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From: Kefeng Wang <wangkefeng.wang@huawei.com>
To: Will Deacon <will.deacon@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] arm64: skip dump_backtrace() in show_regs when user mode pt_regs
Date: Wed, 3 Apr 2019 23:58:44 +0800	[thread overview]
Message-ID: <aed265b0-26bb-0c07-f03d-490a222779a2@huawei.com> (raw)
In-Reply-To: <20190403124420.GF16362@fuggles.cambridge.arm.com>


On 2019/4/3 20:44, Will Deacon wrote:
> On Thu, Mar 28, 2019 at 07:45:27PM +0800, Kefeng Wang wrote:
>> There is no need to call dump_backtrace() when the pt_regs
>> corresponds to user mode, eg,
>>
>> [  334.634005] potentially unexpected fatal signal 11.
>> [  334.634476] CPU: 3 PID: 2049 Comm: test Not tainted 5.1.0-rc2 #24
>> [  334.634745] Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015
>> [  334.635786] pstate: 60001000 (nZCv daif -PAN -UAO)
>> [  334.636131] pc : 0000aaaaad4c0788
>> [  334.636725] lr : 0000ffff83aac6e0
>> [  334.637006] sp : 0000ffffd14e9670
>> [  334.637352] x29: 0000ffffd14e9690 x28: 0000000000000000
>> [  334.637814] x27: 0000000000000000 x26: 0000000000000000
>> [  334.638143] x25: 0000000000000000 x24: 0000000000000000
>> [  334.638460] x23: 0000000000000000 x22: 0000000000000000
>> [  334.639499] x21: 0000aaaaad4c0650 x20: 0000000000000000
>> [  334.640336] x19: 0000aaaaad4c0790 x18: 0000000000000002
>> [  334.641062] x17: 0000ffff83aac600 x16: 0000aaaaad4d0fa0
>> [  334.641474] x15: 0000ffff83c10150 x14: 0000ffff83c101e0
>> [  334.641894] x13: 0000ffff83c12048 x12: 0000000000000000
>> [  334.642421] x11: 0000000000010000 x10: 0000000008000000
>> [  334.642749] x9 : 000000000fffffff x8 : ffffffffffffffff
>> [  334.643378] x7 : 0000000000010000 x6 : 0000ffff83be0b00
>> [  334.643669] x5 : 0000000000000000 x4 : 0000000000000000
>> [  334.644012] x3 : 0000aaaaad4c0754 x2 : 0000ffffd14e97d8
>> [  334.644302] x1 : 0000fffefffffffc x0 : 0000ffff00000000
>> [  334.645211] Call trace:
>>
>> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
>> ---
>>  arch/arm64/kernel/process.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
>> index 3767fb21a5b8..de224f1512ca 100644
>> --- a/arch/arm64/kernel/process.c
>> +++ b/arch/arm64/kernel/process.c
>> @@ -298,7 +298,8 @@ void __show_regs(struct pt_regs *regs)
>>  void show_regs(struct pt_regs * regs)
>>  {
>>  	__show_regs(regs);
>> -	dump_backtrace(regs, NULL);
>> +	if (!user_mode(regs))
>> +		dump_backtrace(regs, NULL);
>>  }
> Wouldn't this check be better off inside dump_backtrace()?

show_stack() call dump_backtrace() with pr_regs=NULL, so only judge it in show_regs().

Or using following changes?

diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 8ad119c3f665..66abe3ada3c7 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -106,6 +106,9 @@ void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 
        pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
 
+       if (regs && user_mode(regs))
+               return;
+
        if (!tsk)
                tsk = current;
 
@@ -181,10 +184,8 @@ static int __die(const char *str, int err, struct pt_regs *regs)
                 TASK_COMM_LEN, tsk->comm, task_pid_nr(tsk),
                 end_of_stack(tsk));
 
-       if (!user_mode(regs)) {
-               dump_backtrace(regs, tsk);
-               dump_instr(KERN_EMERG, regs);
-       }
+       dump_backtrace(regs, tsk);
+       dump_instr(KERN_EMERG, regs);
 
        return ret;
 }





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  reply	other threads:[~2019-04-03 15:59 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-28 11:45 [PATCH] arm64: skip dump_backtrace() in show_regs when user mode pt_regs Kefeng Wang
2019-04-03 12:44 ` Will Deacon
2019-04-03 15:58   ` Kefeng Wang [this message]
2019-04-05 16:42     ` Will Deacon
2019-04-07  7:38       ` Kefeng Wang
2019-04-08 17:05         ` Will Deacon

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