diff options
authorMichael Neuling <mikey@neuling.org>2018-09-24 17:27:04 +1000
committerMichael Ellerman <mpe@ellerman.id.au>2018-09-25 22:51:08 +1000
commitcf13435b730a502e814c63c84d93db131e563f5f (patch)
parentpowerpc/pseries: Fix unitialized timer reset on migration (diff)
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>
1 files changed, 9 insertions, 2 deletions
diff --git a/arch/powerpc/kernel/tm.S b/arch/powerpc/kernel/tm.S
index 6bffbc5affe7..183e8d75936f 100644
--- a/arch/powerpc/kernel/tm.S
+++ b/arch/powerpc/kernel/tm.S
@@ -176,13 +176,20 @@ _GLOBAL(tm_reclaim)
std r1, PACATMSCRATCH(r13)
ld r1, PACAR1(r13)
- /* Store the PPR in r11 and reset to decent value */
std r11, GPR11(r1) /* Temporary stash */
+ /*
+ * Store r13 away so we can free up the scratch SPR for the SLB fault
+ * handler (needed once we start accessing the thread_struct).
+ */
+ std r11, GPR13(r1)
/* Reset MSR RI so we can take SLB faults again */
li r11, MSR_RI
mtmsrd r11, 1
+ /* Store the PPR in r11 and reset to decent value */
mfspr r11, SPRN_PPR
@@ -211,7 +218,7 @@ _GLOBAL(tm_reclaim)
ld r4, GPR7(r1) /* user r7 */
ld r5, GPR11(r1) /* user r11 */
ld r6, GPR12(r1) /* user r12 */
- GET_SCRATCH0(8) /* user r13 */
+ ld r8, GPR13(r1) /* user r13 */
std r3, GPR1(r7)
std r4, GPR7(r7)
std r5, GPR11(r7)