x86/Kconfig: Only allow CONFIG_X86_KERNEL_IBT with ld.lld >= 14.0.0

With CONFIG_X86_KERNEL_IBT=y and a version of ld.lld prior to 14.0.0,
there are numerous objtool warnings along the lines of:

  warning: objtool: .plt+0x6: indirect jump found in RETPOLINE build

This is a known issue that has been resolved in ld.lld 14.0.0. Prevent
CONFIG_X86_KERNEL_IBT from being selectable when using one of these
problematic ld.lld versions.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220318230747.3900772-3-nathan@kernel.org

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 921e4eb..8757926 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1875,6 +1875,8 @@ config X86_KERNEL_IBT
        prompt "Indirect Branch Tracking"
        bool
        depends on X86_64 && CC_HAS_IBT && STACK_VALIDATION
+       # https://github.com/llvm/llvm-project/commit/9d7001eba9c4cb311e03cd8cdc231f9e579f2d0f
+       depends on !LD_IS_LLD || LLD_VERSION >= 140000
        help
          Build the kernel with support for Indirect Branch Tracking, a
          hardware support course-grain forward-edge Control Flow Integrity