Enable Clang's Source-based Code Coverage and MC/DC for x86-64 [LWN.net]

From:		Sasha Levin <sashal-AT-kernel.org>
To:		nathan-AT-kernel.org
Subject:		[RFC PATCH 0/4] Enable Clang's Source-based Code Coverage and MC/DC for x86-64
Date:		Tue, 14 Oct 2025 19:26:35 -0400
Message-ID:		<20251014232639.673260-1-sashal@kernel.org>
Cc:		Matt.Kelly2-AT-boeing.com, akpm-AT-linux-foundation.org, andrew.j.oppelt-AT-boeing.com, anton.ivanov-AT-cambridgegreys.com, ardb-AT-kernel.org, arnd-AT-arndb.de, bhelgaas-AT-google.com, bp-AT-alien8.de, chuck.wolber-AT-boeing.com, dave.hansen-AT-linux.intel.com, dvyukov-AT-google.com, hpa-AT-zytor.com, jinghao7-AT-illinois.edu, johannes-AT-sipsolutions.net, jpoimboe-AT-kernel.org, justinstitt-AT-google.com, kees-AT-kernel.org, kent.overstreet-AT-linux.dev, linux-arch-AT-vger.kernel.org, linux-efi-AT-vger.kernel.org, linux-kbuild-AT-vger.kernel.org, linux-kernel-AT-vger.kernel.org, linux-trace-kernel-AT-vger.kernel.org, linux-um-AT-lists.infradead.org, llvm-AT-lists.linux.dev, luto-AT-kernel.org, marinov-AT-illinois.edu, masahiroy-AT-kernel.org, maskray-AT-google.com, mathieu.desnoyers-AT-efficios.com, matthew.l.weber3-AT-boeing.com, mhiramat-AT-kernel.org, mingo-AT-redhat.com, morbo-AT-google.com, ndesaulniers-AT-google.com, oberpar-AT-linux.ibm.com, paulmck-AT-kernel.org, peterz-AT-infradead.org, richard-AT-nod.at, rostedt-AT-goodmis.org, samitolvanen-AT-google.com, samuel.sarkisian-AT-boeing.com, sashal-AT-kernel.org, steven.h.vanderleest-AT-boeing.com, tglx-AT-linutronix.de, tingxur-AT-illinois.edu, tyxu-AT-illinois.edu, wentaoz5-AT-illinois.edu, x86-AT-kernel.org
Archive-link:		Article

This series adds support for Clang's Source-based Code Coverage to the
Linux kernel, enabling more accurate coverage measurement at the source
level compared to gcov. This is particularly valuable for safety-critical
use cases (automotive, medical, aerospace) where MC/DC coverage is required
for certification.

Changes since previous patchset [1]:
- Rebased on v6.18-rc1
- Adapted to lib/crypto reorganization (curve25519 exclusion moved to
  lib/crypto/Makefile)
- Minor correctness fixes throughout the codebase

The implementation has been tested with a kernel build using Clang 18+ and
boots successfully in a KVM environment with instrumentation enabled.

[1] https://lore.kernel.org/all/20240905043245.1389509-1-went...

Wentao Zhang (4):
  llvm-cov: add Clang's Source-based Code Coverage support
  llvm-cov: add Clang's MC/DC support
  x86: disable llvm-cov instrumentation
  x86: enable llvm-cov support

 Makefile                          |   9 ++
 arch/Kconfig                      |   1 +
 arch/x86/Kconfig                  |   2 +
 arch/x86/crypto/Makefile          |   1 +
 arch/x86/kernel/vmlinux.lds.S     |   2 +
 include/asm-generic/vmlinux.lds.h |  36 +++++
 kernel/Makefile                   |   1 +
 kernel/llvm-cov/Kconfig           | 121 ++++++++++++++
 kernel/llvm-cov/Makefile          |   8 +
 kernel/llvm-cov/fs.c              | 253 ++++++++++++++++++++++++++++++
 kernel/llvm-cov/llvm-cov.h        | 157 ++++++++++++++++++
 lib/crypto/Makefile               |   3 +-
 scripts/Makefile.lib              |  23 +++
 scripts/mod/modpost.c             |   2 +
 14 files changed, 618 insertions(+), 1 deletion(-)
 create mode 100644 kernel/llvm-cov/Kconfig
 create mode 100644 kernel/llvm-cov/Makefile
 create mode 100644 kernel/llvm-cov/fs.c
 create mode 100644 kernel/llvm-cov/llvm-cov.h

-- 
2.51.0