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Date: Thu, 9 Feb 2012 16:06:13 +0100
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: perl fork error: child_info_fork::abort: data segment start: - example code!
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On Feb  9 14:50, Heiko Elger wrote:
> Corinna Vinschen writes:
> 
> > So with the latest snapshot we can at least see which DLL is affected
> > by this problem.  Then we can check where this DLL is really supposed to
> > be in memory (objdump -h) and then we can check what really is at this
> > location in the process VM (/proc/$PID/maps)
> [...]
> Using SEP there is a service running called sysplant ("Application and Device 
> Control", system32\Drivers\SysPlant.sys).
> Disabling this service on cmd line (cmd.exe) 
>     sc config sysplant start= disabled
> rebooting all seems to work fine!
> 
> I will contact Symantec for more details about this service.
> 
> The output of objdump -h is the following:
> $ objdump -h cygperl5_10.dll
> 
> cygperl5_10.dll:     file format pei-i386
> 
> Sections:
> Idx Name          Size      VMA       LMA       File off  Algn
>   0 .text         001386fc  57011000  57011000  00000400  2**4
>                   CONTENTS, ALLOC, LOAD, READONLY, CODE, DATA
>   1 .data         0001f1e4  5714a000  5714a000  00138c00  2**5
>                   CONTENTS, ALLOC, LOAD, DATA
>   2 .rdata        00000780  5716a000  5716a000  00157e00  2**2
>                   CONTENTS, ALLOC, LOAD, READONLY, DATA
>   3 .eh_frame     00000004  5716b000  5716b000  00158600  2**2
>                   CONTENTS, ALLOC, LOAD, DATA
>   4 .bss          00000610  5716c000  5716c000  00000000  2**5
>                   ALLOC
>   5 .edata        0000dcd0  5716d000  5716d000  00158800  2**2
>                   CONTENTS, ALLOC, LOAD, READONLY, DATA
>   6 .idata        00001a08  5717b000  5717b000  00166600  2**2
>                   CONTENTS, ALLOC, LOAD, DATA
>   7 .reloc        00008818  5717d000  5717d000  00168200  2**2
>                   CONTENTS, ALLOC, LOAD, READONLY, DATA
>   8 .gnu_debuglink 00000014  57186000  57186000  00170c00  2**2
>                   CONTENTS, READONLY
> 
> What is the recommended address layout?
> Should DATA be mapped to 0x5714a000 and BSS to 0x5716c000?

DLLs (and FWIW all binary images) are mapped as one piece into the VM of
the process.  From the above you can see that the start address of the
DLL is supposed to be 57010000 (== VMA(.text) - 4K) Since the image is
mapped in a single piece, the address you see in the object header are
real VM addresses.  Unless, of course, the DLL is rebased on the fly
by the Windows loader.  But that only means the *entire* DLL is rebased,
so the relative offsets of the segments from the load address are the
same as they are in the file header.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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