From: Ard Biesheuvel Date: Wed, 1 Jan 2025 11:51:20 +0000 (+0100) Subject: x86/sev: Disable UBSAN on SEV code that may execute very early X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=99b863d2e87210c70354a1c75cc5bcc7a3afdc01;p=users%2Fdwmw2%2Flinux.git x86/sev: Disable UBSAN on SEV code that may execute very early Clang 14 and older may emit UBSAN instrumentation into code that is inlined into functions marked with __no_sanitize_undefined¹. This may result in faults when the code is executed very early, which may be the case for functions annotated as __head. Now that this requirement is strictly enforced, the build will fail in this case with the following message Absolute reference to symbol '.data' not permitted in .head.text Work around this by disabling UBSAN instrumentation on all SEV core code. ¹ https://lore.kernel.org/r/20250101024348.GA1828419@ax162 [ bp: Add a footnote with Nathan's detailed explanation and a Fixes tag ] Fixes: 3b6f99a94b04 ("x86/boot: Disable UBSAN in early boot code") Signed-off-by: Ard Biesheuvel Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Nathan Chancellor Link: https://lore.kernel.org/r/20250101115119.114584-2-ardb@kernel.org --- diff --git a/arch/x86/coco/sev/Makefile b/arch/x86/coco/sev/Makefile index 4e375e7305acd..08de375593074 100644 --- a/arch/x86/coco/sev/Makefile +++ b/arch/x86/coco/sev/Makefile @@ -13,3 +13,6 @@ KCOV_INSTRUMENT_core.o := n # With some compiler versions the generated code results in boot hangs, caused # by several compilation units. To be safe, disable all instrumentation. KCSAN_SANITIZE := n + +# Clang 14 and older may fail to respect __no_sanitize_undefined when inlining +UBSAN_SANITIZE := n