3 files changed, 50 insertions, 32 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
diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index c83c115858c1..b2c002993d78 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -452,9 +452,20 @@ static long restore_tm_sigcontexts(struct task_struct *tsk,
 	if (MSR_TM_RESV(msr))
 		return -EINVAL;
 
-	/* pull in MSR TM from user context */
+	/* pull in MSR TS bits from user context */
 	regs->msr = (regs->msr & ~MSR_TS_MASK) | (msr & MSR_TS_MASK);
 
+	/*
+	 * Ensure that TM is enabled in regs->msr before we leave the signal
+	 * handler. It could be the case that (a) user disabled the TM bit
+	 * through the manipulation of the MSR bits in uc_mcontext or (b) the
+	 * TM bit was disabled because a sufficient number of context switches
+	 * happened whilst in the signal handler and load_tm overflowed,
+	 * disabling the TM bit. In either case we can end up with an illegal
+	 * TM state leading to a TM Bad Thing when we return to userspace.
+	 */
+	regs->msr |= MSR_TM;
+
 	/* pull in MSR LE from user context */
 	regs->msr = (regs->msr & ~MSR_LE) | (msr & MSR_LE);
 
diff --git a/arch/powerpc/kernel/trace/ftrace_64_mprofile.S b/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
index c98e90b4ea7b..b4e2b7165f79 100644
--- a/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
+++ b/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
@@ -181,34 +181,25 @@ _GLOBAL(ftrace_stub)
 	 *  - we have no stack frame and can not allocate one
 	 *  - LR points back to the original caller (in A)
 	 *  - CTR holds the new NIP in C
-	 *  - r0 & r12 are free
-	 *
-	 * r0 can't be used as the base register for a DS-form load or store, so
-	 * we temporarily shuffle r1 (stack pointer) into r0 and then put it back.
+	 *  - r0, r11 & r12 are free
 	 */
 livepatch_handler:
 	CURRENT_THREAD_INFO(r12, r1)
 
-	/* Save stack pointer into r0 */
-	mr	r0, r1
-
 	/* Allocate 3 x 8 bytes */
-	ld	r1, TI_livepatch_sp(r12)
-	addi	r1, r1, 24
-	std	r1, TI_livepatch_sp(r12)
+	ld	r11, TI_livepatch_sp(r12)
+	addi	r11, r11, 24
+	std	r11, TI_livepatch_sp(r12)
 
 	/* Save toc & real LR on livepatch stack */
-	std	r2,  -24(r1)
+	std	r2,  -24(r11)
 	mflr	r12
-	std	r12, -16(r1)
+	std	r12, -16(r11)
 
 	/* Store stack end marker */
 	lis     r12, STACK_END_MAGIC@h
 	ori     r12, r12, STACK_END_MAGIC@l
-	std	r12, -8(r1)
-
-	/* Restore real stack pointer */
-	mr	r1, r0
+	std	r12, -8(r11)
 
 	/* Put ctr in r12 for global entry and branch there */
 	mfctr	r12
@@ -216,36 +207,30 @@ livepatch_handler:
 
 	/*
 	 * Now we are returning from the patched function to the original
-	 * caller A. We are free to use r0 and r12, and we can use r2 until we
+	 * caller A. We are free to use r11, r12 and we can use r2 until we
 	 * restore it.
 	 */
 
 	CURRENT_THREAD_INFO(r12, r1)
 
-	/* Save stack pointer into r0 */
-	mr	r0, r1
-
-	ld	r1, TI_livepatch_sp(r12)
+	ld	r11, TI_livepatch_sp(r12)
 
 	/* Check stack marker hasn't been trashed */
 	lis     r2,  STACK_END_MAGIC@h
 	ori     r2,  r2, STACK_END_MAGIC@l
-	ld	r12, -8(r1)
+	ld	r12, -8(r11)
 1:	tdne	r12, r2
 	EMIT_BUG_ENTRY 1b, __FILE__, __LINE__ - 1, 0
 
 	/* Restore LR & toc from livepatch stack */
-	ld	r12, -16(r1)
+	ld	r12, -16(r11)
 	mtlr	r12
-	ld	r2,  -24(r1)
+	ld	r2,  -24(r11)
 
 	/* Pop livepatch stack frame */
-	CURRENT_THREAD_INFO(r12, r0)
-	subi	r1, r1, 24
-	std	r1, TI_livepatch_sp(r12)
-
-	/* Restore real stack pointer */
-	mr	r1, r0
+	CURRENT_THREAD_INFO(r12, r1)
+	subi	r11, r11, 24
+	std	r11, TI_livepatch_sp(r12)
 
 	/* Return to original caller of live patched function */
 	blr