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SubjectRe: magic file entry to understand core dumps
Andrew C. Esh wrote:

> [andrewes@andrewes andrewes]$ file core
> core: ELF 32-bit LSB core file i386 (386 and up) Version 1
>
> It knows it's a core file, but doesn't give the "executable name" that
> you need in order to start gdb.
>
> Solution 2: Add an entry to /etc/magic to allow "file" to decode an
> ELF core file. This may not be possible, if "file" is too simple to
> deal with the complexities of finding the executable name. BTW: My
> "file" is about a year old. I can't tell what version it is. It's ELF.

I don't know whether it works 100% of the time or not, but the magic file
from Debian-1.1 seems to do this ok.

bash$ file core
core: ELF 32-bit LSB core file of 'dump' (signal 11), Intel 80386, version 1, stripped

The relevant rule is:

#------------------------------------------------------------------------------
# elf: file(1) magic for ELF executables
#
# We have to check the byte order flag to see what byte order all the
# other stuff in the header is in.
#
# Byte order is probably big-endian for MIPS RS3000 and Amdahl.
# MIPS RS3000 may also be for MIPS RS2000.
#
# updated by Daniel Quinlan (quinlan@yggdrasil.com)
0 string \177ELF ELF
>4 byte 0 invalid class
>4 byte 1 32-bit
>4 byte 2 64-bit
>5 byte 0 invalid byte order
>5 byte 1 LSB
>>16 leshort 0 no file type,
>>16 leshort 1 relocatable,
>>16 leshort 2 executable,
>>16 leshort 3 shared object,
# replaced by new entry from Peter Tobias <tobias@server.et-inf.fho-emden.de>
#>>16 leshort 4 core file,
>>16 leshort 4 core file
>>>576 string >\0 of '%s'
>>>400 lelong >0 (signal %d),
# end of replacement entry
>>16 leshort &0xff00 processor-specific,
>>18 leshort 0 no machine,
>>18 leshort 1 AT&T WE32100 - invalid byte order,
>>18 leshort 2 SPARC - invalid byte order,
>>18 leshort 3 Intel 80386,
>>18 leshort 4 Motorola 68000 - invalid byte order,
>>18 leshort 5 Motorola 88000 - invalid byte order,
>>18 leshort 6 Intel 80486,
>>18 leshort 7 Intel 80860,
>>18 leshort 8 MIPS RS3000,
>>18 leshort 9 Amdahl,
>>20 lelong 0 invalid version
>>20 lelong 1 version 1
>>36 lelong 1 MathCoPro/FPU/MAU Required
>5 byte 2 MSB
>>16 beshort 0 no file type,
>>16 beshort 1 relocatable,
>>16 beshort 2 executable,
>>16 beshort 3 shared object,
>>16 beshort 4 core file,
>>16 beshort &0xff00 processor-specific,
>>18 beshort 0 no machine,
>>18 beshort 1 AT&T WE32100,
>>18 beshort 2 SPARC,
>>18 beshort 3 Intel 80386 - invalid byte order,
>>18 beshort 4 Motorola 68000,
>>18 beshort 5 Motorola 88000,
>>18 beshort 6 Intel 80486 - invalid byte order,
>>18 beshort 7 Intel 80860,
>>18 beshort 8 MIPS RS3000,
>>18 leshort 9 Amdahl,
>>20 belong 0 invalid version
>>20 belong 1 version 1
>>36 belong 1 MathCoPro/FPU/MAU Required


regards
Terry


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