[PATCH v3 05/39] x86/ibt: Add ANNOTATE_NOENDBR

Peter Zijlstra
2022-03-03T11:31:12Z

In order to have objtool warn about code references to !ENDBR
instruction, we need an annotation to allow this for non-control-flow
instances -- consider text range checks, text patching, or return
trampolines etc.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
include/linux/objtool.h | 16 ++++++++++++++++
1 file changed, 16 insertions(+)

--- a/include/linux/objtool.h
+++ b/include/linux/objtool.h
@@ -77,6 +77,12 @@ struct unwind_hint {
#define STACK_FRAME_NON_STANDARD_FP(func)
#endif

+#define ANNOTATE_NOENDBR \
+ "986: \n\t" \
+ ".pushsection .discard.noendbr\n\t" \
+ _ASM_PTR " 986b\n\t" \
+ ".popsection\n\t"
+
#else /* __ASSEMBLY__ */

/*
@@ -129,6 +135,13 @@ struct unwind_hint {
.popsection
.endm

+.macro ANNOTATE_NOENDBR
+.Lhere_\@:
+ .pushsection .discard.noendbr
+ .quad .Lhere_\@
+ .popsection
+.endm
+
#endif /* __ASSEMBLY__ */

#else /* !CONFIG_STACK_VALIDATION */
@@ -139,12 +152,15 @@ struct unwind_hint {
"\n\t"
#define STACK_FRAME_NON_STANDARD(func)
#define STACK_FRAME_NON_STANDARD_FP(func)
+#define ANNOTATE_NOENDBR
#else
#define ANNOTATE_INTRA_FUNCTION_CALL
.macro UNWIND_HINT sp_reg:req sp_offset=0 type:req end=0
.endm
.macro STACK_FRAME_NON_STANDARD func:req
.endm
+.macro ANNOTATE_NOENDBR
+.endm
#endif

#endif /* CONFIG_STACK_VALIDATION */