#include <cstdlib>
#include <iostream>
#include <limits.h>
+#include <link.h>
#include <unistd.h>
#ifdef __GNUC__
#include <folly/experimental/symbolizer/LineReader.h>
+/*
+ * This is declared in `link.h' on Linux platforms, but apparently not on the
+ * Mac version of the file. It's harmless to declare again, in any case.
+ *
+ * Note that declaring it with `extern "C"` results in linkage conflicts.
+ */
+extern struct r_debug _r_debug;
+
namespace folly {
namespace symbolizer {
namespace {
-/**
- * Read a hex value.
- */
-uintptr_t readHex(StringPiece& sp) {
- uintptr_t val = 0;
- const char* p = sp.begin();
- for (; p != sp.end(); ++p) {
- unsigned int v;
- if (*p >= '0' && *p <= '9') {
- v = (*p - '0');
- } else if (*p >= 'a' && *p <= 'f') {
- v = (*p - 'a') + 10;
- } else if (*p >= 'A' && *p <= 'F') {
- v = (*p - 'A') + 10;
- } else {
- break;
- }
- val = (val << 4) + v;
- }
- sp.assign(p, sp.end());
- return val;
-}
-
-/**
- * Skip over non-space characters.
- */
-void skipNS(StringPiece& sp) {
- const char* p = sp.begin();
- for (; p != sp.end() && (*p != ' ' && *p != '\t'); ++p) { }
- sp.assign(p, sp.end());
-}
-
-/**
- * Skip over space and tab characters.
- */
-void skipWS(StringPiece& sp) {
- const char* p = sp.begin();
- for (; p != sp.end() && (*p == ' ' || *p == '\t'); ++p) { }
- sp.assign(p, sp.end());
-}
-
-/**
- * Parse a line from /proc/self/maps
- */
-bool parseProcMapsLine(StringPiece line,
- uintptr_t& from,
- uintptr_t& to,
- uintptr_t& fileOff,
- bool& isSelf,
- StringPiece& fileName) {
- isSelf = false;
- // from to perm offset dev inode path
- // 00400000-00405000 r-xp 00000000 08:03 35291182 /bin/cat
- if (line.empty()) {
- return false;
- }
-
- // Remove trailing newline, if any
- if (line.back() == '\n') {
- line.pop_back();
- }
-
- // from
- from = readHex(line);
- if (line.empty() || line.front() != '-') {
- return false;
- }
- line.pop_front();
-
- // to
- to = readHex(line);
- if (line.empty() || line.front() != ' ') {
- return false;
- }
- line.pop_front();
-
- // perms
- skipNS(line);
- if (line.empty() || line.front() != ' ') {
- return false;
- }
- line.pop_front();
-
- uintptr_t fileOffset = readHex(line);
- if (line.empty() || line.front() != ' ') {
- return false;
- }
- line.pop_front();
- // main mapping starts at 0 but there can be multi-segment binary
- // such as
- // from to perm offset dev inode path
- // 00400000-00405000 r-xp 00000000 08:03 54011424 /bin/foo
- // 00600000-00605000 r-xp 00020000 08:03 54011424 /bin/foo
- // 00800000-00805000 r-xp 00040000 08:03 54011424 /bin/foo
- // if the offset > 0, this indicates to the caller that the baseAddress
- // need to be used for undo relocation step.
- fileOff = fileOffset;
-
- // dev
- skipNS(line);
- if (line.empty() || line.front() != ' ') {
- return false;
- }
- line.pop_front();
-
- // inode
- skipNS(line);
- if (line.empty() || line.front() != ' ') {
- return false;
- }
-
- // if inode is 0, such as in case of ANON pages, there should be atleast
- // one white space before EOL
- skipWS(line);
- if (line.empty()) {
- // There will be no fileName for ANON text pages
- // if the parsing came this far without a fileName, then from/to address
- // may contain text in ANON pages.
- isSelf = true;
- fileName.clear();
- return true;
- }
-
- fileName = line;
- return true;
-}
-
ElfCache* defaultElfCache() {
static constexpr size_t defaultCapacity = 500;
static auto cache = new ElfCache(defaultCapacity);
void Symbolizer::symbolize(const uintptr_t* addresses,
SymbolizedFrame* frames,
- size_t addressCount) {
+ size_t addrCount) {
size_t remaining = 0;
- for (size_t i = 0; i < addressCount; ++i) {
+ for (size_t i = 0; i < addrCount; ++i) {
auto& frame = frames[i];
if (!frame.found) {
++remaining;
return;
}
- int fd = openNoInt("/proc/self/maps", O_RDONLY);
- if (fd == -1) {
+ if (_r_debug.r_version != 1) {
return;
}
- char selfFile[PATH_MAX + 8];
+ char selfPath[PATH_MAX + 8];
ssize_t selfSize;
- if ((selfSize = readlink("/proc/self/exe", selfFile, PATH_MAX + 1)) == -1) {
- // something terribly wrong
+ if ((selfSize = readlink("/proc/self/exe", selfPath, PATH_MAX + 1)) == -1) {
+ // Something has gone terribly wrong.
return;
}
- selfFile[selfSize] = '\0';
-
- char buf[PATH_MAX + 100]; // Long enough for any line
- LineReader reader(fd, buf, sizeof(buf));
-
- while (remaining != 0) {
- StringPiece line;
- if (reader.readLine(line) != LineReader::kReading) {
- break;
- }
-
- // Parse line
- uintptr_t from;
- uintptr_t to;
- uintptr_t fileOff;
- uintptr_t base;
- bool isSelf = false; // fileName can potentially be '/proc/self/exe'
- StringPiece fileName;
- if (!parseProcMapsLine(line, from, to, fileOff, isSelf, fileName)) {
+ selfPath[selfSize] = '\0';
+
+ for (auto lmap = _r_debug.r_map;
+ lmap != nullptr && remaining != 0;
+ lmap = lmap->l_next) {
+ // The empty string is used in place of the filename for the link_map
+ // corresponding to the running executable. Additionally, the `l_addr' is
+ // 0 and the link_map appears to be first in the list---but none of this
+ // behavior appears to be documented, so checking for the empty string is
+ // as good as anything.
+ auto const objPath = lmap->l_name[0] != '\0' ? lmap->l_name : selfPath;
+
+ auto const elfFile = cache_->getFile(objPath);
+ if (!elfFile) {
continue;
}
- base = from;
- bool first = true;
- std::shared_ptr<ElfFile> elfFile;
-
- // case of text on ANON?
- // Recompute from/to/base from the executable
- if (isSelf && fileName.empty()) {
- elfFile = cache_->getFile(selfFile);
-
- if (elfFile != nullptr) {
- auto textSection = elfFile->getSectionByName(".text");
- base = elfFile->getBaseAddress();
- from = textSection->sh_addr;
- to = from + textSection->sh_size;
- fileName = selfFile;
- first = false; // no need to get this file again from the cache
- }
- }
+ // Get the address at which the object is loaded. We have to use the ELF
+ // header for the running executable, since its `l_addr' is zero, but we
+ // should use `l_addr' for everything else---in particular, if the object
+ // is position-independent, getBaseAddress() (which is p_vaddr) will be 0.
+ auto const base = lmap->l_addr != 0
+ ? lmap->l_addr
+ : elfFile->getBaseAddress();
- // See if any addresses are here
- for (size_t i = 0; i < addressCount; ++i) {
+ for (size_t i = 0; i < addrCount && remaining != 0; ++i) {
auto& frame = frames[i];
if (frame.found) {
continue;
}
- uintptr_t address = addresses[i];
-
- if (from > address || address >= to) {
- continue;
- }
-
- // Found
- frame.found = true;
- --remaining;
-
- // Open the file on first use
- if (first) {
- first = false;
- elfFile = cache_->getFile(fileName);
+ auto const addr = addresses[i];
+ // Get the unrelocated, ELF-relative address.
+ auto const adjusted = addr - base;
- // Need to get the correct base address as from
- // when fileOff > 0
- if (fileOff && elfFile != nullptr) {
- base = elfFile->getBaseAddress();
- }
+ if (elfFile->getSectionContainingAddress(adjusted)) {
+ frame.set(elfFile, adjusted);
+ --remaining;
}
-
- if (!elfFile) {
- continue;
- }
-
- // Undo relocation
- frame.set(elfFile, address - base);
}
}
-
- closeNoInt(fd);
}
namespace {
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