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[POWERPC] Clear RI bit in MSR before restoring r13 when returning to userspace

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Some instruction tracing tools use the RI (recoverable interrupt) bit
in the MSR to indicate when it's safe to single-step.  Currently we
clear RI after restoring r13 when returning to userspace.  However,
if we single-step past the point where r13 is restored, we'll corrupt
r13 in the exception entry code and not restore it.  This moves the
clearing of RI to just before r13 is restored so this doesn't happen.

Signed-off-by: Paul Mackerras <paulus@samba.org>
This commit is contained in:
Paul Mackerras 2007-02-07 13:13:26 +11:00
parent 449d846dbc
commit e56a6e20f3
1 changed files with 34 additions and 27 deletions
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61
arch/powerpc/kernel/entry_64.S
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@ -172,13 +172,18 @@ syscall_error_cont:
stdcx. r0,0,r1 /* to clear the reservation */
andi. r6,r8,MSR_PR
ld r4,_LINK(r1)
/*
* Clear RI before restoring r13. If we are returning to
* userspace and we take an exception after restoring r13,
* we end up corrupting the userspace r13 value.
*/
li r12,MSR_RI
andc r11,r10,r12
mtmsrd r11,1 /* clear MSR.RI */
beq- 1f
ACCOUNT_CPU_USER_EXIT(r11, r12)
ld r13,GPR13(r1) /* only restore r13 if returning to usermode */
1: ld r2,GPR2(r1)
li r12,MSR_RI
andc r11,r10,r12
mtmsrd r11,1 /* clear MSR.RI */
ld r1,GPR1(r1)
mtlr r4
mtcr r5
@ -488,42 +493,44 @@ END_FW_FTR_SECTION_IFSET(FW_FEATURE_ISERIES)
#endif
stb r5,PACASOFTIRQEN(r13)
ld r3,_MSR(r1)
andi. r0,r3,MSR_RI
beq- unrecov_restore
/* extract EE bit and use it to restore paca->hard_enabled */
ld r3,_MSR(r1)
rldicl r4,r3,49,63 /* r0 = (r3 >> 15) & 1 */
stb r4,PACAHARDIRQEN(r13)
andi. r0,r3,MSR_PR
ld r4,_CTR(r1)
ld r0,_LINK(r1)
mtctr r4
mtlr r0
ld r4,_XER(r1)
mtspr SPRN_XER,r4
REST_8GPRS(5, r1)
andi. r0,r3,MSR_RI
beq- unrecov_restore
stdcx. r0,0,r1 /* to clear the reservation */
/*
* Clear RI before restoring r13. If we are returning to
* userspace and we take an exception after restoring r13,
* we end up corrupting the userspace r13 value.
*/
mfmsr r4
andc r4,r4,r0 /* r0 contains MSR_RI here */
mtmsrd r4,1
/*
* r13 is our per cpu area, only restore it if we are returning to
* userspace
*/
andi. r0,r3,MSR_PR
beq 1f
ACCOUNT_CPU_USER_EXIT(r3, r4)
ACCOUNT_CPU_USER_EXIT(r2, r4)
REST_GPR(13, r1)
1:
ld r3,_CTR(r1)
ld r0,_LINK(r1)
mtctr r3
mtlr r0
ld r3,_XER(r1)
mtspr SPRN_XER,r3
REST_8GPRS(5, r1)
stdcx. r0,0,r1 /* to clear the reservation */
mfmsr r0
li r2, MSR_RI
andc r0,r0,r2
mtmsrd r0,1
ld r0,_MSR(r1)
mtspr SPRN_SRR1,r0
mtspr SPRN_SRR1,r3
ld r2,_CCR(r1)
mtcrf 0xFF,r2