Re: Build kernels with -ffreestanding?
> Date: Wed, 28 Dec 2016 22:59:18 +0100 (CET)
> From: Mark Kettenis <mark.kette...@xs4all.nl>
>
> > Date: Wed, 28 Dec 2016 08:29:05 +0100
> > From: Martin Pieuchot <m...@openbsd.org>
> >
> > On 28/12/16(Wed) 01:05, Jeremie Courreges-Anglas wrote:
> > > Mark Kettenis <mark.kette...@xs4all.nl> writes:
> > >
> > > >> Date: Sat, 24 Dec 2016 00:08:35 +0100 (CET)
> > > >> From: Mark Kettenis <mark.kette...@xs4all.nl>
> > > >>
> > > >> We already do this on some architectures, but not on amd64 for
> > > >> example. The main reason is that this disables memcpy() optimizations
> > > >> that have a measurable impact on the network stack performance.
> > > >>
> > > >> We can get those optimizations back by doing:
> > > >>
> > > >> #define memcpy(d, s, n) __builtin_memcpy((d), (s), (n))
> > > >>
> > > >> I verified that gcc still does proper bounds checking on
> > > >> __builtin_memcpy(), so we don't lose that.
> > > >>
> > > >> The nice thing about this solution is that we can choose explicitly
> > > >> which optimizations we want. And as you can see the kernel makefile
> > > >> gets simpler ;).
> > > >>
> > > >> Of course the real reason why I'm looking into this is that clang
> > > >> makes it really hard to build kernels without -ffreestanding.
> > > >>
> > > >> The diff below implements this strategy, and enabled the optimizations
> > > >> for memcpy() and memset(). We can add others if we think there is a
> > > >> benefit. I've tested the diff on amd64. We may need to put an #undef
> > > >> memcpy somewhere for platforms that use the generic C code for memcpy.
> > > >>
> > > >> Thoughts?
> > > >
> > > > So those #undefs are necessary. New diff below. Tested on armv7,
> > > > hppa and sparc64 now as well.
> > >
> > > I think this is the way to go; can't help tests on other archs, though.
> > > ok jca@ fwiw
> >
> > For the archives, Hrvoje Popovski measured a performance impact when using
> > a kernel with this diff to forward packets. I guess we're missing some
> > defines.
>
> The most likely candidate is memmove. Here is a diff that adds it.
Scrap that; memcmp needs this too. New diff below.
Index: arch/amd64/conf/Makefile.amd64
===
RCS file: /cvs/src/sys/arch/amd64/conf/Makefile.amd64,v
retrieving revision 1.74
diff -u -p -r1.74 Makefile.amd64
--- arch/amd64/conf/Makefile.amd64 29 Nov 2016 09:08:34 - 1.74
+++ arch/amd64/conf/Makefile.amd64 28 Dec 2016 22:19:20 -
@@ -29,9 +29,7 @@ CWARNFLAGS= -Werror -Wall -Wimplicit-fun
CMACHFLAGS=-mcmodel=kernel -mno-red-zone -mno-sse2 -mno-sse -mno-3dnow \
-mno-mmx -msoft-float -fno-omit-frame-pointer
-CMACHFLAGS+= -fno-builtin-printf -fno-builtin-snprintf \
- -fno-builtin-vsnprintf -fno-builtin-log \
- -fno-builtin-log2 -fno-builtin-malloc ${NOPIE_FLAGS}
+CMACHFLAGS+= -ffreestanding ${NOPIE_FLAGS}
.if ${IDENT:M-DNO_PROPOLICE}
CMACHFLAGS+= -fno-stack-protector
.endif
Index: lib/libkern/memcmp.c
===
RCS file: /cvs/src/sys/lib/libkern/memcmp.c,v
retrieving revision 1.6
diff -u -p -r1.6 memcmp.c
--- lib/libkern/memcmp.c10 Jun 2014 04:16:57 - 1.6
+++ lib/libkern/memcmp.c28 Dec 2016 22:19:21 -
@@ -34,6 +34,8 @@
#include
+#undef memcmp
+
/*
* Compare memory regions.
*/
Index: lib/libkern/memcpy.c
===
RCS file: /cvs/src/sys/lib/libkern/memcpy.c,v
retrieving revision 1.3
diff -u -p -r1.3 memcpy.c
--- lib/libkern/memcpy.c12 Jun 2013 16:44:22 - 1.3
+++ lib/libkern/memcpy.c28 Dec 2016 22:19:21 -
@@ -32,6 +32,8 @@
#include
#include
+#undef memcpy
+
/*
* This is designed to be small, not fast.
*/
Index: lib/libkern/memmove.c
===
RCS file: /cvs/src/sys/lib/libkern/memmove.c,v
retrieving revision 1.1
diff -u -p -r1.1 memmove.c
--- lib/libkern/memmove.c 11 Jun 2013 18:04:41 - 1.1
+++ lib/libkern/memmove.c 28 Dec 2016 22:19:21 -
@@ -32,6 +32,8 @@
#include
#include
+#undef memmove
+
/*
* This is designed to be small, not fast.
*/
Index: lib/libkern/memset.c
===
RCS file: /cvs/src/sys/lib/libk
Re: Build kernels with -ffreestanding?
> Date: Wed, 28 Dec 2016 08:29:05 +0100
> From: Martin Pieuchot <m...@openbsd.org>
>
> On 28/12/16(Wed) 01:05, Jeremie Courreges-Anglas wrote:
> > Mark Kettenis <mark.kette...@xs4all.nl> writes:
> >
> > >> Date: Sat, 24 Dec 2016 00:08:35 +0100 (CET)
> > >> From: Mark Kettenis <mark.kette...@xs4all.nl>
> > >>
> > >> We already do this on some architectures, but not on amd64 for
> > >> example. The main reason is that this disables memcpy() optimizations
> > >> that have a measurable impact on the network stack performance.
> > >>
> > >> We can get those optimizations back by doing:
> > >>
> > >> #define memcpy(d, s, n) __builtin_memcpy((d), (s), (n))
> > >>
> > >> I verified that gcc still does proper bounds checking on
> > >> __builtin_memcpy(), so we don't lose that.
> > >>
> > >> The nice thing about this solution is that we can choose explicitly
> > >> which optimizations we want. And as you can see the kernel makefile
> > >> gets simpler ;).
> > >>
> > >> Of course the real reason why I'm looking into this is that clang
> > >> makes it really hard to build kernels without -ffreestanding.
> > >>
> > >> The diff below implements this strategy, and enabled the optimizations
> > >> for memcpy() and memset(). We can add others if we think there is a
> > >> benefit. I've tested the diff on amd64. We may need to put an #undef
> > >> memcpy somewhere for platforms that use the generic C code for memcpy.
> > >>
> > >> Thoughts?
> > >
> > > So those #undefs are necessary. New diff below. Tested on armv7,
> > > hppa and sparc64 now as well.
> >
> > I think this is the way to go; can't help tests on other archs, though.
> > ok jca@ fwiw
>
> For the archives, Hrvoje Popovski measured a performance impact when using
> a kernel with this diff to forward packets. I guess we're missing some
> defines.
The most likely candidate is memmove. Here is a diff that adds it.
Index: arch/amd64/conf/Makefile.amd64
===
RCS file: /cvs/src/sys/arch/amd64/conf/Makefile.amd64,v
retrieving revision 1.74
diff -u -p -r1.74 Makefile.amd64
--- arch/amd64/conf/Makefile.amd64 29 Nov 2016 09:08:34 - 1.74
+++ arch/amd64/conf/Makefile.amd64 28 Dec 2016 21:48:52 -
@@ -29,9 +29,7 @@ CWARNFLAGS= -Werror -Wall -Wimplicit-fun
CMACHFLAGS=-mcmodel=kernel -mno-red-zone -mno-sse2 -mno-sse -mno-3dnow \
-mno-mmx -msoft-float -fno-omit-frame-pointer
-CMACHFLAGS+= -fno-builtin-printf -fno-builtin-snprintf \
- -fno-builtin-vsnprintf -fno-builtin-log \
- -fno-builtin-log2 -fno-builtin-malloc ${NOPIE_FLAGS}
+CMACHFLAGS+= -ffreestanding ${NOPIE_FLAGS}
.if ${IDENT:M-DNO_PROPOLICE}
CMACHFLAGS+= -fno-stack-protector
.endif
Index: lib/libkern/memcpy.c
===
RCS file: /cvs/src/sys/lib/libkern/memcpy.c,v
retrieving revision 1.3
diff -u -p -r1.3 memcpy.c
--- lib/libkern/memcpy.c12 Jun 2013 16:44:22 - 1.3
+++ lib/libkern/memcpy.c28 Dec 2016 21:48:53 -
@@ -32,6 +32,8 @@
#include
#include
+#undef memcpy
+
/*
* This is designed to be small, not fast.
*/
Index: lib/libkern/memmove.c
===
RCS file: /cvs/src/sys/lib/libkern/memmove.c,v
retrieving revision 1.1
diff -u -p -r1.1 memmove.c
--- lib/libkern/memmove.c 11 Jun 2013 18:04:41 - 1.1
+++ lib/libkern/memmove.c 28 Dec 2016 21:48:53 -
@@ -32,6 +32,8 @@
#include
#include
+#undef memmove
+
/*
* This is designed to be small, not fast.
*/
Index: lib/libkern/memset.c
===
RCS file: /cvs/src/sys/lib/libkern/memset.c,v
retrieving revision 1.7
diff -u -p -r1.7 memset.c
--- lib/libkern/memset.c10 Jun 2014 04:16:57 - 1.7
+++ lib/libkern/memset.c28 Dec 2016 21:48:53 -
@@ -39,6 +39,8 @@
#include
#include
+#undef memset
+
#definewsize sizeof(u_int)
#definewmask (wsize - 1)
Index: sys/systm.h
===
RCS file: /cvs/src/sys/sys/systm.h,v
retrieving revision 1.120
diff -u -p -r1.120 systm.h
--- sys/systm.h 19 Dec 2016 08:36:50 - 1.120
+++ sys/systm.h 28 Dec 2016 21:48:53 -
@@ -330,6 +330,10 @@ extern int (*mountroot)(void);
#include
+#define memcpy(d, s, n)__builtin_memcpy((d), (s), (n))
+#define memmove(d, s, n) __builtin_memmove((d), (s), (n))
+#define memset(b, c, n)__builtin_memset((b), (c), (n))
+
#if defined(DDB) || defined(KGDB)
/* debugger entry points */
void Debugger(void); /* in DDB only */
Re: Build kernels with -ffreestanding?
>> Am 28.12.2016 um 08:29 schrieb Martin Pieuchot <m...@openbsd.org>: >> >> On 28/12/16(Wed) 01:05, Jeremie Courreges-Anglas wrote: >> Mark Kettenis <mark.kette...@xs4all.nl> writes: >> >>>> Date: Sat, 24 Dec 2016 00:08:35 +0100 (CET) >>>> From: Mark Kettenis <mark.kette...@xs4all.nl> >>>> >>>> We already do this on some architectures, but not on amd64 for >>>> example. The main reason is that this disables memcpy() optimizations >>>> that have a measurable impact on the network stack performance. >>>> >>>> We can get those optimizations back by doing: >>>> >>>> #define memcpy(d, s, n) __builtin_memcpy((d), (s), (n)) >>>> >>>> I verified that gcc still does proper bounds checking on >>>> __builtin_memcpy(), so we don't lose that. >>>> >>>> The nice thing about this solution is that we can choose explicitly >>>> which optimizations we want. And as you can see the kernel makefile >>>> gets simpler ;). >>>> >>>> Of course the real reason why I'm looking into this is that clang >>>> makes it really hard to build kernels without -ffreestanding. >>>> >>>> The diff below implements this strategy, and enabled the optimizations >>>> for memcpy() and memset(). We can add others if we think there is a >>>> benefit. I've tested the diff on amd64. We may need to put an #undef >>>> memcpy somewhere for platforms that use the generic C code for memcpy. >>>> >>>> Thoughts? >>> >>> So those #undefs are necessary. New diff below. Tested on armv7, >>> hppa and sparc64 now as well. >> >> I think this is the way to go; can't help tests on other archs, though. >> ok jca@ fwiw > > For the archives, Hrvoje Popovski measured a performance impact when using > a kernel with this diff to forward packets. I guess we're missing some > defines. I'm late to the game - but does this diff remove all the other optimizations as well? (eg. bcopy, memcmp, memmove, strchr, ...) I did some performance testing when I added them for amd64 in libc and it made a noticeable difference - not just for memcpy+memset. Reyk
Re: Build kernels with -ffreestanding?
On 28/12/16(Wed) 01:05, Jeremie Courreges-Anglas wrote: > Mark Kettenis <mark.kette...@xs4all.nl> writes: > > >> Date: Sat, 24 Dec 2016 00:08:35 +0100 (CET) > >> From: Mark Kettenis <mark.kette...@xs4all.nl> > >> > >> We already do this on some architectures, but not on amd64 for > >> example. The main reason is that this disables memcpy() optimizations > >> that have a measurable impact on the network stack performance. > >> > >> We can get those optimizations back by doing: > >> > >> #define memcpy(d, s, n) __builtin_memcpy((d), (s), (n)) > >> > >> I verified that gcc still does proper bounds checking on > >> __builtin_memcpy(), so we don't lose that. > >> > >> The nice thing about this solution is that we can choose explicitly > >> which optimizations we want. And as you can see the kernel makefile > >> gets simpler ;). > >> > >> Of course the real reason why I'm looking into this is that clang > >> makes it really hard to build kernels without -ffreestanding. > >> > >> The diff below implements this strategy, and enabled the optimizations > >> for memcpy() and memset(). We can add others if we think there is a > >> benefit. I've tested the diff on amd64. We may need to put an #undef > >> memcpy somewhere for platforms that use the generic C code for memcpy. > >> > >> Thoughts? > > > > So those #undefs are necessary. New diff below. Tested on armv7, > > hppa and sparc64 now as well. > > I think this is the way to go; can't help tests on other archs, though. > ok jca@ fwiw For the archives, Hrvoje Popovski measured a performance impact when using a kernel with this diff to forward packets. I guess we're missing some defines.
Re: Build kernels with -ffreestanding?
Mark Kettenis <mark.kette...@xs4all.nl> writes: >> Date: Sat, 24 Dec 2016 00:08:35 +0100 (CET) >> From: Mark Kettenis <mark.kette...@xs4all.nl> >> >> We already do this on some architectures, but not on amd64 for >> example. The main reason is that this disables memcpy() optimizations >> that have a measurable impact on the network stack performance. >> >> We can get those optimizations back by doing: >> >> #define memcpy(d, s, n) __builtin_memcpy((d), (s), (n)) >> >> I verified that gcc still does proper bounds checking on >> __builtin_memcpy(), so we don't lose that. >> >> The nice thing about this solution is that we can choose explicitly >> which optimizations we want. And as you can see the kernel makefile >> gets simpler ;). >> >> Of course the real reason why I'm looking into this is that clang >> makes it really hard to build kernels without -ffreestanding. >> >> The diff below implements this strategy, and enabled the optimizations >> for memcpy() and memset(). We can add others if we think there is a >> benefit. I've tested the diff on amd64. We may need to put an #undef >> memcpy somewhere for platforms that use the generic C code for memcpy. >> >> Thoughts? > > So those #undefs are necessary. New diff below. Tested on armv7, > hppa and sparc64 now as well. I think this is the way to go; can't help tests on other archs, though. ok jca@ fwiw -- jca | PGP : 0x1524E7EE / 5135 92C1 AD36 5293 2BDF DDCC 0DFA 74AE 1524 E7EE
Re: Build kernels with -ffreestanding?
On Sat, Dec 24, 2016 at 12:08:35AM +0100, Mark Kettenis wrote: > We can get those optimizations back by doing: > > #define memcpy(d, s, n) __builtin_memcpy((d), (s), (n)) You might still want to put a prototype in, just before the define. Joerg
Re: Build kernels with -ffreestanding?
> Date: Sun, 25 Dec 2016 09:40:05 +1100
> From: Jonathan Gray <j...@jsg.id.au>
>
> On Sat, Dec 24, 2016 at 05:07:11PM +0100, Mark Kettenis wrote:
> > > Date: Sat, 24 Dec 2016 00:08:35 +0100 (CET)
> > > From: Mark Kettenis <mark.kette...@xs4all.nl>
> > >
> > > We already do this on some architectures, but not on amd64 for
> > > example. The main reason is that this disables memcpy() optimizations
> > > that have a measurable impact on the network stack performance.
> > >
> > > We can get those optimizations back by doing:
> > >
> > > #define memcpy(d, s, n) __builtin_memcpy((d), (s), (n))
> > >
> > > I verified that gcc still does proper bounds checking on
> > > __builtin_memcpy(), so we don't lose that.
> > >
> > > The nice thing about this solution is that we can choose explicitly
> > > which optimizations we want. And as you can see the kernel makefile
> > > gets simpler ;).
> > >
> > > Of course the real reason why I'm looking into this is that clang
> > > makes it really hard to build kernels without -ffreestanding.
> > >
> > > The diff below implements this strategy, and enabled the optimizations
> > > for memcpy() and memset(). We can add others if we think there is a
> > > benefit. I've tested the diff on amd64. We may need to put an #undef
> > > memcpy somewhere for platforms that use the generic C code for memcpy.
> > >
> > > Thoughts?
> >
> > So those #undefs are necessary. New diff below. Tested on armv7,
> > hppa and sparc64 now as well.
macppc tested now as well
> I agree this is the way we want to go. It also avoids having
> to expand the list to -fno-builtin-free etc for newer versions of gcc.
>
> Why build the memcpy/memset in libkern at all if we go this route?
__builtin_memcpy() may still expand to an explicit memset() call if
the compiler decides not to inline it.
> > Index: sys/systm.h
> > ===
> > RCS file: /cvs/src/sys/sys/systm.h,v
> > retrieving revision 1.119
> > diff -u -p -r1.119 systm.h
> > --- sys/systm.h 24 Sep 2016 18:35:52 - 1.119
> > +++ sys/systm.h 24 Dec 2016 16:05:48 -
> > @@ -306,6 +306,9 @@ extern int (*mountroot)(void);
> >
> > #include
> >
> > +#define memcpy(d, s, n) __builtin_memcpy((d), (s), (n))
> > +#define memset(b, c, n) __builtin_memset((b), (c), (n))
> > +
> > #if defined(DDB) || defined(KGDB)
> > /* debugger entry points */
> > void Debugger(void); /* in DDB only */
> > Index: lib/libkern/memcpy.c
> > ===
> > RCS file: /cvs/src/sys/lib/libkern/memcpy.c,v
> > retrieving revision 1.3
> > diff -u -p -r1.3 memcpy.c
> > --- lib/libkern/memcpy.c12 Jun 2013 16:44:22 - 1.3
> > +++ lib/libkern/memcpy.c24 Dec 2016 16:05:48 -
> > @@ -32,6 +32,8 @@
> > #include
> > #include
> >
> > +#undef memcpy
> > +
> > /*
> > * This is designed to be small, not fast.
> > */
> > Index: lib/libkern/memset.c
> > ===
> > RCS file: /cvs/src/sys/lib/libkern/memset.c,v
> > retrieving revision 1.7
> > diff -u -p -r1.7 memset.c
> > --- lib/libkern/memset.c10 Jun 2014 04:16:57 - 1.7
> > +++ lib/libkern/memset.c24 Dec 2016 16:05:48 -
> > @@ -39,6 +39,8 @@
> > #include
> > #include
> >
> > +#undef memset
> > +
> > #definewsize sizeof(u_int)
> > #definewmask (wsize - 1)
> >
> > Index: arch/amd64/conf/Makefile.amd64
> > ===
> > RCS file: /cvs/src/sys/arch/amd64/conf/Makefile.amd64,v
> > retrieving revision 1.74
> > diff -u -p -r1.74 Makefile.amd64
> > --- arch/amd64/conf/Makefile.amd64 29 Nov 2016 09:08:34 - 1.74
> > +++ arch/amd64/conf/Makefile.amd64 24 Dec 2016 16:05:49 -
> > @@ -29,9 +29,7 @@ CWARNFLAGS= -Werror -Wall -Wimplicit-fun
> >
> > CMACHFLAGS=-mcmodel=kernel -mno-red-zone -mno-sse2 -mno-sse
> > -mno-3dnow \
> > -mno-mmx -msoft-float -fno-omit-frame-pointer
> > -CMACHFLAGS+= -fno-builtin-printf -fno-builtin-snprintf \
> > - -fno-builtin-vsnprintf -fno-builtin-log \
> > - -fno-builtin-log2 -fno-builtin-malloc ${NOPIE_FLAGS}
> > +CMACHFLAGS+= -ffreestanding ${NOPIE_FLAGS}
> > .if ${IDENT:M-DNO_PROPOLICE}
> > CMACHFLAGS+= -fno-stack-protector
> > .endif
> >
>
Re: Build kernels with -ffreestanding?
On Sat, Dec 24, 2016 at 05:07:11PM +0100, Mark Kettenis wrote:
> > Date: Sat, 24 Dec 2016 00:08:35 +0100 (CET)
> > From: Mark Kettenis <mark.kette...@xs4all.nl>
> >
> > We already do this on some architectures, but not on amd64 for
> > example. The main reason is that this disables memcpy() optimizations
> > that have a measurable impact on the network stack performance.
> >
> > We can get those optimizations back by doing:
> >
> > #define memcpy(d, s, n) __builtin_memcpy((d), (s), (n))
> >
> > I verified that gcc still does proper bounds checking on
> > __builtin_memcpy(), so we don't lose that.
> >
> > The nice thing about this solution is that we can choose explicitly
> > which optimizations we want. And as you can see the kernel makefile
> > gets simpler ;).
> >
> > Of course the real reason why I'm looking into this is that clang
> > makes it really hard to build kernels without -ffreestanding.
> >
> > The diff below implements this strategy, and enabled the optimizations
> > for memcpy() and memset(). We can add others if we think there is a
> > benefit. I've tested the diff on amd64. We may need to put an #undef
> > memcpy somewhere for platforms that use the generic C code for memcpy.
> >
> > Thoughts?
>
> So those #undefs are necessary. New diff below. Tested on armv7,
> hppa and sparc64 now as well.
I agree this is the way we want to go. It also avoids having
to expand the list to -fno-builtin-free etc for newer versions of gcc.
Why build the memcpy/memset in libkern at all if we go this route?
>
> Index: sys/systm.h
> ===
> RCS file: /cvs/src/sys/sys/systm.h,v
> retrieving revision 1.119
> diff -u -p -r1.119 systm.h
> --- sys/systm.h 24 Sep 2016 18:35:52 - 1.119
> +++ sys/systm.h 24 Dec 2016 16:05:48 -
> @@ -306,6 +306,9 @@ extern int (*mountroot)(void);
>
> #include
>
> +#define memcpy(d, s, n) __builtin_memcpy((d), (s), (n))
> +#define memset(b, c, n) __builtin_memset((b), (c), (n))
> +
> #if defined(DDB) || defined(KGDB)
> /* debugger entry points */
> void Debugger(void); /* in DDB only */
> Index: lib/libkern/memcpy.c
> ===
> RCS file: /cvs/src/sys/lib/libkern/memcpy.c,v
> retrieving revision 1.3
> diff -u -p -r1.3 memcpy.c
> --- lib/libkern/memcpy.c 12 Jun 2013 16:44:22 - 1.3
> +++ lib/libkern/memcpy.c 24 Dec 2016 16:05:48 -
> @@ -32,6 +32,8 @@
> #include
> #include
>
> +#undef memcpy
> +
> /*
> * This is designed to be small, not fast.
> */
> Index: lib/libkern/memset.c
> ===
> RCS file: /cvs/src/sys/lib/libkern/memset.c,v
> retrieving revision 1.7
> diff -u -p -r1.7 memset.c
> --- lib/libkern/memset.c 10 Jun 2014 04:16:57 - 1.7
> +++ lib/libkern/memset.c 24 Dec 2016 16:05:48 -
> @@ -39,6 +39,8 @@
> #include
> #include
>
> +#undef memset
> +
> #define wsize sizeof(u_int)
> #define wmask (wsize - 1)
>
> Index: arch/amd64/conf/Makefile.amd64
> ===
> RCS file: /cvs/src/sys/arch/amd64/conf/Makefile.amd64,v
> retrieving revision 1.74
> diff -u -p -r1.74 Makefile.amd64
> --- arch/amd64/conf/Makefile.amd6429 Nov 2016 09:08:34 - 1.74
> +++ arch/amd64/conf/Makefile.amd6424 Dec 2016 16:05:49 -
> @@ -29,9 +29,7 @@ CWARNFLAGS= -Werror -Wall -Wimplicit-fun
>
> CMACHFLAGS= -mcmodel=kernel -mno-red-zone -mno-sse2 -mno-sse -mno-3dnow \
> -mno-mmx -msoft-float -fno-omit-frame-pointer
> -CMACHFLAGS+= -fno-builtin-printf -fno-builtin-snprintf \
> - -fno-builtin-vsnprintf -fno-builtin-log \
> - -fno-builtin-log2 -fno-builtin-malloc ${NOPIE_FLAGS}
> +CMACHFLAGS+= -ffreestanding ${NOPIE_FLAGS}
> .if ${IDENT:M-DNO_PROPOLICE}
> CMACHFLAGS+= -fno-stack-protector
> .endif
>
Re: Build kernels with -ffreestanding?
> Date: Sat, 24 Dec 2016 00:08:35 +0100 (CET)
> From: Mark Kettenis <mark.kette...@xs4all.nl>
>
> We already do this on some architectures, but not on amd64 for
> example. The main reason is that this disables memcpy() optimizations
> that have a measurable impact on the network stack performance.
>
> We can get those optimizations back by doing:
>
> #define memcpy(d, s, n) __builtin_memcpy((d), (s), (n))
>
> I verified that gcc still does proper bounds checking on
> __builtin_memcpy(), so we don't lose that.
>
> The nice thing about this solution is that we can choose explicitly
> which optimizations we want. And as you can see the kernel makefile
> gets simpler ;).
>
> Of course the real reason why I'm looking into this is that clang
> makes it really hard to build kernels without -ffreestanding.
>
> The diff below implements this strategy, and enabled the optimizations
> for memcpy() and memset(). We can add others if we think there is a
> benefit. I've tested the diff on amd64. We may need to put an #undef
> memcpy somewhere for platforms that use the generic C code for memcpy.
>
> Thoughts?
So those #undefs are necessary. New diff below. Tested on armv7,
hppa and sparc64 now as well.
Index: sys/systm.h
===
RCS file: /cvs/src/sys/sys/systm.h,v
retrieving revision 1.119
diff -u -p -r1.119 systm.h
--- sys/systm.h 24 Sep 2016 18:35:52 - 1.119
+++ sys/systm.h 24 Dec 2016 16:05:48 -
@@ -306,6 +306,9 @@ extern int (*mountroot)(void);
#include
+#define memcpy(d, s, n) __builtin_memcpy((d), (s), (n))
+#define memset(b, c, n) __builtin_memset((b), (c), (n))
+
#if defined(DDB) || defined(KGDB)
/* debugger entry points */
void Debugger(void); /* in DDB only */
Index: lib/libkern/memcpy.c
===
RCS file: /cvs/src/sys/lib/libkern/memcpy.c,v
retrieving revision 1.3
diff -u -p -r1.3 memcpy.c
--- lib/libkern/memcpy.c12 Jun 2013 16:44:22 - 1.3
+++ lib/libkern/memcpy.c24 Dec 2016 16:05:48 -
@@ -32,6 +32,8 @@
#include
#include
+#undef memcpy
+
/*
* This is designed to be small, not fast.
*/
Index: lib/libkern/memset.c
===
RCS file: /cvs/src/sys/lib/libkern/memset.c,v
retrieving revision 1.7
diff -u -p -r1.7 memset.c
--- lib/libkern/memset.c10 Jun 2014 04:16:57 - 1.7
+++ lib/libkern/memset.c24 Dec 2016 16:05:48 -
@@ -39,6 +39,8 @@
#include
#include
+#undef memset
+
#definewsize sizeof(u_int)
#definewmask (wsize - 1)
Index: arch/amd64/conf/Makefile.amd64
===
RCS file: /cvs/src/sys/arch/amd64/conf/Makefile.amd64,v
retrieving revision 1.74
diff -u -p -r1.74 Makefile.amd64
--- arch/amd64/conf/Makefile.amd64 29 Nov 2016 09:08:34 - 1.74
+++ arch/amd64/conf/Makefile.amd64 24 Dec 2016 16:05:49 -
@@ -29,9 +29,7 @@ CWARNFLAGS= -Werror -Wall -Wimplicit-fun
CMACHFLAGS=-mcmodel=kernel -mno-red-zone -mno-sse2 -mno-sse -mno-3dnow \
-mno-mmx -msoft-float -fno-omit-frame-pointer
-CMACHFLAGS+= -fno-builtin-printf -fno-builtin-snprintf \
- -fno-builtin-vsnprintf -fno-builtin-log \
- -fno-builtin-log2 -fno-builtin-malloc ${NOPIE_FLAGS}
+CMACHFLAGS+= -ffreestanding ${NOPIE_FLAGS}
.if ${IDENT:M-DNO_PROPOLICE}
CMACHFLAGS+= -fno-stack-protector
.endif
Build kernels with -ffreestanding?
We already do this on some architectures, but not on amd64 for
example. The main reason is that this disables memcpy() optimizations
that have a measurable impact on the network stack performance.
We can get those optimizations back by doing:
#define memcpy(d, s, n) __builtin_memcpy((d), (s), (n))
I verified that gcc still does proper bounds checking on
__builtin_memcpy(), so we don't lose that.
The nice thing about this solution is that we can choose explicitly
which optimizations we want. And as you can see the kernel makefile
gets simpler ;).
Of course the real reason why I'm looking into this is that clang
makes it really hard to build kernels without -ffreestanding.
The diff below implements this strategy, and enabled the optimizations
for memcpy() and memset(). We can add others if we think there is a
benefit. I've tested the diff on amd64. We may need to put an #undef
memcpy somewhere for platforms that use the generic C code for memcpy.
Thoughts?
Index: sys/systm.h
===
RCS file: /cvs/src/sys/sys/systm.h,v
retrieving revision 1.120
diff -u -p -r1.120 systm.h
--- sys/systm.h 19 Dec 2016 08:36:50 - 1.120
+++ sys/systm.h 23 Dec 2016 22:53:15 -
@@ -330,6 +330,9 @@ extern int (*mountroot)(void);
#include
+#define memcpy(d, s, n) __builtin_memcpy((d), (s), (n))
+#define memset(b, c, n) __builtin_memset((b), (c), (n))
+
#if defined(DDB) || defined(KGDB)
/* debugger entry points */
void Debugger(void); /* in DDB only */
Index: arch/amd64/conf/Makefile.amd64
===
RCS file: /cvs/src/sys/arch/amd64/conf/Makefile.amd64,v
retrieving revision 1.74
diff -u -p -r1.74 Makefile.amd64
--- arch/amd64/conf/Makefile.amd64 29 Nov 2016 09:08:34 - 1.74
+++ arch/amd64/conf/Makefile.amd64 23 Dec 2016 22:53:15 -
@@ -29,9 +29,7 @@ CWARNFLAGS= -Werror -Wall -Wimplicit-fun
CMACHFLAGS=-mcmodel=kernel -mno-red-zone -mno-sse2 -mno-sse -mno-3dnow \
-mno-mmx -msoft-float -fno-omit-frame-pointer
-CMACHFLAGS+= -fno-builtin-printf -fno-builtin-snprintf \
- -fno-builtin-vsnprintf -fno-builtin-log \
- -fno-builtin-log2 -fno-builtin-malloc ${NOPIE_FLAGS}
+CMACHFLAGS+= -ffreestanding ${NOPIE_FLAGS}
.if ${IDENT:M-DNO_PROPOLICE}
CMACHFLAGS+= -fno-stack-protector
.endif
