linux-kernel - Re: kdb: kgdb: CONFIG_DEBUG

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Message-ID: <CA+icZUWECpybkd8AxhvzboE0c54PkoLEZGBSXU-hbOVmEChaug@mail.gmail.com>
Date:	Tue, 9 Apr 2013 16:26:40 +0200
From:	Sedat Dilek <sedat.dilek@...il.com>
To:	Jason Wessel <jason.wessel@...driver.com>
Cc:	kgdb-bugreport@...ts.sourceforge.net,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: kdb: kgdb: CONFIG_DEBUG_RODATA setting?

On Tue, Apr 9, 2013 at 4:14 PM, Jason Wessel <jason.wessel@...driver.com> wrote:
> On 04/09/2013 08:06 AM, Sedat Dilek wrote:
>
>>  config DEBUG_RODATA
>>       bool "Write protect kernel read-only data structures"
>> -     default y
>>       depends on DEBUG_KERNEL
>> +     default n if KGDB
>> +     default y
>>       ---help---
>>         Mark the kernel read-only data as write-protected in the pagetables,
>>         in order to catch accidental (and incorrect) writes to such const
>
>
> This is wrong and should not be merged.
>
> A) You should not change these defaults in this manner
>
> B) You have pointed out that the documentation is currently
>    incorrect. The CONFIG_DEBUG_RODATA constraints were removed some time
>    ago, per commit 3751d3e85cf693e10e2c47c03c8caa65e171099b (x86,kgdb:
>    Fix DEBUG_RODATA limitation using text_poke())
>

OK (B) has to be changed then.
I had a look at the new WIKI [1] and FAQ [2].

The new FAQ does not list any recommended kconfig-settings.
This is what I have:

$ egrep -i 'kdb|kgdb|debug_rodata|early_printk|frame_pointer' .config
CONFIG_SCHED_OMIT_FRAME_POINTER=y
CONFIG_SERIAL_KGDB_NMI=y
CONFIG_ARCH_WANT_FRAME_POINTERS=y
CONFIG_FRAME_POINTER=y
CONFIG_HAVE_ARCH_KGDB=y
CONFIG_KGDB=y
CONFIG_KGDB_SERIAL_CONSOLE=y
# CONFIG_KGDB_TESTS is not set
CONFIG_KGDB_LOW_LEVEL_TRAP=y
CONFIG_KGDB_KDB=y
CONFIG_KDB_KEYBOARD=y
CONFIG_KDB_CONTINUE_CATASTROPHIC=0
CONFIG_EARLY_PRINTK=y
CONFIG_EARLY_PRINTK_DBGP=y
CONFIG_DEBUG_RODATA=y
# CONFIG_DEBUG_RODATA_TEST is not set

OK? Sth. missing?

Booting with...

*** Configure kdb for early debugging: earlyprintk=vga ekgdboc=kbd ***

...shows me nothing here.

Might be the problem in Linux-Next [3,4] is not triggable with kdb/kgdb.

Thanks for your help in advance.

Regards,
- Sedat -

[1] https://kgdb.wiki.kernel.org/index.php/Main_Page
[2] https://kgdb.wiki.kernel.org/index.php/KDB_FAQ
[3] http://marc.info/?t=136545603700003&r=1&w=2
[4] http://marc.info/?t=136545773000008&r=1&w=2


> Jason.
>
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