linux-kernel - Re: [PATCH v5 16/20] scripts/gdb: Add internal helper and convenience function for per-cpu lookup

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Date:	Tue, 29 Jan 2013 15:25:55 +0100
From:	Jan Kiszka <jan.kiszka@...mens.com>
To:	Borislav Petkov <bp@...en8.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Jason Wessel <jason.wessel@...driver.com>,
	kgdb-bugreport@...ts.sourceforge.net,
	Andi Kleen <andi@...stfloor.org>,
	Tom Tromey <tromey@...hat.com>,
	Ben Widawsky <ben@...dawsk.net>,
	"David S. Miller" <davem@...emloft.net>, sparclinux@...r.kernel.org
Subject: Re: [PATCH v5 16/20] scripts/gdb: Add internal helper and convenience
 function for per-cpu lookup

On 2013-01-29 15:12, Borislav Petkov wrote:
> On Tue, Jan 29, 2013 at 02:56:56PM +0100, Jan Kiszka wrote:
>> Let me guess: You are dumping a weird QEMU/KVM CPU, right?
> 
> Nah, I actually have the silicon! :-)
> 
> Joking, of course. I wish. I'm booting the guest with -cpu phenom (it
> has been like that since forever in my boot-kernel-in-kvm script) but
> the host is Intel.
> 
> If I do this on an AMD host, all is ok:
> 
> (gdb) p $lx_per_cpu("cpu_info").x86_vendor_id
> $1 = "AuthenticAMD\000\000\000"
> (gdb) p $lx_per_cpu("cpu_info").x86_model_id
> $2 = "AMD Phenom(tm) 9550 Quad-Core Processor", '\000' <repeats 24 times>
> (gdb)

Remains a bug of QEMU, though possibly a minor one.

> 
> [ … ]
> 
>>>> +class PerCpu(gdb.Function):
>>>> +	__doc__ = "Return per-cpu variable.\n" \
>>>> +		  "\n" \
>>>> +		  "$lx_per_cpu(\"VAR\"[, CPU]): Return the per-cpu variable called VAR for the\n" \
>>>> +		  "given CPU number. If CPU is omitted, the CPU of the current context is used.\n" \
>>>> +		  "Note that VAR has to be quoted as string."
>>>
>>>
>>> Ok, seriously now:
>>>
>>> apropos shows the "Return per-cpu... " line above. Have you found out
>>> which gdb command shows the rest? help and info both say "Undefined
>>> command".
>>
>> help function lx_...
>>
>> It took me a while to find this, too.
> 
> Maybe worth documenting it then at the end of gdb-kernel-debugging.txt?
> 

Done. Will come with v6 (if needed), otherwise as an add-on patch.

Thanks,
Jan

-- 
Siemens AG, Corporate Technology, CT RTC ITP SDP-DE
Corporate Competence Center Embedded Linux
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