[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: Marc Singer <elf@buici.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index 6abafb6..aaa4740 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -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 @@
.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 @@
/*
* 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 @@
* 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 @@
* 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 @@
* 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 @@
* 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
/*
