab, |
|
const ElfW(Shdr) * opd, char *tmp_buf, int tmp_buf_size) { |
|
if (symtab == nullptr) { |
|
return SYMBOL_NOT_FOUND; |
|
} |
|
|
|
// Read multiple symbols at once to save read() calls. |
|
ElfW(Sym) *buf = reinterpret_cast<ElfW(Sym) *>(tmp_buf); |
|
const int buf_entries = tmp_buf_size / sizeof(buf[0]); |
|
|
|
const int num_symbols = symtab->sh_size / symtab->sh_entsize; |
|
|
|
// On platforms using an .opd section (PowerPC & IA64), a function symbol |
|
// has the address of a function descriptor, which contains the real |
|
// starting address. However, we do not always want to use the real |
|
// starting address because we sometimes want to symbolize a function |
|
// pointer into the .opd section, e.g. FindSymbol(&foo,...). |
|
const bool pc_in_opd = |
|
kPlatformUsesOPDSections && opd != nullptr && InSection(pc, opd); |
|
const bool deref_function_descriptor_pointer = |
|
kPlatformUsesOPDSections && opd != nullptr && !pc_in_opd; |
|
|
|
ElfW(Sym) best_match; |
|
SafeMemZero(&best_match, sizeof(best_match)); |
|
bool found_match = false; |
|
for (int i = 0; i < num_symbols;) { |
|
off_t offset = symtab->sh_offset + i * symtab->sh_entsize; |
|
const int num_remaining_symbols = num_symbols - i; |
|
const int entries_in_chunk = std::min(num_remaining_symbols, buf_entries); |
|
const int bytes_in_chunk = entries_in_chunk * sizeof(buf[0]); |
|
const ssize_t len = ReadFromOffset(fd, buf, bytes_in_chunk, offset); |
|
SAFE_ASSERT(len % sizeof(buf[0]) == 0); |
|
const ssize_t num_symbols_in_buf = len / sizeof(buf[0]); |
|
SAFE_ASSERT(num_symbols_in_buf <= entries_in_chunk); |
|
for (int j = 0; j < num_symbols_in_buf; ++j) { |
|
const ElfW(Sym) &symbol = buf[j]; |
|
|
|
// For a DSO, a symbol address is relocated by the loading address. |
|
// We keep the original address for opd redirection below. |
|
const char *const original_start_address = |
|
reinterpret_cast<const char *>(symbol.st_value); |
|
const char *start_address = |
|
ComputeOffset(original_start_address, relocation); |
|
|
|
#ifdef __arm__ |
|
// ARM functions are always aligned to multiples of two bytes; the |
|
// lowest-order bit in start_address is ignored by the CPU and indicates |
|
// whether the function contains ARM (0) or Thumb (1) code. We don't care |
|
// about what encoding is being used; we just want the real start address |
|
// of the function. |
|
start_address = reinterpret_cast<const char *>( |
|
reinterpret_cast<uintptr_t>(start_address) & ~1); |
|
#endif |
|
|
|
if (deref_function_descriptor_pointer && |
|
InSection(original_start_address, opd)) { |
|
// The opd section is mapped into memory. Just dereference |
|
// start_address to get the first double word, which points to the |
|
// function entry. |
|
start_address = *reinterpret_cast<const char *const *>(start_address); |
|
} |
|
|
|
// If pc is inside the .opd section, it points to a function descriptor. |
|
const size_t size = pc_in_opd ? kFunctionDescriptorSize : symbol.st_size; |
|
const void *const end_address = ComputeOffset(start_address, size); |
|
if (symbol.st_value != 0 && // Skip null value symbols. |
|
symbol.st_shndx != 0 && // Skip undefined symbols. |
|
#ifdef STT_TLS |
|
ELF_ST_TYPE(symbol.st_info) != STT_TLS && // Skip thread-local data. |
|
#endif // STT_TLS |
|
((start_address <= pc && pc < end_address) || |
|
(start_address == pc && pc == end_address))) { |
|
if (!found_match || ShouldPickFirstSymbol(symbol, best_match)) { |
|
found_match = true; |
|
best_match = symbol; |
|
} |
|
} |
|
} |
|
i += num_symbols_in_buf; |
|
} |
|
|
|
if (found_match) { |
|
const size_t off = strtab->sh_offset + best_match.st_name; |
|
const ssize_t n_read = ReadFromOffset(fd, out, out_size, off); |
|
if (n_read <= 0) { |
|
// This should never happen. |
|
ABSL_RAW_LOG(WARNING, |
|
"Unable to read from fd %d at offset %zu: n_read = %zd", fd, |
|
off, n_read); |
|
return SYMBOL_NOT_FOUND; |
|
} |
|
ABSL_RAW_CHECK(n_read <= out_size, "ReadFromOffset read too much data."); |
|
|
|
// strtab->sh_offset points into .strtab-like section that contains |
|
// NUL-terminated strings: '\0foo\0barbaz\0...". |
|
// |
|
// sh_offset+st_name points to the start of symbol name, but we don't know |
|
// how long the symbol is, so we try to read as much as we have space for, |
|
// and usually over-read (i.e. there is a NUL somewhere before n_read). |
|
if (memchr(out, '\0', n_read) == nullptr) { |
|
// Either out_size was too small (n_read == out_size and no NUL), or |
|
// we tried to read past the EOF (n_read < out_size) and .strtab is |
|
// corrupt (missing terminating NUL; should never happen for valid ELF). |
|
out[n_read - 1] = '\0'; |
|
return SYMBOL_TRUNCATED; |
|
} |
|
return SYMBOL_FOUND; |
|
} |
|
|
|
return SYMBOL_NOT_FOUND; |
|
} |
|
|
|
// Get the symbol name of "pc" from the file pointed by "fd". Process |
|
// both regular and dynamic symbol tables if necessary. |
|
// See FindSymbol() comment for description of return value. |
|
FindSymbolResult Symbolizer::GetSymbolFromObjectFile( |
|
const ObjFile &obj, const void *const pc, const ptrdiff_t relocation, |
|
char *out, int out_size, char *tmp_buf, int tmp_buf_size) { |
|
ElfW(Shdr) symtab; |
|
ElfW(Shdr) strtab; |
|
ElfW(Shdr) opd; |
|
ElfW(Shdr) *opd_ptr = nullptr; |
|
|
|
// On platforms using an .opd sections for function descriptor, read |
|
// the section header. The .opd section is in data segment and should be |
|
// loaded but we check that it is mapped just to be extra careful. |
|
if (kPlatformUsesOPDSections) { |
|
if (GetSectionHeaderByName(obj.fd, kOpdSectionName, |
|
sizeof(kOpdSectionName) - 1, &opd) && |
|
FindObjFile(reinterpret_cast<const char *>(opd.sh_addr) + relocation, |
|
opd.sh_size) != nullptr) { |
|
opd_ptr = &opd; |
|
} else { |
|
return SYMBOL_NOT_FOUND; |
|
} |
|
} |
|
|
|
// Consult a regular symbol table, then fall back to the dynamic symbol table. |
|
for (const auto symbol_table_type : {SHT_SYMTAB, SHT_DYNSYM}) { |
|
if (!GetSectionHeaderByType(obj.fd, obj.elf_header.e_shnum, |
|
obj.elf_header.e_shoff, symbol_table_type, |
|
&symtab, tmp_buf, tmp_buf_size)) { |
|
continue; |
|
} |
|
if (!ReadFromOffsetExact( |
|
obj.fd, &strtab, sizeof(strtab), |
|
obj.elf_header.e_shoff + symtab.sh_link * sizeof(symtab))) { |
|
continue; |
|
} |
|
const FindSymbolResult rc = |
|
FindSymbol(pc, obj.fd, out, out_size, relocation, &strtab, &symtab, |
|
opd_ptr, tmp_buf, tmp_buf_size); |
|
if (rc != SYMBOL_NOT_FOUND) { |
|
return rc; |
|
} |
|
} |
|
|
|
return SYMBOL_NOT_FOUND; |
|
} |
|
|
|
namespace { |
|
// Thin wrapper around a file descriptor so that the file descriptor |
|
// gets closed for sure. |
|
class FileDescriptor { |
|
public: |
|
explicit FileDescriptor(int fd) : fd_(fd) {} |
|
FileDescriptor(const FileDescriptor &) = delete; |
|
FileDescriptor &operator=(const FileDescriptor &) = delete; |
|
|
|
~FileDescriptor() { |
|
if (fd_ >= 0) { |
|
NO_INTR(close(fd_)); |
|
} |
|
} |
|
|
|
int get() const { return fd_; } |
|
|
|
private: |
|
const int fd_; |
|
}; |
|
|
|
// Helper class for reading lines from file. |
|
// |
|
// Note: we don't use ProcMapsIterator since the object is big (it has |
|
// a 5k array member) and uses async-unsafe functions such as sscanf() |
|
// and snprintf(). |
|
class LineReader { |
|
public: |
|
explicit LineReader(int fd, char *buf, int buf_len) |
|
: fd_(fd), |
|
buf_len_(buf_len), |
|
buf_(buf), |
|
bol_(buf), |
|
eol_(buf), |
|
eod_(buf) {} |
|
|
|
LineReader(const LineReader &) = delete; |
|
LineReader &operator=(const LineReader &) = delete; |
|
|
|
// Read '\n'-terminated line from file. On success, modify "bol" |
|
// and "eol", then return true. Otherwise, return false. |
|
// |
|
// Note: if the last line doesn't end with '\n', the line will be |
|
// dropped. It's an intentional behavior to make the code simple. |
|
bool ReadLine(const char **bol, const char **eol) { |
|
if (BufferIsEmpty()) { // First time. |
|
const ssize_t num_bytes = ReadPersistent(fd_, buf_, buf_len_); |
|
if (num_bytes <= 0) { // EOF or error. |
|
return false; |
|
} |
|
eod_ = buf_ + num_bytes; |
|
bol_ = buf_; |
|
} else { |
|
bol_ = eol_ + 1; // Advance to the next line in the buffer. |
|
SAFE_ASSERT(bol_ <= eod_); // "bol_" can point to "eod_". |
|
if (!HasCompleteLine()) { |
|
const int incomplete_line_length = eod_ - bol_; |
|
// Move the trailing incomplete line to the beginning. |
|
memmove(buf_, bol_, incomplete_line_length); |
|
// Read text from file and append it. |
|
char *const append_pos = buf_ + incomplete_line_length; |
|
const int capacity_left = buf_len_ - incomplete_line_length; |
|
const ssize_t num_bytes = |
|
ReadPersistent(fd_, append_pos, capacity_left); |
|
if (num_bytes <= 0) { // EOF or error. |
|
return false; |
|
} |
|
eod_ = append_pos + num_bytes; |
|
bol_ = buf_; |
|
} |
|
} |
|
eol_ = FindLineFeed(); |
|
if (eol_ == nullptr) { // '\n' not found. Malformed line. |
|
return false; |
|
} |
|
*eol_ = '\0'; // Replace '\n' with '\0'. |
|
|
|
*bol = bol_; |
|
*eol = eol_; |
|
return true; |
|
} |
|
|
|
private: |
|
char *FindLineFeed() const { |
|
return reinterpret_cast<char *>(memchr(bol_, '\n', eod_ - bol_)); |
|
} |
|
|
|
bool BufferIsEmpty() const { return buf_ == eod_; } |
|
|
|
bool HasCompleteLine() const { |
|
return !BufferIsEmpty() && FindLineFeed() != nullptr; |
|
} |
|
|
|
const int fd_; |
|
const int buf_len_; |
|
char *const buf_; |
|
char *bol_; |
|
char *eol_; |
|
const char *eod_; // End of data in "buf_". |
|
}; |
|
} // namespace |
|
|
|
// Place the hex number read from "start" into "*hex". The pointer to |
|
// the first non-hex character or "end" is returned. |
|
static const char *GetHex(const char *start, const char *end, |
|
uint64_t *const value) { |
|
uint64_t hex = 0; |
|
const char *p; |
|
for (p = start; p < end; ++p) { |
|
int ch = *p; |
|
if ((ch >= '0' && ch <= '9') || (ch >= 'A' && ch <= 'F') || |
|
(ch >= 'a' && ch <= 'f')) { |
|
hex = (hex << 4) | (ch < 'A' ? ch - '0' : (ch & 0xF) + 9); |
|
} else { // Encountered the first non-hex character. |
|
break; |
|
} |
|
} |
|
SAFE_ASSERT(p <= end); |
|
*value = hex; |
|
return p; |
|
} |
|
|
|
static const char *GetHex(const char *start, const char *end, |
|
const void **const addr) { |
|
uint64_t hex = 0; |
|
const char *p = GetHex(start, end, &hex); |
|
*addr = reinterpret_cast<void *>(hex); |
|
return p; |
|
} |
|
|
|
// Normally we are only interested in "r?x" maps. |
|
// On the PowerPC, function pointers point to descriptors in the .opd |
|
// section. The descriptors themselves are not executable code, so |
|
// we need to relax the check below to "r??". |
|
static bool ShouldUseMapping(const char *const flags) { |
|
return flags[0] == 'r' && (kPlatformUsesOPDSections || flags[2] == 'x'); |
|
} |
|
|
|
// Read /proc/self/maps and run "callback" for each mmapped file found. If |
|
// "callback" returns false, stop scanning and return true. Else continue |
|
// scanning /proc/self/maps. Return true if no parse error is found. |
|
static ABSL_ATTRIBUTE_NOINLINE bool ReadAddrMap( |
|
bool (*callback)(const char *filename, const void *const start_addr, |
|
const void *const end_addr, uint64_t offset, void *arg), |
|
void *arg, void *tmp_buf, int tmp_buf_size) { |
|
// Use /proc/self/task/<pid>/maps instead of /proc/self/maps. The latter |
|
// requires kernel to stop all threads, and is significantly slower when there |
|
// are 1000s of threads. |
|
char maps_path[80]; |
|
snprintf(maps_path, sizeof(maps_path), "/proc/self/task/%d/maps", getpid()); |
|
|
|
int maps_fd; |
|
NO_INTR(maps_fd = open(maps_path, O_RDONLY)); |
|
FileDescriptor wrapped_maps_fd(maps_fd); |
|
if (wrapped_maps_fd.get() < 0) { |
|
ABSL_RAW_LOG(WARNING, "%s: errno=%d", maps_path, errno); |
|
return false; |
|
} |
|
|
|
// Iterate over maps and look for the map containing the pc. Then |
|
// look into the symbol tables inside. |
|
LineReader reader(wrapped_maps_fd.get(), static_cast<char *>(tmp_buf), |
|
tmp_buf_size); |
|
while (true) { |
|
const char *cursor; |
|
const char *eol; |
|
if (!reader.ReadLine(&cursor, &eol)) { // EOF or malformed line. |
|
break; |
|
} |
|
|
|
const char *line = cursor; |
|
const void *start_address; |
|
// Start parsing line in /proc/self/maps. Here is an example: |
|
// |
|
// 08048000-0804c000 r-xp 00000000 08:01 2142121 /bin/cat |
|
// |
|
// We want start address (08048000), end address (0804c000), flags |
|
// (r-xp) and file name (/bin/cat). |
|
|
|
// Read start address. |
|
cursor = GetHex(cursor, eol, &start_address); |
|
if (cursor == eol || *cursor != '-') { |
|
ABSL_RAW_LOG(WARNING, "Corrupt /proc/self/maps line: %s", line); |
|
return false; |
|
} |
|
++cursor; // Skip '-'. |
|
|
|
// Read end address. |
|
const void *end_address; |
|
cursor = GetHex(cursor, eol, &end_address); |
|
if (cursor == eol || *cursor != ' ') { |
|
ABSL_RAW_LOG(WARNING, "Corrupt /proc/self/maps line: %s", line); |
|
return false; |
|
} |
|
++cursor; // Skip ' '. |
|
|
|
// Read flags. Skip flags until we encounter a space or eol. |
|
const char *const flags_start = cursor; |
|
while (cursor < eol && *cursor != ' ') { |
|
++cursor; |
|
} |
|
// We expect at least four letters for flags (ex. "r-xp"). |
|
if (cursor == eol || cursor < flags_start + 4) { |
|
ABSL_RAW_LOG(WARNING, "Corrupt /proc/self/maps: %s", line); |
|
return false; |
|
} |
|
|
|
// Check flags. |
|
if (!ShouldUseMapping(flags_start)) { |
|
continue; // We skip this map. |
|
} |
|
++cursor; // Skip ' '. |
|
|
|
// Read file offset. |
|
uint64_t offset; |
|
cursor = GetHex(cursor, eol, &offset); |
|
++cursor; // Skip ' '. |
|
|
|
// Skip to file name. "cursor" now points to dev. We need to skip at least |
|
// two spaces for dev and inode. |
|
int num_spaces = 0; |
|
while (cursor < eol) { |
|
if (*cursor == ' ') { |
|
++num_spaces; |
|
} else if (num_spaces >= 2) { |
|
// The first non-space character after skipping two spaces |
|
// is the beginning of the file name. |
|
break; |
|
} |
|
++cursor; |
|
} |
|
|
|
// Check whether this entry corresponds to our hint table for the true |
|
// filename. |
|
bool hinted = |
|
GetFileMappingHint(&start_address, &end_address, &offset, &cursor); |
|
if (!hinted && (cursor == eol || cursor[0] == '[')) { |
|
// not an object file, typically [vdso] or [vsyscall] |
|
continue; |
|
} |
|
if (!callback(cursor, start_address, end_address, offset, arg)) break; |
|
} |
|
return true; |
|
} |
|
|
|
// Find the objfile mapped in address region containing [addr, addr + len). |
|
ObjFile *Symbolizer::FindObjFile(const void *const addr, size_t len) { |
|
for (int i = 0; i < 2; ++i) { |
|
if (!ok_) return nullptr; |
|
|
|
// Read /proc/self/maps if necessary |
|
if (!addr_map_read_) { |
|
addr_map_read_ = true; |
|
if (!ReadAddrMap(RegisterObjFile, this, tmp_buf_, TMP_BUF_SIZE)) { |
|
ok_ = false; |
|
return nullptr; |
|
} |
|
} |
|
|
|
int lo = 0; |
|
int hi = addr_map_.Size(); |
|
while (lo < hi) { |
|
int mid = (lo + hi) / 2; |
|
if (addr < addr_map_.At(mid)->end_addr) { |
|
hi = mid; |
|
} else { |
|
lo = mid + 1; |
|
} |
|
} |
|
if (lo != addr_map_.Size()) { |
|
ObjFile *obj = addr_map_.At(lo); |
|
SAFE_ASSERT(obj->end_addr > addr); |
|
if (addr >= obj->start_addr && |
|
reinterpret_cast<const char *>(addr) + len <= obj->end_addr) |
|
return obj; |
|
} |
|
|
|
// The address mapping may have changed since it was last read. Retry. |
|
ClearAddrMap(); |
|
} |
|
return nullptr; |
|
} |
|
|
|
void Symbolizer::ClearAddrMap() { |
|
for (int i = 0; i != addr_map_.Size(); i++) { |
|
ObjFile *o = addr_map_.At(i); |
|
base_internal::LowLevelAlloc::Free(o->filename); |
|
if (o->fd >= 0) { |
|
NO_INTR(close(o->fd)); |
|
} |
|
} |
|
addr_map_.Clear(); |
|
addr_map_read_ = false; |
|
} |
|
|
|
// Callback for ReadAddrMap to register objfiles in an in-memory table. |
|
bool Symbolizer::RegisterObjFile(const char *filename, |
|
const void *const start_addr, |
|
const void *const end_addr, uint64_t offset, |
|
void *arg) { |
|
Symbolizer *impl = static_cast<Symbolizer *>(arg); |
|
|
|
// Files are supposed to be added in the increasing address order. Make |
|
// sure that's the case. |
|
int addr_map_size = impl->addr_map_.Size(); |
|
if (addr_map_size != 0) { |
|
ObjFile *old = impl->addr_map_.At(addr_map_size - 1); |
|
if (old->end_addr > end_addr) { |
|
ABSL_RAW_LOG(ERROR, |
|
"Unsorted addr map entry: 0x%" PRIxPTR ": %s <-> 0x%" PRIxPTR |
|
": %s", |
|
reinterpret_cast<uintptr_t>(end_addr), filename, |
|
reinterpret_cast<uintptr_t>(old->end_addr), old->filename); |
|
return true; |
|
} else if (old->end_addr == end_addr) { |
|
// The same entry appears twice. This sometimes happens for [vdso]. |
|
if (old->start_addr != start_addr || |
|
strcmp(old->filename, filename) != 0) { |
|
ABSL_RAW_LOG(ERROR, |
|
"Duplicate addr 0x%" PRIxPTR ": %s <-> 0x%" PRIxPTR ": %s", |
|
reinterpret_cast<uintptr_t>(end_addr), filename, |
|
reinterpret_cast<uintptr_t>(old->end_addr), old->filename); |
|
} |
|
return true; |
|
} else if (old->end_addr == start_addr && |
|
reinterpret_cast<uintptr_t>(old->start_addr) - old->offset == |
|
reinterpret_cast<uintptr_t>(start_addr) - offset && |
|
strcmp(old->filename, filename) == 0) { |
|
// Two contiguous map entries that span a contiguous region of the file, |
|
// perhaps because some part of the file was mlock()ed. Combine them. |
|
old->end_addr = end_addr; |
|
return true; |
|
} |
|
} |
|
ObjFile *obj = impl->addr_map_.Add(); |
|
obj->filename = impl->CopyString(filename); |
|
obj->start_addr = start_addr; |
|
obj->end_addr = end_addr; |
|
obj->offset = offset; |
|
obj->elf_type = -1; // filled on demand |
|
obj->fd = -1; // opened on demand |
|
return true; |
|
} |
|
|
|
// This function wraps the Demangle function to provide an interface |
|
// where the input symbol is demangled in-place. |
|
// To keep stack consumption low, we would like this function to not |
|
// get inlined. |
|
static ABSL_ATTRIBUTE_NOINLINE void DemangleInplace(char *out, int out_size, |
|
char *tmp_buf, |
|
int tmp_buf_size) { |
|
if (Demangle(out, tmp_buf, tmp_buf_size)) { |
|
// Demangling succeeded. Copy to out if the space allows. |
|
int len = strlen(tmp_buf); |
|
if (len + 1 <= out_size) { // +1 for '\0'. |
|
SAFE_ASSERT(len < tmp_buf_size); |
|
memmove(out, tmp_buf, len + 1); |
|
} |
|
} |
|
} |
|
|
|
SymbolCacheLine *Symbolizer::GetCacheLine(const void *const pc) { |
|
uintptr_t pc0 = reinterpret_cast<uintptr_t>(pc); |
|
pc0 >>= 3; // drop the low 3 bits |
|
|
|
// Shuffle bits. |
|
pc0 ^= (pc0 >> 6) ^ (pc0 >> 12) ^ (pc0 >> 18); |
|
return &symbol_cache_[pc0 % SYMBOL_CACHE_LINES]; |
|
} |
|
|
|
void Symbolizer::AgeSymbols(SymbolCacheLine *line) { |
|
for (uint32_t &age : line->age) { |
|
++age; |
|
} |
|
} |
|
|
|
const char *Symbolizer::FindSymbolInCache(const void *const pc) { |
|
if (pc == nullptr) return nullptr; |
|
|
|
SymbolCacheLine *line = GetCacheLine(pc); |
|
for (size_t i = 0; i < ABSL_ARRAYSIZE(line->pc); ++i) { |
|
if (line->pc[i] == pc) { |
|
AgeSymbols(line); |
|
line->age[i] = 0; |
|
return line->name[i]; |
|
} |
|
} |
|
return nullptr; |
|
} |
|
|
|
const char *Symbolizer::InsertSymbolInCache(const void *const pc, |
|
const char *name) { |
|
SAFE_ASSERT(pc != nullptr); |
|
|
|
SymbolCacheLine *line = GetCacheLine(pc); |
|
uint32_t max_age = 0; |
|
int oldest_index = -1; |
|
for (size_t i = 0; i < ABSL_ARRAYSIZE(line->pc); ++i) { |
|
if (line->pc[i] == nullptr) { |
|
AgeSymbols(line); |
|
line->pc[i] = pc; |
|
line->name[i] = CopyString(name); |
|
line->age[i] = 0; |
|
return line->name[i]; |
|
} |
|
if (line->age[i] >= max_age) { |
|
max_age = line->age[i]; |
|
oldest_index = i; |
|
} |
|
} |
|
|
|
AgeSymbols(line); |
|
ABSL_RAW_CHECK(oldest_index >= 0, "Corrupt cache"); |
|
base_internal::LowLevelAlloc::Free(line->name[oldest_index]); |
|
line->pc[oldest_index] = pc; |
|
line->name[oldest_index] = CopyString(name); |
|
line->age[oldest_index] = 0; |
|
return line->name[oldest_index]; |
|
} |
|
|
|
static void MaybeOpenFdFromSelfExe(ObjFile *obj) { |
|
if (memcmp(obj->start_addr, ELFMAG, SELFMAG) != 0) { |
|
return; |
|
} |
|
int fd = open("/proc/self/exe", O_RDONLY); |
|
if (fd == -1) { |
|
return; |
|
} |
|
// Verify that contents of /proc/self/exe matches in-memory image of |
|
// the binary. This can fail if the "deleted" binary is in fact not |
|
// the main executable, or for binaries that have the first PT_LOAD |
|
// segment smaller than 4K. We do it in four steps so that the |
|
// buffer is smaller and we don't consume too much stack space. |
|
const char *mem = reinterpret_cast<const char *>(obj->start_addr); |
|
for (int i = 0; i < 4; ++i) { |
|
char buf[1024]; |
|
ssize_t n = read(fd, buf, sizeof(buf)); |
|
if (n != sizeof(buf) || memcmp(buf, mem, sizeof(buf)) != 0) { |
|
close(fd); |
|
return; |
|
} |
|
mem += sizeof(buf); |
|
} |
|
obj->fd = fd; |
|
} |
|
|
|
static bool MaybeInitializeObjFile(ObjFile *obj) { |
|
if (obj->fd < 0) { |
|
obj->fd = open(obj->filename, O_RDONLY); |
|
|
|
if (obj->fd < 0) { |
|
// Getting /proc/self/exe here means that we were hinted. |
|
if (strcmp(obj->filename, "/proc/self/exe") == 0) { |
|
// /proc/self/exe may be inaccessible (due to setuid, etc.), so try |
|
// accessing the binary via argv0. |
|
if (argv0_value != nullptr) { |
|
obj->fd = open(argv0_value, O_RDONLY); |
|
} |
|
} else { |
|
MaybeOpenFdFromSelfExe(obj); |
|
} |
|
} |
|
|
|
if (obj->fd < 0) { |
|
ABSL_RAW_LOG(WARNING, "%s: open failed: errno=%d", obj->filename, errno); |
|
return false; |
|
} |
|
obj->elf_type = FileGetElfType(obj->fd); |
|
if (obj->elf_type < 0) { |
|
ABSL_RAW_LOG(WARNING, "%s: wrong elf type: %d", obj->filename, |
|
obj->elf_type); |
|
return false; |
|
} |
|
|
|
if (!ReadFromOffsetExact(obj->fd, &obj->elf_header, sizeof(obj->elf_header), |
|
0)) { |
|
ABSL_RAW_LOG(WARNING, "%s: failed to read elf header", obj->filename); |
|
return false; |
|
} |
|
const int phnum = obj->elf_header.e_phnum; |
|
const int phentsize = obj->elf_header.e_phentsize; |
|
size_t phoff = obj->elf_header.e_phoff; |
|
size_t num_executable_load_segments = 0; |
|
for (int j = 0; j < phnum; j++) { |
|
ElfW(Phdr) phdr; |
|
if (!ReadFromOffsetExact(obj->fd, &phdr, sizeof(phdr), phoff)) { |
|
ABSL_RAW_LOG(WARNING, "%s: failed to read program header %d", |
|
obj->filename, j); |
|
return false; |
|
} |
|
phoff += phentsize; |
|
constexpr int rx = PF_X | PF_R; |
|
if (phdr.p_type != PT_LOAD || (phdr.p_flags & rx) != rx) { |
|
// Not a LOAD segment, or not executable code. |
|
continue; |
|
} |
|
if (num_executable_load_segments < obj->phdr.size()) { |
|
memcpy(&obj->phdr[num_executable_load_segments++], &phdr, sizeof(phdr)); |
|
} else { |
|
ABSL_RAW_LOG(WARNING, "%s: too many executable LOAD segments", |
|
obj->filename); |
|
break; |
|
} |
|
} |
|
if (num_executable_load_segments == 0) { |
|
// This object has no "r-x" LOAD segments. That's unexpected. |
|
ABSL_RAW_LOG(WARNING, "%s: no executable LOAD segments", obj->filename); |
|
return false; |
|
} |
|
} |
|
return true; |
|
} |
|
|
|
// The implementation of our symbolization routine. If it |
|
// successfully finds the symbol containing "pc" and obtains the |
|
// symbol name, returns pointer to that symbol. Otherwise, returns nullptr. |
|
// If any symbol decorators have been installed via InstallSymbolDecorator(), |
|
// they are called here as well. |
|
// To keep stack consumption low, we would like this function to not |
|
// get inlined. |
|
const char *Symbolizer::GetUncachedSymbol(const void *pc) { |
|
ObjFile *const obj = FindObjFile(pc, 1); |
|
ptrdiff_t relocation = 0; |
|
int fd = -1; |
|
if (obj != nullptr) { |
|
if (MaybeInitializeObjFile(obj)) { |
|
const size_t start_addr = reinterpret_cast<size_t>(obj->start_addr); |
|
if (obj->elf_type == ET_DYN && start_addr >= obj->offset) { |
|
// This object was relocated. |
|
// |
|
// For obj->offset > 0, adjust the relocation since a mapping at offset |
|
// X in the file will have a start address of [true relocation]+X. |
|
relocation = start_addr - obj->offset; |
|
|
|
// Note: some binaries have multiple "rx" LOAD segments. We must |
|
// find the right one. |
|
ElfW(Phdr) *phdr = nullptr; |
|
for (size_t j = 0; j < obj->phdr.size(); j++) { |
|
ElfW(Phdr) &p = obj->phdr[j]; |
|
if (p.p_type != PT_LOAD) { |
|
// We only expect PT_LOADs. This must be PT_NULL that we didn't |
|
// write over (i.e. we exhausted all interesting PT_LOADs). |
|
ABSL_RAW_CHECK(p.p_type == PT_NULL, "unexpected p_type"); |
|
break; |
|
} |
|
if (pc < reinterpret_cast<void *>(start_addr + p.p_memsz)) { |
|
phdr = &p; |
|
break; |
|
} |
|
} |
|
if (phdr == nullptr) { |
|
// That's unexpected. Hope for the best. |
|
ABSL_RAW_LOG( |
|
WARNING, |
|
"%s: unable to find LOAD segment for pc: %p, start_addr: %zx", |
|
obj->filename, pc, start_addr); |
|
} else { |
|
// Adjust relocation in case phdr.p_vaddr != 0. |
|
// This happens for binaries linked with `lld --rosegment`, and for |
|
// binaries linked with BFD `ld -z separate-code`. |
|
relocation -= phdr->p_vaddr - phdr->p_offset; |
|
} |
|
} |
|
|
|
fd = obj->fd; |
|
if (GetSymbolFromObjectFile(*obj, pc, relocation, symbol_buf_, |
|
sizeof(symbol_buf_), tmp_buf_, |
|
sizeof(tmp_buf_)) == SYMBOL_FOUND) { |
|
// Only try to demangle the symbol name if it fit into symbol_buf_. |
|
DemangleInplace(symbol_buf_, sizeof(symbol_buf_), tmp_buf_, |
|
sizeof(tmp_buf_)); |
|
} |
|
} |
|
} else { |
|
#if ABSL_HAVE_VDSO_SUPPORT |
|
VDSOSupport vdso; |
|
if (vdso.IsPresent()) { |
|
VDSOSupport::SymbolInfo symbol_info; |
|
if (vdso.LookupSymbolByAddress(pc, &symbol_info)) { |
|
// All VDSO symbols are known to be short. |
|
size_t len = strlen(symbol_info.name); |
|
ABSL_RAW_CHECK(len + 1 < sizeof(symbol_buf_), |
|
"VDSO symbol unexpectedly long"); |
|
memcpy(symbol_buf_, symbol_info.name, len + 1); |
|
} |
|
} |
|
#endif |
|
} |
|
|
|
if (g_decorators_mu.TryLock()) { |
|
if (g_num_decorators > 0) { |
|
SymbolDecoratorArgs decorator_args = { |
|
pc, relocation, fd, symbol_buf_, sizeof(symbol_buf_), |
|
tmp_buf_, sizeof(tmp_buf_), nullptr}; |
|
for (int i = 0; i < g_num_decorators; ++i) { |
|
decorator_args.arg = g_decorators[i].arg; |
|
g_decorators[i].fn(&decorator_args); |
|
} |
|
} |
|
g_decorators_mu.Unlock(); |
|
} |
|
if (symbol_buf_[0] == '\0') { |
|
return nullptr; |
|
} |
|
symbol_buf_[sizeof(symbol_buf_) - 1] = '\0'; // Paranoia. |
|
return InsertSymbolInCache(pc, symbol_buf_); |
|
} |
|
|
|
const char *Symbolizer::GetSymbol(const void *pc) { |
|
const char *entry = FindSymbolInCache(pc); |
|
if (entry != nullptr) { |
|
return entry; |
|
} |
|
symbol_buf_[0] = '\0'; |
|
|
|
#ifdef __hppa__ |
|
{ |
|
// In some contexts (e.g., return addresses), PA-RISC uses the lowest two |
|
// bits of the address to indicate the privilege level. Clear those bits |
|
// before trying to symbolize. |
|
const auto pc_bits = reinterpret_cast<uintptr_t>(pc); |
|
const auto address = pc_bits & ~0x3; |
|
entry = GetUncachedSymbol(reinterpret_cast<const void *>(address)); |
|
if (entry != nullptr) { |
|
return entry; |
|
} |
|
|
|
// In some contexts, PA-RISC also uses bit 1 of the address to indicate that |
|
// this is a cross-DSO function pointer. Such function pointers actually |
|
// point to a procedure label, a struct whose first 32-bit (pointer) element |
|
// actually points to the function text. With no symbol found for this |
|
// address so far, try interpreting it as a cross-DSO function pointer and |
|
// see how that goes. |
|
if (pc_bits & 0x2) { |
|
return GetUncachedSymbol(*reinterpret_cast<const void *const *>(address)); |
|
} |
|
|
|
return nullptr; |
|
} |
|
#else |
|
return GetUncachedSymbol(pc); |
|
#endif |
|
} |
|
|
|
bool RemoveAllSymbolDecorators(void) { |
|
if (!g_decorators_mu.TryLock()) { |
|
// Someone else is using decorators. Get out. |
|
return false; |
|
} |
|
g_num_decorators = 0; |
|
g_decorators_mu.Unlock(); |
|
return true; |
|
} |
|
|
|
bool RemoveSymbolDecorator(int ticket) { |
|
if (!g_decorators_mu.TryLock()) { |
|
// Someone else is using decorators. Get out. |
|
return false; |
|
} |
|
for (int i = 0; i < g_num_decorators; ++i) { |
|
if (g_decorators[i].ticket == ticket) { |
|
while (i < g_num_decorators - 1) { |
|
g_decorators[i] = g_decorators[i + 1]; |
|
++i; |
|
} |
|
g_num_decorators = i; |
|
break; |
|
} |
|
} |
|
g_decorators_mu.Unlock(); |
|
return true; // Decorator is known to be removed. |
|
} |
|
|
|
int InstallSymbolDecorator(SymbolDecorator decorator, void *arg) { |
|
static int ticket = 0; |
|
|
|
if (!g_decorators_mu.TryLock()) { |
|
// Someone else is using decorators. Get out. |
|
return -2; |
|
} |
|
int ret = ticket; |
|
if (g_num_decorators >= kMaxDecorators) { |
|
ret = -1; |
|
} else { |
|
g_decorators[g_num_decorators] = {decorator, arg, ticket++}; |
|
++g_num_decorators; |
|
} |
|
g_decorators_mu.Unlock(); |
|
return ret; |
|
} |
|
|
|
bool RegisterFileMappingHint(const void *start, const void *end, uint64_t offset, |
|
const char *filename) { |
|
SAFE_ASSERT(start <= end); |
|
SAFE_ASSERT(filename != nullptr); |
|
|
|
InitSigSafeArena(); |
|
|
|
if (!g_file_mapping_mu.TryLock()) { |
|
return false; |
|
} |
|
|
|
bool ret = true; |
|
if (g_num_file_mapping_hints >= kMaxFileMappingHints) { |
|
ret = false; |
|
} else { |
|
// TODO(ckennelly): Move this into a string copy routine. |
|
int len = strlen(filename); |
|
char *dst = static_cast<char *>( |
|
base_internal::LowLevelAlloc::AllocWithArena(len + 1, SigSafeArena())); |
|
ABSL_RAW_CHECK(dst != nullptr, "out of memory"); |
|
memcpy(dst, filename, len + 1); |
|
|
|
auto &hint = g_file_mapping_hints[g_num_file_mapping_hints++]; |
|
hint.start = start; |
|
hint.end = end; |
|
hint.offset = offset; |
|
hint.filename = dst; |
|
} |
|
|
|
g_file_mapping_mu.Unlock(); |
|
return ret; |
|
} |
|
|
|
bool GetFileMappingHint(const void **start, const void **end, uint64_t *offset, |
|
const char **filename) { |
|
if (!g_file_mapping_mu.TryLock()) { |
|
return false; |
|
} |
|
bool found = false; |
|
for (int i = 0; i < g_num_file_mapping_hints; i++) { |
|
if (g_file_mapping_hints[i].start <= *start && |
|
*end <= g_file_mapping_hints[i].end) { |
|
// We assume that the start_address for the mapping is the base |
|
// address of the ELF section, but when [start_address,end_address) is |
|
// not strictly equal to [hint.start, hint.end), that assumption is |
|
// invalid. |
|
// |
|
// This uses the hint's start address (even though hint.start is not |
|
// necessarily equal to start_address) to ensure the correct |
|
// relocation is computed later. |
|
*start = g_file_mapping_hints[i].start; |
|
*end = g_file_mapping_hints[i].end; |
|
*offset = g_file_mapping_hints[i].offset; |
|
*filename = g_file_mapping_hints[i].filename; |
|
found = true; |
|
break; |
|
} |
|
} |
|
g_file_mapping_mu.Unlock(); |
|
return found; |
|
} |
|
|
|
} // namespace debugging_internal |
|
|
|
bool Symbolize(const void *pc, char *out, int out_size) { |
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// Symbolization is very slow under tsan. |
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ABSL_ANNOTATE_IGNORE_READS_AND_WRITES_BEGIN(); |
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SAFE_ASSERT(out_size >= 0); |
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debugging_internal::Symbolizer *s = debugging_internal::AllocateSymbolizer(); |
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const char *name = s->GetSymbol(pc); |
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bool ok = false; |
|
if (name != nullptr && out_size > 0) { |
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strncpy(out, name, out_size); |
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ok = true; |
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if (out[out_size - 1] != '\0') { |
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// strncpy() does not '\0' terminate when it truncates. Do so, with |
|
// trailing ellipsis. |
|
static constexpr char kEllipsis[] = "..."; |
|
int ellipsis_size = |
|
std::min(implicit_cast<int>(strlen(kEllipsis)), out_size - 1); |
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memcpy(out + out_size - ellipsis_size - 1, kEllipsis, ellipsis_size); |
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out[out_size - 1] = '\0'; |
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} |
|
} |
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debugging_internal::FreeSymbolizer(s); |
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ABSL_ANNOTATE_IGNORE_READS_AND_WRITES_END(); |
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return ok; |
|
} |
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|
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ABSL_NAMESPACE_END |
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} // namespace absl |
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|
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extern "C" bool AbslInternalGetFileMappingHint(const void **start, |
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const void **end, uint64_t *offset, |
|
const char **filename) { |
|
return absl::debugging_internal::GetFileMappingHint(start, end, offset, |
|
filename); |
|
}
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