Re: Strange problem with /proc/ksyms

From: Steffen Persvold (sp@scali.com)
Date: Sat May 11 2002 - 20:41:07 EST


On Sun, 12 May 2002, Steffen Persvold wrote:

> Hi guys,
>
> I've discovered this wierd problem with /proc/ksyms on RedHat's
> 2.4.18-4smp (i686 build) for 7.3. The thing is that with utilities like
> 'cat' and 'grep' it seems like the whole list isn't showing :
>
> [root@puma1 root]# uname -a
> Linux puma1.office.scali.no 2.4.18-4smp #1 SMP Thu May 2 18:32:34 EDT 2002 i686 unknown
>
> [root@puma1 root]# grep del_timer /proc/ksyms
> [root@puma1 root]# grep printk /proc/ksyms
> c011c870 printk_Rsmp_1b7d4074
>
> [root@puma1 root]# cat /proc/ksyms >cat_test
> [root@puma1 root]# ls -l cat_test
> -rw-r--r-- 1 root root 28519 May 4 02:48 cat_test
>
>
> But if I use 'dd', all of it is listed :
>
> [root@puma1 root]# dd if=/proc/ksyms of=dd_test
> 149+1 records in
> 149+1 records out
> [root@puma1 root]# ls -l dd_test
> -rw-r--r-- 1 root root 76683 May 4 02:49 dd_test
> [root@puma1 root]# grep printk dd_test
> c011c870 printk_Rsmp_1b7d4074
> c03d9488 tux_Dprintk_Rsmp_a12c9a12
> c03d9484 tux_TDprintk_Rsmp_c0ce7778
> [root@puma1 root]# grep del_timer dd_test
> c0124900 del_timer_Rsmp_fc62f16d
> c0124960 del_timer_sync_Rsmp_daff266a
>
>
> What could this be ? Buffering issues ? I haven't seen this on a stock
> 2.4.18 kernel.
>

Hmm, I've tested some more with 'dd' and different bs sizes, and I found
the following :

[root@puma2 root]# dd bs=1024 if=/proc/ksyms of=dd_test
70+1 records in
70+1 records out
[root@puma2 root]# ls -l dd_test
-rw-r--r-- 1 root root 72586 May 4 03:09 dd_test

[root@puma2 root]# dd bs=4095 if=/proc/ksyms of=dd_test
1+17 records in
1+17 records out
[root@puma2 root]# ls -l dd_test
-rw-r--r-- 1 root root 72586 May 4 03:10 dd_test

[root@puma2 root]# dd bs=4096 if=/proc/ksyms of=dd_test
0+6 records in
0+6 records out
[root@puma2 root]# ls -l dd_test
-rw-r--r-- 1 root root 24422 May 4 03:10 dd_test

So you can see, the moment I go to 4k (and above) of buffer space the
output gets truncated. Ideas ?

Thanks,

-- 
  Steffen Persvold   | Scalable Linux Systems |   Try out the world's best
 mailto:sp@scali.com |  http://www.scali.com  | performing MPI implementation:
Tel: (+47) 2262 8950 |   Olaf Helsets vei 6   |      - ScaMPI 1.13.8 -
Fax: (+47) 2262 8951 |   N0621 Oslo, NORWAY   | >320MBytes/s and <4uS latency

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