linux-kernel - Re: [PATCH 1/4] kgdb: x86: Return all segment registers also in 64-bit mode

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Date:	Fri, 16 Mar 2012 10:57:59 -0500
From:	Jason Wessel <jason.wessel@...driver.com>
To:	Jan Kiszka <jan.kiszka@...mens.com>
CC:	<linux-kernel@...r.kernel.org>,
	<kgdb-bugreport@...ts.sourceforge.net>
Subject: Re: [PATCH 1/4] kgdb: x86: Return all segment registers also in 64-bit
 mode

On 03/16/2012 07:17 AM, Jan Kiszka wrote:
> Even if the content is always 0, gdb expects us to return also ds,
> es, fs, and gs while in x86-64 mode. Do this to avoid ugly errors on
> "info registers".
>
> Signed-off-by: Jan Kiszka <jan.kiszka@...mens.com>
> ---
>  arch/x86/include/asm/kgdb.h |    6 +++++-
>  arch/x86/kernel/kgdb.c      |    6 ++++--
>  2 files changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/include/asm/kgdb.h b/arch/x86/include/asm/kgdb.h
> index 77e95f5..e857f1a 100644
> --- a/arch/x86/include/asm/kgdb.h
> +++ b/arch/x86/include/asm/kgdb.h
> @@ -64,9 +64,13 @@ enum regnames {
>  	GDB_PS,			/* 17 */
>  	GDB_CS,			/* 18 */
>  	GDB_SS,			/* 19 */
> +	GDB_DS,			/* 20 */
> +	GDB_ES,			/* 21 */
> +	GDB_FS,			/* 22 */
> +	GDB_GS,			/* 23 */
>  };
>  #define GDB_ORIG_AX		57
> -#define DBG_MAX_REG_NUM		20
> +#define DBG_MAX_REG_NUM		24
>  /* 17 64 bit regs and 3 32 bit regs */
>  #define NUMREGBYTES		((17 * 8) + (3 * 4))

You bumped the register numbers correctly, but you also need to add the correct padding to the NUMREGBYTES or you might not get a large enough memory block for the register struct.

You added 2 32 bit regs, so it should change to:

/* 17 64 bit regs and 5 32 bit regs */
#define NUMREGBYTES        ((17 * 8) + (5 * 4))


The rest should be fine.   I can test this and add it to the merge queue with the NUMREGBYTES change, unless you disagree.

Cheers,
Jason.
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