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SubjectRe: [PATCH v5] gcov: Clang support
On Wed, 17 Apr 2019 15:53:28 -0700 Tri Vo <trong@android.com> wrote:

> 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().

checkpatch speaketh truth.

Also, I'll change those Co-authored-by's to the documented Co-developed-by.


From: Andrew Morton <akpm@linux-foundation.org>
Subject: gcov-clang-support-checkpatch-fixes

WARNING: Non-standard signature: Co-authored-by:
#31:
Co-authored-by: Nick Desaulniers <ndesaulniers@google.com>

WARNING: Non-standard signature: Co-authored-by:
#32:
Co-authored-by: Tri Vo <trong@android.com>

WARNING: Possible unnecessary 'out of memory' message
#158: FILE: kernel/gcov/clang.c:90:
+ if (!info) {
+ pr_warn_ratelimited("failed to allocate gcov info\n");

WARNING: Possible unnecessary 'out of memory' message
#193: FILE: kernel/gcov/clang.c:125:
+ if (!info) {
+ pr_warn_ratelimited("failed to allocate gcov function info for %s\n",

WARNING: line over 80 characters
#546: FILE: kernel/gcov/clang.c:478:
+ pos += store_gcov_u32(buffer, pos, fi_ptr->cfg_checksum);

total: 0 errors, 5 warnings, 663 lines checked

NOTE: For some of the reported defects, checkpatch may be able to
mechanically convert to the typical style using --fix or --fix-inplace.

./patches/gcov-clang-support.patch has style problems, please review.

NOTE: If any of the errors are false positives, please report
them to the maintainer, see CHECKPATCH in MAINTAINERS.

Please run checkpatch prior to sending patches

Cc: Daniel Mentz <danielmentz@google.com>
Cc: Greg Hackmann <ghackmann@android.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Peter Oberparleiter <oberpar@linux.ibm.com>
Cc: Petri Gynther <pgynther@google.com>
Cc: Prasad Sodagudi <psodagud@quicinc.com>
Cc: Trilok Soni <tsoni@quicinc.com>
Cc: Tri Vo <trong@android.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

kernel/gcov/clang.c | 9 ++-------
1 file changed, 2 insertions(+), 7 deletions(-)

--- a/kernel/gcov/clang.c~gcov-clang-support-checkpatch-fixes
+++ a/kernel/gcov/clang.c
@@ -86,10 +86,8 @@ void llvm_gcov_init(llvm_gcov_callback w
{
struct gcov_info *info = kzalloc(sizeof(*info), GFP_KERNEL);

- if (!info) {
- pr_warn_ratelimited("failed to allocate gcov info\n");
+ if (!info)
return;
- }

INIT_LIST_HEAD(&info->head);
INIT_LIST_HEAD(&info->functions);
@@ -121,11 +119,8 @@ void llvm_gcda_emit_function(u32 ident,
{
struct gcov_fn_info *info = kzalloc(sizeof(*info), GFP_KERNEL);

- if (!info) {
- pr_warn_ratelimited("failed to allocate gcov function info for %s\n",
- function_name ?: "UNKNOWN");
+ if (!info)
return;
- }

INIT_LIST_HEAD(&info->head);
info->ident = ident;
_
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