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authorLinus Torvalds <torvalds@linux-foundation.org>2017-10-09 19:08:32 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-10-09 19:08:32 -0700
commit529a86e063e9ff625c4ff247d8aa17d8072444fb (patch)
tree4de0e0ef1ef874addbd09195c8ba7105501efaf1
parentMerge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net (diff)
parentpowerpc/tm: Fix illegal TM state in signal handler (diff)
downloadlinux-dev-529a86e063e9ff625c4ff247d8aa17d8072444fb.tar.xz
linux-dev-529a86e063e9ff625c4ff247d8aa17d8072444fb.zip
Merge branch 'ppc-bundle' (bundle from Michael Ellerman)
Merge powerpc transactional memory fixes from Michael Ellerman: "I figured I'd still send you the commits using a bundle to make sure it works in case I need to do it again in future" This fixes transactional memory state restore for powerpc. * bundle'd patches from Michael Ellerman: powerpc/tm: Fix illegal TM state in signal handler powerpc/64s: Use emergency stack for kernel TM Bad Thing program checks
-rw-r--r--arch/powerpc/kernel/exceptions-64s.S24
-rw-r--r--arch/powerpc/kernel/signal_64.c13
2 files changed, 35 insertions, 2 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);