Subject: [PATCH] recordmcount: arm64: replace the ignored mcount call into nop

From: [email-masked] (libin)
Date: Fri, 30 Oct 2015 14:00:28 +0800

? 2015/10/29 23:09, Will Deacon ??:
> On Thu, Oct 29, 2015 at 09:35:42PM +0800, kbuild test robot wrote:
>> [auto build test ERROR on arm64/for-next/core -- if it's inappropriate base, please suggest rules for selecting the more suitable base]
>>
>> url:    https://github.com/0day-ci/linux/commits/Li-Bin/recordmcount-arm64-replace-the-ignored-mcount-call-into-nop/20151028-160846
>> config: arm64-allmodconfig (attached as .config)
>> reproduce:
>>         wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
>>         chmod +x ~/bin/make.cross
>>         # save the attached .config to linux build tree
>>         make.cross ARCH=arm64 
>>
>> All errors (new ones prefixed by >>):
>>
>>>> /bin/bash: line 1: 117734 Segmentation fault      ./scripts/recordmcount "arch/arm64/kernel/traps.o"
>> --
>>>> /bin/bash: line 1: 113824 Segmentation fault      ./scripts/recordmcount "arch/arm64/mm/fault.o"
> 
> I can reproduce this locally with an allmodconfig build. The offset
> parameter to make_nop_arm64 is nuts:
> 
>   Program received signal SIGSEGV, Segmentation fault.
>   make_nop_arm64 (map=0x7ffff7fef000, offset=2600547309829750784) at scripts/recordmcount.c:170
>   170		if (*ptr != 0x94000000)
> 
> Both shdr->sh_offset (0x17000000000000) and relp->r_offset (0x2400000000000000)
> look dodgy in the caller.
> 

The allmodconfig configs the CONFIG_CPU_BIG_ENDIAN, and the test system is little eddian, so
it triggers the error.

It is a bug in nop_mcount:
...
if (mcountsym == Elf_r_sym(relp) && !is_fake_mcount(relp)) {
        if (make_nop) {
                ret = make_nop((void *)ehdr, shdr->sh_offset + relp->r_offset);
        }
...

shdr->sh_offset and welp->r_offset should handle endianness properly as _w(shdr->sh_offset)/
_w(relp->r_offset). I will post a patchset including this patch soon.

Thanks,

Li Bin

> Li, can you take a look please?
> 
> Will
> 
> .
>