From: David Gibson <david@gibson.dropbear.id.au>
To: Milton Miller <miltonm@bga.com>
Cc: linuxppc-dev@ozlabs.org, Paul Mackerras <paulus@samba.org>,
Rob Landley <rob@landley.net>
Subject: Re: [PATCH 6/15] bootwrapper: help for 64 bit cpus
Date: Mon, 24 Sep 2007 13:14:51 +1000 [thread overview]
Message-ID: <20070924031451.GG8058@localhost.localdomain> (raw)
In-Reply-To: <boot-8-06.miltonm@bga.com>
On Fri, Sep 21, 2007 at 06:04:37PM -0500, Milton Miller wrote:
> Add code to check if the processor is in 64 or 32 bit mode using
> only instructions from the 32 bit subset. If the processor is in
> 64 bit mode, switch to 32 bit mode by clearing MSR[SF].
>
> Also add a 64 bit procedure descriptor to use as a elf64 entry
> point.
>
> Signed-off-by: Milton Miller <miltonm@bga.com>
> ---
> vs 12173
> correct comment (equal vs not-equal)
>
> Index: kernel/arch/powerpc/boot/crt0.S
> ===================================================================
> --- kernel.orig/arch/powerpc/boot/crt0.S 2007-07-10 03:33:36.000000000 -0500
> +++ kernel/arch/powerpc/boot/crt0.S 2007-07-10 03:39:08.000000000 -0500
> @@ -17,11 +17,47 @@
> _zimage_start_opd:
> .long _zimage_start, 0, 0, 0
>
> + /* a procedure descriptor used when pretending to be elf64_powerpc */
> + .balign 8
> + .globl _zimage_start_64
> +_zimage_start_64:
Hrm, I'd prefer _zimage_start_opd64 in analogy with the COFF opd entry
above.
> + .long 0, _zimage_start /* big endian, supported reloc ppc32 */
> + .long 0, 0, 0, 0, 0, 0
> +
> +
> .weak _zimage_start
> .globl _zimage_start
> _zimage_start:
> .globl _zimage_start_lib
> _zimage_start_lib:
> + /* Check if the processor is running in 32 bit mode, using
> + * only 32 bit instructions which should be safe on 32 and
> + * 64 bit processors.
> + *
> + * Subtract bottom 32 bits of MSR from full value recording
> + * the result. Since MSR[SF] is in the high word, we will
> + * be equal iff in 32 bit mode (either the processor is
> + * a 32 bit processor or MSR[SF] = 0).
> + */
> + mfmsr r0 /* grab whole msr */
> + rlwinm r8,r0,0,0,31 /* extract bottom word */
> + subf. r8,r8,r0 /* subtract, same? */
> + beq 0f /* yes: we are 32 bit mode */
> +
> + /* We are in 64-bit mode. This program must run in 32 bit
> + * mode. Assume we are actually running somewhere in the
> + * low 32 bits of the address space, so we can just turn
> + * off MSR[SF] which is bit 0.
> + */
> + .machine push
> + .machine "ppc64"
> + rldicl r0,r0,0,1
> + sync
> + mtmsrd r0
> + isync
> + .machine pop
> +0: /* We are now in 32-bit mode */
> +
> /* Work out the offset between the address we were linked at
> and the address where we're running. */
> bl 1f
> _______________________________________________
> Linuxppc-dev mailing list
> Linuxppc-dev@ozlabs.org
> https://ozlabs.org/mailman/listinfo/linuxppc-dev
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
next prev parent reply other threads:[~2007-09-24 3:14 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-09-21 23:02 [PATCH 0/15] bootwrapper: kexec and external payloads Milton Miller
2007-09-21 23:03 ` [PATCH 1/15] boot: find initrd location from device-tree Milton Miller
2007-09-24 2:58 ` David Gibson
2007-09-24 5:50 ` Rob Landley
2007-09-24 8:02 ` Milton Miller
2007-09-25 3:27 ` David Gibson
2007-09-26 5:49 ` Milton Miller
2007-09-21 23:03 ` [PATCH 2/15] boot: record header bytes in gunzip_start Milton Miller
2007-09-24 2:59 ` David Gibson
2007-09-21 23:03 ` [PATCH 3/15] boot: simplfy gunzip_finish Milton Miller
2007-09-21 23:03 ` [PATCH 4/15] bootwrapper: smp support code Milton Miller
2007-09-21 23:04 ` [PATCH 5/15] bootwrapper: occuppied memory ranges Milton Miller
2007-09-24 3:09 ` David Gibson
2007-09-24 9:33 ` Milton Miller
2007-09-21 23:04 ` [PATCH 6/15] bootwrapper: help for 64 bit cpus Milton Miller
2007-09-24 3:14 ` David Gibson [this message]
2007-09-21 23:04 ` [PATCH 7/15] bootwrapper: Add kexec callable zImage wrapper Milton Miller
2007-09-24 3:23 ` David Gibson
2007-09-21 23:05 ` [PATCH 8/15] bootwrapper: convert flatdevtree to version 16 Milton Miller
2007-09-24 3:36 ` David Gibson
2007-09-24 6:54 ` Milton Miller
2007-09-25 3:46 ` David Gibson
2007-09-26 16:19 ` Milton Miller
2007-09-27 2:45 ` David Gibson
2007-09-27 15:44 ` Milton Miller
2007-09-28 2:40 ` David Gibson
2007-09-28 15:16 ` Milton Miller
2007-10-03 5:29 ` David Gibson
2007-09-21 23:05 ` [PATCH 9/15] bootwrapper: rtas support Milton Miller
2007-09-24 3:46 ` David Gibson
2007-09-21 23:05 ` [PATCH 10/15] bootwrapper: add cpio file extraction library Milton Miller
2007-09-21 23:06 ` [PATCH 11/15] bootwrapper: allow vmlinuz to be an external payload Milton Miller
2007-09-21 23:06 ` [PATCH 12/15] bootwrapper: kexec extract vmlinux from initramfs Milton Miller
2007-09-21 23:06 ` [PATCH 13/15] bootwrapper: attach an empty vmlinux Milton Miller
2007-09-24 4:03 ` David Gibson
2007-09-21 23:08 ` [PATCH 14/15] boot: add a hook to start cpus Milton Miller
2007-09-21 23:08 ` [PATCH 15/15] bootwrapper: recheck for command line after fixups Milton Miller
2007-09-21 23:08 ` [PATCH 1/2] qemu platform, v2 Milton Miller
2007-09-22 9:55 ` Christoph Hellwig
2007-09-22 19:16 ` Rob Landley
2007-09-23 4:27 ` Paul Mackerras
2007-09-23 22:01 ` Rob Landley
2007-09-28 16:53 ` Segher Boessenkool
2007-09-28 20:14 ` Rob Landley
2007-10-01 5:33 ` David Gibson
2007-10-17 20:28 ` Grant Likely
2007-10-17 23:09 ` Rob Landley
2007-10-18 9:59 ` Matt Sealey
2007-10-18 17:19 ` Milton Miller
2007-10-18 17:29 ` Grant Likely
2007-10-19 6:28 ` Rob Landley
2007-09-24 4:00 ` David Gibson
2007-09-24 7:46 ` Christoph Hellwig
2007-09-24 9:48 ` Milton Miller
2007-09-21 23:08 ` [PATCH 2/2] qemu platform rom, v2 Milton Miller
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:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20070924031451.GG8058@localhost.localdomain \
--to=david@gibson.dropbear.id.au \
--cc=linuxppc-dev@ozlabs.org \
--cc=miltonm@bga.com \
--cc=paulus@samba.org \
--cc=rob@landley.net \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* 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).