diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2022-08-19 13:01:35 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2022-08-19 13:24:33 +0200 |
| commit | 332924973725e8cdcc783c175f68cf7e162cb9e5 (patch) | |
| tree | b76aac38d4f92e8851fe474a237195aed5607373 /arch/x86 | |
| parent | 4e3aa9238277597c6c7624f302d81a7b568b6f2d (diff) | |
x86/nospec: Fix i386 RSB stuffing
Turns out that i386 doesn't unconditionally have LFENCE, as such the
loop in __FILL_RETURN_BUFFER isn't actually speculation safe on such
chips.
Fixes: ba6e31af2be9 ("x86/speculation: Add LFENCE to RSB fill sequence")
Reported-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/Yv9tj9vbQ9nNlXoY@worktop.programming.kicks-ass.net
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/include/asm/nospec-branch.h | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h index 10731ccfed37..c936ce9f0c47 100644 --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -50,6 +50,7 @@ * the optimal version - two calls, each with their own speculation * trap should their return address end up getting used, in a loop. */ +#ifdef CONFIG_X86_64 #define __FILL_RETURN_BUFFER(reg, nr) \ mov $(nr/2), reg; \ 771: \ @@ -60,6 +61,17 @@ jnz 771b; \ /* barrier for jnz misprediction */ \ lfence; +#else +/* + * i386 doesn't unconditionally have LFENCE, as such it can't + * do a loop. + */ +#define __FILL_RETURN_BUFFER(reg, nr) \ + .rept nr; \ + __FILL_RETURN_SLOT; \ + .endr; \ + add $(BITS_PER_LONG/8) * nr, %_ASM_SP; +#endif /* * Stuff a single RSB slot. |