Re: port-hppa/56867: hppa: intermittent SIGSEGV reports in t_ptrace_wait's stepN and setstepN test cases

[Nick Hudson <nick.hudson%gmx.co.uk@localhost>]

On 09/06/2022 06:40, Tom Lane wrote:
> The following reply was made to PR port-hppa/56867; it has been noted by GNATS.
>
> From: Tom Lane <tgl%sss.pgh.pa.us@localhost>
> To: gnats-bugs%netbsd.org@localhost
> Cc:
> Subject: Re: port-hppa/56867: hppa: intermittent SIGSEGV reports in t_ptrace_wait's stepN and setstepN test cases
> Date: Thu, 09 Jun 2022 01:39:23 -0400
>
>   I've managed to resurrect my NetBSD/hppa installation, and resumed
>   investigating this issue.

YAY. :)


>   My theory that there's something wrong with
>   ITLBMISS processing seems to be backwards: after adding some hacky
>   instrumentation, I found that the test passes when an ITLBMISS trap
>   occurs upon trying to execute the modified instruction stream, while
>   it fails when one does not.  That led me to guess that what's missing
>   is a TLB flush operation, and sure enough this quick-hack patch seems
>   to fix it:
>
>   Index: sys/arch/hppa/hppa/pmap.c
>   ===================================================================
>   RCS file: /cvsroot/src/sys/arch/hppa/hppa/pmap.c,v
>   retrieving revision 1.117
>   diff -u -r1.117 pmap.c
>   --- sys/arch/hppa/hppa/pmap.c   26 May 2022 05:34:04 -0000      1.117
>   +++ sys/arch/hppa/hppa/pmap.c   9 Jun 2022 03:36:33 -0000
>   @@ -1874,9 +1874,12 @@
>    pmap_procwr(struct proc *p, vaddr_t va, size_t len)
>    {
>           pmap_t pmap = p->p_vmspace->vm_map.pmap;
>   +       pa_space_t sp = pmap->pm_space;
>
>   -       fdcache(pmap->pm_space, va, len);
>   -       ficache(pmap->pm_space, va, len);
>   +       fdcache(sp, va, len);
>   +       ficache(sp, va, len);
>   +       pdtlb(sp, va);
>   +       pitlb(sp, va);
>    }

I dont this is right. The process mappings aren't changing. Will think
about it some more.

Thanks for poking at all of this.

Nick