linux-kernel - Re: [PATCH v10 06/11] arm64: Make profile_pc() use arch_stack

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Message-ID: <bc165886-3939-a5e5-b905-23f9a2f3e0f8@linux.microsoft.com>
Date:   Wed, 27 Oct 2021 11:15:22 -0500
From:   "Madhavan T. Venkataraman" <madvenka@...ux.microsoft.com>
To:     Mark Rutland <mark.rutland@....com>
Cc:     broonie@...nel.org, jpoimboe@...hat.com, ardb@...nel.org,
        nobuta.keiya@...itsu.com, sjitindarsingh@...il.com,
        catalin.marinas@....com, will@...nel.org, jmorris@...ei.org,
        linux-arm-kernel@...ts.infradead.org,
        live-patching@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v10 06/11] arm64: Make profile_pc() use arch_stack_walk()



On 10/27/21 8:32 AM, Mark Rutland wrote:
> On Thu, Oct 14, 2021 at 09:58:42PM -0500, madvenka@...ux.microsoft.com wrote:
>> From: "Madhavan T. Venkataraman" <madvenka@...ux.microsoft.com>
>>
>> Currently, profile_pc() in ARM64 code walks the stack using
>> start_backtrace() and unwind_frame(). Make it use arch_stack_walk()
>> instead. This makes maintenance easier.
>>
>> Signed-off-by: Madhavan T. Venkataraman <madvenka@...ux.microsoft.com>
>> ---
>>  arch/arm64/kernel/time.c | 22 +++++++++++++---------
>>  1 file changed, 13 insertions(+), 9 deletions(-)
>>
>> diff --git a/arch/arm64/kernel/time.c b/arch/arm64/kernel/time.c
>> index eebbc8d7123e..671b3038a772 100644
>> --- a/arch/arm64/kernel/time.c
>> +++ b/arch/arm64/kernel/time.c
>> @@ -32,22 +32,26 @@
>>  #include <asm/stacktrace.h>
>>  #include <asm/paravirt.h>
>>  
>> +static bool profile_pc_cb(void *arg, unsigned long pc)
>> +{
>> +	unsigned long *prof_pc = arg;
>> +
>> +	if (in_lock_functions(pc))
>> +		return true;
>> +	*prof_pc = pc;
>> +	return false;
>> +}
>> +
>>  unsigned long profile_pc(struct pt_regs *regs)
>>  {
>> -	struct stackframe frame;
>> +	unsigned long prof_pc = 0;
>>  
>>  	if (!in_lock_functions(regs->pc))
>>  		return regs->pc;
> 
> This can go -- the first call to profile_pc_cb() will use regs->pc.
> 

Agreed.

> With that gone, and the include updates to use <linux/stacktrace.h>:
> 
> Reviewed-by: Mark Rutland <mark.rutland@....com>
> 

I will make the two changes.

Madhavan