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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: 59dc5bfca0 ("powerpc/64s: avoid reloading (H)SRR registers if they are still valid")
Reported-by: Sachin Sant <sachinp@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Tested-by: Sachin Sant <sachinp@linux.vnet.ibm.com>
Link: https://lore.kernel.org/r/20211221135101.2085547-1-mpe@ellerman.id.au
This commit is contained in:
Michael Ellerman 2021-12-22 00:50:59 +11:00
parent 5b09250cca
commit 314f6c23dd
1 changed files with 2 additions and 0 deletions
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2
arch/powerpc/kernel/interrupt_64.S
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@ -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