From: Peter Oberparleiter <oberpar@linux.ibm.com>
To: Sasha Levin <sashal@kernel.org>, linux-kernel@vger.kernel.org
Cc: Andrew Morton <akpm@linux-foundation.org>,
Chuck Wolber <chuck@wolber.net>,
Frantisek Hrbata <fhrbata@redhat.com>,
Marco Elver <elver@google.com>,
Masami Hiramatsu <mhiramat@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@kernel.org>
Subject: Re: [PATCH v2 17/20] gcov: fix gcov_info_add() merge semantics for IOR counters
Date: Thu, 5 Nov 2026 18:50:34 +0100 [thread overview]
Message-ID: <f94b603b-1e5d-45c0-871b-4bc96941b47a@linux.ibm.com> (raw)
In-Reply-To: <20261103015238.3780910-18-sashal@kernel.org>
On 03.11.2026 02:52, Sasha Levin wrote:
> gcov_info_add() unconditionally uses += to merge all counter types.
> This is wrong for counters that use IOR merge semantics (bitwise OR),
> such as GCOV_COUNTER_IOR and GCC 14's GCOV_COUNTER_CONDS (MC/DC
> condition coverage). These counters store bitsets that must be merged
> with |=, not accumulated with +=.
>
> Detect IOR merge semantics by comparing the merge function pointer
> against __gcov_merge_ior, matching how GCC's own libgcov identifies
> merge semantics. This fixes the pre-existing bug for GCOV_COUNTER_IOR
> and also enables correct merging for MC/DC condition coverage data.
>
> Fixes: 5f41ea0386a5 ("gcov: add support for gcc 4.7 gcov format")
> Signed-off-by: Sasha Levin <sashal@kernel.org>
Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
--
Peter Oberparleiter
Linux on IBM Z Development - IBM Germany R&D
next prev parent reply other threads:[~2026-11-05 17:50 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-03 1:52 [PATCH v2 00/20] Unify code coverage and add Clang source-based coverage with MC/DC Sasha Levin
2026-11-03 1:52 ` [PATCH v2 01/20] coverage: move gcov and kcov under kernel/coverage/ Sasha Levin
2026-11-05 17:38 ` Peter Oberparleiter
2026-11-03 1:52 ` [PATCH v2 02/20] kbuild: unify static coverage instrumentation as COVERAGE_PROFILE Sasha Levin
2026-11-03 1:52 ` [PATCH v2 03/20] coverage: add a common debugfs interface Sasha Levin
2026-11-05 17:49 ` Peter Oberparleiter
2026-11-06 1:05 ` Sasha Levin
2026-11-03 1:52 ` [PATCH v2 04/20] compiler_types.h: Don't instrument __always_inline functions for coverage Sasha Levin
2026-11-03 1:52 ` [PATCH v2 05/20] context_tracking: Always inline the empty stubs called from noinstr code Sasha Levin
2026-11-03 1:52 ` [PATCH v2 06/20] lockdep: " Sasha Levin
2026-11-03 1:52 ` [PATCH v2 07/20] perf: Always inline the empty perf_lopwr_cb() stub Sasha Levin
2026-11-03 1:52 ` [PATCH v2 08/20] rseq: Always inline the empty stubs called from noinstr code Sasha Levin
2026-11-03 1:52 ` [PATCH v2 09/20] x86: Always inline " Sasha Levin
2026-11-03 1:52 ` [PATCH v2 10/20] x86/sev: Use non-instrumented bitops in the GHCB accessors Sasha Levin
2026-11-04 13:36 ` Sean Christopherson
2026-11-03 1:52 ` [PATCH v2 11/20] objtool: Detect code coverage instrumentation in noinstr code Sasha Levin
2026-11-03 1:52 ` [PATCH v2 12/20] x86/sev: Stop excluding noinstr.o from code coverage Sasha Levin
2026-11-03 1:52 ` [PATCH v2 13/20] x86/entry: Stop excluding the entry code from KCOV Sasha Levin
2026-11-03 1:52 ` [PATCH v2 14/20] coverage: add Clang's source-based code coverage Sasha Levin
2026-11-03 1:52 ` [PATCH v2 15/20] x86: Enable " Sasha Levin
2026-11-03 1:52 ` [PATCH v2 16/20] coverage: add MC/DC measurement Sasha Levin
2026-11-03 1:52 ` [PATCH v2 17/20] gcov: fix gcov_info_add() merge semantics for IOR counters Sasha Levin
2026-11-05 17:50 ` Peter Oberparleiter [this message]
2026-11-03 1:52 ` [PATCH v2 18/20] kconfig: add CC_HAS_CONDITION_COVERAGE for MC/DC support detection Sasha Levin
2026-11-03 1:52 ` [PATCH v2 19/20] gcov: add MC/DC condition coverage support Sasha Levin
2026-11-05 17:56 ` Peter Oberparleiter
2026-11-06 1:05 ` Sasha Levin
2026-11-03 1:52 ` [PATCH v2 20/20] Documentation: dev-tools: document the common code coverage interface Sasha Levin
2026-11-05 17:36 ` [PATCH v2 00/20] Unify code coverage and add Clang source-based coverage with MC/DC Peter Oberparleiter
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