linux-kernel - Re: [PATCH] scripts/gdb: fix lx-dmesg when CONFIG_PRINTK

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Date:   Thu, 10 Oct 2019 17:13:56 +0200
From:   Jan Kiszka <jan.kiszka@...mens.com>
To:     Joel Colledge <joel.colledge@...bit.com>,
        Kieran Bingham <kbingham@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scripts/gdb: fix lx-dmesg when CONFIG_PRINTK_CALLER is
 set

On 25.09.19 17:03, Joel Colledge wrote:
> When CONFIG_PRINTK_CALLER is set, struct printk_log contains an
> additional member caller_id. As a result, the offset of the log text is
> different.
> 
> This fixes the following error:
> 
>   (gdb) lx-dmesg
>   Python Exception <class 'ValueError'> embedded null character:
>   Error occurred in Python command: embedded null character
> 
> Signed-off-by: Joel Colledge <joel.colledge@...bit.com>
> ---
>  scripts/gdb/linux/constants.py.in | 1 +
>  scripts/gdb/linux/dmesg.py        | 4 +++-
>  2 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/scripts/gdb/linux/constants.py.in b/scripts/gdb/linux/constants.py.in
> index 2efbec6b6b8d..3c9794a0bf55 100644
> --- a/scripts/gdb/linux/constants.py.in
> +++ b/scripts/gdb/linux/constants.py.in
> @@ -74,4 +74,5 @@ LX_CONFIG(CONFIG_GENERIC_CLOCKEVENTS_BROADCAST)
>  LX_CONFIG(CONFIG_HIGH_RES_TIMERS)
>  LX_CONFIG(CONFIG_NR_CPUS)
>  LX_CONFIG(CONFIG_OF)
> +LX_CONFIG(CONFIG_PRINTK_CALLER)
>  LX_CONFIG(CONFIG_TICK_ONESHOT)
> diff --git a/scripts/gdb/linux/dmesg.py b/scripts/gdb/linux/dmesg.py
> index 6d2e09a2ad2f..1352680ef731 100644
> --- a/scripts/gdb/linux/dmesg.py
> +++ b/scripts/gdb/linux/dmesg.py
> @@ -14,6 +14,7 @@
>  import gdb
>  import sys
>  
> +from linux import constants
>  from linux import utils
>  
>  
> @@ -53,7 +54,8 @@ class LxDmesg(gdb.Command):
>                  continue
>  
>              text_len = utils.read_u16(log_buf[pos + 10:pos + 12])
> -            text = log_buf[pos + 16:pos + 16 + text_len].decode(
> +            text_start = pos + (20 if constants.LX_CONFIG_PRINTK_CALLER else 16)
> +            text = log_buf[text_start:text_start + text_len].decode(
>                  encoding='utf8', errors='replace')
>              time_stamp = utils.read_u64(log_buf[pos:pos + 8])
>  
> 

Sorry for the delay:

Reviewed-by: Jan Kiszka <jan.kiszka@...mens.com>

I suspect we will see more in nearer future with upcoming printk rework...

Jan

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