Messages in this thread | | | From | "kumar M" <> | Subject | Re: exporting kernel symbols | Date | Mon, 28 Jan 2002 13:13:38 +0000 |
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Hi Keith,
Thank you for the info. It was very informative. My problem is funny. On a freshly installed RedHat 7.1 machine with 2.4.2-2 kernel, a 'make modules' throws up errors such as : ---------------------------------------- /usr/src/linux-2.4/include/linux/module.h:173: nondigits in number and not hexadecimal /usr/src/linux-2.4/include/linux/module.h:173: parse error before `62dada05' /usr/src/linux-2.4/include/linux/module.h:173: `inter_module_register_R_ver_str' declared as function returning a function /usr/src/linux-2.4/include/linux/module.h:173: warning: function declaration isn't a prototype .......................................................
So we do a 'make mrproper' and 'make menuconfig' and save and exit without any changes to configuration. Then we rebuild the kernel. make dep & make modules are done smoothly.
Can you let us know why we should be doing make mrproper on a system freshly installed with redhat 7.1(2.4.2-2smp)
Thanks !
Kumar
>From: Keith Owens <kaos@ocs.com.au> >To: "kumar M" <kumarm4@hotmail.com> >CC: linux-kernel@vger.kernel.org >Subject: Re: exporting kernel symbols >Date: Mon, 28 Jan 2002 10:37:44 +1100 > >On Sun, 27 Jan 2002 15:16:10 +0000, >"kumar M" <kumarm4@hotmail.com> wrote: > >I am interested in knowing how mangling the name of symbols > >exported by the kernel to include the checksum of the information related >to > >that symbol is done, whenever MOD VERSIONS > >is used for building a module. Is there any documentation on the > >process of the checksum computation, and which portion of the linux > >sources I need to go through to understand this ? > >genksyms.c in the modutils source package[1]. The make dep process >pre-processes the C sources from each directory feeding the cpp output >into genksyms. genksyms calculates a hash for each exported symbol >based on its type, return values, parameters etc., recursively >descending parameter types as required. > >The resulting hashes are written out as #defines to change foo to >foo_Rxxxxxxxx. The defines are read back in when the real compile is >done, change references to foo into foo_Rxxxxxxxx. In the kernel the >original symbols are used but the export list includes the suffix. In >modules, external references include the suffix. > >In theory if a module refers to a symbol and the hashes for that symbol >match then the symbol has not changed its ABI and it is safe to load >the module, even if the kernel and module are from different versions. >In practice, modversions relies far too much on human processes and is >prone to false positives. The hashes can match when the ABI is >different because of human error[2], especially when people compile >drivers outside the kernel tree. Kernel and modutils 2.5 will have a >completely different method for checking ABI compatibility, if kbuild >2.5 ever gets in. > >[1] http://kernel.org/pub/linux/utils/kernel/modutils/v2.4 >[2] http://prdownloads.sourceforge.net/kbuild/kbuild-2.5-history.tar.bz2 >
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