Tuesday, April 29, 2014

Valgrind Notes

Couple notes.

1. Command line for running valgrind with vogl capturing glxspheres64 from the vogl_build/bin directory:

valgrind --tool=memcheck --leak-check=full --error-limit=no --trace-children=yes --time-stamp=yes --log-file=/tmp/blah.log -- ../../bin/steamlauncher.sh --amd64 --gameid ./glxspheres64

2. Found some good stuff. Also a few things like this... :)

                // Get some entropy from the heap.
                p[i] = vogl_malloc(65536 * (i + 1));
                if (p[i])
                    for (uint j = 0; j < 16; j++)
                        gen.update_obj_bits(reinterpret_cast<const uint64_t *>(p)[j]);

2. Adding --track-origins=yes to the command line slows Valgrind down quite a bit but can really help. It added the line in bold for this stack trace (which wasn't making sense until we got this hint):

Uninitialised byte(s) found during client check request                                                                                                                             
   at 0x5422873: vogl_trace_stream_start_of_file_packet::compute_crc() const (vogl_trace_stream_types.h:185)
   by 0x54227B1: vogl_trace_stream_start_of_file_packet::check_crc(unsigned int) const (vogl_trace_stream_types.h:231)
   by 0x5421EE8: vogl_trace_stream_start_of_file_packet::full_validation(unsigned int) const (vogl_trace_stream_types.h:242)
   by 0x5420CB7: vogl_trace_file_writer::open(char const*, vogl_archive_blob_manager*, bool, bool, unsigned int) (vogl_trace_file_writer.cpp:82)
   by 0x517BAC0: vogl_global_init() (vogl_intercept.cpp:799) 
   by 0x92E236F: pthread_once (pthread_once.S:103)
   by 0x517A970: vogl_entrypoint_prolog(gl_entrypoint_id_t) (vogl_intercept.cpp:865) 
   by 0x50B3382: vogl_glXChooseVisual(_XDisplay const*, int, int const*) (gl_glx_func_defs.inc:91640)
   by 0x50B3302: glXChooseVisual (gl_glx_func_defs.inc:91635)
   by 0x403C84: main (glxspheres.c:716)
 Address 0x59632bd is 149 bytes inside data symbol "_ZZL21get_vogl_trace_writervE19s_vogl_trace_writer"
 Uninitialised value was created by a stack allocation
   at 0x5536214: vogl::init_uuid() (vogl_uuid.cpp:53)

3. And finally, if that doesn't do it, you can use code like this to help even more:

      #include "memcheck.h"
      uintptr_t addr = VALGRIND_CHECK_MEM_IS_DEFINED(ptr, len);
      if (addr)
          printf("VALGRIND_CHECK_MEM failed: %p %u\n", ptr, len);
          printf("  addr = %p\n", (void *)addr);

Documentation for these markups (and much, much more) here:


Just grab valgrind.h and memcheck.h. We've checked them into the extlib/valgrind directory in vogl.

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