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

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Date:   Fri, 28 Apr 2023 16:57:47 -0700
From:   Josh Poimboeuf <jpoimboe@...nel.org>
To:     Oleg Nesterov <oleg@...hat.com>
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 Fri, Apr 28, 2023 at 08:55:13AM +0200, Oleg Nesterov wrote:
> 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?

I'd rather not, that's a little *too* clever, IMO.

-- 
Josh