linux-kernel - Re: [PATCH v4 3/4] MIPS: Return earlier in die() if notify_die() returns NOTIFY

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Date:   Mon, 21 Aug 2023 10:28:51 +0800
From:   Tiezhu Yang <yangtiezhu@...ngson.cn>
To:     Huacai Chen <chenhuacai@...nel.org>
Cc:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        "Maciej W. Rozycki" <macro@...am.me.uk>,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        loongson-kernel@...ts.loongnix.cn
Subject: Re: [PATCH v4 3/4] MIPS: Return earlier in die() if notify_die()
 returns NOTIFY_STOP



On 08/20/2023 04:53 PM, Huacai Chen wrote:
> Hi, Tiezhu,
>
> On Sun, Aug 20, 2023 at 7:21 AM Tiezhu Yang <yangtiezhu@...ngson.cn> wrote:
>>
>> After the call to oops_exit(), it should not panic or execute
>> the crash kernel if the oops is to be suppressed.
>>
>> Suggested-by: Maciej W. Rozycki <macro@...am.me.uk>
>> Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
>> ---
>>  arch/mips/kernel/traps.c | 6 ++++--
>>  1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
>> index 8e528a8..fd770dc 100644
>> --- a/arch/mips/kernel/traps.c
>> +++ b/arch/mips/kernel/traps.c
>> @@ -412,6 +412,9 @@ void die(const char *str, struct pt_regs *regs)
>>
>>         oops_exit();
>>
>> +       if (ret == NOTIFY_STOP)
>> +               return;
>> +
>>         if (in_interrupt())
>>                 panic("Fatal exception in interrupt");
>>
>> @@ -421,8 +424,7 @@ void die(const char *str, struct pt_regs *regs)
>>         if (regs && kexec_should_crash(current))
>>                 crash_kexec(regs);
>>
>> -       if (ret != NOTIFY_STOP)
>> -               make_task_dead(SIGSEGV);
>> +       make_task_dead(SIGSEGV);
> Then you call make_task_dead() at the end unconditionally, and die()
> becomes a noreturn function again.

No, it can return if (ret == NOTIFY_STOP), so die() is a return
function now, please see objdump -d arch/mips/kernel/traps.o.

Thanks,
Tiezhu