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From:   Jinyang He <hejinyang@loongson.cn>
To:     Huacai Chen <chenhuacai@kernel.org>,
        WANG Xuerui <kernel@xen0n.name>
Cc:     Tiezhu Yang <yangtiezhu@loongson.cn>, loongarch@lists.linux.dev,
        linux-kernel@vger.kernel.org
Subject: [PATCH] LoongArch: Fix irq enable in exception handlers
Date:   Wed, 21 Dec 2022 15:42:38 +0800
Message-Id: <20221221074238.6699-1-hejinyang@loongson.cn>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

The interrupt state can be got by regs->csr_prmd. Once previous
interrupt state is disable, we shouldn't enable interrupt if we
triggered exception which can be triggered in kernel mode. So
conditionally enable interrupt. For those do_\exception which
can not triggered in kernel mode but need enable interrupt, call
die_if_kernel() firstly. And for do_lsx, do_lasx and do_lbt cannot
triggered in kernel mode, too.

Signed-off-by: Jinyang He <hejinyang@loongson.cn>
---
 arch/loongarch/kernel/traps.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/arch/loongarch/kernel/traps.c b/arch/loongarch/kernel/traps.c
index 1ea14f6c18d3..3ac7b32d1e15 100644
--- a/arch/loongarch/kernel/traps.c
+++ b/arch/loongarch/kernel/traps.c
@@ -340,9 +340,9 @@ asmlinkage void noinstr do_fpe(struct pt_regs *regs, unsigned long fcsr)
 
 	/* Clear FCSR.Cause before enabling interrupts */
 	write_fcsr(LOONGARCH_FCSR0, fcsr & ~mask_fcsr_x(fcsr));
-	local_irq_enable();
 
 	die_if_kernel("FP exception in kernel code", regs);
+	local_irq_enable();
 
 	sig = SIGFPE;
 	fault_addr = (void __user *) regs->csr_era;
@@ -432,7 +432,8 @@ asmlinkage void noinstr do_bp(struct pt_regs *regs)
 	unsigned long era = exception_era(regs);
 	irqentry_state_t state = irqentry_enter(regs);
 
-	local_irq_enable();
+	if (regs->csr_prmd & CSR_PRMD_PIE)
+		local_irq_enable();
 	current->thread.trap_nr = read_csr_excode();
 	if (__get_inst(&opcode, (u32 *)era, user))
 		goto out_sigsegv;
@@ -514,7 +515,8 @@ asmlinkage void noinstr do_ri(struct pt_regs *regs)
 	unsigned int __user *era = (unsigned int __user *)exception_era(regs);
 	irqentry_state_t state = irqentry_enter(regs);
 
-	local_irq_enable();
+	if (regs->csr_prmd & CSR_PRMD_PIE)
+		local_irq_enable();
 	current->thread.trap_nr = read_csr_excode();
 
 	if (notify_die(DIE_RI, "RI Fault", regs, 0, current->thread.trap_nr,
@@ -606,8 +608,8 @@ asmlinkage void noinstr do_fpu(struct pt_regs *regs)
 {
 	irqentry_state_t state = irqentry_enter(regs);
 
-	local_irq_enable();
 	die_if_kernel("do_fpu invoked from kernel context!", regs);
+	local_irq_enable();
 	BUG_ON(is_lsx_enabled());
 	BUG_ON(is_lasx_enabled());
 
@@ -623,13 +625,13 @@ asmlinkage void noinstr do_lsx(struct pt_regs *regs)
 {
 	irqentry_state_t state = irqentry_enter(regs);
 
+	die_if_kernel("do_lsx invoked from kernel context!", regs);
 	local_irq_enable();
 	if (!cpu_has_lsx) {
 		force_sig(SIGILL);
 		goto out;
 	}
 
-	die_if_kernel("do_lsx invoked from kernel context!", regs);
 	BUG_ON(is_lasx_enabled());
 
 	preempt_disable();
@@ -645,14 +647,13 @@ asmlinkage void noinstr do_lasx(struct pt_regs *regs)
 {
 	irqentry_state_t state = irqentry_enter(regs);
 
+	die_if_kernel("do_lasx invoked from kernel context!", regs);
 	local_irq_enable();
 	if (!cpu_has_lasx) {
 		force_sig(SIGILL);
 		goto out;
 	}
 
-	die_if_kernel("do_lasx invoked from kernel context!", regs);
-
 	preempt_disable();
 	init_restore_lasx();
 	preempt_enable();
@@ -666,6 +667,7 @@ asmlinkage void noinstr do_lbt(struct pt_regs *regs)
 {
 	irqentry_state_t state = irqentry_enter(regs);
 
+	die_if_kernel("do_lbt invoked from kernel context!", regs);
 	local_irq_enable();
 	force_sig(SIGILL);
 	local_irq_disable();
@@ -677,7 +679,6 @@ asmlinkage void noinstr do_reserved(struct pt_regs *regs)
 {
 	irqentry_state_t state = irqentry_enter(regs);
 
-	local_irq_enable();
 	/*
 	 * Game over - no way to handle this if it ever occurs.	Most probably
 	 * caused by a fatal error after another hardware/software error.
@@ -685,8 +686,8 @@ asmlinkage void noinstr do_reserved(struct pt_regs *regs)
 	pr_err("Caught reserved exception %u on pid:%d [%s] - should not happen\n",
 		read_csr_excode(), current->pid, current->comm);
 	die_if_kernel("do_reserved exception", regs);
+	local_irq_enable();
 	force_sig(SIGUNUSED);
-
 	local_irq_disable();
 
 	irqentry_exit(regs, state);
-- 
2.34.3