9fans - fans of the OS Plan 9 from Bell Labs
 help / color / mirror / Atom feed
From: adventures in9 <adventuresin9@gmail.com>
To: 9fans <9fans@9fans.net>
Subject: Re: [9fans] spim syscall stack adjustment
Date: Fri, 27 Jan 2023 13:10:32 -0800	[thread overview]
Message-ID: <CAPfmpJB0jLgyAc6L6vNC32-Uh1LCfxOe1eCKRW9tr0ORsK32wg@mail.gmail.com> (raw)
In-Reply-To: <Y9M7BfRX0zuSxw01@alice>

I could try and build a spim world without the ADD in syscall to see
what happens.  It might be a week or 2 before I can find the time.

As for why it does it.  I never really looked into it.  I figured it
was just another endian issue.  I had enough bugs that when I got past
that one I just moved on to the next.  But I do need to set up a fresh
9 Front install to go through and get patches for all the mips and
spim stuff.

I also have a big-endian Atheros/Qualcomm chip that I need to get
around to building a kernel for, and then there will be a close to 1
to 1 chip to compare mips and spim stuff.

On Thu, Jan 26, 2023 at 6:47 PM Anthony Martin <ality@pbrane.org> wrote:
> Does anyone know why the libc system call functions for
> spim add four to the stack pointer (R29) before issuing
> the SYSCALL instruction?
> /sys/src/libc/9syscall/mkfile:/spim
> It was introduced in the third edition but there were
> never any spim kernels released so I wasn't able to
> compare the libc additions to the trap code.
> I was watching one of adventuresin9's videos about his
> ongoing port to the MediaTek MT7688 and he mentioned
> having to modify the stack offsets in the syscall trap
> handler just as cherry9 had done for the loongson port.
> Is there any reason not to simply get rid of that ADD $4?
> Cheers,
>   Anthony

9fans: 9fans
Permalink: https://9fans.topicbox.com/groups/9fans/T589fa55313abbdb4-M3df698a73959945f954ae172
Delivery options: https://9fans.topicbox.com/groups/9fans/subscription

      reply	other threads:[~2023-01-27 21:11 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-27  2:46 Anthony Martin
2023-01-27 21:10 ` adventures in9 [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=CAPfmpJB0jLgyAc6L6vNC32-Uh1LCfxOe1eCKRW9tr0ORsK32wg@mail.gmail.com \
    --to=adventuresin9@gmail.com \
    --cc=9fans@9fans.net \


* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).