/*
- * Copyright 2014 Facebook, Inc.
+ * Copyright 2012-present Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
+#include <folly/experimental/symbolizer/Elf.h>
-
-#include "folly/experimental/symbolizer/Elf.h"
-
-#include <sys/mman.h>
-#include <sys/types.h>
-#include <sys/stat.h>
#include <fcntl.h>
+#include <folly/portability/SysMman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <cstring>
#include <string>
#include <glog/logging.h>
-#include "folly/Conv.h"
-#include "folly/Exception.h"
+#include <folly/Conv.h>
+#include <folly/Exception.h>
+#include <folly/ScopeGuard.h>
+
+#ifndef STT_GNU_IFUNC
+#define STT_GNU_IFUNC 10
+#endif
namespace folly {
namespace symbolizer {
ElfFile::ElfFile() noexcept
- : fd_(-1),
- file_(static_cast<char*>(MAP_FAILED)),
- length_(0),
- baseAddress_(0) {
-}
+ : fd_(-1),
+ file_(static_cast<char*>(MAP_FAILED)),
+ length_(0),
+ baseAddress_(0) {}
ElfFile::ElfFile(const char* name, bool readOnly)
- : fd_(-1),
- file_(static_cast<char*>(MAP_FAILED)),
- length_(0),
- baseAddress_(0) {
+ : fd_(-1),
+ file_(static_cast<char*>(MAP_FAILED)),
+ length_(0),
+ baseAddress_(0) {
open(name, readOnly);
}
void ElfFile::open(const char* name, bool readOnly) {
const char* msg = "";
int r = openNoThrow(name, readOnly, &msg);
- folly::checkUnixError(r, msg);
+ if (r == kSystemError) {
+ throwSystemError(msg);
+ } else {
+ CHECK_EQ(r, kSuccess) << msg;
+ }
}
-int ElfFile::openNoThrow(const char* name, bool readOnly, const char** msg)
- noexcept {
+int ElfFile::openNoThrow(
+ const char* name,
+ bool readOnly,
+ const char** msg) noexcept {
FOLLY_SAFE_CHECK(fd_ == -1, "File already open");
+ strncat(filepath_, name, kFilepathMaxLen - 1);
fd_ = ::open(name, readOnly ? O_RDONLY : O_RDWR);
if (fd_ == -1) {
- if (msg) *msg = "open";
- return -1;
+ if (msg) {
+ *msg = "open";
+ }
+ return kSystemError;
}
-
+ // Always close fd and unmap in case of failure along the way to avoid
+ // check failure above if we leave fd != -1 and the object is recycled
+ // like it is inside SignalSafeElfCache
+ auto guard = makeGuard([&] { reset(); });
struct stat st;
int r = fstat(fd_, &st);
if (r == -1) {
- if (msg) *msg = "fstat";
- return -1;
+ if (msg) {
+ *msg = "fstat";
+ }
+ return kSystemError;
}
length_ = st.st_size;
}
file_ = static_cast<char*>(mmap(nullptr, length_, prot, MAP_SHARED, fd_, 0));
if (file_ == MAP_FAILED) {
- if (msg) *msg = "mmap";
- return -1;
+ if (msg) {
+ *msg = "mmap";
+ }
+ return kSystemError;
}
- init();
- return 0;
+ if (!init(msg)) {
+ errno = EINVAL;
+ return kInvalidElfFile;
+ }
+ guard.dismiss();
+ return kSuccess;
+}
+
+int ElfFile::openAndFollow(
+ const char* name,
+ bool readOnly,
+ const char** msg) noexcept {
+ auto result = openNoThrow(name, readOnly, msg);
+ if (!readOnly || result != kSuccess) {
+ return result;
+ }
+
+ /* NOTE .gnu_debuglink specifies only the name of the debugging info file
+ * (with no directory components). GDB checks 3 different directories, but
+ * ElfFile only supports the first version:
+ * - dirname(name)
+ * - dirname(name) + /.debug/
+ * - X/dirname(name)/ - where X is set in gdb's `debug-file-directory`.
+ */
+ auto dirend = strrchr(name, '/');
+ // include ending '/' if any.
+ auto dirlen = dirend != nullptr ? dirend + 1 - name : 0;
+
+ auto debuginfo = getSectionByName(".gnu_debuglink");
+ if (!debuginfo) {
+ return result;
+ }
+
+ // The section starts with the filename, with any leading directory
+ // components removed, followed by a zero byte.
+ auto debugFileName = getSectionBody(*debuginfo);
+ auto debugFileLen = strlen(debugFileName.begin());
+ if (dirlen + debugFileLen >= PATH_MAX) {
+ return result;
+ }
+
+ char linkname[PATH_MAX];
+ memcpy(linkname, name, dirlen);
+ memcpy(linkname + dirlen, debugFileName.begin(), debugFileLen + 1);
+ reset();
+ result = openNoThrow(linkname, readOnly, msg);
+ if (result == kSuccess) {
+ return result;
+ }
+ return openNoThrow(name, readOnly, msg);
}
ElfFile::~ElfFile() {
- destroy();
+ reset();
}
-ElfFile::ElfFile(ElfFile&& other)
- : fd_(other.fd_),
- file_(other.file_),
- length_(other.length_),
- baseAddress_(other.baseAddress_) {
+ElfFile::ElfFile(ElfFile&& other) noexcept
+ : fd_(other.fd_),
+ file_(other.file_),
+ length_(other.length_),
+ baseAddress_(other.baseAddress_) {
+ // copy other.filepath_, leaving filepath_ zero-terminated, always.
+ strncat(filepath_, other.filepath_, kFilepathMaxLen - 1);
+ other.filepath_[0] = 0;
other.fd_ = -1;
other.file_ = static_cast<char*>(MAP_FAILED);
other.length_ = 0;
ElfFile& ElfFile::operator=(ElfFile&& other) {
assert(this != &other);
- destroy();
+ reset();
+ // copy other.filepath_, leaving filepath_ zero-terminated, always.
+ strncat(filepath_, other.filepath_, kFilepathMaxLen - 1);
fd_ = other.fd_;
file_ = other.file_;
length_ = other.length_;
baseAddress_ = other.baseAddress_;
+ other.filepath_[0] = 0;
other.fd_ = -1;
other.file_ = static_cast<char*>(MAP_FAILED);
other.length_ = 0;
return *this;
}
-void ElfFile::destroy() {
+void ElfFile::reset() {
+ filepath_[0] = 0;
+
if (file_ != MAP_FAILED) {
munmap(file_, length_);
+ file_ = static_cast<char*>(MAP_FAILED);
}
if (fd_ != -1) {
close(fd_);
+ fd_ = -1;
}
}
-void ElfFile::init() {
- auto& elfHeader = this->elfHeader();
+bool ElfFile::init(const char** msg) {
+ if (length_ < 4) {
+ if (msg) {
+ *msg = "not an ELF file (too short)";
+ }
+ return false;
+ }
// Validate ELF magic numbers
- FOLLY_SAFE_CHECK(elfHeader.e_ident[EI_MAG0] == ELFMAG0 &&
- elfHeader.e_ident[EI_MAG1] == ELFMAG1 &&
- elfHeader.e_ident[EI_MAG2] == ELFMAG2 &&
- elfHeader.e_ident[EI_MAG3] == ELFMAG3,
- "invalid ELF magic");
+ if (file_[EI_MAG0] != ELFMAG0 || file_[EI_MAG1] != ELFMAG1 ||
+ file_[EI_MAG2] != ELFMAG2 || file_[EI_MAG3] != ELFMAG3) {
+ if (msg) {
+ *msg = "invalid ELF magic";
+ }
+ return false;
+ }
+
+ auto& elfHeader = this->elfHeader();
- // Validate ELF class (32/64 bits)
#define EXPECTED_CLASS P1(ELFCLASS, __ELF_NATIVE_CLASS)
#define P1(a, b) P2(a, b)
-#define P2(a, b) a ## b
- FOLLY_SAFE_CHECK(elfHeader.e_ident[EI_CLASS] == EXPECTED_CLASS,
- "invalid ELF class");
+#define P2(a, b) a##b
+ // Validate ELF class (32/64 bits)
+ if (elfHeader.e_ident[EI_CLASS] != EXPECTED_CLASS) {
+ if (msg) {
+ *msg = "invalid ELF class";
+ }
+ return false;
+ }
#undef P1
#undef P2
#undef EXPECTED_CLASS
// Validate ELF data encoding (LSB/MSB)
-#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
-# define EXPECTED_ENCODING ELFDATA2LSB
-#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
-# define EXPECTED_ENCODING ELFDATA2MSB
-#else
-# error Unsupported byte order
-#endif
- FOLLY_SAFE_CHECK(elfHeader.e_ident[EI_DATA] == EXPECTED_ENCODING,
- "invalid ELF encoding");
-#undef EXPECTED_ENCODING
+ static constexpr auto kExpectedEncoding =
+ kIsLittleEndian ? ELFDATA2LSB : ELFDATA2MSB;
+ if (elfHeader.e_ident[EI_DATA] != kExpectedEncoding) {
+ if (msg) {
+ *msg = "invalid ELF encoding";
+ }
+ return false;
+ }
// Validate ELF version (1)
- FOLLY_SAFE_CHECK(elfHeader.e_ident[EI_VERSION] == EV_CURRENT &&
- elfHeader.e_version == EV_CURRENT,
- "invalid ELF version");
+ if (elfHeader.e_ident[EI_VERSION] != EV_CURRENT ||
+ elfHeader.e_version != EV_CURRENT) {
+ if (msg) {
+ *msg = "invalid ELF version";
+ }
+ return false;
+ }
// We only support executable and shared object files
- FOLLY_SAFE_CHECK(elfHeader.e_type == ET_EXEC || elfHeader.e_type == ET_DYN,
- "invalid ELF file type");
-
- FOLLY_SAFE_CHECK(elfHeader.e_phnum != 0, "no program header!");
- FOLLY_SAFE_CHECK(elfHeader.e_phentsize == sizeof(ElfW(Phdr)),
- "invalid program header entry size");
- FOLLY_SAFE_CHECK(elfHeader.e_shentsize == sizeof(ElfW(Shdr)),
- "invalid section header entry size");
-
- const ElfW(Phdr)* programHeader = &at<ElfW(Phdr)>(elfHeader.e_phoff);
- bool foundBase = false;
- for (size_t i = 0; i < elfHeader.e_phnum; programHeader++, i++) {
- // Program headers are sorted by load address, so the first PT_LOAD
- // header gives us the base address.
- if (programHeader->p_type == PT_LOAD) {
- baseAddress_ = programHeader->p_vaddr;
- foundBase = true;
- break;
+ if (elfHeader.e_type != ET_EXEC && elfHeader.e_type != ET_DYN) {
+ if (msg) {
+ *msg = "invalid ELF file type";
+ }
+ return false;
+ }
+
+ if (elfHeader.e_phnum == 0) {
+ if (msg) {
+ *msg = "no program header!";
+ }
+ return false;
+ }
+
+ if (elfHeader.e_phentsize != sizeof(ElfPhdr)) {
+ if (msg) {
+ *msg = "invalid program header entry size";
+ }
+ return false;
+ }
+
+ if (elfHeader.e_shentsize != sizeof(ElfShdr)) {
+ if (msg) {
+ *msg = "invalid section header entry size";
+ }
+ }
+
+ // Program headers are sorted by load address, so the first PT_LOAD
+ // header gives us the base address.
+ const ElfPhdr* programHeader =
+ iterateProgramHeaders([](auto& h) { return h.p_type == PT_LOAD; });
+
+ if (!programHeader) {
+ if (msg) {
+ *msg = "could not find base address";
}
+ return false;
}
+ baseAddress_ = programHeader->p_vaddr;
- FOLLY_SAFE_CHECK(foundBase, "could not find base address");
+ return true;
}
-const ElfW(Shdr)* ElfFile::getSectionByIndex(size_t idx) const {
+const ElfShdr* ElfFile::getSectionByIndex(size_t idx) const {
FOLLY_SAFE_CHECK(idx < elfHeader().e_shnum, "invalid section index");
- return &at<ElfW(Shdr)>(elfHeader().e_shoff + idx * sizeof(ElfW(Shdr)));
+ return &at<ElfShdr>(elfHeader().e_shoff + idx * sizeof(ElfShdr));
}
-folly::StringPiece ElfFile::getSectionBody(const ElfW(Shdr)& section) const {
+folly::StringPiece ElfFile::getSectionBody(const ElfShdr& section) const {
return folly::StringPiece(file_ + section.sh_offset, section.sh_size);
}
-void ElfFile::validateStringTable(const ElfW(Shdr)& stringTable) const {
- FOLLY_SAFE_CHECK(stringTable.sh_type == SHT_STRTAB,
- "invalid type for string table");
+void ElfFile::validateStringTable(const ElfShdr& stringTable) const {
+ FOLLY_SAFE_CHECK(
+ stringTable.sh_type == SHT_STRTAB, "invalid type for string table");
const char* start = file_ + stringTable.sh_offset;
// First and last bytes must be 0
- FOLLY_SAFE_CHECK(stringTable.sh_size == 0 ||
- (start[0] == '\0' && start[stringTable.sh_size - 1] == '\0'),
- "invalid string table");
+ FOLLY_SAFE_CHECK(
+ stringTable.sh_size == 0 ||
+ (start[0] == '\0' && start[stringTable.sh_size - 1] == '\0'),
+ "invalid string table");
}
-const char* ElfFile::getString(const ElfW(Shdr)& stringTable, size_t offset)
- const {
+const char* ElfFile::getString(const ElfShdr& stringTable, size_t offset)
+ const {
validateStringTable(stringTable);
- FOLLY_SAFE_CHECK(offset < stringTable.sh_size,
- "invalid offset in string table");
+ FOLLY_SAFE_CHECK(
+ offset < stringTable.sh_size, "invalid offset in string table");
return file_ + stringTable.sh_offset + offset;
}
-const char* ElfFile::getSectionName(const ElfW(Shdr)& section) const {
+const char* ElfFile::getSectionName(const ElfShdr& section) const {
if (elfHeader().e_shstrndx == SHN_UNDEF) {
- return nullptr; // no section name string table
+ return nullptr; // no section name string table
}
- const ElfW(Shdr)& sectionNames = *getSectionByIndex(elfHeader().e_shstrndx);
+ const ElfShdr& sectionNames = *getSectionByIndex(elfHeader().e_shstrndx);
return getString(sectionNames, section.sh_name);
}
-const ElfW(Shdr)* ElfFile::getSectionByName(const char* name) const {
+const ElfShdr* ElfFile::getSectionByName(const char* name) const {
if (elfHeader().e_shstrndx == SHN_UNDEF) {
- return nullptr; // no section name string table
+ return nullptr; // no section name string table
}
// Find offset in the section name string table of the requested name
- const ElfW(Shdr)& sectionNames = *getSectionByIndex(elfHeader().e_shstrndx);
+ const ElfShdr& sectionNames = *getSectionByIndex(elfHeader().e_shstrndx);
const char* foundName = iterateStrings(
- sectionNames,
- [&] (const char* s) { return !strcmp(name, s); });
+ sectionNames, [&](const char* s) { return !strcmp(name, s); });
if (foundName == nullptr) {
return nullptr;
}
size_t offset = foundName - (file_ + sectionNames.sh_offset);
// Find section with the appropriate sh_name offset
- const ElfW(Shdr)* foundSection = iterateSections(
- [&](const ElfW(Shdr)& sh) {
- if (sh.sh_name == offset) {
- return true;
- }
- return false;
- });
+ const ElfShdr* foundSection = iterateSections([&](const ElfShdr& sh) {
+ if (sh.sh_name == offset) {
+ return true;
+ }
+ return false;
+ });
return foundSection;
}
ElfFile::Symbol ElfFile::getDefinitionByAddress(uintptr_t address) const {
- Symbol foundSymbol {nullptr, nullptr};
+ Symbol foundSymbol{nullptr, nullptr};
- auto findSection = [&](const ElfW(Shdr)& section) {
- auto findSymbols = [&](const ElfW(Sym)& sym) {
+ auto findSection = [&](const ElfShdr& section) {
+ auto findSymbols = [&](const ElfSym& sym) {
if (sym.st_shndx == SHN_UNDEF) {
- return false; // not a definition
+ return false; // not a definition
}
if (address >= sym.st_value && address < sym.st_value + sym.st_size) {
foundSymbol.first = §ion;
return false;
};
- return iterateSymbolsWithType(section, STT_OBJECT, findSymbols) ||
- iterateSymbolsWithType(section, STT_FUNC, findSymbols);
+ return iterateSymbolsWithTypes(
+ section, {STT_OBJECT, STT_FUNC, STT_GNU_IFUNC}, findSymbols);
};
// Try the .dynsym section first if it exists, it's smaller.
ElfFile::Symbol ElfFile::getSymbolByName(const char* name) const {
Symbol foundSymbol{nullptr, nullptr};
- auto findSection = [&](const ElfW(Shdr)& section) -> bool {
+ auto findSection = [&](const ElfShdr& section) -> bool {
// This section has no string table associated w/ its symbols; hence we
// can't get names for them
if (section.sh_link == SHN_UNDEF) {
return false;
}
- auto findSymbols = [&](const ElfW(Sym)& sym) -> bool {
+ auto findSymbols = [&](const ElfSym& sym) -> bool {
if (sym.st_shndx == SHN_UNDEF) {
- return false; // not a definition
+ return false; // not a definition
}
if (sym.st_name == 0) {
- return false; // no name for this symbol
+ return false; // no name for this symbol
}
- const char* sym_name = getString(
- *getSectionByIndex(section.sh_link), sym.st_name);
+ const char* sym_name =
+ getString(*getSectionByIndex(section.sh_link), sym.st_name);
if (strcmp(sym_name, name) == 0) {
foundSymbol.first = §ion;
foundSymbol.second = &sym;
return false;
};
- return iterateSymbolsWithType(section, STT_OBJECT, findSymbols) ||
- iterateSymbolsWithType(section, STT_FUNC, findSymbols);
+ return iterateSymbolsWithTypes(
+ section, {STT_OBJECT, STT_FUNC, STT_GNU_IFUNC}, findSymbols);
};
// Try the .dynsym section first if it exists, it's smaller.
iterateSectionsWithType(SHT_DYNSYM, findSection) ||
- iterateSectionsWithType(SHT_SYMTAB, findSection);
+ iterateSectionsWithType(SHT_SYMTAB, findSection);
return foundSymbol;
}
-const ElfW(Shdr)* ElfFile::getSectionContainingAddress(ElfW(Addr) addr) const {
- return iterateSections([&](const ElfW(Shdr)& sh) -> bool {
+const ElfShdr* ElfFile::getSectionContainingAddress(ElfAddr addr) const {
+ return iterateSections([&](const ElfShdr& sh) -> bool {
return (addr >= sh.sh_addr) && (addr < (sh.sh_addr + sh.sh_size));
});
}
}
if (symbol.second->st_name == 0) {
- return nullptr; // symbol has no name
+ return nullptr; // symbol has no name
}
if (symbol.first->sh_link == SHN_UNDEF) {
- return nullptr; // symbol table has no strings
+ return nullptr; // symbol table has no strings
}
- return getString(*getSectionByIndex(symbol.first->sh_link),
- symbol.second->st_name);
+ return getString(
+ *getSectionByIndex(symbol.first->sh_link), symbol.second->st_name);
}
-} // namespace symbolizer
-} // namespace folly
-
+} // namespace symbolizer
+} // namespace folly
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