Commit
ab234a260b1f ("x86/pv: Rework arch_local_irq_restore() to not
use popf") replaced "push %reg; popf" with something like: "test
$0x200, %reg; jz 1f; sti; 1:", which breaks the pushf/popf symmetry
that commit
ea24213d8088 ("objtool: Add UACCESS validation") relies
on.
The result is:
drivers/gpu/drm/amd/amdgpu/si.o: warning: objtool: si_common_hw_init()+0xf36: PUSHF stack exhausted
Meanwhile, commit
c9c324dc22aa ("objtool: Support stack layout changes
in alternatives") makes that we can actually use stack-ops in
alternatives, which means we can revert
1ff865e343c2 ("x86,smap: Fix
smap_{save,restore}() alternatives").
That in turn means we can limit the PUSHF/POPF handling of
ea24213d8088 to those instructions that are in alternatives.
Fixes: ab234a260b1f ("x86/pv: Rework arch_local_irq_restore() to not use popf")
Reported-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/YEY4rIbQYa5fnnEp@hirez.programming.kicks-ass.net
unsigned long flags;
asm volatile ("# smap_save\n\t"
- ALTERNATIVE("jmp 1f", "", X86_FEATURE_SMAP)
- "pushf; pop %0; " __ASM_CLAC "\n\t"
- "1:"
+ ALTERNATIVE("", "pushf; pop %0; " __ASM_CLAC "\n\t",
+ X86_FEATURE_SMAP)
: "=rm" (flags) : : "memory", "cc");
return flags;
static __always_inline void smap_restore(unsigned long flags)
{
asm volatile ("# smap_restore\n\t"
- ALTERNATIVE("jmp 1f", "", X86_FEATURE_SMAP)
- "push %0; popf\n\t"
- "1:"
+ ALTERNATIVE("", "push %0; popf\n\t",
+ X86_FEATURE_SMAP)
: : "g" (flags) : "memory", "cc");
}
if (update_cfi_state(insn, &state->cfi, op))
return 1;
+ if (!insn->alt_group)
+ continue;
+
if (op->dest.type == OP_DEST_PUSHF) {
if (!state->uaccess_stack) {
state->uaccess_stack = 1;