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x86/Kconfig: Fix CONFIG_CC_HAS_SANE_STACKPROTECTOR when cross compiling with clang

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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>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: 0fb7e506d5
Link: https://github.com/llvm/llvm-project/issues/48553
Link: https://lkml.kernel.org/r/20220617180845.2788442-1-nathan@kernel.org
This commit is contained in:
Nathan Chancellor 2022-06-17 11:08:46 -07:00 committed by Borislav Petkov
parent 32346491dd
commit 1b8667812b
1 changed files with 2 additions and 2 deletions
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4
arch/x86/Kconfig
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@ -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