linux-kernel - Re: [PATCH] x86/show_trace_log_lvl: ensure stack pointer is aligned, again

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Message-ID: <20230428065513.GA22111@redhat.com>
Date:   Fri, 28 Apr 2023 08:55:13 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Josh Poimboeuf <jpoimboe@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vernon Lovejoy <vlovejoy@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/show_trace_log_lvl: ensure stack pointer is aligned,
 again

On 04/27, Josh Poimboeuf wrote:
>
> On Thu, Apr 27, 2023 at 04:00:54PM +0200, Oleg Nesterov wrote:
> > +	stack = PTR_ALIGN(stack, sizeof(long));
> >  	for ( ; stack; stack = PTR_ALIGN(stack_info.next_sp, sizeof(long))) {
> >  		const char *stack_name;
>
> Seems reasonable, though 'stack' is already initialized a few lines
> above this, so it would be cleaner to do the PTR_ALIGN then.  Or even
> better, just move it all to the for loop:
>
> 	for (stack = PTR_ALIGN(stack ? : get_stack_pointer(task, regs));
> 	     stack;
> 	     stack = PTR_ALIGN(stack_info.next_sp, sizeof(long))) {

We decided to make the simplest one-liner fix, but I was thinking about

	for ( stack = stack ? : get_stack_pointer(task, regs);
	     (stack = PTR_ALIGN(stack, sizeof(long)));
	      stack = stack_info.next_sp)
	{
		...

to factout out the annoying PTR_ALIGN(). Will it work for you?

Oleg.