powerpc/64/syscall: Reconcile interrupts

This reconciles interrupts in the system call case like all other
interrupts. This allows system_call_common to be shared with the scv
system call implementation in a subsequent patch.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200225173541.1549955-31-npiggin@gmail.com

arch/powerpc/kernel/entry_64.S

@@ -119,6 +119,17 @@ END_BTB_FLUSH_SECTION
 	ld	r11,exception_marker@toc(r2)
 	std	r11,-16(r10)		/* "regshere" marker */
 
+	/*
+	 * RECONCILE_IRQ_STATE without calling trace_hardirqs_off(), which
+	 * would clobber syscall parameters. Also we always enter with IRQs
+	 * enabled and nothing pending. system_call_exception() will call
+	 * trace_hardirqs_off().
+	 */
+	li	r11,IRQS_ALL_DISABLED
+	li	r12,PACA_IRQ_HARD_DIS
+	stb	r11,PACAIRQSOFTMASK(r13)
+	stb	r12,PACAIRQHAPPENED(r13)
+
 	/* Calling convention has r9 = orig r0, r10 = regs */
 	mr	r9,r0
 	bl	system_call_exception

arch/powerpc/kernel/syscall_64.c

@@ -17,13 +17,19 @@
 
 typedef long (*syscall_fn)(long, long, long, long, long, long);
 
-/* Has to run notrace because it is entered "unreconciled" */
-notrace long system_call_exception(long r3, long r4, long r5, long r6, long r7, long r8,
-			   unsigned long r0, struct pt_regs *regs)
+/* Has to run notrace because it is entered not completely "reconciled" */
+notrace long system_call_exception(long r3, long r4, long r5,
+				   long r6, long r7, long r8,
+				   unsigned long r0, struct pt_regs *regs)
 {
 	unsigned long ti_flags;
 	syscall_fn f;
 
+	if (IS_ENABLED(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG))
+		BUG_ON(irq_soft_mask_return() != IRQS_ALL_DISABLED);
+
+	trace_hardirqs_off(); /* finish reconciling */
+
 	if (IS_ENABLED(CONFIG_PPC_BOOK3S))
 		BUG_ON(!(regs->msr & MSR_RI));
 	BUG_ON(!(regs->msr & MSR_PR));
@@ -44,16 +50,6 @@ notrace long system_call_exception(long r3, long r4, long r5, long r6, long r7,
 
 	kuap_check_amr();
 
-	/*
-	 * A syscall should always be called with interrupts enabled
-	 * so we just unconditionally hard-enable here. When some kind
-	 * of irq tracing is used, we additionally check that condition
-	 * is correct
-	 */
-	if (IS_ENABLED(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG)) {
-		WARN_ON(irq_soft_mask_return() != IRQS_ENABLED);
-		WARN_ON(local_paca->irq_happened);
-	}
 	/*
 	 * This is not required for the syscall exit path, but makes the
 	 * stack frame look nicer. If this was initialised in the first stack
@@ -62,7 +58,7 @@ notrace long system_call_exception(long r3, long r4, long r5, long r6, long r7,
 	 */
 	regs->softe = IRQS_ENABLED;
 
-	__hard_irq_enable();
+	local_irq_enable();
 
 	ti_flags = current_thread_info()->flags;
 	if (unlikely(ti_flags & _TIF_SYSCALL_DOTRACE)) {