powerpc/64s: move context tracking exit to interrupt exit path

The interrupt handler wrapper functions are not the ideal place to
maintain context tracking because after they return, the low level exit
code must then determine if there are interrupts to replay, or if the
task should be preempted, etc. Those paths (e.g., schedule_user) include
their own exception_enter/exit pairs to fix this up but it's a bit hacky
(see schedule_user() comments).

Ideally context tracking will go to user mode only when there are no
more interrupts or context switches or other exit processing work to
handle.

64e can not do this because it does not use the C interrupt exit code.

Signed-off-by: Nicholas Piggin <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

1 files changed, 16 insertions, 2 deletions

diff --git a/arch/powerpc/kernel/syscall_64.c b/arch/powerpc/kernel/syscall_64.c
index 45c4420fe339..a2102e7a2713 100644
--- a/arch/powerpc/kernel/syscall_64.c
+++ b/arch/powerpc/kernel/syscall_64.c
@@ -255,9 +255,9 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 		ret |= _TIF_RESTOREALL;
 	}
 
-again:
 	local_irq_disable();
 
+again:
 	ti_flags = READ_ONCE(*ti_flagsp);
 	while (unlikely(ti_flags & (_TIF_USER_WORK_MASK & ~_TIF_RESTORE_TM))) {
 		local_irq_enable();
@@ -307,6 +307,7 @@ again:
 	if (unlikely(!__prep_irq_for_enabled_exit(!scv))) {
 		user_exit_irqoff();
 		local_irq_enable();
+		local_irq_disable();
 		goto again;
 	}
 
@@ -341,6 +342,7 @@ notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs, unsigned
 	BUG_ON(!(regs->msr & MSR_PR));
 	BUG_ON(!FULL_REGS(regs));
 	BUG_ON(regs->softe != IRQS_ENABLED);
+	CT_WARN_ON(ct_state() == CONTEXT_USER);
 
 	/*
 	 * We don't need to restore AMR on the way back to userspace for KUAP.
@@ -383,8 +385,14 @@ again:
 		}
 	}
 
-	if (unlikely(!prep_irq_for_enabled_exit(true, !irqs_disabled_flags(flags))))
+	user_enter_irqoff();
+
+	if (unlikely(!__prep_irq_for_enabled_exit(true))) {
+		user_exit_irqoff();
+		local_irq_enable();
+		local_irq_disable();
 		goto again;
+	}
 
 #ifdef CONFIG_PPC_BOOK3E
 	if (unlikely(ts->debug.dbcr0 & DBCR0_IDM)) {
@@ -425,6 +433,12 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs, unsign
 		unrecoverable_exception(regs);
 	BUG_ON(regs->msr & MSR_PR);
 	BUG_ON(!FULL_REGS(regs));
+	/*
+	 * CT_WARN_ON comes here via program_check_exception,
+	 * so avoid recursion.
+	 */
+	if (TRAP(regs) != 0x700)
+		CT_WARN_ON(ct_state() == CONTEXT_USER);
 
 	amr = kuap_get_and_check_amr();