linux-kernel - Re: [PATCH 1/2] stacktrace: fix print_stack

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Date:   Wed, 9 Nov 2016 19:10:34 +0300
From:   Andrey Ryabinin <aryabinin@...tuozzo.com>
To:     Andrey Konovalov <andreyknvl@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        <kasan-dev@...glegroups.com>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>, <mingo@...hat.com>
CC:     <kcc@...gle.com>
Subject: Re: [PATCH 1/2] stacktrace: fix print_stack_trace printing timestamp
 twice

On 11/08/2016 10:37 PM, Andrey Konovalov wrote:
> Right now print_stack_trace prints timestamp twice, the first time
> it's done by printk when printing spaces, the second - by print_ip_sym.
> As a result, stack traces in KASAN reports have double timestamps:
> [   18.822232] Allocated by task 3838:
> [   18.822232]  [   18.822232] [<ffffffff8107e236>] save_stack_trace+0x16/0x20
> [   18.822232]  [   18.822232] [<ffffffff81509bd6>] save_stack+0x46/0xd0
> [   18.822232]  [   18.822232] [<ffffffff81509e4b>] kasan_kmalloc+0xab/0xe0
> ....
> 
> Fix by calling printk only once.
> 
> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>


Right, since commit 4bcc595ccd80 ("printk: reinstate KERN_CONT for printing continuation lines")
printk requires KERN_CONT to continue log messages, and print_ip_sym() doesn't have it.

After a small nit bellow fixed:
	Acked-by: Andrey Ryabinin <aryabinin@...tuozzo.com>

> ---
>  kernel/stacktrace.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/stacktrace.c b/kernel/stacktrace.c
> index b6e4c16..56f510f 100644
> --- a/kernel/stacktrace.c
> +++ b/kernel/stacktrace.c
> @@ -14,13 +14,15 @@
>  void print_stack_trace(struct stack_trace *trace, int spaces)
>  {
>  	int i;
> +	unsigned long ip;

This can be inside for loop.
>  
>  	if (WARN_ON(!trace->entries))
>  		return;
>  
>  	for (i = 0; i < trace->nr_entries; i++) {
> -		printk("%*c", 1 + spaces, ' ');
> -		print_ip_sym(trace->entries[i]);
> +		ip = trace->entries[i];
> +		printk("%*c[<%p>] %pS\n", 1 + spaces, ' ',
> +				(void *) ip, (void *) ip);
>  	}
>  }
>  EXPORT_SYMBOL_GPL(print_stack_trace);
>