UBUNTU: SAUCE: powerpc/64s: Use emergency stack for kernel TM Bad Thing program checks

[mirror_ubuntu-zesty-kernel.git] / arch / powerpc / kernel / exceptions-64s.S

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 78456131385dda57b4093f2fadc4f3a49a01159d..6e670a4693ebaec8e0265ac6ddb8ea88dc6e4ef2 100644 (file)
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -766,7 +766,29 @@ EXC_REAL(program_check, 0x700, 0x800)
 EXC_VIRT(program_check, 0x4700, 0x4800, 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