debug core file of size 50GB using GDB in RHEL5

debug core file of size 50GB using GDB in RHEL5

[santoshp]

Hi All,
I got a core file of size 50GB in Redhat Enterprise Linux 5 in amd64
machine, but not able to load the core using gdb? Is there any core size
restrictions in gdb which stops it to work here.

When I try to load the core using gdb, this is what I get:

$gdb ./s_server core.2135

warning: Couldn't find general-purpose registers in core file.

warning: Couldn't find general-purpose registers in core file.
#0  0x0000000000000000 in ?? ()

Any pointers?

Thanks,
Santosh
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Re: debug core file of size 50GB using GDB in RHEL5

[Jan Kratochvil]

Hi,

On Mon, 28 Feb 2011 09:29:11 +0100, santoshp wrote:
> I got a core file of size 50GB in Redhat Enterprise Linux 5 in amd64

Please provide exact versions of gdb and kernel.  Best to submit it to
http://bugzilla.redhat.com when you did not test it on FSF GDB.  You should
provide also the output of:
	readelf -Wa core.2135
	eu-readelf -a core.2135

You could also test FSF GDB HEAD first:
	http://www.gnu.org/software/gdb/current/


Thanks,
Jan

Re: debug core file of size 50GB using GDB in RHEL5

[santoshp]

Hi Jan,
Here is the info you asked for:

1) kernel version:
2.6.18-194.32.1.el5

2) gdb version: (gdb --version)
GNU gdb Red Hat Linux (6.5-37.el5_2.2rh)
This GDB was configured as "x86_64-redhat-linux-gnu".

3) readelf -Wa core.2135
ELF Header:
  Magic:   7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
  Class:                             ELF64
  Data:                              2's complement, little endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              CORE (Core file)
  Machine:                           Advanced Micro Devices X86-64
  Version:                           0x1
  Entry point address:               0x0
  Start of program headers:          64 (bytes into file)
  Start of section headers:          0 (bytes into file)
  Flags:                             0x0
  Size of this header:               64 (bytes)
  Size of program headers:           56 (bytes)
  Number of program headers:         0
  Size of section headers:           0 (bytes)
  Number of section headers:         0
  Section header string table index: 0

There are no sections in this file.

There are no sections in this file.

There are no program headers in this file.

There are no relocations in this file.

There are no unwind sections in this file.

No version information found in this file.
No note segments present in the core file.

4) eu-readelf -a core.2135
ELF Header:
  Magic:   7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
  Class:                             ELF64
  Data:                              2's complement, little endian
  Ident Version:                     1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              CORE (Core file)
  Machine:                           AMD x86-64
  Version:                           1 (current)
  Entry point address:               0
  Start of program headers:          64 (bytes into file)
  Start of section headers:          0 (bytes into file)
  Flags:
  Size of this header:               64 (bytes)
  Size of program header entries:    56 (bytes)
  Number of program headers entries: 0
  Size of section header entries:    0 (bytes)
  Number of section headers entries: 0 ([0] not available)
  Section header string table index: 0

Section Headers:
[Nr] Name                 Type         Addr             Off      Size     ES
Flags Lk Inf Al


Thanks,
Santosh





santoshp wrote:
> 
> Hi All,
> I got a core file of size 50GB in Redhat Enterprise Linux 5 in amd64
> machine, but not able to load the core using gdb? Is there any core size
> restrictions in gdb which stops it to work here.
> 
> When I try to load the core using gdb, this is what I get:
> 
> $gdb ./s_server core.2135
> 
> warning: Couldn't find general-purpose registers in core file.
> 
> warning: Couldn't find general-purpose registers in core file.
> #0  0x0000000000000000 in ?? ()
> 
> Any pointers?
> 
> Thanks,
> Santosh
> 

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Re: debug core file of size 50GB using GDB in RHEL5

[Jan Kratochvil]

On Mon, 28 Feb 2011 10:09:10 +0100, santoshp wrote:
>   Number of program headers:         0
>   Size of section headers:           0 (bytes)
>   Number of section headers:         0
>   Section header string table index: 0

From this core file no tool can extract anything, the core file is invalid.

It is rather questionable how the core file was generated.

Was it a normal kernel dump (->kernel bug, unrelated to gdb) or by the gdb
gcore command?


Thanks,
Jan

Re: debug core file of size 50GB using GDB in RHEL5

[Andreas Schwab]

santoshp <santosh.pradhan@gmail.com> writes:

> 3) readelf -Wa core.2135
> ELF Header:
>   Magic:   7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
>   Class:                             ELF64
>   Data:                              2's complement, little endian
>   Version:                           1 (current)
>   OS/ABI:                            UNIX - System V
>   ABI Version:                       0
>   Type:                              CORE (Core file)
>   Machine:                           Advanced Micro Devices X86-64
>   Version:                           0x1
>   Entry point address:               0x0
>   Start of program headers:          64 (bytes into file)
>   Start of section headers:          0 (bytes into file)
>   Flags:                             0x0
>   Size of this header:               64 (bytes)
>   Size of program headers:           56 (bytes)
>   Number of program headers:         0

>   Size of section headers:           0 (bytes)
>   Number of section headers:         0
>   Section header string table index: 0
>
> There are no sections in this file.
>
> There are no sections in this file.
>
> There are no program headers in this file.

This corefile is empty.

Andreas.

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Re: debug core file of size 50GB using GDB in RHEL5

[santoshp]

Thanks to all. You are true as the objdump -s does not show any symbols which
tells that the core is not usable for debugging.

Thanks,
Santosh
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Re: debug core file of size 50GB using GDB in RHEL5

[santoshp]

typo corrected.


santoshp wrote:
> 
> Thanks to all. You are true as the objdump -d(-D) or "readelf -s" on core
> file does not show any symbols which tells that the core is not usable for
> debugging.
> 
> Thanks,
> Santosh
> 

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Re: debug core file of size 50GB using GDB in RHEL5

[Michael Snyder]

santoshp wrote:
> Thanks to all. You are true as the objdump -s does not show any symbols which
> tells that the core is not usable for debugging.
> 
> Thanks,
> Santosh

Point of interest -- core files never have symbols.
But they have section headers and such.

Re: debug core file of size 50GB using GDB in RHEL5

[Andreas Schwab]

Michael Snyder <msnyder@vmware.com> writes:

> Point of interest -- core files never have symbols.
> But they have section headers and such.

Actually they don't have sections either, only segments.

Andreas.

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