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Date: Tue, 27 Dec 2022 17:30:19 +0800
From: Jinyang He <hejinyang@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>
Cc: WANG Xuerui <kernel@...0n.name>,
Tiezhu Yang <yangtiezhu@...ngson.cn>,
loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] LoongArch: Fix irq enable in exception handlers
On 2022-12-27 15:37, Huacai Chen wrote:
> Hi, Jinyang,
>
> Move die_if_kernel to irq disabled context to solve what?
For more strict logical. If the code flow go to die in die_if_kernel(),
its interrupt state is enable, that means it may cause schedule.
So I think it is better to call die_if_kernel() firstly.
> And LBT is
> surely allowed to be triggered in kernel context.
I'm not familar with lbt, I just not see any lbt codes in kernel. Plz,
how lbt exception triggered, and how kernel trigger lbt exception?
Thanks,
Jinyang
>
> Huacai
>
> On Wed, Dec 21, 2022 at 3:43 PM Jinyang He <hejinyang@...ngson.cn> wrote:
>> 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@...ngson.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
>>
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