Re: [jeyu:modules-next 3/11] arc4.c:(___ksymtab+arc4_setkey+0x8): undefined reference to `no symbol'

[Jessica Yu <jeyu@kernel.org>]

+++ Matthias Maennich [11/09/19 06:21 +0100]:
>On Wed, Sep 11, 2019 at 03:11:53AM +0800, kbuild test robot wrote:
>>tree:   https://kernel.googlesource.com/pub/scm/linux/kernel/git/jeyu/linux.git modules-next
>>head:   32bca2df7da27be34371a37f9bb5e2b85fdd92bd
>>commit: 8651ec01daedad26290f76beeb4736f9d2da4b87 [3/11] module: add support for symbol namespaces.
>>config: arm64-defconfig (attached as .config)
>>compiler: aarch64-linux-gcc (GCC) 7.4.0
>>reproduce:
>>       wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>>       chmod +x ~/bin/make.cross
>>       git checkout 8651ec01daedad26290f76beeb4736f9d2da4b87
>>       # save the attached .config to linux build tree
>>       GCC_VERSION=7.4.0 make.cross ARCH=arm64
>>
>>If you fix the issue, kindly add following tag
>>Reported-by: kbuild test robot <lkp@intel.com>
>>
>>All errors (new ones prefixed by >>):
>>
>>  lib/crypto/arc4.o: In function `__ksymtab_arc4_setkey':
>>>>arc4.c:(___ksymtab+arc4_setkey+0x8): undefined reference to `no symbol'
>>  lib/crypto/arc4.o: In function `__ksymtab_arc4_crypt':
>>>>arc4.c:(___ksymtab+arc4_crypt+0x8): undefined reference to `no symbol'
>
>Hmm, this is caused by the relative relocation of the 'namespace_offset'
>struct member to NULL in case there is no namespace defined:
>
>#define __KSYMTAB_ENTRY(sym, sec)					\
>	__ADDRESSABLE(sym)						\
>	asm("	.section \"___ksymtab" sec "+" #sym "\", \"a\"	\n"	\
>	    "	.balign 4					\n"	\
>	    "__ksymtab_" #sym ":				\n"	\
>	    "	.long	" #sym "- .				\n"	\
>	    "	.long	__kstrtab_" #sym "- .			\n"	\
>	    "	.long	0 - .					\n"	\
>	    	       ^^^^^^^
>	    "	.previous					\n")
>
>struct kernel_symbol {
>	int value_offset;
>	int name_offset;
>	int namespace_offset;
>};
>
>That is apparently not an issue on x86, but on arm. Not sure how to
>express a relative relocation to NULL then.
>
>I will try to solve this somehow, just wanted to check if somebody knows the
>trick here.

(Adding more CC's..)

Do we have to have a place-relative relocation there? If we can't find
a workaround, having just .long 0 for a null namespace seemed to fix the
build issues on arm64 for me at least..



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