Huge pages and gdb

Huge pages and gdb

[Erez Zilber]

Hi,

My application (running on RHEL 6) calls mmap() to map huge pages.
After it crashed, I opened gdb with the core file and tried to take a
look in the huge-pages buffer that was mmapped. I got the following
error:

gdb) p pool->mem
$2 = 0x7f3201400000 <Address 0x7f3201400000 out of bounds>
(gdb) p pool->mem[0]
Cannot access memory at address 0x7f3201400000

How can I solve this so I will be able to view the contents of the buffer?

Thanks,
Erez

Re: Huge pages and gdb

[Andreas Schwab]

Erez Zilber <erezzi.list@gmail.com> writes:

> My application (running on RHEL 6) calls mmap() to map huge pages.
> After it crashed, I opened gdb with the core file and tried to take a
> look in the huge-pages buffer that was mmapped. I got the following
> error:
>
> gdb) p pool->mem
> $2 = 0x7f3201400000 <Address 0x7f3201400000 out of bounds>
> (gdb) p pool->mem[0]
> Cannot access memory at address 0x7f3201400000

If gdb cannot access the memory then it is not part of the core file.
Please check with "info target" whether one of the segments cover the
address range.  If not, then either the address really is invalid, or it
is an issue with the core producer and gdb cannot do anything about
that.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: Huge pages and gdb

[Jan Kratochvil]

On Wed, 23 Mar 2011 18:09:47 +0100, Andreas Schwab wrote:
> Erez Zilber <erezzi.list@gmail.com> writes:
> > (gdb) p pool->mem[0]
> > Cannot access memory at address 0x7f3201400000
> 
> If gdb cannot access the memory then it is not part of the core file.

And which pages are / are not dumped to the core file you can configure by:
/usr/share/doc/kernel-doc-*/Documentation/filesystems/proc.txt
  3.4   /proc/<pid>/coredump_filter - Core dump filtering settings


Regards,
Jan

Re: Huge pages and gdb

[Erez Zilber]

On Wed, Mar 23, 2011 at 7:14 PM, Jan Kratochvil
<jan.kratochvil@redhat.com> wrote:
> On Wed, 23 Mar 2011 18:09:47 +0100, Andreas Schwab wrote:
>> Erez Zilber <erezzi.list@gmail.com> writes:
>> > (gdb) p pool->mem[0]
>> > Cannot access memory at address 0x7f3201400000
>>
>> If gdb cannot access the memory then it is not part of the core file.
>
> And which pages are / are not dumped to the core file you can configure by:
> /usr/share/doc/kernel-doc-*/Documentation/filesystems/proc.txt
>  3.4   /proc/<pid>/coredump_filter - Core dump filtering settings
>
>
> Regards,
> Jan
>

Thanks!