CODEWITHSUNDEEP
gdbcoredumpcrash-dumpsdwarfgoogle-breakpad
patraulea
patraulea

Reputation: 884

Why does breakpad minidump-2-core need debug symbols to generate core files?

The test code below produces a breakpad minidump, and GDB cannot display the stack from the dmp converted to core using minidump-2-core.

Why does minidump-2-core need debug symbols in order to recreate the core dump ? Shouldn't GDB extract the debug symbols from the actual ELF binaries (and if needed locate separate debug symbol files by reading the ELF headers of the binaries) ?

#include <filesystem>
#include <client/linux/handler/exception_handler.h>
#include <client/linux/handler/minidump_descriptor.h>

int main(int argc, char *argv[])
{
    google_breakpad::MinidumpDescriptor descriptor(std::filesystem::current_path());
    auto handler = new google_breakpad::ExceptionHandler{descriptor,
        NULL, NULL, NULL, true, -1}; // filterCb, dumpCb, cbCtx, install, clientFd
    *(char *)(size_t)argc = 0;
    delete handler;
    return 0;
}

$ g++ -I ~/breakpad/src -std=c++2a -Wall -ggdb -pthread -o test test.cc ~/breakpad/src/client/linux/libbreakpad_client.a

$ minidump-2-core -v *.dmp > minicore 2> info
$ gdb ./test ./minicore
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x0000558c55693f94 in ?? ()
(gdb) info shared
No shared libraries loaded at this time.
(gdb) info proc map
(gdb) quit

$ minidump-2-core -h
The shared library list will by default have filenames as the runtime expects.
 Default:    /lib64/libpthread.so.0
 -f:         /lib64/libpthread-2.19.so
 -i:         /lib64/<module id>-libpthread.so.0
 -f -i:      /lib64/<module id>-libpthread-2.19.so
 -S /foo/:   /foo/libpthread.so.0

Options:
  -v         Enable verbose output
  -o <file>  Write coredump to specified file (otherwise use stdout).
  -f         Use the filename rather than the soname in the sharedlib list.
             The soname is what the runtime system uses, but the filename is
             how it's stored on disk.
  -i         Prefix sharedlib names with ID (when available).  This makes it
             easier to have a single directory full of symbols.
  -S <dir>   Set soname base directory.  This will force all debug/symbol
             lookups to be done in this directory rather than the filesystem
             layout as it exists in the crashing image.  This path should end
             with a slash if it's a directory.  e.g. /var/lib/breakpad/

Upvotes: 0

Views: 259

Answers (1)

patraulea
patraulea

Reputation: 884

GDB 8 on some distros includes a workaround from 2007 linked below which enables it to read mini-core files generated with md2core correctly: https://sourceware.org/legacy-ml/binutils/2007-08/msg00047.html

The workaround was removed in newer GDB releases, and also in some GDB distro binaries, which no longer read mini-core files correctly: https://sourceware.org/legacy-ml/gdb-patches/2020-03/msg00106.html

A fix has just been committed on 2024.05.13 to the breakpad repo, and core files produced by md2core binaries which include this commit should be handled correctly by (all) GDB versions: https://github.com/google/breakpad/commit/417f5dbd0af9f96ca3e5faa99f41c064b89b40fd

Upvotes: 0

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