[PATCH 1/2] powerpc/interrupt: Refactor interrupt_exit_user_prepare() and syscall_exit_prepare()

[Christophe Leroy]

Last part of interrupt_exit_user_prepare() and syscall_exit_prepare()
are identical.

Create a __interrupt_exit_user_prepare() function that is called by
both.

Note that it replaces a local_irq_save(flags) by local_irq_disable().
This is similar because the flags are never used. On ppc 8xx it is
more efficient because it doesn't require reading MSR.

Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
---
It requires the following commits that are in powerpc/fixes-test:
5d510ed78bcf powerpc/syscall: Calling kuap_save_and_lock() is wrong
a78339698ab1 powerpc/interrupts: Fix kuep_unlock() call

Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
---
 arch/powerpc/kernel/interrupt.c | 147 ++++++++++----------------------
 1 file changed, 44 insertions(+), 103 deletions(-)

diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
index e0938ba298f2..d896fc6ed0be 100644
--- a/arch/powerpc/kernel/interrupt.c
+++ b/arch/powerpc/kernel/interrupt.c
@@ -231,56 +231,15 @@ static notrace void booke_load_dbcr0(void)
 #endif
 }
 
-/*
- * This should be called after a syscall returns, with r3 the return value
- * from the syscall. If this function returns non-zero, the system call
- * exit assembly should additionally load all GPR registers and CTR and XER
- * from the interrupt frame.
- *
- * The function graph tracer can not trace the return side of this function,
- * because RI=0 and soft mask state is "unreconciled", so it is marked notrace.
- */
-notrace unsigned long syscall_exit_prepare(unsigned long r3,
-					   struct pt_regs *regs,
-					   long scv)
+static notrace unsigned long __interrupt_exit_user_prepare(struct pt_regs *regs, unsigned long ret,
+							   bool is_not_scv)
 {
 	unsigned long ti_flags;
-	unsigned long ret = 0;
-	bool is_not_scv = !IS_ENABLED(CONFIG_PPC_BOOK3S_64) || !scv;
 
 	CT_WARN_ON(ct_state() == CONTEXT_USER);
 
 	kuap_assert_locked();
 
-	regs->result = r3;
-
-	/* Check whether the syscall is issued inside a restartable sequence */
-	rseq_syscall(regs);
-
-	ti_flags = current_thread_info()->flags;
-
-	if (unlikely(r3 >= (unsigned long)-MAX_ERRNO) && is_not_scv) {
-		if (likely(!(ti_flags & (_TIF_NOERROR | _TIF_RESTOREALL)))) {
-			r3 = -r3;
-			regs->ccr |= 0x10000000; /* Set SO bit in CR */
-		}
-	}
-
-	if (unlikely(ti_flags & _TIF_PERSYSCALL_MASK)) {
-		if (ti_flags & _TIF_RESTOREALL)
-			ret = _TIF_RESTOREALL;
-		else
-			regs->gpr[3] = r3;
-		clear_bits(_TIF_PERSYSCALL_MASK, &current_thread_info()->flags);
-	} else {
-		regs->gpr[3] = r3;
-	}
-
-	if (unlikely(ti_flags & _TIF_SYSCALL_DOTRACE)) {
-		do_syscall_trace_leave(regs);
-		ret |= _TIF_RESTOREALL;
-	}
-
 	local_irq_disable();
 
 again:
@@ -303,7 +262,7 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 		ti_flags = READ_ONCE(current_thread_info()->flags);
 	}
 
-	if (IS_ENABLED(CONFIG_PPC_BOOK3S) && IS_ENABLED(CONFIG_PPC_FPU)) {
+	if (IS_ENABLED(CONFIG_PPC_BOOK3S_64) && IS_ENABLED(CONFIG_PPC_FPU)) {
 		if (IS_ENABLED(CONFIG_PPC_TRANSACTIONAL_MEM) &&
 				unlikely((ti_flags & _TIF_RESTORE_TM))) {
 			restore_tm_state(regs);
@@ -352,81 +311,63 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
 	return ret;
 }
 
-notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs, unsigned long msr)
+/*
+ * This should be called after a syscall returns, with r3 the return value
+ * from the syscall. If this function returns non-zero, the system call
+ * exit assembly should additionally load all GPR registers and CTR and XER
+ * from the interrupt frame.
+ *
+ * The function graph tracer can not trace the return side of this function,
+ * because RI=0 and soft mask state is "unreconciled", so it is marked notrace.
+ */
+notrace unsigned long syscall_exit_prepare(unsigned long r3,
+					   struct pt_regs *regs,
+					   long scv)
 {
 	unsigned long ti_flags;
-	unsigned long flags;
 	unsigned long ret = 0;
+	bool is_not_scv = !IS_ENABLED(CONFIG_PPC_BOOK3S_64) || !scv;
 
-	if (!IS_ENABLED(CONFIG_BOOKE) && !IS_ENABLED(CONFIG_40x))
-		BUG_ON(!(regs->msr & MSR_RI));
-	BUG_ON(!(regs->msr & MSR_PR));
-	BUG_ON(arch_irq_disabled_regs(regs));
-	CT_WARN_ON(ct_state() == CONTEXT_USER);
+	regs->result = r3;
 
-	/*
-	 * We don't need to restore AMR on the way back to userspace for KUAP.
-	 * AMR can only have been unlocked if we interrupted the kernel.
-	 */
-	kuap_assert_locked();
+	/* Check whether the syscall is issued inside a restartable sequence */
+	rseq_syscall(regs);
 
-	local_irq_save(flags);
+	ti_flags = current_thread_info()->flags;
 
-again:
-	ti_flags = READ_ONCE(current_thread_info()->flags);
-	while (unlikely(ti_flags & (_TIF_USER_WORK_MASK & ~_TIF_RESTORE_TM))) {
-		local_irq_enable(); /* returning to user: may enable */
-		if (ti_flags & _TIF_NEED_RESCHED) {
-			schedule();
-		} else {
-			if (ti_flags & _TIF_SIGPENDING)
-				ret |= _TIF_RESTOREALL;
-			do_notify_resume(regs, ti_flags);
+	if (unlikely(r3 >= (unsigned long)-MAX_ERRNO) && is_not_scv) {
+		if (likely(!(ti_flags & (_TIF_NOERROR | _TIF_RESTOREALL)))) {
+			r3 = -r3;
+			regs->ccr |= 0x10000000; /* Set SO bit in CR */
 		}
-		local_irq_disable();
-		ti_flags = READ_ONCE(current_thread_info()->flags);
 	}
 
-	if (IS_ENABLED(CONFIG_PPC_BOOK3S_64) && IS_ENABLED(CONFIG_PPC_FPU)) {
-		if (IS_ENABLED(CONFIG_PPC_TRANSACTIONAL_MEM) &&
-				unlikely((ti_flags & _TIF_RESTORE_TM))) {
-			restore_tm_state(regs);
-		} else {
-			unsigned long mathflags = MSR_FP;
-
-			if (cpu_has_feature(CPU_FTR_VSX))
-				mathflags |= MSR_VEC | MSR_VSX;
-			else if (cpu_has_feature(CPU_FTR_ALTIVEC))
-				mathflags |= MSR_VEC;
-
-			/* See above restore_math comment */
-			if ((regs->msr & mathflags) != mathflags)
-				restore_math(regs);
-		}
+	if (unlikely(ti_flags & _TIF_PERSYSCALL_MASK)) {
+		if (ti_flags & _TIF_RESTOREALL)
+			ret = _TIF_RESTOREALL;
+		else
+			regs->gpr[3] = r3;
+		clear_bits(_TIF_PERSYSCALL_MASK, &current_thread_info()->flags);
+	} else {
+		regs->gpr[3] = r3;
 	}
 
-	user_enter_irqoff();
-
-	if (unlikely(!__prep_irq_for_enabled_exit(true))) {
-		user_exit_irqoff();
-		local_irq_enable();
-		local_irq_disable();
-		goto again;
+	if (unlikely(ti_flags & _TIF_SYSCALL_DOTRACE)) {
+		do_syscall_trace_leave(regs);
+		ret |= _TIF_RESTOREALL;
 	}
 
-	booke_load_dbcr0();
-
-#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
-	local_paca->tm_scratch = regs->msr;
-#endif
-
-	account_cpu_user_exit();
+	return __interrupt_exit_user_prepare(regs, ret, is_not_scv);
+}
 
-	/* Restore user access locks last */
-	kuap_user_restore(regs);
-	kuep_unlock();
+notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs, unsigned long msr)
+{
+	if (!IS_ENABLED(CONFIG_BOOKE) && !IS_ENABLED(CONFIG_40x))
+		BUG_ON(!(regs->msr & MSR_RI));
+	BUG_ON(!(regs->msr & MSR_PR));
+	BUG_ON(arch_irq_disabled_regs(regs));
 
-	return ret;
+	return __interrupt_exit_user_prepare(regs, 0, true);
 }
 
 void preempt_schedule_irq(void);
-- 
2.25.0