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| author | Peter Zijlstra <peterz@infradead.org> | 2021-03-08 17:46:04 +0300 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2021-03-12 11:15:49 +0300 |
| commit | ba08abca66d46381df60842f64f70099d5482b92 (patch) | |
| tree | 4c95d9c8d8a57e79b4942d841fb45b1c787f7c90 /arch | |
| parent | a38fd8748464831584a19438cbb3082b5a2dab15 (diff) | |
| download | linux-ba08abca66d46381df60842f64f70099d5482b92.tar.xz | |
objtool,x86: Fix uaccess PUSHF/POPF validation
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
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/include/asm/smap.h | 10 |
1 files changed, 4 insertions, 6 deletions
diff --git a/arch/x86/include/asm/smap.h b/arch/x86/include/asm/smap.h index 8b58d6975d5d..0bc9b0895f33 100644 --- a/arch/x86/include/asm/smap.h +++ b/arch/x86/include/asm/smap.h @@ -58,9 +58,8 @@ static __always_inline unsigned long smap_save(void) 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; @@ -69,9 +68,8 @@ static __always_inline unsigned long smap_save(void) 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"); } |