[ofa-general] Re: Question about registering the [vdso] memory section in user level

[Michael S. Tsirkin]

> Quoting Dotan Barak <dotanb at dev.mellanox.co.il>:
> Subject: Question about registering the [vdso] memory section in user level
> 
> Hi.
> 
> In our regression, there is a test case in which we register the last 
> VMA of a process that has a read permission.
> Only in kernel 2.6.20-rc5 i get a failure.
> 
> Here is the last line that i got from executing "cat /proc/1873/maps":
> 
> 
> In kernel 2.6.16.21-0.8-smp:
> 2b42d103f000-2b42d1116000 r--p 00000000 08:07 647899                     
> /usr/lib/locale/en_US.utf8/LC_COLLATE
> 2b42d1116000-2b42d1117000 r--p 00000000 08:07 633217                     
> /usr/lib/locale/en_US.utf8/LC_TIME
> 2b42d1117000-2b42d1118000 r--p 00000000 08:07 647880                     
> /usr/lib/locale/en_US.utf8/LC_NUMERIC
> 2b42d1118000-2b42d114b000 r--p 00000000 08:07 647898                     
> /usr/lib/locale/en_US.utf8/LC_CTYPE
> 2b42d114b000-2b42d114c000 rw-p 2b42d114b000 00:00 0
> 7fffda251000-7fffda267000 rw-p 7fffda251000 00:00 0                      
> [stack]
> ffffffffff600000-ffffffffffe00000 ---p 00000000 00:00 0                  
> [vdso]
> 
> In kernel 2.6.20-rc5:
> 2ba22fd99000-2ba22fd9b000 rw-p 0000a000 08:03 309500                     
> /lib64/libnss_files-2.3.4.so
> 2ba22fd9b000-2ba232be6000 r--p 00000000 08:03 68735                      
> /usr/lib/locale/locale-archive
> 2ba232be6000-2ba232bec000 r--s 00000000 08:03 97940                      
> /usr/lib64/gconv/gconv-modules.cache
> 2ba232bec000-2ba232bee000 rw-p 2ba232bec000 00:00 0
> 7fff7ae2d000-7fff7ae43000 rw-p 7fff7ae2d000 00:00 0                      
> [stack]
> ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  
> [vdso]
> 
> It seems that in kernel 2.6.20-rc5 the last VMA which has a read 
> permission is the [vdso] section but when i try
> to register it i get a failure.
> 
> Is it wrong to register this section?

Yes, you can't DMA to VDSO VMA I don't think.

-- 
MST