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authorGravatar Abseil Team <absl-team@google.com>2018-02-27 13:38:47 -0800
committerGravatar Gennadiy Rozental <rogeeff@google.com>2018-02-28 12:52:04 -0500
commit7fda099641d0f7302654bef69727eea5aeecbbca (patch)
tree742ece5d84ba4017820c186fbcc61141eae99841 /absl
parent0d40cb771eec8741f44e5979cfccf1eeeedb012a (diff)
Changes imported from Abseil "staging" branch:
- f0a03a750a36dfbd7ab06d2913430ed5f988fd68 Add absl::RegisterSymbolizer() to mutex_nonprod.cc for AP... by Derek Mauro <dmauro@google.com> - f34a2ee35b4f6b321c570c51b0c381647176df63 Add the async signal-safe Symbolizer to Abseil. by Derek Mauro <dmauro@google.com> - 6a29ec2d6dc080691f6d32e1982201d1d173bdb3 Document preferred placement of ABSL_CONST_INIT attribute... by Abseil Team <absl-team@google.com> - 6f04ed6aa9c19bd717f0e8f422a97f3e3368cf30 Internal change. by Abseil Team <absl-team@google.com> - 0af9a330aff8fc0b41dcb3fe519930c36b01a9ef Declare absl::raw_logging_internal::SafeWriteToStderr in ... by Abseil Team <absl-team@google.com> - 223ff26745d31dfb4b59c36f3dee5441506af3c2 Fix ABSL_ARRAYSIZE() to handle rvalues. by Xiaoyi Zhang <zhangxy@google.com> GitOrigin-RevId: f0a03a750a36dfbd7ab06d2913430ed5f988fd68 Change-Id: I491f9cc81ca3ee078fb737cbf8fa9bf6a730eee1
Diffstat (limited to 'absl')
-rw-r--r--absl/base/attributes.h11
-rw-r--r--absl/base/internal/raw_logging.cc12
-rw-r--r--absl/base/internal/raw_logging.h7
-rw-r--r--absl/base/macros.h2
-rw-r--r--absl/debugging/BUILD.bazel36
-rw-r--r--absl/debugging/CMakeLists.txt32
-rw-r--r--absl/debugging/internal/symbolize.h122
-rw-r--r--absl/debugging/symbolize.cc21
-rw-r--r--absl/debugging/symbolize.h35
-rw-r--r--absl/debugging/symbolize_elf.inc1473
-rw-r--r--absl/debugging/symbolize_test.cc450
-rw-r--r--absl/debugging/symbolize_unimplemented.inc35
-rw-r--r--absl/synchronization/internal/mutex_nonprod.cc2
13 files changed, 2221 insertions, 17 deletions
diff --git a/absl/base/attributes.h b/absl/base/attributes.h
index c44b2e89..a4ec7e7c 100644
--- a/absl/base/attributes.h
+++ b/absl/base/attributes.h
@@ -543,11 +543,18 @@
// not compile (on supported platforms) unless the variable has a constant
// initializer. This is useful for variables with static and thread storage
// duration, because it guarantees that they will not suffer from the so-called
-// "static init order fiasco".
+// "static init order fiasco". Prefer to put this attribute on the most visible
+// declaration of the variable, if there's more than one, because code that
+// accesses the variable can then use the attribute for optimization.
//
// Example:
//
-// ABSL_CONST_INIT static MyType my_var = MakeMyType(...);
+// class MyClass {
+// public:
+// ABSL_CONST_INIT static MyType my_var;
+// };
+//
+// MyType MyClass::my_var = MakeMyType(...);
//
// Note that this attribute is redundant if the variable is declared constexpr.
#if ABSL_HAVE_CPP_ATTRIBUTE(clang::require_constant_initialization)
diff --git a/absl/base/internal/raw_logging.cc b/absl/base/internal/raw_logging.cc
index a332ec73..1ce13888 100644
--- a/absl/base/internal/raw_logging.cc
+++ b/absl/base/internal/raw_logging.cc
@@ -104,12 +104,6 @@ inline static bool VADoRawLog(char** buf, int* size,
static constexpr int kLogBufSize = 3000;
-namespace absl {
-namespace raw_logging_internal {
-void SafeWriteToStderr(const char *s, size_t len);
-} // namespace raw_logging_internal
-} // namespace absl
-
namespace {
// CAVEAT: vsnprintf called from *DoRawLog below has some (exotic) code paths
@@ -188,12 +182,6 @@ void RawLogVA(absl::LogSeverity severity, const char* file, int line,
namespace absl {
namespace raw_logging_internal {
-
-// Writes the provided buffer directly to stderr, in a safe, low-level manner.
-//
-// In POSIX this means calling write(), which is async-signal safe and does
-// not malloc. If the platform supports the SYS_write syscall, we invoke that
-// directly to side-step any libc interception.
void SafeWriteToStderr(const char *s, size_t len) {
#if defined(ABSL_HAVE_SYSCALL_WRITE)
syscall(SYS_write, STDERR_FILENO, s, len);
diff --git a/absl/base/internal/raw_logging.h b/absl/base/internal/raw_logging.h
index 1b2a44b7..a2b7207a 100644
--- a/absl/base/internal/raw_logging.h
+++ b/absl/base/internal/raw_logging.h
@@ -74,6 +74,13 @@ namespace raw_logging_internal {
void RawLog(absl::LogSeverity severity, const char* file, int line,
const char* format, ...) ABSL_PRINTF_ATTRIBUTE(4, 5);
+// Writes the provided buffer directly to stderr, in a safe, low-level manner.
+//
+// In POSIX this means calling write(), which is async-signal safe and does
+// not malloc. If the platform supports the SYS_write syscall, we invoke that
+// directly to side-step any libc interception.
+void SafeWriteToStderr(const char *s, size_t len);
+
// compile-time function to get the "base" filename, that is, the part of
// a filename after the last "/" or "\" path separator. The search starts at
// the end of the std::string; the second parameter is the length of the std::string.
diff --git a/absl/base/macros.h b/absl/base/macros.h
index 5ae0f05b..114a7be1 100644
--- a/absl/base/macros.h
+++ b/absl/base/macros.h
@@ -46,7 +46,7 @@
namespace absl {
namespace macros_internal {
template <typename T, size_t N>
-char (&ArraySizeHelper(T (&array)[N]))[N];
+auto ArraySizeHelper(const T (&array)[N]) -> char (&)[N];
} // namespace macros_internal
} // namespace absl
#define ABSL_ARRAYSIZE(array) \
diff --git a/absl/debugging/BUILD.bazel b/absl/debugging/BUILD.bazel
index 20b455b8..d62a781d 100644
--- a/absl/debugging/BUILD.bazel
+++ b/absl/debugging/BUILD.bazel
@@ -41,6 +41,42 @@ cc_library(
)
cc_library(
+ name = "symbolize",
+ srcs = [
+ "symbolize.cc",
+ "symbolize_elf.inc",
+ "symbolize_unimplemented.inc",
+ ],
+ hdrs = [
+ "internal/symbolize.h",
+ "symbolize.h",
+ ],
+ copts = ABSL_DEFAULT_COPTS,
+ deps = [
+ ":debugging_internal",
+ ":demangle_internal",
+ "//absl/base",
+ "//absl/base:core_headers",
+ "//absl/base:malloc_internal",
+ ],
+)
+
+cc_test(
+ name = "symbolize_test",
+ srcs = ["symbolize_test.cc"],
+ copts = ABSL_TEST_COPTS,
+ deps = [
+ ":stack_consumption",
+ ":symbolize",
+ "//absl/base",
+ "//absl/base:core_headers",
+ "//absl/base:malloc_extension",
+ "//absl/memory",
+ "@com_google_googletest//:gtest",
+ ],
+)
+
+cc_library(
name = "debugging_internal",
srcs = [
"internal/address_is_readable.cc",
diff --git a/absl/debugging/CMakeLists.txt b/absl/debugging/CMakeLists.txt
index 758c00fe..b9aec5fa 100644
--- a/absl/debugging/CMakeLists.txt
+++ b/absl/debugging/CMakeLists.txt
@@ -17,6 +17,7 @@
list(APPEND DEBUGGING_PUBLIC_HEADERS
"leak_check.h"
"stacktrace.h"
+ "symbolize.h"
)
@@ -25,6 +26,7 @@ list(APPEND DEBUGGING_INTERNAL_HEADERS
"internal/demangle.h"
"internal/elf_mem_image.h"
"internal/stacktrace_config.h"
+ "internal/symbolize.h"
"internal/vdso_support.h"
)
@@ -32,13 +34,21 @@ list(APPEND DEBUGGING_INTERNAL_HEADERS
list(APPEND STACKTRACE_SRC
"stacktrace.cc"
"internal/address_is_readable.cc"
- "internal/demangle.cc"
"internal/elf_mem_image.cc"
"internal/vdso_support.cc"
${DEBUGGING_PUBLIC_HEADERS}
${DEBUGGING_INTERNAL_HEADERS}
)
+list(APPEND SYMBOLIZE_SRC
+ "symbolize.cc"
+ "symbolize_elf.inc"
+ "symbolize_unimplemented.inc"
+ "internal/demangle.cc"
+ ${DEBUGGING_PUBLIC_HEADERS}
+ ${DEBUGGING_INTERNAL_HEADERS}
+)
+
absl_library(
TARGET
absl_stacktrace
@@ -48,6 +58,14 @@ absl_library(
stacktrace
)
+absl_library(
+ TARGET
+ absl_symbolize
+ SOURCES
+ ${SYMBOLIZE_SRC}
+ EXPORT_NAME
+ symbolize
+)
list(APPEND LEAK_CHECK_SRC
"leak_check.cc"
@@ -112,9 +130,19 @@ absl_test(
SOURCES
${DEMANGLE_TEST_SRC}
PUBLIC_LIBRARIES
- absl_stacktrace absl_stack_consumption
+ absl_symbolize absl_stack_consumption
)
+list(APPEND SYMBOLIZE_TEST_SRC "symbolize_test.cc")
+
+absl_test(
+ TARGET
+ symbolize_test
+ SOURCES
+ ${SYMBOLIZE_TEST_SRC}
+ PUBLIC_LIBRARIES
+ absl_symbolize absl_stack_consumption
+)
# test leak_check_test
list(APPEND LEAK_CHECK_TEST_SRC "leak_check_test.cc")
diff --git a/absl/debugging/internal/symbolize.h b/absl/debugging/internal/symbolize.h
new file mode 100644
index 00000000..802ea222
--- /dev/null
+++ b/absl/debugging/internal/symbolize.h
@@ -0,0 +1,122 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// This file contains internal parts of the Abseil symbolizer.
+// Do not depend on the anything in this file, it may change at anytime.
+
+#ifndef ABSL_DEBUGGING_INTERNAL_SYMBOLIZE_H_
+#define ABSL_DEBUGGING_INTERNAL_SYMBOLIZE_H_
+
+#include <cstddef>
+#include <cstdint>
+
+#ifdef ABSL_INTERNAL_HAVE_ELF_SYMBOLIZE
+#error ABSL_INTERNAL_HAVE_ELF_SYMBOLIZE cannot be directly set
+#elif defined(__ELF__) && defined(__GLIBC__) && !defined(__native_client__) && \
+ !defined(__asmjs__)
+#define ABSL_INTERNAL_HAVE_ELF_SYMBOLIZE 1
+
+#include <elf.h>
+#include <link.h> // For ElfW() macro.
+#include <functional>
+#include <string>
+
+namespace absl {
+namespace debugging_internal {
+
+// Iterates over all sections, invoking callback on each with the section name
+// and the section header.
+//
+// Returns true on success; otherwise returns false in case of errors.
+//
+// This is not async-signal-safe.
+bool ForEachSection(
+ int fd, const std::function<bool(const std::string& name, const ElfW(Shdr) &)>&
+ callback);
+
+// Gets the section header for the given name, if it exists. Returns true on
+// success. Otherwise, returns false.
+bool GetSectionHeaderByName(int fd, const char *name, size_t name_len,
+ ElfW(Shdr) *out);
+
+} // namespace debugging_internal
+} // namespace absl
+
+#endif // ABSL_INTERNAL_HAVE_ELF_SYMBOLIZE
+
+namespace absl {
+namespace debugging_internal {
+
+struct SymbolDecoratorArgs {
+ // The program counter we are getting symbolic name for.
+ const void *pc;
+ // 0 for main executable, load address for shared libraries.
+ ptrdiff_t relocation;
+ // Read-only file descriptor for ELF image covering "pc",
+ // or -1 if no such ELF image exists in /proc/self/maps.
+ int fd;
+ // Output buffer, size.
+ // Note: the buffer may not be empty -- default symbolizer may have already
+ // produced some output, and earlier decorators may have adorned it in
+ // some way. You are free to replace or augment the contents (within the
+ // symbol_buf_size limit).
+ char *const symbol_buf;
+ size_t symbol_buf_size;
+ // Temporary scratch space, size.
+ // Use that space in preference to allocating your own stack buffer to
+ // conserve stack.
+ char *const tmp_buf;
+ size_t tmp_buf_size;
+ // User-provided argument
+ void* arg;
+};
+using SymbolDecorator = void (*)(const SymbolDecoratorArgs *);
+
+// Installs a function-pointer as a decorator. Returns a value less than zero
+// if the system cannot install the decorator. Otherwise, returns a unique
+// identifier corresponding to the decorator. This identifier can be used to
+// uninstall the decorator - See RemoveSymbolDecorator() below.
+int InstallSymbolDecorator(SymbolDecorator decorator, void* arg);
+
+// Removes a previously installed function-pointer decorator. Parameter "ticket"
+// is the return-value from calling InstallSymbolDecorator().
+bool RemoveSymbolDecorator(int ticket);
+
+// Remove all installed decorators. Returns true if successful, false if
+// symbolization is currently in progress.
+bool RemoveAllSymbolDecorators(void);
+
+// Registers an address range to a file mapping.
+//
+// Preconditions:
+// start <= end
+// filename != nullptr
+//
+// Returns true if the file was successfully registered.
+bool RegisterFileMappingHint(
+ const void* start, const void* end, uint64_t offset, const char* filename);
+
+// Looks up the file mapping registered by RegisterFileMappingHint for an
+// address range. If there is one, the file name is stored in *filename and
+// *start and *end are modified to reflect the registered mapping. Returns
+// whether any hint was found.
+bool GetFileMappingHint(const void** start,
+ const void** end,
+ uint64_t * offset,
+ const char** filename);
+
+} // namespace debugging_internal
+} // namespace absl
+
+#endif // ABSL_DEBUGGING_INTERNAL_SYMBOLIZE_H_
diff --git a/absl/debugging/symbolize.cc b/absl/debugging/symbolize.cc
new file mode 100644
index 00000000..355bf9ff
--- /dev/null
+++ b/absl/debugging/symbolize.cc
@@ -0,0 +1,21 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/debugging/symbolize.h"
+
+#ifdef ABSL_INTERNAL_HAVE_ELF_SYMBOLIZE
+#include "absl/debugging/symbolize_elf.inc"
+#else
+#include "absl/debugging/symbolize_unimplemented.inc"
+#endif
diff --git a/absl/debugging/symbolize.h b/absl/debugging/symbolize.h
new file mode 100644
index 00000000..073a4479
--- /dev/null
+++ b/absl/debugging/symbolize.h
@@ -0,0 +1,35 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_DEBUGGING_SYMBOLIZE_H_
+#define ABSL_DEBUGGING_SYMBOLIZE_H_
+
+#include "absl/debugging/internal/symbolize.h"
+
+namespace absl {
+
+// Initializes this module. Symbolize() may fail prior calling this function.
+// `argv0` is the path to this program, which is usually obtained in main()
+// though argv[0].
+void InitializeSymbolizer(const char* argv0);
+
+// Symbolizes a program counter. On success, returns true and write the
+// symbol name to "out". The symbol name is demangled if possible
+// (supports symbols generated by GCC 3.x or newer), may be truncated, and
+// will be '\0' terminated. Otherwise, returns false.
+bool Symbolize(const void *pc, char *out, int out_size);
+
+} // namespace absl
+
+#endif // ABSL_DEBUGGING_SYMBOLIZE_H_
diff --git a/absl/debugging/symbolize_elf.inc b/absl/debugging/symbolize_elf.inc
new file mode 100644
index 00000000..e21439ce
--- /dev/null
+++ b/absl/debugging/symbolize_elf.inc
@@ -0,0 +1,1473 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// This library provides Symbolize() function that symbolizes program
+// counters to their corresponding symbol names on linux platforms.
+// This library has a minimal implementation of an ELF symbol table
+// reader (i.e. it doesn't depend on libelf, etc.).
+//
+// The algorithm used in Symbolize() is as follows.
+//
+// 1. Go through a list of maps in /proc/self/maps and find the map
+// containing the program counter.
+//
+// 2. Open the mapped file and find a regular symbol table inside.
+// Iterate over symbols in the symbol table and look for the symbol
+// containing the program counter. If such a symbol is found,
+// obtain the symbol name, and demangle the symbol if possible.
+// If the symbol isn't found in the regular symbol table (binary is
+// stripped), try the same thing with a dynamic symbol table.
+//
+// Note that Symbolize() is originally implemented to be used in
+// signal handlers, hence it doesn't use malloc() and other unsafe
+// operations. It should be both thread-safe and async-signal-safe.
+//
+// Implementation note:
+//
+// We don't use heaps but only use stacks. We want to reduce the
+// stack consumption so that the symbolizer can run on small stacks.
+//
+// Here are some numbers collected with GCC 4.1.0 on x86:
+// - sizeof(Elf32_Sym) = 16
+// - sizeof(Elf32_Shdr) = 40
+// - sizeof(Elf64_Sym) = 24
+// - sizeof(Elf64_Shdr) = 64
+//
+// This implementation is intended to be async-signal-safe but uses some
+// functions which are not guaranteed to be so, such as memchr() and
+// memmove(). We assume they are async-signal-safe.
+
+#include <dlfcn.h>
+#include <elf.h>
+#include <fcntl.h>
+#include <link.h> // For ElfW() macro.
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <algorithm>
+#include <atomic>
+#include <cerrno>
+#include <cinttypes>
+#include <climits>
+#include <cstdint>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+
+#include "absl/base/casts.h"
+#include "absl/base/dynamic_annotations.h"
+#include "absl/base/internal/low_level_alloc.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/base/internal/spinlock.h"
+#include "absl/base/port.h"
+#include "absl/debugging/internal/demangle.h"
+#include "absl/debugging/internal/vdso_support.h"
+
+namespace absl {
+
+// Value of argv[0]. Used by MaybeInitializeObjFile().
+static char *argv0_value = nullptr;
+
+void InitializeSymbolizer(const char *argv0) {
+ if (argv0_value != nullptr) {
+ free(argv0_value);
+ argv0_value = nullptr;
+ }
+ if (argv0 != nullptr && argv0[0] != '\0') {
+ argv0_value = strdup(argv0);
+ }
+}
+
+namespace debugging_internal {
+namespace {
+
+// Re-runs fn until it doesn't cause EINTR.
+#define NO_INTR(fn) \
+ do { \
+ } while ((fn) < 0 && errno == EINTR)
+
+// On Linux, ELF_ST_* are defined in <linux/elf.h>. To make this portable
+// we define our own ELF_ST_BIND and ELF_ST_TYPE if not available.
+#ifndef ELF_ST_BIND
+#define ELF_ST_BIND(info) (((unsigned char)(info)) >> 4)
+#endif
+
+#ifndef ELF_ST_TYPE
+#define ELF_ST_TYPE(info) (((unsigned char)(info)) & 0xF)
+#endif
+
+// Some platforms use a special .opd section to store function pointers.
+const char kOpdSectionName[] = ".opd";
+
+#if (defined(__powerpc__) && !(_CALL_ELF > 1)) || defined(__ia64)
+// Use opd section for function descriptors on these platforms, the function
+// address is the first word of the descriptor.
+enum { kPlatformUsesOPDSections = 1 };
+#else // not PPC or IA64
+enum { kPlatformUsesOPDSections = 0 };
+#endif
+
+// This works for PowerPC & IA64 only. A function descriptor consist of two
+// pointers and the first one is the function's entry.
+const size_t kFunctionDescriptorSize = sizeof(void *) * 2;
+
+const int kMaxDecorators = 10; // Seems like a reasonable upper limit.
+
+struct InstalledSymbolDecorator {
+ SymbolDecorator fn;
+ void *arg;
+ int ticket;
+};
+
+int g_num_decorators;
+InstalledSymbolDecorator g_decorators[kMaxDecorators];
+
+struct FileMappingHint {
+ const void *start;
+ const void *end;
+ uint64_t offset;
+ const char *filename;
+};
+
+// Protects g_decorators.
+// We are using SpinLock and not a Mutex here, because we may be called
+// from inside Mutex::Lock itself, and it prohibits recursive calls.
+// This happens in e.g. base/stacktrace_syscall_unittest.
+// Moreover, we are using only TryLock(), if the decorator list
+// is being modified (is busy), we skip all decorators, and possibly
+// loose some info. Sorry, that's the best we could do.
+base_internal::SpinLock g_decorators_mu(base_internal::kLinkerInitialized);
+
+const int kMaxFileMappingHints = 8;
+int g_num_file_mapping_hints;
+FileMappingHint g_file_mapping_hints[kMaxFileMappingHints];
+// Protects g_file_mapping_hints.
+base_internal::SpinLock g_file_mapping_mu(base_internal::kLinkerInitialized);
+
+// Async-signal-safe function to zero a buffer.
+// memset() is not guaranteed to be async-signal-safe.
+static void SafeMemZero(void* p, size_t size) {
+ unsigned char *c = static_cast<unsigned char *>(p);
+ while (size--) {
+ *c++ = 0;
+ }
+}
+
+struct ObjFile {
+ ObjFile()
+ : filename(nullptr),
+ start_addr(nullptr),
+ end_addr(nullptr),
+ offset(0),
+ fd(-1),
+ elf_type(-1) {
+ SafeMemZero(&elf_header, sizeof(elf_header));
+ }
+
+ char *filename;
+ const void *start_addr;
+ const void *end_addr;
+ uint64_t offset;
+
+ // The following fields are initialized on the first access to the
+ // object file.
+ int fd;
+ int elf_type;
+ ElfW(Ehdr) elf_header;
+};
+
+// Build 4-way associative cache for symbols. Within each cache line, symbols
+// are replaced in LRU order.
+enum {
+ ASSOCIATIVITY = 4,
+};
+struct SymbolCacheLine {
+ const void *pc[ASSOCIATIVITY];
+ char *name[ASSOCIATIVITY];
+
+ // age[i] is incremented when a line is accessed. it's reset to zero if the
+ // i'th entry is read.
+ uint32_t age[ASSOCIATIVITY];
+};
+
+// ---------------------------------------------------------------
+// An async-signal-safe arena for LowLevelAlloc
+static std::atomic<base_internal::LowLevelAlloc::Arena *> g_sig_safe_arena;
+
+static base_internal::LowLevelAlloc::Arena *SigSafeArena() {
+ return g_sig_safe_arena.load(std::memory_order_acquire);
+}
+
+static void InitSigSafeArena() {
+ if (SigSafeArena() == nullptr) {
+ base_internal::LowLevelAlloc::Arena *new_arena =
+ base_internal::LowLevelAlloc::NewArena(
+ base_internal::LowLevelAlloc::kAsyncSignalSafe);
+ base_internal::LowLevelAlloc::Arena *old_value = nullptr;
+ if (!g_sig_safe_arena.compare_exchange_strong(old_value, new_arena,
+ std::memory_order_release,
+ std::memory_order_relaxed)) {
+ // We lost a race to allocate an arena; deallocate.
+ base_internal::LowLevelAlloc::DeleteArena(new_arena);
+ }
+ }
+}
+
+// ---------------------------------------------------------------
+// An AddrMap is a vector of ObjFile, using SigSafeArena() for allocation.
+
+class AddrMap {
+ public:
+ AddrMap() : size_(0), allocated_(0), obj_(nullptr) {}
+ ~AddrMap() { base_internal::LowLevelAlloc::Free(obj_); }
+ int Size() const { return size_; }
+ ObjFile *At(int i) { return &obj_[i]; }
+ ObjFile *Add();
+ void Clear();
+
+ private:
+ int size_; // count of valid elements (<= allocated_)
+ int allocated_; // count of allocated elements
+ ObjFile *obj_; // array of allocated_ elements
+ AddrMap(const AddrMap &) = delete;
+ AddrMap &operator=(const AddrMap &) = delete;
+};
+
+void AddrMap::Clear() {
+ for (int i = 0; i != size_; i++) {
+ At(i)->~ObjFile();
+ }
+ size_ = 0;
+}
+
+ObjFile *AddrMap::Add() {
+ if (size_ == allocated_) {
+ int new_allocated = allocated_ * 2 + 50;
+ ObjFile *new_obj_ =
+ static_cast<ObjFile *>(base_internal::LowLevelAlloc::AllocWithArena(
+ new_allocated * sizeof(*new_obj_), SigSafeArena()));
+ if (obj_) {
+ memcpy(new_obj_, obj_, allocated_ * sizeof(*new_obj_));
+ base_internal::LowLevelAlloc::Free(obj_);
+ }
+ obj_ = new_obj_;
+ allocated_ = new_allocated;
+ }
+ return new (&obj_[size_++]) ObjFile;
+}
+
+// ---------------------------------------------------------------
+
+enum FindSymbolResult { SYMBOL_NOT_FOUND = 1, SYMBOL_TRUNCATED, SYMBOL_FOUND };
+
+class Symbolizer {
+ public:
+ Symbolizer();
+ ~Symbolizer();
+ const char *GetSymbol(const void *const pc);
+
+ private:
+ char *CopyString(const char *s) {
+ int len = strlen(s);
+ char *dst = static_cast<char *>(
+ base_internal::LowLevelAlloc::AllocWithArena(len + 1, SigSafeArena()));
+ ABSL_RAW_CHECK(dst != nullptr, "out of memory");
+ memcpy(dst, s, len + 1);
+ return dst;
+ }
+ ObjFile *FindObjFile(const void *const start,
+ size_t size) ABSL_ATTRIBUTE_NOINLINE;
+ static bool RegisterObjFile(const char *filename,
+ const void *const start_addr,
+ const void *const end_addr, uint64_t offset,
+ void *arg);
+ SymbolCacheLine *GetCacheLine(const void *const pc);
+ const char *FindSymbolInCache(const void *const pc);
+ const char *InsertSymbolInCache(const void *const pc, const char *name);
+ void AgeSymbols(SymbolCacheLine *line);
+ void ClearAddrMap();
+ FindSymbolResult GetSymbolFromObjectFile(const ObjFile &obj,
+ const void *const pc,
+ const ptrdiff_t relocation,
+ char *out, int out_size,
+ char *tmp_buf, int tmp_buf_size);
+
+ enum {
+ SYMBOL_BUF_SIZE = 2048,
+ TMP_BUF_SIZE = 1024,
+ SYMBOL_CACHE_LINES = 128,
+ };
+
+ AddrMap addr_map_;
+
+ bool ok_;
+ bool addr_map_read_;
+
+ char symbol_buf_[SYMBOL_BUF_SIZE];
+
+ // tmp_buf_ will be used to store arrays of ElfW(Shdr) and ElfW(Sym)
+ // so we ensure that tmp_buf_ is properly aligned to store either.
+ alignas(16) char tmp_buf_[TMP_BUF_SIZE];
+ static_assert(alignof(ElfW(Shdr)) <= 16,
+ "alignment of tmp buf too small for Shdr");
+ static_assert(alignof(ElfW(Sym)) <= 16,
+ "alignment of tmp buf too small for Sym");
+
+ SymbolCacheLine symbol_cache_[SYMBOL_CACHE_LINES];
+};
+
+static std::atomic<Symbolizer *> g_cached_symbolizer;
+
+} // namespace
+
+static int SymbolizerSize() {
+ int pagesize = getpagesize();
+ return ((sizeof(Symbolizer) - 1) / pagesize + 1) * pagesize;
+}
+
+// Return (and set null) g_cached_symbolized_state if it is not null.
+// Otherwise return a new symbolizer.
+static Symbolizer *AllocateSymbolizer() {
+ InitSigSafeArena();
+ Symbolizer *symbolizer =
+ g_cached_symbolizer.exchange(nullptr, std::memory_order_acquire);
+ if (symbolizer != nullptr) {
+ return symbolizer;
+ }
+ return new (base_internal::LowLevelAlloc::AllocWithArena(
+ SymbolizerSize(), SigSafeArena())) Symbolizer();
+}
+
+// Set g_cached_symbolize_state to s if it is null, otherwise
+// delete s.
+static void FreeSymbolizer(Symbolizer *s) {
+ Symbolizer *old_cached_symbolizer = nullptr;
+ if (!g_cached_symbolizer.compare_exchange_strong(old_cached_symbolizer, s,
+ std::memory_order_release,
+ std::memory_order_relaxed)) {
+ s->~Symbolizer();
+ base_internal::LowLevelAlloc::Free(s);
+ }
+}
+
+Symbolizer::Symbolizer() : ok_(true), addr_map_read_(false) {
+ for (SymbolCacheLine &symbol_cache_line : symbol_cache_) {
+ for (size_t j = 0; j < ABSL_ARRAYSIZE(symbol_cache_line.name); ++j) {
+ symbol_cache_line.pc[j] = nullptr;
+ symbol_cache_line.name[j] = nullptr;
+ symbol_cache_line.age[j] = 0;
+ }
+ }
+}
+
+Symbolizer::~Symbolizer() {
+ for (SymbolCacheLine &symbol_cache_line : symbol_cache_) {
+ for (char *s : symbol_cache_line.name) {
+ base_internal::LowLevelAlloc::Free(s);
+ }
+ }
+ ClearAddrMap();
+}
+
+// We don't use assert() since it's not guaranteed to be
+// async-signal-safe. Instead we define a minimal assertion
+// macro. So far, we don't need pretty printing for __FILE__, etc.
+#define SAFE_ASSERT(expr) ((expr) ? static_cast<void>(0) : abort())
+
+// Read up to "count" bytes from file descriptor "fd" into the buffer
+// starting at "buf" while handling short reads and EINTR. On
+// success, return the number of bytes read. Otherwise, return -1.
+static ssize_t ReadPersistent(int fd, void *buf, size_t count) {
+ SAFE_ASSERT(fd >= 0);
+ SAFE_ASSERT(count <= SSIZE_MAX);
+ char *buf0 = reinterpret_cast<char *>(buf);
+ size_t num_bytes = 0;
+ while (num_bytes < count) {
+ ssize_t len;
+ NO_INTR(len = read(fd, buf0 + num_bytes, count - num_bytes));
+ if (len < 0) { // There was an error other than EINTR.
+ ABSL_RAW_LOG(WARNING, "read failed: errno=%d", errno);
+ return -1;
+ }
+ if (len == 0) { // Reached EOF.
+ break;
+ }
+ num_bytes += len;
+ }
+ SAFE_ASSERT(num_bytes <= count);
+ return static_cast<ssize_t>(num_bytes);
+}
+
+// Read up to "count" bytes from "offset" in the file pointed by file
+// descriptor "fd" into the buffer starting at "buf". On success,
+// return the number of bytes read. Otherwise, return -1.
+static ssize_t ReadFromOffset(const int fd, void *buf, const size_t count,
+ const off_t offset) {
+ off_t off = lseek(fd, offset, SEEK_SET);
+ if (off == (off_t)-1) {
+ ABSL_RAW_LOG(WARNING, "lseek(%d, %ju, SEEK_SET) failed: errno=%d", fd,
+ static_cast<uintmax_t>(offset), errno);
+ return -1;
+ }
+ return ReadPersistent(fd, buf, count);
+}
+
+// Try reading exactly "count" bytes from "offset" bytes in a file
+// pointed by "fd" into the buffer starting at "buf" while handling
+// short reads and EINTR. On success, return true. Otherwise, return
+// false.
+static bool ReadFromOffsetExact(const int fd, void *buf, const size_t count,
+ const off_t offset) {
+ ssize_t len = ReadFromOffset(fd, buf, count, offset);
+ return len >= 0 && static_cast<size_t>(len) == count;
+}
+
+// Returns elf_header.e_type if the file pointed by fd is an ELF binary.
+static int FileGetElfType(const int fd) {
+ ElfW(Ehdr) elf_header;
+ if (!ReadFromOffsetExact(fd, &elf_header, sizeof(elf_header), 0)) {
+ return -1;
+ }
+ if (memcmp(elf_header.e_ident, ELFMAG, SELFMAG) != 0) {
+ return -1;
+ }
+ return elf_header.e_type;
+}
+
+// Read the section headers in the given ELF binary, and if a section
+// of the specified type is found, set the output to this section header
+// and return true. Otherwise, return false.
+// To keep stack consumption low, we would like this function to not get
+// inlined.
+static ABSL_ATTRIBUTE_NOINLINE bool GetSectionHeaderByType(
+ const int fd, ElfW(Half) sh_num, const off_t sh_offset, ElfW(Word) type,
+ ElfW(Shdr) * out, char *tmp_buf, int tmp_buf_size) {
+ ElfW(Shdr) *buf = reinterpret_cast<ElfW(Shdr) *>(tmp_buf);
+ const int buf_entries = tmp_buf_size / sizeof(buf[0]);
+ const int buf_bytes = buf_entries * sizeof(buf[0]);
+
+ for (int i = 0; i < sh_num;) {
+ const ssize_t num_bytes_left = (sh_num - i) * sizeof(buf[0]);
+ const ssize_t num_bytes_to_read =
+ (buf_bytes > num_bytes_left) ? num_bytes_left : buf_bytes;
+ const off_t offset = sh_offset + i * sizeof(buf[0]);
+ const ssize_t len = ReadFromOffset(fd, buf, num_bytes_to_read, offset);
+ if (len % sizeof(buf[0]) != 0) {
+ ABSL_RAW_LOG(
+ WARNING,
+ "Reading %zd bytes from offset %ju returned %zd which is not a "
+ "multiple of %zu.",
+ num_bytes_to_read, static_cast<uintmax_t>(offset), len,
+ sizeof(buf[0]));
+ return false;
+ }
+ const ssize_t num_headers_in_buf = len / sizeof(buf[0]);
+ SAFE_ASSERT(num_headers_in_buf <= buf_entries);
+ for (int j = 0; j < num_headers_in_buf; ++j) {
+ if (buf[j].sh_type == type) {
+ *out = buf[j];
+ return true;
+ }
+ }
+ i += num_headers_in_buf;
+ }
+ return false;
+}
+
+// There is no particular reason to limit section name to 63 characters,
+// but there has (as yet) been no need for anything longer either.
+const int kMaxSectionNameLen = 64;
+
+bool ForEachSection(int fd,
+ const std::function<bool(const std::string &name,
+ const ElfW(Shdr) &)> &callback) {
+ 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) {
+ 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 + 1];
+ 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;
+ }
+ header_name[n_read] = '\0';
+
+ std::string name(header_name);
+ 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);
+}
+
+// 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 = original_start_address + relocation;
+
+ 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 =
+ reinterpret_cast<const char *>(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 first.
+ if (!GetSectionHeaderByType(obj.fd, obj.elf_header.e_shnum,
+ obj.elf_header.e_shoff, SHT_SYMTAB, &symtab,
+ tmp_buf, tmp_buf_size)) {
+ return SYMBOL_NOT_FOUND;
+ }
+ if (!ReadFromOffsetExact(
+ obj.fd, &strtab, sizeof(strtab),
+ obj.elf_header.e_shoff + symtab.sh_link * sizeof(symtab))) {
+ return SYMBOL_NOT_FOUND;
+ }
+ 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; // Found the symbol in a regular symbol table.
+ }
+
+ // If the symbol is not found, then consult a dynamic symbol table.
+ if (!GetSectionHeaderByType(obj.fd, obj.elf_header.e_shnum,
+ obj.elf_header.e_shoff, SHT_DYNSYM, &symtab,
+ tmp_buf, tmp_buf_size)) {
+ return SYMBOL_NOT_FOUND;
+ }
+ if (!ReadFromOffsetExact(
+ obj.fd, &strtab, sizeof(strtab),
+ obj.elf_header.e_shoff + symtab.sh_link * sizeof(symtab))) {
+ return SYMBOL_NOT_FOUND;
+ }
+ return FindSymbol(pc, obj.fd, out, out_size, relocation, &strtab, &symtab,
+ opd_ptr, tmp_buf, tmp_buf_size);
+}
+
+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;
+}
+
+// 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. 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**".
+ if (memcmp(flags_start, "r-x", 3) != 0 && // Not a "r-x" map.
+ !(kPlatformUsesOPDSections && flags_start[0] == 'r')) {
+ 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;
+ }
+ }
+ 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;
+ }
+ }
+ 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::GetSymbol(const void *const pc) {
+ const char *entry = FindSymbolInCache(pc);
+ if (entry != nullptr) {
+ return entry;
+ }
+ symbol_buf_[0] = '\0';
+
+ ObjFile *const obj = FindObjFile(pc, 1);
+ ptrdiff_t relocation = 0;
+ int fd = -1;
+ if (obj != nullptr) {
+ if (MaybeInitializeObjFile(obj)) {
+ if (obj->elf_type == ET_DYN &&
+ reinterpret_cast<uint64_t>(obj->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 = reinterpret_cast<ptrdiff_t>(obj->start_addr) - obj->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_);
+}
+
+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 false;
+ }
+ 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 std::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) {
+ // Symbolization is very slow under tsan.
+ ANNOTATE_IGNORE_READS_AND_WRITES_BEGIN();
+ SAFE_ASSERT(out_size >= 0);
+ debugging_internal::Symbolizer *s = debugging_internal::AllocateSymbolizer();
+ const char *name = s->GetSymbol(pc);
+ bool ok = false;
+ if (name != nullptr && out_size > 0) {
+ strncpy(out, name, out_size);
+ ok = true;
+ if (out[out_size - 1] != '\0') {
+ // 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);
+ memcpy(out + out_size - ellipsis_size - 1, kEllipsis, ellipsis_size);
+ out[out_size - 1] = '\0';
+ }
+ }
+ debugging_internal::FreeSymbolizer(s);
+ ANNOTATE_IGNORE_READS_AND_WRITES_END();
+ return ok;
+}
+
+} // namespace absl
diff --git a/absl/debugging/symbolize_test.cc b/absl/debugging/symbolize_test.cc
new file mode 100644
index 00000000..52c69155
--- /dev/null
+++ b/absl/debugging/symbolize_test.cc
@@ -0,0 +1,450 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/debugging/symbolize.h"
+
+#ifndef _WIN32
+#include <fcntl.h>
+#include <sys/mman.h>
+#endif
+
+#include <cstring>
+#include <iostream>
+#include <memory>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/base/attributes.h"
+#include "absl/base/casts.h"
+#include "absl/base/internal/malloc_extension.h"
+#include "absl/base/internal/per_thread_tls.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/base/optimization.h"
+#include "absl/debugging/internal/stack_consumption.h"
+#include "absl/memory/memory.h"
+
+using testing::Contains;
+
+// Functions to symbolize. Use C linkage to avoid mangled names.
+extern "C" {
+void nonstatic_func() { ABSL_BLOCK_TAIL_CALL_OPTIMIZATION(); }
+static void static_func() { ABSL_BLOCK_TAIL_CALL_OPTIMIZATION(); }
+} // extern "C"
+
+struct Foo {
+ static void func(int x);
+};
+
+// A C++ method that should have a mangled name.
+void ABSL_ATTRIBUTE_NOINLINE Foo::func(int) {
+ ABSL_BLOCK_TAIL_CALL_OPTIMIZATION();
+}
+
+// Thread-local data may confuse the symbolizer, ensure that it does not.
+// Variable sizes and order are important.
+#if ABSL_PER_THREAD_TLS
+static ABSL_PER_THREAD_TLS_KEYWORD char symbolize_test_thread_small[1];
+static ABSL_PER_THREAD_TLS_KEYWORD char
+ symbolize_test_thread_big[2 * 1024 * 1024];
+#endif
+
+// Used below to hopefully inhibit some compiler/linker optimizations
+// that may remove kHpageTextPadding, kPadding0, and kPadding1 from
+// the binary.
+static volatile bool volatile_bool = false;
+
+// Force the binary to be large enough that a THP .text remap will succeed.
+static constexpr size_t kHpageSize = 1 << 21;
+const char kHpageTextPadding[kHpageSize * 4] ABSL_ATTRIBUTE_SECTION_VARIABLE(
+ ".text") = "";
+
+#ifdef ABSL_INTERNAL_HAVE_ELF_SYMBOLIZE
+
+static char try_symbolize_buffer[4096];
+
+// A wrapper function for absl::Symbolize() to make the unit test simple. The
+// limit must be < sizeof(try_symbolize_buffer). Returns null if
+// absl::Symbolize() returns false, otherwise returns try_symbolize_buffer with
+// the result of absl::Symbolize().
+static const char *TrySymbolizeWithLimit(void *pc, int limit) {
+ ABSL_RAW_CHECK(limit <= sizeof(try_symbolize_buffer),
+ "try_symbolize_buffer is too small");
+
+ // Use the heap to facilitate heap and buffer sanitizer tools.
+ auto heap_buffer = absl::make_unique<char[]>(sizeof(try_symbolize_buffer));
+ bool found = absl::Symbolize(pc, heap_buffer.get(), limit);
+ if (found) {
+ ABSL_RAW_CHECK(strnlen(heap_buffer.get(), limit) < limit,
+ "absl::Symbolize() did not properly terminate the string");
+ strncpy(try_symbolize_buffer, heap_buffer.get(),
+ sizeof(try_symbolize_buffer));
+ }
+
+ return found ? try_symbolize_buffer : nullptr;
+}
+
+// A wrapper for TrySymbolizeWithLimit(), with a large limit.
+static const char *TrySymbolize(void *pc) {
+ return TrySymbolizeWithLimit(pc, sizeof(try_symbolize_buffer));
+}
+
+TEST(Symbolize, Cached) {
+ // Compilers should give us pointers to them.
+ EXPECT_STREQ("nonstatic_func", TrySymbolize((void *)(&nonstatic_func)));
+
+ // The name of an internal linkage symbol is not specified; allow either a
+ // mangled or an unmangled name here.
+ const char *static_func_symbol = TrySymbolize((void *)(&static_func));
+ EXPECT_TRUE(strcmp("static_func", static_func_symbol) == 0 ||
+ strcmp("static_func()", static_func_symbol) == 0);
+
+ EXPECT_TRUE(nullptr == TrySymbolize(nullptr));
+}
+
+TEST(Symbolize, Truncation) {
+ constexpr char kNonStaticFunc[] = "nonstatic_func";
+ EXPECT_STREQ("nonstatic_func",
+ TrySymbolizeWithLimit((void *)(&nonstatic_func),
+ strlen(kNonStaticFunc) + 1));
+ EXPECT_STREQ("nonstatic_...",
+ TrySymbolizeWithLimit((void *)(&nonstatic_func),
+ strlen(kNonStaticFunc) + 0));
+ EXPECT_STREQ("nonstatic...",
+ TrySymbolizeWithLimit((void *)(&nonstatic_func),
+ strlen(kNonStaticFunc) - 1));
+ EXPECT_STREQ("n...", TrySymbolizeWithLimit((void *)(&nonstatic_func), 5));
+ EXPECT_STREQ("...", TrySymbolizeWithLimit((void *)(&nonstatic_func), 4));
+ EXPECT_STREQ("..", TrySymbolizeWithLimit((void *)(&nonstatic_func), 3));
+ EXPECT_STREQ(".", TrySymbolizeWithLimit((void *)(&nonstatic_func), 2));
+ EXPECT_STREQ("", TrySymbolizeWithLimit((void *)(&nonstatic_func), 1));
+ EXPECT_EQ(nullptr, TrySymbolizeWithLimit((void *)(&nonstatic_func), 0));
+}
+
+TEST(Symbolize, SymbolizeWithDemangling) {
+ Foo::func(100);
+ EXPECT_STREQ("Foo::func()", TrySymbolize((void *)(&Foo::func)));
+}
+
+// Tests that verify that Symbolize stack footprint is within some limit.
+#ifdef ABSL_INTERNAL_HAVE_DEBUGGING_STACK_CONSUMPTION
+
+static void *g_pc_to_symbolize;
+static char g_symbolize_buffer[4096];
+static char *g_symbolize_result;
+
+static void SymbolizeSignalHandler(int signo) {
+ if (absl::Symbolize(g_pc_to_symbolize, g_symbolize_buffer,
+ sizeof(g_symbolize_buffer))) {
+ g_symbolize_result = g_symbolize_buffer;
+ } else {
+ g_symbolize_result = nullptr;
+ }
+}
+
+// Call Symbolize and figure out the stack footprint of this call.
+static const char *SymbolizeStackConsumption(void *pc, int *stack_consumed) {
+ g_pc_to_symbolize = pc;
+ *stack_consumed = absl::debugging_internal::GetSignalHandlerStackConsumption(
+ SymbolizeSignalHandler);
+ return g_symbolize_result;
+}
+
+static int GetStackConsumptionUpperLimit() {
+ // Symbolize stack consumption should be within 2kB.
+ const int kStackConsumptionUpperLimit = 2048;
+ // Account for ASan/TSan instrumentation requiring additional stack space.
+ size_t multiplier = 0;
+ if (absl::base_internal::MallocExtension::instance()->GetNumericProperty(
+ "dynamic_tool.stack_size_multiplier", &multiplier)) {
+ return kStackConsumptionUpperLimit * multiplier;
+ }
+ return kStackConsumptionUpperLimit;
+}
+
+TEST(Symbolize, SymbolizeStackConsumption) {
+ int stack_consumed = 0;
+
+ const char *symbol =
+ SymbolizeStackConsumption((void *)(&nonstatic_func), &stack_consumed);
+ EXPECT_STREQ("nonstatic_func", symbol);
+ EXPECT_GT(stack_consumed, 0);
+ EXPECT_LT(stack_consumed, GetStackConsumptionUpperLimit());
+
+ // The name of an internal linkage symbol is not specified; allow either a
+ // mangled or an unmangled name here.
+ symbol = SymbolizeStackConsumption((void *)(&static_func), &stack_consumed);
+ EXPECT_TRUE(strcmp("static_func", symbol) == 0 ||
+ strcmp("static_func()", symbol) == 0);
+ EXPECT_GT(stack_consumed, 0);
+ EXPECT_LT(stack_consumed, GetStackConsumptionUpperLimit());
+}
+
+TEST(Symbolize, SymbolizeWithDemanglingStackConsumption) {
+ Foo::func(100);
+ int stack_consumed = 0;
+
+ const char *symbol =
+ SymbolizeStackConsumption((void *)(&Foo::func), &stack_consumed);
+
+ EXPECT_STREQ("Foo::func()", symbol);
+ EXPECT_GT(stack_consumed, 0);
+ EXPECT_LT(stack_consumed, GetStackConsumptionUpperLimit());
+}
+
+#endif // ABSL_INTERNAL_HAVE_DEBUGGING_STACK_CONSUMPTION
+
+// Use a 64K page size for PPC.
+const size_t kPageSize = 64 << 10;
+// We place a read-only symbols into the .text section and verify that we can
+// symbolize them and other symbols after remapping them.
+const char kPadding0[kPageSize * 4] ABSL_ATTRIBUTE_SECTION_VARIABLE(".text") =
+ "";
+const char kPadding1[kPageSize * 4] ABSL_ATTRIBUTE_SECTION_VARIABLE(".text") =
+ "";
+
+static int FilterElfHeader(struct dl_phdr_info *info, size_t size, void *data) {
+ for (int i = 0; i < info->dlpi_phnum; i++) {
+ if (info->dlpi_phdr[i].p_type == PT_LOAD &&
+ info->dlpi_phdr[i].p_flags == (PF_R | PF_X)) {
+ const void *const vaddr =
+ absl::bit_cast<void *>(info->dlpi_addr + info->dlpi_phdr[i].p_vaddr);
+ const auto segsize = info->dlpi_phdr[i].p_memsz;
+
+ const char *self_exe;
+ if (info->dlpi_name != nullptr && info->dlpi_name[0] != '\0') {
+ self_exe = info->dlpi_name;
+ } else {
+ self_exe = "/proc/self/exe";
+ }
+
+ absl::debugging_internal::RegisterFileMappingHint(
+ vaddr, reinterpret_cast<const char *>(vaddr) + segsize,
+ info->dlpi_phdr[i].p_offset, self_exe);
+
+ return 1;
+ }
+ }
+
+ return 1;
+}
+
+TEST(Symbolize, SymbolizeWithMultipleMaps) {
+ // Force kPadding0 and kPadding1 to be linked in.
+ if (volatile_bool) {
+ ABSL_RAW_LOG(INFO, "%s", kPadding0);
+ ABSL_RAW_LOG(INFO, "%s", kPadding1);
+ }
+
+ // Verify we can symbolize everything.
+ char buf[512];
+ memset(buf, 0, sizeof(buf));
+ absl::Symbolize(kPadding0, buf, sizeof(buf));
+ EXPECT_STREQ("kPadding0", buf);
+
+ memset(buf, 0, sizeof(buf));
+ absl::Symbolize(kPadding1, buf, sizeof(buf));
+ EXPECT_STREQ("kPadding1", buf);
+
+ // Specify a hint for the executable segment.
+ dl_iterate_phdr(FilterElfHeader, nullptr);
+
+ // Reload at least one page out of kPadding0, kPadding1
+ const char *ptrs[] = {kPadding0, kPadding1};
+
+ for (const char *ptr : ptrs) {
+ const int kMapFlags = MAP_ANONYMOUS | MAP_PRIVATE;
+ void *addr = mmap(nullptr, kPageSize, PROT_READ, kMapFlags, 0, 0);
+ ASSERT_NE(addr, MAP_FAILED);
+
+ // kPadding[0-1] is full of zeroes, so we can remap anywhere within it, but
+ // we ensure there is at least a full page of padding.
+ void *remapped = reinterpret_cast<void *>(
+ reinterpret_cast<uintptr_t>(ptr + kPageSize) & ~(kPageSize - 1ULL));
+
+ const int kMremapFlags = (MREMAP_MAYMOVE | MREMAP_FIXED);
+ void *ret = mremap(addr, kPageSize, kPageSize, kMremapFlags, remapped);
+ ASSERT_NE(ret, MAP_FAILED);
+ }
+
+ // Invalidate the symbolization cache so we are forced to rely on the hint.
+ absl::Symbolize(nullptr, buf, sizeof(buf));
+
+ // Verify we can still symbolize.
+ const char *expected[] = {"kPadding0", "kPadding1"};
+ const size_t offsets[] = {0, kPageSize, 2 * kPageSize, 3 * kPageSize};
+
+ for (int i = 0; i < 2; i++) {
+ for (size_t offset : offsets) {
+ memset(buf, 0, sizeof(buf));
+ absl::Symbolize(ptrs[i] + offset, buf, sizeof(buf));
+ EXPECT_STREQ(expected[i], buf);
+ }
+ }
+}
+
+// Appends std::string(*args->arg) to args->symbol_buf.
+static void DummySymbolDecorator(
+ const absl::debugging_internal::SymbolDecoratorArgs *args) {
+ std::string *message = static_cast<std::string *>(args->arg);
+ strncat(args->symbol_buf, message->c_str(),
+ args->symbol_buf_size - strlen(args->symbol_buf) - 1);
+}
+
+TEST(Symbolize, InstallAndRemoveSymbolDecorators) {
+ int ticket_a;
+ std::string a_message("a");
+ EXPECT_GE(ticket_a = absl::debugging_internal::InstallSymbolDecorator(
+ DummySymbolDecorator, &a_message),
+ 0);
+
+ int ticket_b;
+ std::string b_message("b");
+ EXPECT_GE(ticket_b = absl::debugging_internal::InstallSymbolDecorator(
+ DummySymbolDecorator, &b_message),
+ 0);
+
+ int ticket_c;
+ std::string c_message("c");
+ EXPECT_GE(ticket_c = absl::debugging_internal::InstallSymbolDecorator(
+ DummySymbolDecorator, &c_message),
+ 0);
+
+ char *address = reinterpret_cast<char *>(1);
+ EXPECT_STREQ("abc", TrySymbolize(address++));
+
+ EXPECT_TRUE(absl::debugging_internal::RemoveSymbolDecorator(ticket_b));
+
+ EXPECT_STREQ("ac", TrySymbolize(address++));
+
+ // Cleanup: remove all remaining decorators so other stack traces don't
+ // get mystery "ac" decoration.
+ EXPECT_TRUE(absl::debugging_internal::RemoveSymbolDecorator(ticket_a));
+ EXPECT_TRUE(absl::debugging_internal::RemoveSymbolDecorator(ticket_c));
+}
+
+// Some versions of Clang with optimizations enabled seem to be able
+// to optimize away the .data section if no variables live in the
+// section. This variable should get placed in the .data section, and
+// the test below checks for the existence of a .data section.
+static int in_data_section = 1;
+
+TEST(Symbolize, ForEachSection) {
+ int fd = TEMP_FAILURE_RETRY(open("/proc/self/exe", O_RDONLY));
+ ASSERT_NE(fd, -1);
+
+ std::vector<std::string> sections;
+ ASSERT_TRUE(absl::debugging_internal::ForEachSection(
+ fd, [&sections](const std::string &name, const ElfW(Shdr) &) {
+ sections.push_back(name);
+ return true;
+ }));
+
+ // Check for the presence of common section names.
+ EXPECT_THAT(sections, Contains(".text"));
+ EXPECT_THAT(sections, Contains(".rodata"));
+ EXPECT_THAT(sections, Contains(".bss"));
+ ++in_data_section;
+ EXPECT_THAT(sections, Contains(".data"));
+
+ close(fd);
+}
+
+// x86 specific tests. Uses some inline assembler.
+extern "C" {
+inline void *ABSL_ATTRIBUTE_ALWAYS_INLINE inline_func() {
+ void *pc = nullptr;
+#if defined(__i386__) || defined(__x86_64__)
+ __asm__ __volatile__("call 1f; 1: pop %0" : "=r"(pc));
+#endif
+ return pc;
+}
+
+void *ABSL_ATTRIBUTE_NOINLINE non_inline_func() {
+ void *pc = nullptr;
+#if defined(__i386__) || defined(__x86_64__)
+ __asm__ __volatile__("call 1f; 1: pop %0" : "=r"(pc));
+#endif
+ return pc;
+}
+
+void ABSL_ATTRIBUTE_NOINLINE TestWithPCInsideNonInlineFunction() {
+#if defined(ABSL_HAVE_ATTRIBUTE_NOINLINE) && \
+ (defined(__i386__) || defined(__x86_64__))
+ void *pc = non_inline_func();
+ const char *symbol = TrySymbolize(pc);
+ ABSL_RAW_CHECK(symbol != nullptr, "TestWithPCInsideNonInlineFunction failed");
+ ABSL_RAW_CHECK(strcmp(symbol, "non_inline_func") == 0,
+ "TestWithPCInsideNonInlineFunction failed");
+ std::cout << "TestWithPCInsideNonInlineFunction passed" << std::endl;
+#endif
+}
+
+void ABSL_ATTRIBUTE_NOINLINE TestWithPCInsideInlineFunction() {
+#if defined(ABSL_HAVE_ATTRIBUTE_ALWAYS_INLINE) && \
+ (defined(__i386__) || defined(__x86_64__))
+ void *pc = inline_func(); // Must be inlined.
+ const char *symbol = TrySymbolize(pc);
+ ABSL_RAW_CHECK(symbol != nullptr, "TestWithPCInsideInlineFunction failed");
+ ABSL_RAW_CHECK(strcmp(symbol, __FUNCTION__) == 0,
+ "TestWithPCInsideInlineFunction failed");
+ std::cout << "TestWithPCInsideInlineFunction passed" << std::endl;
+#endif
+}
+}
+
+// Test with a return address.
+void ABSL_ATTRIBUTE_NOINLINE TestWithReturnAddress() {
+#if defined(ABSL_HAVE_ATTRIBUTE_NOINLINE)
+ void *return_address = __builtin_return_address(0);
+ const char *symbol = TrySymbolize(return_address);
+ ABSL_RAW_CHECK(symbol != nullptr, "TestWithReturnAddress failed");
+ ABSL_RAW_CHECK(strcmp(symbol, "main") == 0, "TestWithReturnAddress failed");
+ std::cout << "TestWithReturnAddress passed" << std::endl;
+#endif
+}
+
+#else // Symbolizer unimplemented
+
+TEST(Symbolize, Unimplemented) {
+ char buf[64];
+ EXPECT_FALSE(absl::Symbolize((void *)(&nonstatic_func), buf, sizeof(buf)));
+ EXPECT_FALSE(absl::Symbolize((void *)(&static_func), buf, sizeof(buf)));
+ EXPECT_FALSE(absl::Symbolize((void *)(&Foo::func), buf, sizeof(buf)));
+}
+
+#endif
+
+int main(int argc, char **argv) {
+ // Make sure kHpageTextPadding is linked into the binary.
+ if (volatile_bool) {
+ ABSL_RAW_LOG(INFO, "%s", kHpageTextPadding);
+ }
+
+#if ABSL_PER_THREAD_TLS
+ // Touch the per-thread variables.
+ symbolize_test_thread_small[0] = 0;
+ symbolize_test_thread_big[0] = 0;
+#endif
+
+ absl::InitializeSymbolizer(argv[0]);
+ testing::InitGoogleTest(&argc, argv);
+
+#ifdef ABSL_INTERNAL_HAVE_ELF_SYMBOLIZE
+ TestWithPCInsideInlineFunction();
+ TestWithPCInsideNonInlineFunction();
+ TestWithReturnAddress();
+#endif
+
+ return RUN_ALL_TESTS();
+}
diff --git a/absl/debugging/symbolize_unimplemented.inc b/absl/debugging/symbolize_unimplemented.inc
new file mode 100644
index 00000000..2a3f4acb
--- /dev/null
+++ b/absl/debugging/symbolize_unimplemented.inc
@@ -0,0 +1,35 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <cstdint>
+
+#include "absl/base/internal/raw_logging.h"
+
+namespace absl {
+
+namespace debugging_internal {
+
+int InstallSymbolDecorator(SymbolDecorator, void*) { return -1; }
+bool RemoveSymbolDecorator(int) { return false; }
+bool RemoveAllSymbolDecorators(void) { return false; }
+bool RegisterFileMappingHint(const void *, const void *, uint64_t, const char *) {
+ return false;
+}
+
+} // namespace debugging_internal
+
+void InitializeSymbolizer(const char*) {}
+bool Symbolize(const void *, char *, int) { return false; }
+
+} // namespace absl
diff --git a/absl/synchronization/internal/mutex_nonprod.cc b/absl/synchronization/internal/mutex_nonprod.cc
index 62d19816..45c60326 100644
--- a/absl/synchronization/internal/mutex_nonprod.cc
+++ b/absl/synchronization/internal/mutex_nonprod.cc
@@ -313,4 +313,6 @@ bool Condition::Eval() const {
return (this->eval_ == nullptr) || (*this->eval_)(this);
}
+void RegisterSymbolizer(bool (*)(const void*, char*, int)) {}
+
} // namespace absl