powerpc/64s: Mask NIP before checking against SRR0

When CONFIG_PPC_RFI_SRR_DEBUG=y we check that NIP and SRR0 match when returning from interrupts. This can trigger falsely if NIP has either of its two low bits set via sigreturn or ptrace, while SRR0 has its low two bits masked in hardware. As a quick fix make sure to mask the low bits before doing the check. Fixes: 59dc5bf ("powerpc/64s: avoid reloading (H)SRR registers if they are still valid") Reported-by: Sachin Sant <[email protected]> Signed-off-by: Michael Ellerman <[email protected]> Tested-by: Sachin Sant <[email protected]> Link: https://lore.kernel.org/r/[email protected]
pop-os · Dec 24, 2021 · 314f6c2 · 314f6c2
1 parent 5b09250
commit 314f6c2
Showing 1 changed file with 2 additions and 0 deletions.
diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S
@@ -30,6 +30,7 @@ COMPAT_SYS_CALL_TABLE:
 	.ifc \srr,srr
 	mfspr	r11,SPRN_SRR0
 	ld	r12,_NIP(r1)
+	clrrdi  r12,r12,2
 100:	tdne	r11,r12
 	EMIT_BUG_ENTRY 100b,__FILE__,__LINE__,(BUGFLAG_WARNING | BUGFLAG_ONCE)
 	mfspr	r11,SPRN_SRR1
@@ -39,6 +40,7 @@ COMPAT_SYS_CALL_TABLE:
 	.else
 	mfspr	r11,SPRN_HSRR0
 	ld	r12,_NIP(r1)
+	clrrdi  r12,r12,2
 100:	tdne	r11,r12
 	EMIT_BUG_ENTRY 100b,__FILE__,__LINE__,(BUGFLAG_WARNING | BUGFLAG_ONCE)
 	mfspr	r11,SPRN_HSRR1