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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

  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

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