From b56cbdd23834a65682c0b46f367f8679e83bc894 Mon Sep 17 00:00:00 2001 From: Abseil Team Date: Fri, 18 Sep 2020 15:55:15 -0700 Subject: Abseil LTS 20200923 What's New: * `absl::StatusOr` has been released. See our [blog post](https://abseil.io/blog/2020-091021-status) for more information. * Abseil Flags reflection interfaces have been released. * Abseil Flags memory usage has been significantly optimized. * Abseil now supports a "hardened" build mode. This build mode enables runtime checks that guard against programming errors that may lead to security vulnerabilities. Notable Fixes: * Sanitizer dynamic annotations like `AnnotateRWLockCreate` that are also defined by the compiler sanitizer implementation are no longer also defined by Abseil. * Sanitizer macros are now prefixed with `ABSL_` to avoid naming collisions. * Sanitizer usage is now automatically detected and no longer requires macros like `ADDRESS_SANITIZER` to be defined on the command line. Breaking Changes: * Abseil no longer contains a `dynamic_annotations` library. Users using a supported build system (Bazel or CMake) are unaffected by this, but users manually specifying link libraries may get an error about a missing linker input. Baseline: 7680a5f8efe32de4753baadbd63e74e59d95bac1 Cherry picks: None --- absl/debugging/symbolize_elf.inc | 120 ++++++++++++++++++++++++++++++++------- 1 file changed, 100 insertions(+), 20 deletions(-) (limited to 'absl/debugging/symbolize_elf.inc') diff --git a/absl/debugging/symbolize_elf.inc b/absl/debugging/symbolize_elf.inc index c371635f..7c36fd13 100644 --- a/absl/debugging/symbolize_elf.inc +++ b/absl/debugging/symbolize_elf.inc @@ -57,6 +57,7 @@ #include #include +#include #include #include #include @@ -74,6 +75,7 @@ #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 @@ -82,6 +84,12 @@ ABSL_NAMESPACE_BEGIN 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; @@ -149,13 +157,15 @@ struct FileMappingHint { // 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); +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. -base_internal::SpinLock g_file_mapping_mu(base_internal::kLinkerInitialized); +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. @@ -175,6 +185,7 @@ struct ObjFile { fd(-1), elf_type(-1) { SafeMemZero(&elf_header, sizeof(elf_header)); + SafeMemZero(&phdr[0], sizeof(phdr)); } char *filename; @@ -187,6 +198,10 @@ struct ObjFile { 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 phdr; }; // Build 4-way associative cache for symbols. Within each cache line, symbols @@ -496,7 +511,7 @@ static ABSL_ATTRIBUTE_NOINLINE bool GetSectionHeaderByType( const int kMaxSectionNameLen = 64; bool ForEachSection(int fd, - const std::function &callback) { ElfW(Ehdr) elf_header; if (!ReadFromOffsetExact(fd, &elf_header, sizeof(elf_header), 0)) { @@ -518,7 +533,7 @@ bool ForEachSection(int fd, return false; } off_t name_offset = shstrtab.sh_offset + out.sh_name; - char header_name[kMaxSectionNameLen + 1]; + char header_name[kMaxSectionNameLen]; ssize_t n_read = ReadFromOffset(fd, &header_name, kMaxSectionNameLen, name_offset); if (n_read == -1) { @@ -527,9 +542,8 @@ bool ForEachSection(int fd, // Long read? return false; } - header_name[n_read] = '\0'; - std::string name(header_name); + absl::string_view name(header_name, strnlen(header_name, n_read)); if (!callback(name, out)) { break; } @@ -1264,6 +1278,36 @@ static bool MaybeInitializeObjFile(ObjFile *obj) { 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; + int 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; } @@ -1287,23 +1331,52 @@ const char *Symbolizer::GetSymbol(const void *const pc) { int fd = -1; if (obj != nullptr) { if (MaybeInitializeObjFile(obj)) { - if (obj->elf_type == ET_DYN && - reinterpret_cast(obj->start_addr) >= obj->offset) { + const size_t start_addr = reinterpret_cast(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 = reinterpret_cast(obj->start_addr) - obj->offset; + relocation = start_addr - obj->offset; + + // Note: some binaries have multiple "rx" LOAD segments. We must + // find the right one. + ElfW(Phdr) *phdr = nullptr; + for (int 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(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_)); + 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 @@ -1374,7 +1447,7 @@ int InstallSymbolDecorator(SymbolDecorator decorator, void *arg) { if (!g_decorators_mu.TryLock()) { // Someone else is using decorators. Get out. - return false; + return -2; } int ret = ticket; if (g_num_decorators >= kMaxDecorators) { @@ -1402,7 +1475,7 @@ bool RegisterFileMappingHint(const void *start, const void *end, uint64_t offset if (g_num_file_mapping_hints >= kMaxFileMappingHints) { ret = false; } else { - // TODO(ckennelly): Move this into a std::string copy routine. + // TODO(ckennelly): Move this into a string copy routine. int len = strlen(filename); char *dst = static_cast( base_internal::LowLevelAlloc::AllocWithArena(len + 1, SigSafeArena())); @@ -1453,7 +1526,7 @@ bool GetFileMappingHint(const void **start, const void **end, uint64_t *offset, bool Symbolize(const void *pc, char *out, int out_size) { // Symbolization is very slow under tsan. - ANNOTATE_IGNORE_READS_AND_WRITES_BEGIN(); + 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); @@ -1472,9 +1545,16 @@ bool Symbolize(const void *pc, char *out, int out_size) { } } debugging_internal::FreeSymbolizer(s); - ANNOTATE_IGNORE_READS_AND_WRITES_END(); + 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); +} -- cgit v1.2.3