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Subject[tip: x86/build] x86/Kconfig: Fix CONFIG_CC_HAS_SANE_STACKPROTECTOR when cross compiling with clang
The following commit has been merged into the x86/build branch of tip:

Commit-ID: b230402b0dbd6930a616a07641f0bbc30325881e
Gitweb: https://git.kernel.org/tip/b230402b0dbd6930a616a07641f0bbc30325881e
Author: Nathan Chancellor <nathan@kernel.org>
AuthorDate: Fri, 17 Jun 2022 11:08:46 -07:00
Committer: Dave Hansen <dave.hansen@linux.intel.com>
CommitterDate: Wed, 06 Jul 2022 14:57:10 -07:00

x86/Kconfig: Fix CONFIG_CC_HAS_SANE_STACKPROTECTOR when cross compiling with clang

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.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://github.com/chimera-linux/cports/commit/0fb7e506d5f83fdf2104feb22cdac34934561226
Link: https://github.com/llvm/llvm-project/issues/48553
Link: https://lkml.kernel.org/r/20220617180845.2788442-1-nathan@kernel.org
---
arch/x86/Kconfig | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index b0142e0..b7767ba 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -386,8 +386,8 @@ 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
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