linux-kernel - Re: CRC calculation in Module.symvers

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Date:	Wed, 07 Sep 2011 14:54:54 +0200
From:	Michal Marek <mmarek@...e.cz>
To:	Shakthi Kannan <shakthimaan@...il.com>
Cc:	linux-kernel@[209.132.180.67]
Subject: Re: CRC calculation in Module.symvers

On 7.9.2011 07:58, Shakthi Kannan wrote:
> 1. How the CRC is computed for an exported symbol present in
> Module.symvers file, and

The symbol type is recursively expanded and a checksum is computed from
the expanded


> 2. Given a kernel .c file, how can I obtain the CRC checksums for a symbol.
> 
> For linux-3.0.2 (example), I compiled with CONFIG_MODVERSIONS=y, and
> running 'make' built vmlinux, and generated the Module.symvers file. I
> believe genksyms is used to create the Module.symvers file?
> 
> I had referred the "Kernel Symbols and CONFIG_MODVERSIONS"
> documentation [1] written by Mark McLoughlin. I tried the following in
> the top-level kernel sources:
> 
>  $ gcc -E -D__GENKSYMS__ -DCONFIG_MODVERSIONS -DEXPORT_SYMTAB
> crypto/api.c -I/tmp/linux-3.0.2/include
> -I/tmp/linux-3.0.2/arch/x86/include | ./scripts/genksyms/genksyms

You need at least -include include/generated/autoconf.h, but the easies
would be

$ make V=1 crypto/api.symtypes

this will generate a file with the symbol expansions. And if you copy
the commandline without the >/dev/null redirection, you'll see the
calculated checksums on standard output.

Michal
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