On Fri, Feb 09, 2024 at 11:06:02AM -0800, Pawan Gupta wrote:
> (Though, there was a comment on avoiding the macro alltogether, to which
> I replied that it complicates 32-bit.)
Hmm, so this seems to build the respective entry_{32,64}.S TUs fine:
---
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index e81cabcb758f..7d1e5fe66495 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -313,12 +313,9 @@
*
* Note: Only the memory operand variant of VERW clears the CPU buffers.
*/
-.macro EXEC_VERW
- verw _ASM_RIP(mds_verw_sel)
-.endm
.macro CLEAR_CPU_BUFFERS
- ALTERNATIVE "", __stringify(EXEC_VERW), X86_FEATURE_CLEAR_CPU_BUF
+ ALTERNATIVE "", __stringify(verw _ASM_RIP(mds_verw_sel)), X86_FEATURE_CLEAR_CPU_BUF
.endm
#else /* __ASSEMBLY__ */
---
and looking at the asm:
64-bit:
# 317 "./arch/x86/include/asm/nospec-branch.h"
.macro CLEAR_CPU_BUFFERS
ALTERNATIVE "", "verw mds_verw_sel (% rip)", ( 3*32+18)
.endm
23: 0f 00 2d 00 00 00 00 verw 0x0(%rip) # 2a <.altinstr_replacement+0x2a>
32-bit:
.macro CLEAR_CPU_BUFFERS
ALTERNATIVE "", "verw mds_verw_sel", ( 3*32+18)
.endm
13d: 0f 00 2d 00 00 00 00 verw 0x0
it makes sense.
So what complications do you mean?
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
