[PATCH v1 1/2] powerpc/64s: system call scv tabort fix for corrupt irq soft-mask state

[Nicholas Piggin <npiggin@gmail.com>]

If a system call is made with a transaction active, the kernel
immediately aborts it and returns. scv system calls disable irqs even
earlier in their interrupt handler, and tabort_syscall does not fix this
up.

This can result in irq soft-mask state being messed up on the next
kernel entry, and crashing at BUG_ON(arch_irq_disabled_regs(regs)) in
the kernel exit handlers, or possibly worse.

Fix this by having tabort_syscall setting irq soft-mask back to enabled.

Reported-by: Eirik Fuller <efuller@redhat.com>
Fixes: 7fa95f9adaee7 ("powerpc/64s: system call support for scv/rfscv instructions")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/kernel/interrupt_64.S | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S
index d4212d2ff0b5..44f99df36fb2 100644
--- a/arch/powerpc/kernel/interrupt_64.S
+++ b/arch/powerpc/kernel/interrupt_64.S
@@ -438,6 +438,10 @@ _ASM_NOKPROBE_SYMBOL(tabort_syscall)
 	li	r9, (TM_CAUSE_SYSCALL|TM_CAUSE_PERSISTENT)
 	TABORT(R9)
 
+	/* scv has disabled irqs so must re-enable. sc just remains enabled */
+	li	r9,IRQS_ENABLED
+	stb	r9,PACAIRQSOFTMASK(r13)
+
 	/*
 	 * Return directly to userspace. We have corrupted user register state,
 	 * but userspace will never see that register state. Execution will
-- 
2.23.0