linux-kernel - Re: [PATCH v3 9/9] powerpc/traps: Add line prefix in show

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Date:   Wed, 1 Aug 2018 08:41:15 +0200
From:   Christophe LEROY <christophe.leroy@....fr>
To:     Murilo Opsfelder Araujo <muriloo@...ux.ibm.com>,
        linux-kernel@...r.kernel.org
Cc:     Alastair D'Silva <alastair@...ilva.org>,
        Andrew Donnellan <andrew.donnellan@....ibm.com>,
        Balbir Singh <bsingharora@...il.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Cyril Bur <cyrilbur@...il.com>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Joe Perches <joe@...ches.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Michael Neuling <mikey@...ling.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Paul Mackerras <paulus@...ba.org>,
        Simon Guo <wei.guo.simon@...il.com>,
        Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>,
        "Tobin C . Harding" <me@...in.cc>, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v3 9/9] powerpc/traps: Add line prefix in
 show_instructions()



Le 31/07/2018 à 16:50, Murilo Opsfelder Araujo a écrit :
> Remove "Instruction dump:" line by adding a prefix to display current->comm
> and current->pid, along with the instructions dump.
> 
> The prefix can serve as a glue that links the instructions dump to its
> originator, allowing messages to be interleaved in the logs.
> 
> Before this patch, a page fault looked like:
> 
>    pandafault[10524]: segfault (11) at 100007d0 nip 1000061c lr 7fffbd295100 code 2 in pandafault[10000000+10000]
>    Instruction dump:
>    4bfffeec 4bfffee8 3c401002 38427f00 fbe1fff8 f821ffc1 7c3f0b78 3d22fffe
>    392988d0 f93f0020 e93f0020 39400048 <99490000> 39200000 7d234b78 383f0040
> 
> After this patch, it looks like:
> 
>    pandafault[10850]: segfault (11) at 100007d0 nip 1000061c lr 7fff9f3e5100 code 2 in pandafault[10000000+10000]
>    pandafault[10850]: code: 4bfffeec 4bfffee8 3c401002 38427f00 fbe1fff8 f821ffc1 7c3f0b78 3d22fffe
>    pandafault[10850]: code: 392988d0 f93f0020 e93f0020 39400048 <99490000> 39200000 7d234b78 383f0040
> 
> Signed-off-by: Murilo Opsfelder Araujo <muriloo@...ux.ibm.com>

Does the script scripts/decode_stacktrace.sh also works with this format 
change ?

> ---
>   arch/powerpc/kernel/process.c | 7 +++++--
>   1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> index e78799a8855a..d12143e7d8f9 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -1265,16 +1265,19 @@ static int instructions_to_print = 16;
>   void show_instructions(struct pt_regs *regs)
>   {
>   	int i;
> +	const char *prefix = KERN_INFO "%s[%d]: code: ";
>   	unsigned long pc = regs->nip - (instructions_to_print * 3 / 4 *
>   			sizeof(int));
>   
> -	printk("Instruction dump:");
> +	printk(prefix, current->comm, current->pid);
>   
>   	for (i = 0; i < instructions_to_print; i++) {
>   		int instr;
>   
> -		if (!(i % 8))
> +		if (!(i % 8) && (i > 0)) {
>   			pr_cont("\n");
> +			printk(prefix, current->comm, current->pid);
> +		}
>   
>   #if !defined(CONFIG_BOOKE)
>   		/* If executing with the IMMU off, adjust pc rather
>