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powerpc/tm: Fix userspace r13 corruption
When we treclaim we store the userspace checkpointed r13 to a scratch SPR and then later save the scratch SPR to the user thread struct. Unfortunately, this doesn't work as accessing the user thread struct can take an SLB fault and the SLB fault handler will write the same scratch SPRG that now contains the userspace r13. To fix this, we store r13 to the kernel stack (which can't fault) before we access the user thread struct. Found by running P8 guest + powervm + disable_1tb_segments + TM. Seen as a random userspace segfault with r13 looking like a kernel address. Signed-off-by: Michael Neuling <mikey@neuling.org> Reviewed-by: Breno Leitao <leitao@debian.org> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
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parent
8604895a34
commit
cf13435b73
1 changed files with 9 additions and 2 deletions
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@ -176,13 +176,20 @@ _GLOBAL(tm_reclaim)
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std r1, PACATMSCRATCH(r13)
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std r1, PACATMSCRATCH(r13)
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ld r1, PACAR1(r13)
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ld r1, PACAR1(r13)
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/* Store the PPR in r11 and reset to decent value */
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std r11, GPR11(r1) /* Temporary stash */
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std r11, GPR11(r1) /* Temporary stash */
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/*
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* Store r13 away so we can free up the scratch SPR for the SLB fault
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* handler (needed once we start accessing the thread_struct).
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*/
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GET_SCRATCH0(r11)
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std r11, GPR13(r1)
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/* Reset MSR RI so we can take SLB faults again */
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/* Reset MSR RI so we can take SLB faults again */
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li r11, MSR_RI
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li r11, MSR_RI
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mtmsrd r11, 1
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mtmsrd r11, 1
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/* Store the PPR in r11 and reset to decent value */
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mfspr r11, SPRN_PPR
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mfspr r11, SPRN_PPR
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HMT_MEDIUM
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HMT_MEDIUM
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@ -211,7 +218,7 @@ _GLOBAL(tm_reclaim)
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ld r4, GPR7(r1) /* user r7 */
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ld r4, GPR7(r1) /* user r7 */
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ld r5, GPR11(r1) /* user r11 */
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ld r5, GPR11(r1) /* user r11 */
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ld r6, GPR12(r1) /* user r12 */
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ld r6, GPR12(r1) /* user r12 */
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GET_SCRATCH0(8) /* user r13 */
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ld r8, GPR13(r1) /* user r13 */
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std r3, GPR1(r7)
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std r3, GPR1(r7)
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std r4, GPR7(r7)
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std r4, GPR7(r7)
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std r5, GPR11(r7)
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std r5, GPR11(r7)
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