/hmmtrace

A quick and dirty tool for making sense of mtrace() traces.

Primary LanguagePython

hmmtrace

A quick and dirty tool for making sense of mtrace() traces.

Note that this tool is probably abandoned because mtrace(), as it turns out, has limited use in modern practical projects because of its inability to preserve call chain information that lead to the allocation. It is a "must" in projects that allocate memory with a wrapper like xmalloc or new. Consider using gperftools, Valgrind's Massif and other similar tools instead.

Introduction

mtrace() is a ...

Obtaining the trace

  1. Set the MALLOC_TRACE environment variable to the file you want your trace to be saved into. Then open the program you want to run in the debugger:
$ MALLOC_TRACE=/tmp/gdb.trace gdb
  1. Set a breakpoint at the location from which you want to start the trace and "continue" to it. If you want to start at main(), set it at main().
(gdb) b main
(gdb) c
  1. Call mtrace to begin writing to the trace.
(gdb) call (void)mtrace()

  1. Continue execution and run you program as you would until you decide to stop the trace.

  2. Stop writing to the trace.

(gdb) call (void)muntrace()
  1. Locate the .text segment:
(gdb) info file
...
0x000055555563f0c0 - 0x0000555555db67f5 is .text
...

Write down the first address. It is the offset of the .text segment hmmtrace will need it to decrypt those addresses into source code lines.

Using hmmtrace

Currently only sort by total currently allocated size for each line of code is supported:

$ hmmtrace <tracefile>

You can find out the code location, use addr2line:

$ addr2line -j .text -e /home/undercat/derp/binutils-gdb/gdb/gdb `printf %x $((ADDRESS_SHOWN - TEXT_SEGMENT_OFFSET))`

where TEXT_SEGMENT_OFFSET is the offset of the binary's .text segment as described above. Example:

$ addr2line -j .text -e /home/undercat/derp/binutils-gdb/gdb/gdb `printf %x $((0x55555574d4ce-0x000055555563f0c0))`
/home/../binutils-gdb/gdb/common/common-utils.c:44

TODO

Automate trace acquisition and text segment identification. It should be possible to run it like this:

$ hmmtrace <binary>