linux-kernel - [PATCH v2 0/2] Harden clang against unknown flag options

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Message-Id: <20210916184017.1881473-1-nathan@kernel.org>
Date:   Thu, 16 Sep 2021 11:40:15 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
        llvm@...ts.linux.dev, Nathan Chancellor <nathan@...nel.org>
Subject: [PATCH v2 0/2] Harden clang against unknown flag options

Hi all,

This series cleans up an issue that was noticed by the kernel test robot
where flags that clang does not implement support for are
unconditionally added to the command line, which causes all subsequent
calls to cc-{disable-warning,option} to fail, meaning developers are
flooded with unnecessary and pointless warnings.

The first patch handles the problematic flags with cc-option for clang
and the second patch ensures we catch new additions of unknown flags so
that they can be handled properly.

I intend for this to be merged via the kbuild tree but it can go via
-tip if there is any objection to that.

Cheers,
Nathan

v1 -> v2: https://lore.kernel.org/r/20210824022640.2170859-1-nathan@kernel.org/

* Patch 1: Change prefix to "x86/build" (Borislav).

* Patch 1: Add link to v1 thread for more context (Borislav).

* Patch 1: Add Borislav's ack.

* Patch 2: Expand comment in source to make it clear that clang only
  warns on certain unimplemented optimization flags.

* Series: Add Nick's review.

Nathan Chancellor (2):
  x86/build: Do not add -falign flags unconditionally for clang
  kbuild: Add -Werror=ignored-optimization-argument to CLANG_FLAGS

 arch/x86/Makefile_32.cpu | 12 +++++++++---
 scripts/Makefile.clang   |  5 +++++
 2 files changed, 14 insertions(+), 3 deletions(-)

base-commit: a9086b878b7fd65894eb8cb1fa395dd469970566
-- 
2.33.0