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LLVM uses profiling data that's deliberately similar to GCC, but has a
very different way of exporting that data. LLVM calls llvm_gcov_init()
once per module, and provides a couple of callbacks that we can use to
ask for more data.
We care about the "writeout" callback, which in turn calls back into
compiler-rt/this module to dump all the gathered coverage data to disk:
llvm_gcda_start_file()
llvm_gcda_emit_function()
llvm_gcda_emit_arcs()
llvm_gcda_emit_function()
llvm_gcda_emit_arcs()
[... repeats for each function ...]
llvm_gcda_summary_info()
llvm_gcda_end_file()
This design is much more stateless and unstructured than gcc's, and is
intended to run at process exit. This forces us to keep some local
state about which module we're dealing with at the moment. On the other
hand, it also means we don't depend as much on how LLVM represents
profiling data internally.
See LLVM's lib/Transforms/Instrumentation/GCOVProfiling.cpp for more
details on how this works, particularly GCOVProfiler::emitProfileArcs(),
GCOVProfiler::insertCounterWriteout(), and GCOVProfiler::insertFlush().
[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20190417225328.208129-1-trong@android.com
Signed-off-by: Greg Hackmann <ghackmann@android.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Tri Vo <trong@android.com>
Co-developed-by: Nick Desaulniers <ndesaulniers@google.com>
Co-developed-by: Tri Vo <trong@android.com>
Tested-by: Trilok Soni <tsoni@quicinc.com>
Tested-by: Prasad Sodagudi <psodagud@quicinc.com>
Tested-by: Tri Vo <trong@android.com>
Tested-by: Daniel Mentz <danielmentz@google.com>
Tested-by: Petri Gynther <pgynther@google.com>
Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit e178a5beb36960902379040ee0b667fb0a8eee93)
[trong: removed dependencies on CC_IS_CLANG, CC_IS_GCC from Kconfig and
Makefile. Added GCOV_FORMAT_CLANG as a default choice for gcov
format.]
Bug: 132997968
Test: defconfig + CONFIG_GCOV_KERNEL records coverage
Change-Id: Id72b3ee32571f0e555d5a7407d3f1e933850b390
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Patch series "gcov: add Clang support", v4.
This patch (of 3):
base.c contains a few callbacks specific to GCC's gcov implementation.
Move these into their own module in preparation for Clang support.
Link: http://lkml.kernel.org/r/20190318025411.98014-2-trong@android.com
Signed-off-by: Greg Hackmann <ghackmann@android.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Tri Vo <trong@android.com>
Tested-by: Trilok Soni <tsoni@quicinc.com>
Tested-by: Prasad Sodagudi <psodagud@quicinc.com>
Tested-by: Tri Vo <trong@android.com>
Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Cc: Daniel Mentz <danielmentz@google.com>
Cc: Petri Gynther <pgynther@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit 826eba0d77bc74c4d1c611374b76abfe251e8538)
Bug: 132997968
Test: defconfig + CONFIG_GCOV_KERNEL records coverage
Change-Id: Ice0533106d634b22aeee49b6f542917f45c681f0
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Since also the gcov structures(gcov_info, gcov_fn_info, gcov_ctr_info) can
change between gcc releases, as shown in gcc 4.7, they cannot be defined
in a common header and need to be moved to a specific gcc implemention
file. This also requires to make the gcov_info structure opaque for the
common code and to introduce simple helpers for accessing data inside
gcov_info.
Signed-off-by: Frantisek Hrbata <fhrbata@redhat.com>
Cc: Jan Stancek <jstancek@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Acked-by: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Andy Gospodarek <agospoda@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Enable the use of GCC's coverage testing tool gcov [1] with the Linux
kernel. gcov may be useful for:
* debugging (has this code been reached at all?)
* test improvement (how do I change my test to cover these lines?)
* minimizing kernel configurations (do I need this option if the
associated code is never run?)
The profiling patch incorporates the following changes:
* change kbuild to include profiling flags
* provide functions needed by profiling code
* present profiling data as files in debugfs
Note that on some architectures, enabling gcc's profiling option
"-fprofile-arcs" for the entire kernel may trigger compile/link/
run-time problems, some of which are caused by toolchain bugs and
others which require adjustment of architecture code.
For this reason profiling the entire kernel is initially restricted
to those architectures for which it is known to work without changes.
This restriction can be lifted once an architecture has been tested
and found compatible with gcc's profiling. Profiling of single files
or directories is still available on all platforms (see config help
text).
[1] http://gcc.gnu.org/onlinedocs/gcc/Gcov.html
Signed-off-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Li Wei <W.Li@Sun.COM>
Cc: Michael Ellerman <michaele@au1.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Heiko Carstens <heicars2@linux.vnet.ibm.com>
Cc: Martin Schwidefsky <mschwid2@linux.vnet.ibm.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: WANG Cong <xiyou.wangcong@gmail.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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