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Diffstat (limited to 'third_party/abseil_cpp/absl/debugging/symbolize_elf.inc')
| -rw-r--r-- | third_party/abseil_cpp/absl/debugging/symbolize_elf.inc | 1560 |
1 files changed, 0 insertions, 1560 deletions
diff --git a/third_party/abseil_cpp/absl/debugging/symbolize_elf.inc b/third_party/abseil_cpp/absl/debugging/symbolize_elf.inc deleted file mode 100644 index f4d5727bdeb5..000000000000 --- a/third_party/abseil_cpp/absl/debugging/symbolize_elf.inc +++ /dev/null @@ -1,1560 +0,0 @@ -// 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 -// -// https://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 <array> -#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" -#include "absl/strings/string_view.h" - -namespace absl { -ABSL_NAMESPACE_BEGIN - -// Value of argv[0]. Used by MaybeInitializeObjFile(). -static char *argv0_value = nullptr; - -void InitializeSymbolizer(const char *argv0) { -#ifdef ABSL_HAVE_VDSO_SUPPORT - // We need to make sure VDSOSupport::Init() is called before any setuid or - // chroot calls, so InitializeSymbolizer() should be called very early in the - // life of a program. - absl::debugging_internal::VDSOSupport::Init(); -#endif - 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. -ABSL_CONST_INIT absl::base_internal::SpinLock g_decorators_mu( - absl::kConstInit, absl::base_internal::SCHEDULE_KERNEL_ONLY); - -const int kMaxFileMappingHints = 8; -int g_num_file_mapping_hints; -FileMappingHint g_file_mapping_hints[kMaxFileMappingHints]; -// Protects g_file_mapping_hints. -ABSL_CONST_INIT absl::base_internal::SpinLock g_file_mapping_mu( - absl::kConstInit, absl::base_internal::SCHEDULE_KERNEL_ONLY); - -// 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)); - SafeMemZero(&phdr[0], sizeof(phdr)); - } - - 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; - - // PT_LOAD program header describing executable code. - // Normally we expect just one, but SWIFT binaries have two. - std::array<ElfW(Phdr), 2> phdr; -}; - -// 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 = 3072, - 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() { -#if defined(__wasm__) || defined(__asmjs__) - int pagesize = getpagesize(); -#else - int pagesize = sysconf(_SC_PAGESIZE); -#endif - 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(absl::string_view 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]; - 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); - - 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; - } - } - 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::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)) { - 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_); -} - -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) { - // Symbolization is very slow under tsan. - ABSL_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); - ABSL_ANNOTATE_IGNORE_READS_AND_WRITES_END(); - return ok; -} - -ABSL_NAMESPACE_END -} // namespace absl - -extern "C" bool AbslInternalGetFileMappingHint(const void **start, - const void **end, uint64_t *offset, - const char **filename) { - return absl::debugging_internal::GetFileMappingHint(start, end, offset, - filename); -} |