Messages in this thread | | | Date | Thu, 26 Feb 2009 14:50:51 +0100 | From | Peter Oberparleiter <> | Subject | [PATCH 0/4] gcov kernel support |
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This is a resend of the gcov kernel support patchset (see further below for an in-depth introduction). Patch base is 2.6.29-rc6.
This version fixes a few problems identified by Li Wei <W.Li@Sun.COM>: * node->parent is always NULL, causing NULL-pointer dereference in remove_node() * unsafe list traversing in reset_write() since remove_node may affect multiple list_heads * . and .. in .gcda path strings are not handled correctly
Thanks to Li Wei for reporting these problems and proposing fixes!
Patchset overview:
[PATCH 1/4] kernel: constructor support [PATCH 2/4] seq_file: add function to write binary data [PATCH 3/4] gcov: add gcov profiling infrastructure [PATCH 4/4] gcov: enable GCOV_PROFILE_ALL for x86_64
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Introduction:
This patch set enables the use of GCC's coverage testing tool gcov [1] with the Linux kernel. Coverage data of a running kernel is exported in gcov-compatible format via the "gcov" debugfs directory. To get coverage data for a specific file, change to the kernel build directory and use gcov with the -o option as follows (requires root):
# cd /tmp/linux-out # gcov -o /sys/kernel/debug/gcov/tmp/linux-out/kernel spinlock.c
This will create source code files annotated with execution counts in the current directory. In addition, graphical gcov front-ends such as lcov [2] can be used to automate the process of collecting data for the entire kernel and provide coverage overviews in HTML format.
Known issues:
* some architecture specific problems: the patch has been tested successfully on s390 and x86, the use of gcov profiling flags for the entire kernel needs to be tested per architecture before it can be enabled * GCC's profiling mechanism together with optimization sometimes produces skewed data (see [1]) * GCC's profiling code assumes single-threaded execution * gcov assumes that a program has finished when coverage data is analyzed
Despite these issues, the data which can be obtained has been proven to be sufficiently accurate for most practical uses.
History:
Hubertus Franke <frankeh@us.ibm.com> wrote the first version of this patch around 2002. Since then it has been adapted to new versions of the kernel and GCC with contributions by several people (see file kernel/gcov/fs.c, write me if I missed anyone). Due to regular requests, I rewrote the gcov-kernel patch from scratch so that it would (hopefully) be fit for inclusion into the upstream kernel.
-- [1] http://gcc.gnu.org/onlinedocs/gcc/Gcov.html [2] http://ltp.sourceforge.net/coverage/lcov.php
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