Date: Wed, 23 Jun 2010 09:47:52 +0300 From: Andriy Gapon <avg@icyb.net.ua> To: Hans Petter Selasky <hselasky@c2i.net> Cc: freebsd-hackers@freebsd.org, freebsd-current@freebsd.org Subject: Re: [HEADS UP] Kernel modules don't work properly in FreeBSD 8.1-RC1 Message-ID: <4C21AE18.4050400@icyb.net.ua> In-Reply-To: <201006230238.06831.hselasky@c2i.net> References: <201006230238.06831.hselasky@c2i.net>
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on 23/06/2010 03:38 Hans Petter Selasky said the following:
> Hi,
>
> I'm creating a new thread on this issue.
>
> On Tue, Jun 22, 2010 at 04:39:17PM -0400, Ryan Stone wrote:
>> I saw similar behaviour a couple of years ago when I switched from
>> using gcc 4.0.2 to gcc 4.3.0 to compile some out-of-tree KLD modules.
>> The problem ended up being a change in the linker script used by GNU
>> ld for linking kernel modules. It used to always put some magic
>> symbols used by the linker to implement things like sysinits into the
>> module. It was changed to only provide those symbols, which
>> apparently means that the linker would discard those symbols if
>> nothing referenced them(and nothing did reference them). I had to
>> work around it by adding the following to my link line:
>>
>> -u __start_set_sysinit_set -u __start_set_sysuninit_set \
>> -u __start_set_sysctl_set -u __start_set_modmetadata_set \
>> -u __stop_set_sysinit_set -u __stop_set_sysuninit_set \
>> -u __stop_set_sysctl_set -u __stop_set_modmetadata_set
>
> It appears many kmods are broken because the linker is stripping away static
> data declared with the section attribute in FreeBSD 8.1-RC1.
>
> <cite>
>
> I added those lines to the LDFLAGS in Makefile.kmod in the cuse4bsd port
> made the module and the result loads and creates the /dev/cuse file.
>
> Here's a diff relative to
> /usr/ports/multimedia/cuse4bsd-kmod/work/cuse4bsd-kmod-0.1.11 just so
> it's clear what I did.
>
>
> --- Makefile.kmod.orig 2010-02-11 03:28:02.000000000 -0800
> +++ Makefile.kmod 2010-06-22 14:02:52.000000000 -0700
> @@ -30,4 +30,10 @@
> KMOD= cuse4bsd
> SRCS= cuse4bsd_kmod.c device_if.h bus_if.h vnode_if.h
>
> +LDFLAGS += -u __start_set_sysinit_set -u __start_set_sysuninit_set \
> + -u __start_set_sysctl_set -u __start_set_modmetadata_set \
> + -u __stop_set_sysinit_set -u __stop_set_sysuninit_set \
> + -u __stop_set_sysctl_set -u __stop_set_modmetadata_set
> +
> +
> .include <bsd.kmod.mk>
>
> Running nm -o on the two modules, the difference seems to be that the -u
> results in some additional absolute symbols being defined:
>
> Bad module:
> $ nm -o /boot/modules/cuse4bsd.ko| grep sys
> /boot/modules/cuse4bsd.ko:0000275c r
> __set_sysinit_set_sym_cuse_kern_init_sys_init
> /boot/modules/cuse4bsd.ko:00002758 r
> __set_sysuninit_set_sym_cuse_kern_uninit_sys_uninit
> /boot/modules/cuse4bsd.ko:00003194 d cuse_kern_init_sys_init
> /boot/modules/cuse4bsd.ko:00003184 d cuse_kern_uninit_sys_uninit
I am not sure if this analysis is correct.
I tested on head and stable/8 and my nm output is exactly like above ("bad
module"), still the module loads fine and creates /dev/cuse.
I don't think there were any recent changes related to build infrastructure or
linker in 8.1.
Please consider other possibilities.
> Good module:
>
> $ nm -o ./cuse4bsd.ko | grep sys
> ./cuse4bsd.ko:000028cc r __set_sysinit_set_sym_cuse_kern_init_sys_init
> ./cuse4bsd.ko:000028c8 r __set_sysuninit_set_sym_cuse_kern_uninit_sys_uninit
> ./cuse4bsd.ko: U __start_set_sysctl_set
> ./cuse4bsd.ko:000028cc A __start_set_sysinit_set
> ./cuse4bsd.ko:000028c8 A __start_set_sysuninit_set
> ./cuse4bsd.ko: U __stop_set_sysctl_set
> ./cuse4bsd.ko:000028d0 A __stop_set_sysinit_set
> ./cuse4bsd.ko:000028cc A __stop_set_sysuninit_set
> ./cuse4bsd.ko:00003194 d cuse_kern_init_sys_init
> ./cuse4bsd.ko:00003184 d cuse_kern_uninit_sys_uninit
>
> </cite>
--
Andriy Gapon
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