[PATCH v4 1/9] selftests/powerpc: Test the preservation of FPU and VMX regs across syscall
Cyril Bur
cyrilbur at gmail.com
Tue Feb 16 11:06:25 AEDT 2016
On Mon, 15 Feb 2016 22:29:17 +0530
"Naveen N. Rao" <naveen.n.rao at linux.vnet.ibm.com> wrote:
> On 2016/02/15 04:07PM, Cyril Bur wrote:
> > Test that the non volatile floating point and Altivec registers get
> > correctly preserved across the fork() syscall.
> >
> > fork() works nicely for this purpose, the registers should be the same for
> > both parent and child
> >
> > Signed-off-by: Cyril Bur <cyrilbur at gmail.com>
> > ---
> > tools/testing/selftests/powerpc/Makefile | 3 +-
> > tools/testing/selftests/powerpc/basic_asm.h | 30 ++++
> > tools/testing/selftests/powerpc/math/.gitignore | 2 +
> > tools/testing/selftests/powerpc/math/Makefile | 14 ++
> > tools/testing/selftests/powerpc/math/fpu_asm.S | 161 +++++++++++++++++
> > tools/testing/selftests/powerpc/math/fpu_syscall.c | 90 ++++++++++
> > tools/testing/selftests/powerpc/math/vmx_asm.S | 193 +++++++++++++++++++++
> > tools/testing/selftests/powerpc/math/vmx_syscall.c | 92 ++++++++++
> > 8 files changed, 584 insertions(+), 1 deletion(-)
> > create mode 100644 tools/testing/selftests/powerpc/basic_asm.h
> > create mode 100644 tools/testing/selftests/powerpc/math/.gitignore
> > create mode 100644 tools/testing/selftests/powerpc/math/Makefile
> > create mode 100644 tools/testing/selftests/powerpc/math/fpu_asm.S
> > create mode 100644 tools/testing/selftests/powerpc/math/fpu_syscall.c
> > create mode 100644 tools/testing/selftests/powerpc/math/vmx_asm.S
> > create mode 100644 tools/testing/selftests/powerpc/math/vmx_syscall.c
> >
> > diff --git a/tools/testing/selftests/powerpc/Makefile b/tools/testing/selftests/powerpc/Makefile
> > index 0c2706b..19e8191 100644
> > --- a/tools/testing/selftests/powerpc/Makefile
> > +++ b/tools/testing/selftests/powerpc/Makefile
> > @@ -22,7 +22,8 @@ SUB_DIRS = benchmarks \
> > switch_endian \
> > syscalls \
> > tm \
> > - vphn
> > + vphn \
> > + math
> >
> > endif
> >
> > diff --git a/tools/testing/selftests/powerpc/basic_asm.h b/tools/testing/selftests/powerpc/basic_asm.h
> > new file mode 100644
> > index 0000000..f243da0
> > --- /dev/null
> > +++ b/tools/testing/selftests/powerpc/basic_asm.h
> > @@ -0,0 +1,30 @@
> > +#include <ppc-asm.h>
> > +#include <asm/unistd.h>
> > +
> > +#define LOAD_REG_IMMEDIATE(reg,expr) \
> > + lis reg,(expr)@highest; \
> > + ori reg,reg,(expr)@higher; \
> > + rldicr reg,reg,32,31; \
> > + oris reg,reg,(expr)@high; \
> > + ori reg,reg,(expr)@l;
> > +
> > +/* It is very important to note here that _extra is the extra amount of
> > + * stack space needed.
> > + * This space must be accessed at sp + 32!
>
Hi Naveen,
Thanks for the review.
> This looks to be specific to ABIv2. Is this series limited to ppc64le?
> If so, you might want to ensure this only builds there.
>
Is ABIv1 still in use? Can we still compile for v1?
This is for series 64bit only, I've not really got any reason to believe this
is LE only, shouldn't this work BE? The makefile enforces 64bit, I believe it is
ok for kernel selftests to fail to compile if they aren't going to be able to
run.
> Also:
> #define PPC_ABIV2_MIN_STACK_SIZE 32
>
> or just:
> #define PPC_MIN_STACK 32
>
> ... is helpful. And, you might want to base the rest of your code that
> use PUSH_BASIC_STACK() on that. If we ever want to have these tests run
> anywhere else, that'll help a lot. (See further below)
>
So I thought about it. I agree that it would be nice, I just worry that I might
get rabbitholed, I can see it going further and then providing stack accessors
to abstract out even PPC_MIN_STACK except in a bunch of macros, and that's when
I know I've gone too far.
Perhaps I could look at adding this when I write more tests, I have grand plans
to push way more tests.
> > + */
> > +#define PUSH_BASIC_STACK(_extra) \
> > + mflr r0; \
> > + std r0,16(sp); \
> > + stdu sp,-(_extra + 32)(sp); \
> > + mfcr r0; \
> > + stw r0,8(sp); \
> > + std 2,24(sp);
> ^^
> Better to use r2 here and below.
>
I think the reason I used '2' is that 'r2' isn't actually defined in ppc-asm.h
for userspace, due to conventions, like 'sp', 'toc' has been used. So I could
have used 'toc' but then there was an issue with toc NOT being defined, or
getting undefined in some situations.
> > +
> > +#define POP_BASIC_STACK(_extra) \
> > + ld 2,24(sp); \
> > + lwz r0,8(sp); \
> > + mtcr r0; \
> > + addi sp,sp,(_extra + 32); \
> > + ld r0,16(sp); \
> > + mtlr r0;
> > +
> > diff --git a/tools/testing/selftests/powerpc/math/.gitignore b/tools/testing/selftests/powerpc/math/.gitignore
> > new file mode 100644
> > index 0000000..b19b269
> > --- /dev/null
> > +++ b/tools/testing/selftests/powerpc/math/.gitignore
> > @@ -0,0 +1,2 @@
> > +fpu_syscall
> > +vmx_syscall
> > diff --git a/tools/testing/selftests/powerpc/math/Makefile b/tools/testing/selftests/powerpc/math/Makefile
> > new file mode 100644
> > index 0000000..418bef1
> > --- /dev/null
> > +++ b/tools/testing/selftests/powerpc/math/Makefile
> > @@ -0,0 +1,14 @@
> > +TEST_PROGS := fpu_syscall vmx_syscall
> > +
> > +all: $(TEST_PROGS)
> > +
> > +$(TEST_PROGS): ../harness.c
> > +$(TEST_PROGS): CFLAGS += -O2 -g -pthread -m64 -maltivec
> > +
> > +fpu_syscall: fpu_asm.S
> > +vmx_syscall: vmx_asm.S
> > +
> > +include ../../lib.mk
> > +
> > +clean:
> > + rm -f $(TEST_PROGS) *.o
> > diff --git a/tools/testing/selftests/powerpc/math/fpu_asm.S b/tools/testing/selftests/powerpc/math/fpu_asm.S
> > new file mode 100644
> > index 0000000..8733874
> > --- /dev/null
> > +++ b/tools/testing/selftests/powerpc/math/fpu_asm.S
> > @@ -0,0 +1,161 @@
> > +/*
> > + * Copyright 2015, Cyril Bur, IBM Corp.
> > + *
> > + * This program is free software; you can redistribute it and/or
> > + * modify it under the terms of the GNU General Public License
> > + * as published by the Free Software Foundation; either version
> > + * 2 of the License, or (at your option) any later version.
> > + */
> > +
> > +#include "../basic_asm.h"
> > +
> > +#define PUSH_FPU(pos) \
> > + stfd f14,pos(sp); \
> > + stfd f15,pos+8(sp); \
> > + stfd f16,pos+16(sp); \
> > + stfd f17,pos+24(sp); \
> > + stfd f18,pos+32(sp); \
> > + stfd f19,pos+40(sp); \
> > + stfd f20,pos+48(sp); \
> > + stfd f21,pos+56(sp); \
> > + stfd f22,pos+64(sp); \
> > + stfd f23,pos+72(sp); \
> > + stfd f24,pos+80(sp); \
> > + stfd f25,pos+88(sp); \
> > + stfd f26,pos+96(sp); \
> > + stfd f27,pos+104(sp); \
> > + stfd f28,pos+112(sp); \
> > + stfd f29,pos+120(sp); \
> > + stfd f30,pos+128(sp); \
> > + stfd f31,pos+136(sp);
> > +
> > +#define POP_FPU(pos) \
> > + lfd f14,pos(sp); \
> > + lfd f15,pos+8(sp); \
> > + lfd f16,pos+16(sp); \
> > + lfd f17,pos+24(sp); \
> > + lfd f18,pos+32(sp); \
> > + lfd f19,pos+40(sp); \
> > + lfd f20,pos+48(sp); \
> > + lfd f21,pos+56(sp); \
> > + lfd f22,pos+64(sp); \
> > + lfd f23,pos+72(sp); \
> > + lfd f24,pos+80(sp); \
> > + lfd f25,pos+88(sp); \
> > + lfd f26,pos+96(sp); \
> > + lfd f27,pos+104(sp); \
> > + lfd f28,pos+112(sp); \
> > + lfd f29,pos+120(sp); \
> > + lfd f30,pos+128(sp); \
> > + lfd f31,pos+136(sp);
> > +
> > +#Careful calling this, it will 'clobber' fpu (by design)
> > +#Don't call this from C
> > +FUNC_START(load_fpu)
> > + lfd f14,0(r3)
> > + lfd f15,8(r3)
> > + lfd f16,16(r3)
> > + lfd f17,24(r3)
> > + lfd f18,32(r3)
> > + lfd f19,40(r3)
> > + lfd f20,48(r3)
> > + lfd f21,56(r3)
> > + lfd f22,64(r3)
> > + lfd f23,72(r3)
> > + lfd f24,80(r3)
> > + lfd f25,88(r3)
> > + lfd f26,96(r3)
> > + lfd f27,104(r3)
> > + lfd f28,112(r3)
> > + lfd f29,120(r3)
> > + lfd f30,128(r3)
> > + lfd f31,136(r3)
> > + blr
> > +FUNC_END(load_fpu)
> > +
> > +FUNC_START(check_fpu)
> > + mr r4,r3
> > + li r3,1 #assume a bad result
> > + lfd f0,0(r4)
> > + fcmpu cr1,f0,f14
> > + bne cr1,1f
> > + lfd f0,8(r4)
> > + fcmpu cr1,f0,f15
> > + bne cr1,1f
> > + lfd f0,16(r4)
> > + fcmpu cr1,f0,f16
> > + bne cr1,1f
> > + lfd f0,24(r4)
> > + fcmpu cr1,f0,f17
> > + bne cr1,1f
> > + lfd f0,32(r4)
> > + fcmpu cr1,f0,f18
> > + bne cr1,1f
> > + lfd f0,40(r4)
> > + fcmpu cr1,f0,f19
> > + bne cr1,1f
> > + lfd f0,48(r4)
> > + fcmpu cr1,f0,f20
> > + bne cr1,1f
> > + lfd f0,56(r4)
> > + fcmpu cr1,f0,f21
> > + bne cr1,1f
> > + lfd f0,64(r4)
> > + fcmpu cr1,f0,f22
> > + bne cr1,1f
> > + lfd f0,72(r4)
> > + fcmpu cr1,f0,f23
> > + bne cr1,1f
> > + lfd f0,80(r4)
> > + fcmpu cr1,f0,f24
> > + bne cr1,1f
> > + lfd f0,88(r4)
> > + fcmpu cr1,f0,f25
> > + bne cr1,1f
> > + lfd f0,96(r4)
> > + fcmpu cr1,f0,f26
> > + bne cr1,1f
> > + lfd f0,104(r4)
> > + fcmpu cr1,f0,f27
> > + bne cr1,1f
> > + lfd f0,112(r4)
> > + fcmpu cr1,f0,f28
> > + bne cr1,1f
> > + lfd f0,120(r4)
> > + fcmpu cr1,f0,f29
> > + bne cr1,1f
> > + lfd f0,128(r4)
> > + fcmpu cr1,f0,f30
> > + bne cr1,1f
> > + lfd f0,136(r4)
> > + fcmpu cr1,f0,f31
> > + bne cr1,1f
> > + li r3,0 #Sucess!!!
> > +1: blr
> > +
> > +FUNC_START(test_fpu)
> > + #r3 holds pointer to where to put the result of fork
> > + #r4 holds pointer to the pid
> > + #f14-f31 are non volatiles
> > + PUSH_BASIC_STACK(256)
> > + std r3,40(sp) #Address of darray
>
> So, this could be:
> PUSH_BASIC_STACK(256)
> std r3,PPC_MIN_STACK+8(sp)
>
> ... though I wonder why there is +8 here?
>
I think the +8 is left over from my using +0 for something else and then not
and not going back and being all neat about stack usage. Admittedly I didn't
look over that too hard it being a selftest and all, I'm not sure optimal
stack usage is super important here.
Thanks,
Cyril
>
> - Naveen
>
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