Re: [kvm-unit-tests PATCH v2 3/3] s390x/spec_ex: Add test of EXECUTE with odd target address

[Nina Schoetterl-Glausch <nsg@linux.ibm.com>]

On Tue, 2023-03-14 at 16:25 +0100, Claudio Imbrenda wrote:
> On Tue, 21 Feb 2023 18:48:22 +0100
> Nina Schoetterl-Glausch <nsg@linux.ibm.com> wrote:
> 
> > The EXECUTE instruction executes the instruction at the given target
> > address. This address must be halfword aligned, otherwise a
> > specification exception occurs.
> > Add a test for this.
> > 
> > Signed-off-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
> > ---
> >  s390x/spec_ex.c | 25 +++++++++++++++++++++++++
> >  1 file changed, 25 insertions(+)
> > 
> > diff --git a/s390x/spec_ex.c b/s390x/spec_ex.c
> > index a26c56aa..dd097f9b 100644
> > --- a/s390x/spec_ex.c
> > +++ b/s390x/spec_ex.c
> > @@ -177,6 +177,30 @@ static int short_psw_bit_12_is_0(void)
> >  	return 0;
> >  }
> >  
> > +static int odd_ex_target(void)
> > +{
> > +	uint64_t pre_target_addr;
> > +	int to = 0, from = 0x0dd;
> > +
> > +	asm volatile ( ".pushsection .rodata\n"
> 
> and this should go in a .text.something subsection, as we discussed
> offline

Yes.
> 
> > +		"pre_odd_ex_target:\n"
> 
> shouldn't the label be after the align?

No, larl needs an aligned address, and the ex below adds 1.
That's why it has the pre_ prefix, it's not the ex target itself.
> 
> > +		"	.balign	2\n"
> 
> (i.e. here)
> 
> > +		"	. = . + 1\n"
> > +		"	lr	%[to],%[from]\n"
> > +		"	.popsection\n"
> > +
> > +		"	larl	%[pre_target_addr],pre_odd_ex_target\n"
> > +		"	ex	0,1(%[pre_target_addr])\n"
> > +		: [pre_target_addr] "=&a" (pre_target_addr),
> > +		  [to] "+d" (to)
> > +		: [from] "d" (from)
> > +	);
> > +
> > +	assert((pre_target_addr + 1) & 1);
> > +	report(to != from, "did not perform ex with odd target");
> > +	return 0;
> > +}
> > +
> >  static int bad_alignment(void)
> >  {
> >  	uint32_t words[5] __attribute__((aligned(16)));
> > @@ -218,6 +242,7 @@ static const struct spec_ex_trigger spec_ex_triggers[] = {
> >  	{ "psw_bit_12_is_1", &psw_bit_12_is_1, false, &fixup_invalid_psw },
> >  	{ "short_psw_bit_12_is_0", &short_psw_bit_12_is_0, false, &fixup_invalid_psw },
> >  	{ "psw_odd_address", &psw_odd_address, false, &fixup_invalid_psw },
> > +	{ "odd_ex_target", &odd_ex_target, true, NULL },
> >  	{ "bad_alignment", &bad_alignment, true, NULL },
> >  	{ "not_even", &not_even, true, NULL },
> >  	{ NULL, NULL, false, NULL },
>