linux-kernel - Re: kmemleak hexdump proposal

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Date:	Mon, 29 Jun 2009 13:19:17 +0300
From:	Sergey Senozhatsky <sergey.senozhatsky@...l.by>
To:	Pekka Enberg <penberg@...helsinki.fi>
Cc:	Catalin Marinas <catalin.marinas@....com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: kmemleak hexdump proposal

On (06/29/09 12:43), Pekka Enberg wrote:
> Hi Sergey,
> 
> On Sun, Jun 28, 2009 at 8:36 PM, Sergey
> Senozhatsky<sergey.senozhatsky@...l.by> wrote:
> > What do you think about ability to 'watch' leaked region? (hex + ascii).
> > (done via lib/hexdump.c)
> 
> What's your use case for this? I'm usually more interested in the
> stack trace when there's a memory leak.
> 
>                         Pekka
> 

Hello Pekka,
Well, it's not easy to come up with something strong. 
I agree, that stack gives you almost all you need.

HEX dump can give you a _tip_ in case you're not sure. 

for example:
unreferenced object 0xf6aac7f8 (size 32):
  comm "swapper", pid 1, jiffies 4294877610
HEX dump:
70 6e 70 20 30 30 3a 30 61 00 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a a5  pnp 00:0a.ZZZZZZZZZZZZZZZZZZZZZ.

  backtrace:
    [<c10e92eb>] kmemleak_alloc+0x11b/0x2b0
    [<c10e4b91>] kmem_cache_alloc+0x111/0x1c0
    [<c12c424e>] reserve_range+0x3e/0x1b0
    [<c12c4454>] system_pnp_probe+0x94/0x140
    [<c12baf84>] pnp_device_probe+0x84/0x100
    [<c12f1919>] driver_probe_device+0x89/0x170
    [<c12f1a99>] __driver_attach+0x99/0xa0
    [<c12f1028>] bus_for_each_dev+0x58/0x90
    [<c12f1764>] driver_attach+0x24/0x40
    [<c12f0804>] bus_add_driver+0xc4/0x290
    [<c12f1e10>] driver_register+0x70/0x130
    [<c12bacd6>] pnp_register_driver+0x26/0x40
    [<c15d4620>] pnp_system_init+0x1b/0x2e
    [<c100115f>] do_one_initcall+0x3f/0x1a0
    [<c15aa4af>] kernel_init+0x13e/0x1a6
    [<c1003e07>] kernel_thread_helper+0x7/0x10

- Ah, pnp 00:0a. Got it.
or
- Ah, pnp 00:0a. No.. It's false. (EXAMPLE)

Or something like that :-)

	Sergey
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