1 files changed, 23 insertions, 1 deletions

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 48da0f5d2f7f..b82586c53560 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -734,7 +734,29 @@ EXC_REAL(program_check, 0x700, 0x100)
 EXC_VIRT(program_check, 0x4700, 0x100, 0x700)
 TRAMP_KVM(PACA_EXGEN, 0x700)
 EXC_COMMON_BEGIN(program_check_common)
-        EXCEPTION_PROLOG_COMMON(0x700, PACA_EXGEN)
+        /*
+         * It's possible to receive a TM Bad Thing type program check with
+         * userspace register values (in particular r1), but with SRR1 reporting
+         * that we came from the kernel. Normally that would confuse the bad
+         * stack logic, and we would report a bad kernel stack pointer. Instead
+         * we switch to the emergency stack if we're taking a TM Bad Thing from
+         * the kernel.
+         */
+        li      r10,MSR_PR              /* Build a mask of MSR_PR ..    */
+        oris    r10,r10,0x200000@h      /* .. and SRR1_PROGTM           */
+        and     r10,r10,r12             /* Mask SRR1 with that.         */
+        srdi    r10,r10,8               /* Shift it so we can compare   */
+        cmpldi  r10,(0x200000 >> 8)     /* .. with an immediate.        */
+        bne 1f                          /* If != go to normal path.     */
+
+        /* SRR1 had PR=0 and SRR1_PROGTM=1, so use the emergency stack  */
+        andi.   r10,r12,MSR_PR;         /* Set CR0 correctly for label  */
+                                        /* 3 in EXCEPTION_PROLOG_COMMON */
+        mr      r10,r1                  /* Save r1                      */
+        ld      r1,PACAEMERGSP(r13)     /* Use emergency stack          */
+        subi    r1,r1,INT_FRAME_SIZE    /* alloc stack frame            */
+        b 3f                            /* Jump into the macro !!       */
+1:      EXCEPTION_PROLOG_COMMON(0x700, PACA_EXGEN)
         bl      save_nvgprs
         RECONCILE_IRQ_STATE(r10, r11)
         addi    r3,r1,STACK_FRAME_OVERHEAD