Re: [PATCH] pc-bios/s390x: Pack ResetInfo struct

[Jason J. Herne]

On 8/27/20 6:07 AM, Thomas Huth wrote:
> On 07/02/2020 15.02, Jason J. Herne wrote:
> > On 2/7/20 6:28 AM, Christian Borntraeger wrote:
> > > Jason,
> > >
> > > can you run objdump -Sdr on jump2ipl.o on a broken variant?
> > To keep the volume lower, I've only pasted the output that I think
> > you're interested in. If you want to see the entire thing just let me know.
> >
> > static void jump_to_IPL_2(void)
> > {
> >   1d0:    eb bf f0 58 00 24     stmg    %r11,%r15,88(%r15)
> >   1d6:    a7 fb ff 50           aghi    %r15,-176
> >   1da:    b9 04 00 bf           lgr    %r11,%r15
> >      ResetInfo *current = 0;
> >   1de:    a7 19 00 00           lghi    %r1,0
> >   1e2:    e3 10 b0 a8 00 24     stg    %r1,168(%r11)
> >
> >      void (*ipl)(void) = (void *) (uint64_t) current->ipl_continue;
> >   1e8:    e3 10 b0 a8 00 04     lg    %r1,168(%r11)
> >   1ee:    58 10 10 08           l    %r1,8(%r1)
> >   1f2:    b9 16 00 11           llgfr    %r1,%r1
> >   1f6:    e3 10 b0 a0 00 24     stg    %r1,160(%r11)
> >      *current = save;
> >   1fc:    e3 10 b0 a8 00 04     lg    %r1,168(%r11)
> >   202:    c0 20 00 00 00 00     larl    %r2,202 <jump_to_IPL_2+0x32>
> >              204: R_390_PC32DBL    .bss+0x2
> >   208:    eb 23 20 00 00 04     lmg    %r2,%r3,0(%r2)
> >   20e:    eb 23 10 00 00 24     stmg    %r2,%r3,0(%r1)
> >      ipl(); /* should not return */
> >   214:    e3 10 b0 a0 00 04     lg    %r1,160(%r11)
> >   21a:    0d e1                 basr    %r14,%r1
> > }
> >   21c:    18 00                 lr    %r0,%r0
> >   21e:    eb bf b1 08 00 04     lmg    %r11,%r15,264(%r11)
> >   224:    07 fe                 br    %r14
> >   226:    07 07                 nopr    %r7
>
> I'm currently looking through the past s390-ccw bios patches that still
> might need attention ... was there ever a follow up on this discussion?
> Do we need to clear the registers before jumping to the OS?
> And looking at the disassembly, should we declar the ipl function
> pointer with __attribute__((noreturn)) ?

Janosch has done some cleanup work that has not hit master yet. This work, if accepted, 
would fix this problem and eliminate the need for this patch. So I think we should wait to 
see how that plays out before we revisit this.

--
-- Jason J. Herne (jjherne@linux.ibm.com)