From: Peter Zijlstra peterz@infradead.org
[ Upstream commit 1ff865e343c2b59469d7e41d370a980a3f972c71 ]
As reported by objtool:
lib/ubsan.o: warning: objtool: .altinstr_replacement+0x0: alternative modifies stack lib/ubsan.o: warning: objtool: .altinstr_replacement+0x7: alternative modifies stack
the smap_{save,restore}() alternatives violate (the newly enforced) rule on stack invariance. That is, due to there only being a single ORC table it must be valid to any alternative. These alternatives violate this with the direct result that unwinds will not be correct when it hits between the PUSH and POP instructions.
Rewrite the functions to only have a conditional jump.
Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Reviewed-by: Miroslav Benes mbenes@suse.cz Acked-by: Josh Poimboeuf jpoimboe@redhat.com Link: https://lkml.kernel.org/r/20200429101802.GI13592@hirez.programming.kicks-ass... Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/include/asm/smap.h | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/asm/smap.h b/arch/x86/include/asm/smap.h index 27c47d183f4b..8b58d6975d5d 100644 --- a/arch/x86/include/asm/smap.h +++ b/arch/x86/include/asm/smap.h @@ -57,8 +57,10 @@ static __always_inline unsigned long smap_save(void) { unsigned long flags;
- asm volatile (ALTERNATIVE("", "pushf; pop %0; " __ASM_CLAC, - X86_FEATURE_SMAP) + asm volatile ("# smap_save\n\t" + ALTERNATIVE("jmp 1f", "", X86_FEATURE_SMAP) + "pushf; pop %0; " __ASM_CLAC "\n\t" + "1:" : "=rm" (flags) : : "memory", "cc");
return flags; @@ -66,7 +68,10 @@ static __always_inline unsigned long smap_save(void)
static __always_inline void smap_restore(unsigned long flags) { - asm volatile (ALTERNATIVE("", "push %0; popf", X86_FEATURE_SMAP) + asm volatile ("# smap_restore\n\t" + ALTERNATIVE("jmp 1f", "", X86_FEATURE_SMAP) + "push %0; popf\n\t" + "1:" : : "g" (flags) : "memory", "cc"); }