The following commit has been merged into the x86/core branch of tip: Commit-ID: f8afc9d88e65d189653f363eacc1f3131216ef7c Gitweb: https://git.kernel.org/tip/f8afc9d88e65d189653f363eacc1f3131216ef7c Author: Nathan Chancellor <nathan@xxxxxxxxxx> AuthorDate: Fri, 11 Mar 2022 12:56:42 -07:00 Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CommitterDate: Sat, 12 Mar 2022 13:22:13 +01:00 x86/ibt: Fix CC_HAS_IBT check for clang Commit 41c5ef31ad71 ("x86/ibt: Base IBT bits") added a check for a crash in clang. However, this check does not work for two reasons. The first reason is that '-pg' is missing from the check, which is required for '-mfentry' to do anything. The second reason is that cc-option only uses /dev/null as the input file, which does not show a problem: $ clang --version | head -1 Ubuntu clang version 12.0.1-8build1 $ clang -fcf-protection=branch -mfentry -pg -c -x c /dev/null -o /dev/null $ echo $? 0 $ echo "void a(void) {}" | clang -fcf-protection=branch -mfentry -pg -c -x c - -o /dev/null ... $ echo $? 139 Use this test instead so that the check works for older versions of clang. Fixes: 41c5ef31ad71 ("x86/ibt: Base IBT bits") Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20220311195642.2033108-1-nathan@xxxxxxxxxx --- arch/x86/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 4ca7bfe..870e0d1 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -1867,7 +1867,7 @@ config CC_HAS_IBT # Clang/LLVM >= 14 # fentry check to work around https://reviews.llvm.org/D111108 def_bool ((CC_IS_GCC && $(cc-option, -fcf-protection=branch -mindirect-branch-register)) || \ - (CC_IS_CLANG && $(cc-option, -fcf-protection=branch -mfentry))) && \ + (CC_IS_CLANG && $(success,echo "void a(void) {}" | $(CC) -Werror $(CLANG_FLAGS) -fcf-protection=branch -mfentry -pg -x c - -c -o /dev/null))) && \ $(as-instr,endbr64) config X86_KERNEL_IBT
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