SH2 kernel fails to build with recent GCC

SH2 kernel fails to build with recent GCC

[Rich Felker]

The commit that resolved GCC issue #54089 broke building the kernel
for SH2, by causing GCC to generate calls to new libgcc functions
which the kernel's fake libgcc does not provide. See the GCC issue
tracker for details:

https://gcc.gnu.org/bugzilla/show_bug.cgi?idT089

The relevant commit is linked from comment 16; comments 33-43 (and
perhaps beyond) discuss the issue in detail and possible fixes.

Before I work on a fix, would dropping the kernel's copy of libgcc
functions for SH and using the real libgcc (like some archs do; see
comment 43) be acceptable, or do we need to get updated
libgcc[-compatible] code into the kernel?

Rich

Re: SH2 kernel fails to build with recent GCC

[Geert Uytterhoeven]

Hi Rich,

On Wed, Aug 12, 2015 at 3:56 AM, Rich Felker <dalias@libc.org> wrote:
> The commit that resolved GCC issue #54089 broke building the kernel
> for SH2, by causing GCC to generate calls to new libgcc functions
> which the kernel's fake libgcc does not provide. See the GCC issue
> tracker for details:
>
> https://gcc.gnu.org/bugzilla/show_bug.cgi?idT089
>
> The relevant commit is linked from comment 16; comments 33-43 (and
> perhaps beyond) discuss the issue in detail and possible fixes.
>
> Before I work on a fix, would dropping the kernel's copy of libgcc
> functions for SH and using the real libgcc (like some archs do; see
> comment 43) be acceptable, or do we need to get updated
> libgcc[-compatible] code into the kernel?

Which libgcc functions are missing? I couldn't find that list in the bug
report...

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: SH2 kernel fails to build with recent GCC

[Rich Felker]

On Wed, Aug 12, 2015 at 09:34:32AM +0200, Geert Uytterhoeven wrote:
> Hi Rich,
> 
> On Wed, Aug 12, 2015 at 3:56 AM, Rich Felker <dalias@libc.org> wrote:
> > The commit that resolved GCC issue #54089 broke building the kernel
> > for SH2, by causing GCC to generate calls to new libgcc functions
> > which the kernel's fake libgcc does not provide. See the GCC issue
> > tracker for details:
> >
> > https://gcc.gnu.org/bugzilla/show_bug.cgi?idT089
> >
> > The relevant commit is linked from comment 16; comments 33-43 (and
> > perhaps beyond) discuss the issue in detail and possible fixes.
> >
> > Before I work on a fix, would dropping the kernel's copy of libgcc
> > functions for SH and using the real libgcc (like some archs do; see
> > comment 43) be acceptable, or do we need to get updated
> > libgcc[-compatible] code into the kernel?
> 
> Which libgcc functions are missing? I couldn't find that list in the bug
> report...

At least __ashlsi3_r0 and __lshrsi3_r0. It's been a while since I
tried building with an affected GCC (see the dates on the comments I
linked) so I don't remember if there were any others. I can try to
build again and let you know.

Rich

Re: SH2 kernel fails to build with recent GCC

[Rich Felker]

On Wed, Aug 12, 2015 at 10:01:49AM -0400, Rich Felker wrote:
> On Wed, Aug 12, 2015 at 09:34:32AM +0200, Geert Uytterhoeven wrote:
> > Hi Rich,
> > 
> > On Wed, Aug 12, 2015 at 3:56 AM, Rich Felker <dalias@libc.org> wrote:
> > > The commit that resolved GCC issue #54089 broke building the kernel
> > > for SH2, by causing GCC to generate calls to new libgcc functions
> > > which the kernel's fake libgcc does not provide. See the GCC issue
> > > tracker for details:
> > >
> > > https://gcc.gnu.org/bugzilla/show_bug.cgi?idT089
> > >
> > > The relevant commit is linked from comment 16; comments 33-43 (and
> > > perhaps beyond) discuss the issue in detail and possible fixes.
> > >
> > > Before I work on a fix, would dropping the kernel's copy of libgcc
> > > functions for SH and using the real libgcc (like some archs do; see
> > > comment 43) be acceptable, or do we need to get updated
> > > libgcc[-compatible] code into the kernel?
> > 
> > Which libgcc functions are missing? I couldn't find that list in the bug
> > report...
> 
> At least __ashlsi3_r0 and __lshrsi3_r0. It's been a while since I
> tried building with an affected GCC (see the dates on the comments I
> linked) so I don't remember if there were any others. I can try to
> build again and let you know.

I just retried the build and confirmed that these are the only two
unresolved symbols reported. So just adding them sounds practical.

Rich