On Tue, 2016-02-16 at 11:06 +1100, Cyril Bur wrote: > On Mon, 15 Feb 2016 22:29:17 +0530 > "Naveen N. Rao" <naveen.n....@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 > > > > > > 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? YES! >:E > 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. You definitely need a #define for the minimum stack frame size, based on the ABI version. You can basically do what the kernel does for STACK_FRAME_MIN_SIZE. You also need to cope with the TOC save slot moving between ABIv1 & 2, which shouldn't be hard with a macro for it. > > > + */ > > > +#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. That's true, ppc-asm.h doesn't define r2, instead it defines toc. But you can always use %r2, which is preferable to 2 IMHO. Personally I'd rather you use %r1 than sp, but I won't make you. As someone who has read lots of powerpc assembler %r1 translates as "stack pointer" where as "sp" translates as "huh?". > > > +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. The first free slot is at PPC_MIN_STACK(%r1), so that's what you should use. cheers _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
