From: Nathan Chancellor <nathan@kernel.org>
To: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>,
Nick Desaulniers <ndesaulniers@google.com>,
Tom Rix <trix@redhat.com>, Daniel Kolesa <daniel@octaforge.org>,
linux-kernel@vger.kernel.org, patches@lists.linux.dev,
llvm@lists.linux.dev, Nathan Chancellor <nathan@kernel.org>,
stable@vger.kernel.org
Subject: [PATCH] x86/Kconfig: Fix CONFIG_CC_HAS_SANE_STACKPROTECTOR when cross compiling with clang
Date: Fri, 17 Jun 2022 11:08:46 -0700 [thread overview]
Message-ID: <20220617180845.2788442-1-nathan@kernel.org> (raw)
Chimera Linux notes that CONFIG_CC_HAS_SANE_STACKPROTECTOR cannot be
enabled when cross compiling an x86_64 kernel with clang, even though it
does work when natively compiling.
When building on aarch64:
$ make -sj"$(nproc)" ARCH=x86_64 LLVM=1 defconfig
$ grep STACKPROTECTOR .config
When building on x86_64:
$ make -sj"$(nproc)" ARCH=x86_64 LLVM=1 defconfig
$ grep STACKPROTECTOR .config
CONFIG_CC_HAS_SANE_STACKPROTECTOR=y
CONFIG_HAVE_STACKPROTECTOR=y
CONFIG_STACKPROTECTOR=y
CONFIG_STACKPROTECTOR_STRONG=y
When clang is invoked without a '--target' flag, code is generated for
the default target, which is usually the host (it is configurable via
cmake). As a result, the has-stack-protector scripts will generate code
for the default target but check for x86 specific segment registers,
which cannot succeed if the default target is not x86.
$(CLANG_FLAGS) contains an explicit '--target' flag so pass that
variable along to the has-stack-protector scripts so that the stack
protector can be enabled when cross compiling with clang. The 32-bit
stack protector cannot currently be enabled with clang, as it does not
support '-mstack-protector-guard-symbol', so this results in no
functional change for ARCH=i386 when cross compiling.
Link: https://github.com/chimera-linux/cports/commit/0fb7e506d5f83fdf2104feb22cdac34934561226
Link: https://github.com/llvm/llvm-project/issues/48553
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
Fixes: 2a61f4747eea ("stack-protector: test compiler capability in Kconfig and drop AUTO mode")
might be appropriate; I am conflicted on fixes tags for problems that
that arise due to use cases that were not considered at the time of a
change, as it feels wrong to blame the commit for not looking far enough
into the future where it might be common for people to have workstations
running another architecture other than x86_64.
Chimera appears to use a 5.15 kernel so a
Cc: stable@vger.kernel.org
might be nice but some maintainers are picky about that so I leave it up
to you all.
arch/x86/Kconfig | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index be0b95e51df6..076adde7ead9 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -391,8 +391,8 @@ config PGTABLE_LEVELS
config CC_HAS_SANE_STACKPROTECTOR
bool
- default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
- default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
+ default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC) $(CLANG_FLAGS)) if 64BIT
+ default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC) $(CLANG_FLAGS))
help
We have to make sure stack protector is unconditionally disabled if
the compiler produces broken code or if it does not let us control
base-commit: b13baccc3850ca8b8cccbf8ed9912dbaa0fdf7f3
--
2.36.1
next reply other threads:[~2022-06-17 18:15 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-17 18:08 Nathan Chancellor [this message]
2022-07-01 22:17 ` [PATCH] x86/Kconfig: Fix CONFIG_CC_HAS_SANE_STACKPROTECTOR when cross compiling with clang Nathan Chancellor
2022-07-06 22:25 ` Dave Hansen
2022-07-07 17:17 ` Nathan Chancellor
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