config(8) -x headscratcher

[Kimmo Paasiala]

On Sat, Apr 27, 2013 at 10:05 PM, Wojciech A. Koszek
<wkoszek at freebsd.org> wrote:
> On Sat, Apr 27, 2013 at 06:54:11PM +0300, Kimmo Paasiala wrote:
>> I'm getting a core dump on 'config -x /boot/kernel/kernel' on 9.1-RELEASE i386.
>>
>> Assertion failed: (r != '\0' && ("Char present in the configuration "
>> "string mustn't be equal to 0")), function kernconfdump, file
>> /usr/src/usr.sbin/config/main.c, line 710.
>>
>> I have double checked that my config file is sane and does not have
>> any funny characters anywhere.
>>
>> The system is i386 9.1-RELEASE r249856. The world and kernel are built
>> with clang and I'm suspecting that the use of clang has something to
>> do with this segfault.
>>
>> Looking at the kernel files I can see one very obvious difference.
>> This is the 'elfdump -c kernel | grep -A 8 kern_conf' output (what
>> config -x seems to use for finding out the config file from the kernel
>> image) for the GENERIC kernel from the stock installation:
>>
>>       sh_name: kern_conf
>>       sh_type: SHT_PROGBITS
>>       sh_flags: SHF_ALLOC
>>       sh_addr: 0xc1039f80
>>       sh_offset: 12820352
>>       sh_size: 3771
>>       sh_link: 0
>>       sh_info: 0
>>       sh_addralign: 32
>>
>> And this is from the kernel I have built myself using clang and a
>> custom config file:
>>
>>       sh_name: kern_conf
>>       sh_type: SHT_PROGBITS
>>       sh_flags: SHF_ALLOC
>>       sh_addr: 0xc09aee9c
>>       sh_offset: 5959324
>>       sh_size: 1994
>>       sh_link: 0
>>       sh_info: 0
>>       sh_addralign: 1
>>
>> The align field looks suspicious, config -x seems to use it to check
>> for padding but to me it looks like the logic may not work if the
>> alignment is 1.
>>
>> This the relevant bit from main.c of config(8)
>>
>
> Kimmo,
>
> Lets keep discussion on hackers@ only. I do agree with you that config(8)
> internal implementation might have its issues.
>
> Can you make your kernel configuration file, faulty kernel image and exact
> build instructions available to me?
>
> --
> Wojciech A. Koszek
> wkoszek at FreeBSD.czest.pl
> http://FreeBSD.czest.pl/~wkoszek/

The kernel config file:

http://pastebin.com/j0J9NPCi

My /etc/make.conf:

http://pastebin.com/HYudWCA9

And /etc/src.conf:

http://pastebin.com/ZAKq6ABT

I'll see how I can make the kernel image available.

-Kimmo