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

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Date:   Wed, 27 Oct 2021 11:10:27 -0500
From:   "Madhavan T. Venkataraman" <madvenka@...ux.microsoft.com>
To:     "nobuta.keiya@...itsu.com" <nobuta.keiya@...itsu.com>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "jpoimboe@...hat.com" <jpoimboe@...hat.com>,
        "ardb@...nel.org" <ardb@...nel.org>,
        "sjitindarsingh@...il.com" <sjitindarsingh@...il.com>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "will@...nel.org" <will@...nel.org>,
        "jmorris@...ei.org" <jmorris@...ei.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "live-patching@...r.kernel.org" <live-patching@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v10 06/11] arm64: Make profile_pc() use arch_stack_walk()



On 10/24/21 9:18 PM, nobuta.keiya@...itsu.com wrote:
> Hi,
> 
>> -----Original Message-----
>> From: madvenka@...ux.microsoft.com <madvenka@...ux.microsoft.com>
>> Sent: Friday, October 15, 2021 11:59 AM
>> To: mark.rutland@....com; broonie@...nel.org; jpoimboe@...hat.com; ardb@...nel.org; Nobuta, Keiya/信田 圭哉
>> <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;
>> madvenka@...ux.microsoft.com
>> Subject: [PATCH v10 06/11] arm64: Make profile_pc() use arch_stack_walk()
>>
>> 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;
>>
>> -	start_backtrace(&frame, regs->regs[29], regs->pc);
>> -
>> -	do {
>> -		int ret = unwind_frame(NULL, &frame);
>> -		if (ret < 0)
>> -			return 0;
>> -	} while (in_lock_functions(frame.pc));
>> +	arch_stack_walk(profile_pc_cb, &prof_pc, current, regs);
>>
>> -	return frame.pc;
>> +	return prof_pc;
>>  }
>>  EXPORT_SYMBOL(profile_pc);
>>
>> --
>> 2.25.1
> 
> 
> I've got build error with CONFIG_ACPI=n:
> ====
> arch/arm64/kernel/time.c: In function 'profile_pc':
> arch/arm64/kernel/time.c:52:2: error: implicit declaration of function 'arch_stack_walk' [-Werror=implicit-function-declaration]
>    52 |  arch_stack_walk(profile_pc_cb, &prof_pc, current, regs);
>       |  ^~~~~~~~~~~~~~~
> ====
> 
> I think it should include <linux/stacktrace.h> instead of <asm/stacktrace.h>.
> 

OK. I will fix this.
Thanks for catching this.

Madhavan