[Bug gdb/31578] New: GDB shows wrong offset value using 'info proc mapping'

[Bug gdb/31578] New: GDB shows wrong offset value using 'info proc mapping'

[toyaniv at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31578

            Bug ID: 31578
           Summary: GDB shows wrong offset value using 'info proc mapping'
           Product: gdb
           Version: 12.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: gdb
          Assignee: unassigned at sourceware dot org
          Reporter: toyaniv at gmail dot com
  Target Milestone: ---

Created attachment 15445
  --> https://sourceware.org/bugzilla/attachment.cgi?id=15445&action=edit
info prov mapping with wrong offset on 4th row

solving hackthebox retired pwn challenge I found out that gdb show wrong
offset:

we can see on 3rd (start addr 0x562634049000) that offset is 0x8000 and size is
0x2000
but in 4th (start adr 0x56263404b000) it shows offset 0x9000 instead of
expected offset 0xa000 (0x8000+0x2000)

(gdb) info proc mapping
process 25
Mapped address spaces:

          Start Addr           End Addr       Size     Offset  Perms  objfile
      0x562634041000     0x562634044000     0x3000        0x0  r--p  
/home/ctf/device_control
      0x562634044000     0x562634049000     0x5000     0x3000  r-xp  
/home/ctf/device_control
      0x562634049000     0x56263404b000     0x2000     0x8000  r--p  
/home/ctf/device_control
      0x56263404b000     0x56263404c000     0x1000     0x9000  r--p  
/home/ctf/device_control
      0x56263404c000     0x56263404d000     0x1000     0xa000  rw-p  
/home/ctf/device_control
      0x5626340c8000     0x56263412b000    0x63000        0x0  rw-p   [heap]

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[Bug gdb/31578] GDB shows wrong offset value using 'info proc mapping'

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31578

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tromey at sourceware dot org

--- Comment #1 from Tom Tromey <tromey at sourceware dot org> ---
"info proc mapping" is just a very thin wrapper that
reads /proc/$pid/maps.  Can you examine that file with "cat"?
I suspect there's no gdb problem here.

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[Bug gdb/31578] GDB shows wrong offset value using 'info proc mapping'

[toyaniv at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31578

--- Comment #2 from Yaniv Buta <toyaniv at gmail dot com> ---
(In reply to Tom Tromey from comment #1)
> "info proc mapping" is just a very thin wrapper that
> reads /proc/$pid/maps.  Can you examine that file with "cat"?
> I suspect there's no gdb problem here.

Hi Tom

Thanks for replying that fast.

Indeed, below is that cat command and now it seems as OS bug...
Can you suggest what actually going on ? 
I wonder what makes the offset be miscalculated that way by the OS ...

(gdb) shell
$ uname -a
Linux 0d142311433c 6.6.9-amd64 #1 SMP PREEMPT_DYNAMIC Kali 6.6.9-1kali1
(2024-01-08) x86_64 x86_64 x86_64 GNU/Linux

$ cat /proc/25/maps
562634041000-562634044000 r--p 00000000 08:01 1208457                   
/home/ctf/device_control
562634044000-562634049000 r-xp 00003000 08:01 1208457                   
/home/ctf/device_control
562634049000-56263404b000 r--p 00008000 08:01 1208457                   
/home/ctf/device_control
56263404b000-56263404c000 r--p 00009000 08:01 1208457                   
/home/ctf/device_control
56263404c000-56263404d000 rw-p 0000a000 08:01 1208457                   
/home/ctf/device_control

Thanks,
Yaniv

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[Bug gdb/31578] GDB shows wrong offset value using 'info proc mapping'

[schwab@linux-m68k.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31578

--- Comment #3 from Andreas Schwab <schwab@linux-m68k.org> ---
Why do you think the offset is wrong?

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[Bug gdb/31578] GDB shows wrong offset value using 'info proc mapping'

[toyaniv at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31578

--- Comment #4 from Yaniv Buta <toyaniv at gmail dot com> ---
(In reply to Andreas Schwab from comment #3)
> Why do you think the offset is wrong?

Hello Andreas

Check 4th row in the output display that I attached,
that's because 0x56263404b000- 0x562634041000 is 0xa000 and not 0x9000 as map
/procmap shows under offset column for this row.
(can't see any address overlap as for former rows)

Yaniv

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[Bug gdb/31578] GDB shows wrong offset value using 'info proc mapping'

[schwab@linux-m68k.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31578

--- Comment #5 from Andreas Schwab <schwab@linux-m68k.org> ---
The offset is a _file_ offset, not a vm offset.

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[Bug gdb/31578] GDB shows wrong offset value using 'info proc mapping'

[toyaniv at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31578

Yaniv Buta <toyaniv at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |NOTABUG
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #6 from Yaniv Buta <toyaniv at gmail dot com> ---
not a bug

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[Bug gdb/31578] GDB shows wrong offset value using 'info proc mapping'

[toyaniv at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31578

--- Comment #7 from Yaniv Buta <toyaniv at gmail dot com> ---
(In reply to Andreas Schwab from comment #5)
> The offset is a _file_ offset, not a vm offset.

I closed it
thanks

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[Bug gdb/31578] GDB shows wrong offset value using 'info proc mapping'

[toyaniv at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31578

Yaniv Buta <toyaniv at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |CLOSED

--- Comment #8 from Yaniv Buta <toyaniv at gmail dot com> ---
closed

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