Re: [GIT PULL] kbuild changes for v4.9-rc1

Jiri Slaby
2016-12-18T15:08:17Z

On 12/18/2016, 03:54 PM, Nikolay Borisov wrote:
>
>
> On 18.12.2016 16:45, Jiri Slaby wrote:
>> Moreover, with some modules, __put_user_1 and others are reported
>> instead of mcount.
>
>
> nm vmlinux | grep __fentry__
> nm vmlinux | grep mcount
>
> What do these report ? I bet you that in your vmlinux the first one
> would return something like :
>
> ffffffff822f1810 T __fentry__
> ffffffff827fdc20 r __kcrctab___fentry__
> ffffffff82809461 r __kstrtab___fentry__
> ffffffff827e6c20 R __ksymtab___fentry__
> and nothing for the second. Whereas doing nm on the module in question
> would give nothing for __fentry__ and something like: U mcount

Well, I have just won a beer:
$ nm vmlinux | grep mcount
w __crc_mcount
c0b3bd34 r __kcrctab_mcount
c0b41692 r __kstrtab_mcount
c0b2dd04 R __ksymtab_mcount
c0896130 T mcount
c0c9ee20 T __start_mcount_loc
c0cba89c T __stop_mcount_loc
$ nm vmlinux | grep __fentry__
$ nm sound/soundcore.ko | grep mcount
U mcount

No, I am really not stupid. We compile the kernels like this for over a
decade and it really broke with 4.9. Applying the patch fixes the
problem. Reverting it, makes it recur.

regards,
--
js
suse labs