linux-kernel - Re: kmemleak hexdump proposal

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Message-ID: <20090714103356.GA2929@localdomain.by>
Date:	Tue, 14 Jul 2009 13:33:56 +0300
From:	Sergey Senozhatsky <sergey.senozhatsky@...l.by>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	Pekka Enberg <penberg@...helsinki.fi>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: kmemleak hexdump proposal

On (07/14/09 11:07), Catalin Marinas wrote:
> Hi,
> 
Hello Catalin,

> On Mon, 2009-06-29 at 21:10 +0100, Sergey Senozhatsky wrote:
> > This is actually draft. We'll discuss details during next merge window (or earlier).
> 
> Better earlier (I plan to get some more kmemleak patches into
> linux-next).
> 
> > hex dump prints not more than HEX_MAX_LINES lines by HEX_ROW_SIZE (16 or 32) bytes.
> > ( min(object->size, HEX_MAX_LINES * HEX_ROW_SIZE) ).
> > 
> > Example (HEX_ROW_SIZE 16):
> > 
> > unreferenced object 0xf68b59b8 (size 32):
> >   comm "swapper", pid 1, jiffies 4294877610
> >   hex dump (first 32 bytes):
> >     70 6e 70 20 30 30 3a 30 31 00 5a 5a 5a 5a 5a 5a  pnp 00:01.ZZZZZZ
> >     5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a a5  ZZZZZZZZZZZZZZZ.
> 
> That's my preferred as I do not want to go beyond column 80.
> 
Same with me.

> > diff --git a/mm/kmemleak.c b/mm/kmemleak.c
> > index 5063873..65c5d74 100644
> > --- a/mm/kmemleak.c
> > +++ b/mm/kmemleak.c
> > @@ -160,6 +160,15 @@ struct kmemleak_object {
> >  /* flag set to not scan the object */
> >  #define OBJECT_NO_SCAN         (1 << 2)
> > 
> > +/* number of bytes to print per line; must be 16 or 32 */
> > +#define HEX_ROW_SIZE           32
> 
> 16 here.
> 
OK.

[...]
> > @@ -303,6 +343,11 @@ static void print_unreferenced(struct seq_file *seq,
> >                    object->pointer, object->size);
> >         seq_printf(seq, "  comm \"%s\", pid %d, jiffies %lu\n",
> >                    object->comm, object->pid, object->jiffies);
> > +
> > +       /* check whether hex dump should be printed */
> > +       if (atomic_read(&kmemleak_hex_dump))
> > +               hex_dump_object(seq, object);
> 
> No need for this check, just leave it in all cases (as we now only read
> the reports via the debug/kmemleak file.
>
 
> > @@ -1269,6 +1314,10 @@ static ssize_t kmemleak_write(struct file *file, const char __user *user_buf,
> >                 start_scan_thread();
> >         else if (strncmp(buf, "scan=off", 8) == 0)
> >                 stop_scan_thread();
> > +       else if (strncmp(buf, "hexdump=on", 10) == 0)
> > +               atomic_set(&kmemleak_hex_dump, 1);
> > +       else if (strncmp(buf, "hexdump=off", 11) == 0)
> > +               atomic_set(&kmemleak_hex_dump, 0);
> 
> Same here.
> 

Am I understand correct that no way for user to on/off hexdump?
/* no need for atomic_t kmemleak_hex_dump */


> Thanks.
> 
> -- 
> Catalin
> 

	Sergey
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