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Commit f4619025 authored by Russell King's avatar Russell King Committed by Russell King
Browse files

[ARM] Allow r2 to be passed through the decompressor to the kernel 



This is part of a patch from Marc Singer to allow r2 to be
passed to the kernel.  Marc's original comments follow:

This revised R2 (atags pointer) patch incorporates comments from Nico
Pitre and Ben Dooks. It modifies the head.S files such that the R2
value set by the bootloader is conveyed to the kernel startup code.
The kernel head.S heuristically validates the pointer. It will set R2
to zero if it believes the pointer is invalid. Presently, it requires
that the ATAGS list reside in the first 16KiB of physical RAM.
Relaxing this contraint may be both desirable as well as tricky.

Signed-off-by: default avatarMarc Singer <elf@buici.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 90303b10

arch/arm/boot/compressed/head.S

+25 −21
Original line number Diff line number Diff line
@@ -84,7 +84,7 @@ 
		kputc	#'\n'

		kphex	r5, 8		/* decompressed kernel start */

		kputc	#'-'

		kphex	r8, 8		/* decompressed kernel end  */

		kphex	r9, 8		/* decompressed kernel end  */

		kputc	#'>'

		kphex	r4, 8		/* kernel execution address */

		kputc	#'\n'
@@ -116,7 +116,7 @@ start: 
		.word	start			@ absolute load/run zImage address

		.word	_edata			@ zImage end address

1:		mov	r7, r1			@ save architecture ID

		mov	r8, #0			@ save r0

		mov	r8, r2			@ save atags pointer



#ifndef __ARM_ARCH_2__

		/*
@@ -144,7 +144,7 @@ not_angel: 


		/*

		 * some architecture specific code can be inserted

		 * by the linker here, but it should preserve r7 and r8.

		 * by the linker here, but it should preserve r7, r8, and r9.

		 */



		.text
@@ -249,16 +249,17 @@ not_relocated: mov r0, #0 
 * r5     = decompressed kernel start

 * r6     = processor ID

 * r7     = architecture ID

 * r8-r14 = unused

 * r8     = atags pointer

 * r9-r14 = corrupted

 */

		add	r1, r5, r0		@ end of decompressed kernel

		adr	r2, reloc_start

		ldr	r3, LC1

		add	r3, r2, r3

1:		ldmia	r2!, {r8 - r13}		@ copy relocation code

		stmia	r1!, {r8 - r13}

		ldmia	r2!, {r8 - r13}

		stmia	r1!, {r8 - r13}

1:		ldmia	r2!, {r9 - r14}		@ copy relocation code

		stmia	r1!, {r9 - r14}

		ldmia	r2!, {r9 - r14}

		stmia	r1!, {r9 - r14}

		cmp	r2, r3

		blo	1b
@@ -308,11 +309,12 @@ params: ldr r0, =params_phys 
 *  r4 = kernel execution address

 *  r6 = processor ID

 *  r7 = architecture number

 *  r8 = run-time address of "start"

 *  r8 = atags pointer

 *  r9 = run-time address of "start"  (???)

 * On exit,

 *  r1, r2, r3, r8, r9, r12 corrupted

 *  r1, r2, r3, r9, r10, r12 corrupted

 * This routine must preserve:

 *  r4, r5, r6, r7

 *  r4, r5, r6, r7, r8

 */

		.align	5

cache_on:	mov	r3, #8			@ cache_on function
@@ -326,15 +328,15 @@ __setup_mmu: sub r3, r4, #16384 @ Page directory size 
 * bits for the RAM area only.

 */

		mov	r0, r3

		mov	r8, r0, lsr #18

		mov	r8, r8, lsl #18		@ start of RAM

		add	r9, r8, #0x10000000	@ a reasonable RAM size

		mov	r9, r0, lsr #18

		mov	r9, r9, lsl #18		@ start of RAM

		add	r10, r9, #0x10000000	@ a reasonable RAM size

		mov	r1, #0x12

		orr	r1, r1, #3 << 10

		add	r2, r3, #16384

1:		cmp	r1, r8			@ if virt > start of RAM

		orrhs	r1, r1, #0x0c		@ set cacheable, bufferable

		cmp	r1, r9			@ if virt > end of RAM

		cmp	r1, r10			@ if virt > end of RAM

		bichs	r1, r1, #0x0c		@ clear cacheable, bufferable

		str	r1, [r0], #4		@ 1:1 mapping

		add	r1, r1, #1048576
@@ -403,26 +405,28 @@ __common_cache_on: 
 * r5     = decompressed kernel start

 * r6     = processor ID

 * r7     = architecture ID

 * r8-r14 = unused

 * r8     = atags pointer

 * r9-r14 = corrupted

 */

		.align	5

reloc_start:	add	r8, r5, r0

reloc_start:	add	r9, r5, r0

		debug_reloc_start

		mov	r1, r4

1:

		.rept	4

		ldmia	r5!, {r0, r2, r3, r9 - r13}	@ relocate kernel

		stmia	r1!, {r0, r2, r3, r9 - r13}

		ldmia	r5!, {r0, r2, r3, r10 - r14}	@ relocate kernel

		stmia	r1!, {r0, r2, r3, r10 - r14}

		.endr



		cmp	r5, r8

		cmp	r5, r9

		blo	1b

		debug_reloc_end



call_kernel:	bl	cache_clean_flush

		bl	cache_off

		mov	r0, #0

		mov	r0, #0			@ must be zero

		mov	r1, r7			@ restore architecture number

		mov	r2, r8			@ restore atags pointer

		mov	pc, r4			@ call kernel



/*