On Sat, Oct 26, 2019 at 02:16:19PM +0200, Antoine Brodin wrote:
> On Sat, Oct 26, 2019 at 10:27 AM Konstantin Belousov
> <kostik...@gmail.com> wrote:
> > On Sat, Oct 26, 2019 at 08:24:09AM +0200, Antoine Brodin wrote:
> > > On Fri, Oct 25, 2019 at 10:09 PM Konstantin Belousov <k...@freebsd.org>
> > > wrote:
> > > >
> > > > Author: kib
> > > > Date: Fri Oct 25 20:09:42 2019
> > > > New Revision: 354095
> > > > URL: https://svnweb.freebsd.org/changeset/base/354095
> > > >
> > > > Log:
> > > > amd64: move pcb out of kstack to struct thread.
> > > >
> > > > This saves 320 bytes of the precious stack space.
> > > >
> > > > The only negative aspect of the change I can think of is that the
> > > > struct thread increased by 320 bytes obviously, and that 320 bytes are
> > > > not swapped out anymore. I believe the freed stack space is much more
> > > > important than that. Also, current struct thread size is 1392 bytes
> > > > on amd64, so UMA will allocate two thread structures per (4KB) slab,
> > > > which leaves a space for pcb without increasing zone memory use.
> > > >
> > > > Reviewed by: alc, markj
> > > > Tested by: pho
> > > > Sponsored by: The FreeBSD Foundation
> > > > MFC after: 2 weeks
> > > > Differential revision: https://reviews.freebsd.org/D22138
> > >
> > > Hi,
> > >
> > > It seems that this breaks at least some versions of gcc:
> > >
> > > In file included from /usr/include/sys/proc.h:75,
> > > from /usr/include/sys/user.h:51,
> > > from ./md-unwind-support.h:34,
> > > from
> > > /wrkdirs/usr/ports/lang/gcc10-devel/work/gcc-10-20191020/libgcc/unwind-dw2.c:412:
> > > /usr/include/machine/proc.h:76:13: error: field 'md_pcb' has incomplete
> > > type
> > > 76 | struct pcb md_pcb;
> > > | ^~~~~~
> > >
> >
> > It is very strange. Are gcc 9 or 8 affected ?
>
> gcc 8 and 9 are affected too.
Then this is a completely different cause then I guessed below, and I think
I know why. All of 8/9/10 gcc ports have support for multiarch, and the
error must happen for gcc or xgcc invocation with -m32, am I right ?
If yes, please try the patch at the end of the message instead.
>
> > As a blind guess, please try this patch.
> >
> > diff --git a/sys/amd64/include/pcb.h b/sys/amd64/include/pcb.h
> > index 44e34fa5c83..9758e684da2 100644
> > --- a/sys/amd64/include/pcb.h
> > +++ b/sys/amd64/include/pcb.h
> > @@ -45,7 +45,7 @@
> > #include <machine/fpu.h>
> > #include <machine/segments.h>
> >
> > -#ifdef __amd64__
> > +#if defined(__amd64__) || defined(__x86_64__)
> > /*
> > * NB: The fields marked with (*) are used by kernel debuggers. Their
> > * ABI should be preserved.
>
> I will test this.
Please use this instead
diff --git a/sys/amd64/include/pcb.h b/sys/amd64/include/pcb.h
index 44e34fa5c83..8800b355c9a 100644
--- a/sys/amd64/include/pcb.h
+++ b/sys/amd64/include/pcb.h
@@ -116,6 +116,10 @@ struct susppcb {
/* fpu context for suspend/resume */
void *sp_fpususpend;
};
+#else /* 32bit */
+struct pcb {
+ uint64_t pcb_dummy[40];
+};
#endif
#ifdef _KERNEL
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