[PATCH 1/2] ARM: improvements to compressed/head.S
Nicolas Pitre
nico at fluxnic.net
Wed Feb 16 16:39:02 EST 2011
In the case of a conflict between the memory used by the compressed
kernel with its decompressor code and the memory used for the
decompressed kernel, we currently store the later after the former and
relocate it afterwards.
This would be more efficient to do this the other way around i.e.
relocate the compressed data up front instead, resulting in a smaller
copy. That also has the advantage of making the code smaller and more
straight forward.
Signed-off-by: Nicolas Pitre <nicolas.pitre at linaro.org>
---
arch/arm/boot/compressed/head.S | 239 ++++++++++++++++++---------------------
1 files changed, 110 insertions(+), 129 deletions(-)
diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index 7193884..200625c 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -174,9 +174,7 @@ not_angel:
*/
.text
- adr r0, LC0
- ldmia r0, {r1, r2, r3, r5, r6, r11, ip}
- ldr sp, [r0, #28]
+
#ifdef CONFIG_AUTO_ZRELADDR
@ determine final kernel image address
mov r4, pc
@@ -185,35 +183,108 @@ not_angel:
#else
ldr r4, =zreladdr
#endif
- subs r0, r0, r1 @ calculate the delta offset
- @ if delta is zero, we are
- beq not_relocated @ running at the address we
- @ were linked at.
+ bl cache_on
+
+restart: adr r0, LC0
+ ldmia r0, {r1, r2, r3, r5, r6, r9, r11, r12}
+ ldr sp, [r0, #32]
+
+ /*
+ * We might be running at a different address. We need
+ * to fix up various pointers.
+ */
+ sub r0, r0, r1 @ calculate the delta offset
+ add r5, r5, r0 @ _start
+ add r6, r6, r0 @ _edata
+#ifndef CONFIG_ZBOOT_ROM
+ /* malloc space is above the relocated stack (64k max) */
+ add sp, sp, r0
+ add r10, sp, #0x10000
+#else
/*
- * We're running at a different address. We need to fix
- * up various pointers:
- * r5 - zImage base address (_start)
- * r6 - size of decompressed image
- * r11 - GOT start
- * ip - GOT end
+ * With ZBOOT_ROM the bss/stack is non relocatable,
+ * but someone could still run this code from RAM,
+ * in which case our reference is _edata.
*/
- add r5, r5, r0
+ mov r10, r6
+#endif
+
+/*
+ * Check to see if we will overwrite ourselves.
+ * r4 = final kernel address
+ * r5 = start of this image
+ * r9 = size of decompressed image
+ * r10 = end of this image, including bss/stack/malloc space if non XIP
+ * We basically want:
+ * r4 >= r10 -> OK
+ * r4 + image length <= r5 -> OK
+ */
+ cmp r4, r10
+ bhs wont_overwrite
+ add r10, r4, r9
+ cmp r10, r5
+ bls wont_overwrite
+
+/*
+ * Relocate ourselves past the end of the decompressed kernel.
+ * r5 = start of this image
+ * r6 = _edata
+ * r10 = end of the decompressed kernel
+ * Because we always copy ahead, we need to do it from the end and go
+ * backward in case the source and destination overlap.
+ */
+ /* Round up to next 256-byte boundary. */
+ add r10, r10, #256
+ bic r10, r10, #255
+
+ sub r9, r6, r5 @ size to copy
+ add r9, r9, #31 @ rounded up to a multiple
+ bic r9, r9, #31 @ ... of 32 bytes
+ add r6, r9, r5
+ add r9, r9, r10
+
+1: ldmdb r6!, {r0 - r3, r10 - r12, lr}
+ cmp r6, r5
+ stmdb r9!, {r0 - r3, r10 - r12, lr}
+ bhi 1b
+
+ /* Preserve offset to relocated code. */
+ sub r6, r9, r6
+
+ bl cache_clean_flush
+
+ adr r0, BSYM(restart)
+ add r0, r0, r6
+ mov pc, r0
+
+wont_overwrite:
+/*
+ * If delta is zero, we are running at the address we were linked at.
+ * r0 = delta
+ * r2 = BSS start
+ * r3 = BSS end
+ * r4 = kernel execution address
+ * r7 = architecture ID
+ * r8 = atags pointer
+ * r11 = GOT start
+ * r12 = GOT end
+ * sp = stack pointer
+ */
+ teq r0, #0
+ beq not_relocated
add r11, r11, r0
- add ip, ip, r0
+ add r12, r12, r0
#ifndef CONFIG_ZBOOT_ROM
/*
* If we're running fully PIC === CONFIG_ZBOOT_ROM = n,
* we need to fix up pointers into the BSS region.
- * r2 - BSS start
- * r3 - BSS end
- * sp - stack pointer
+ * Note that the stack pointer has already been fixed up.
*/
add r2, r2, r0
add r3, r3, r0
- add sp, sp, r0
/*
* Relocate all entries in the GOT table.
@@ -221,7 +292,7 @@ not_angel:
1: ldr r1, [r11, #0] @ relocate entries in the GOT
add r1, r1, r0 @ table. This fixes up the
str r1, [r11], #4 @ C references.
- cmp r11, ip
+ cmp r11, r12
blo 1b
#else
@@ -234,7 +305,7 @@ not_angel:
cmphs r3, r1 @ _end < entry
addlo r1, r1, r0 @ table. This fixes up the
str r1, [r11], #4 @ C references.
- cmp r11, ip
+ cmp r11, r12
blo 1b
#endif
@@ -246,76 +317,24 @@ not_relocated: mov r0, #0
cmp r2, r3
blo 1b
- /*
- * The C runtime environment should now be setup
- * sufficiently. Turn the cache on, set up some
- * pointers, and start decompressing.
- */
- bl cache_on
-
- mov r1, sp @ malloc space above stack
- add r2, sp, #0x10000 @ 64k max
-
/*
- * Check to see if we will overwrite ourselves.
- * r4 = final kernel address
- * r5 = start of this image
- * r6 = size of decompressed image
- * r2 = end of malloc space (and therefore this image)
- * We basically want:
- * r4 >= r2 -> OK
- * r4 + image length <= r5 -> OK
+ * The C runtime environment should now be setup sufficiently.
+ * Set up some pointers, and start decompressing.
+ * r4 = kernel execution address
+ * r7 = architecture ID
+ * r8 = atags pointer
*/
- cmp r4, r2
- bhs wont_overwrite
- add r0, r4, r6
- cmp r0, r5
- bls wont_overwrite
-
- mov r5, r2 @ decompress after malloc space
- mov r0, r5
+ mov r0, r4
+ mov r1, sp @ malloc space above stack
+ add r2, sp, #0x10000 @ 64k max
mov r3, r7
bl decompress_kernel
-
- add r0, r0, #127 + 128 @ alignment + stack
- bic r0, r0, #127 @ align the kernel length
-/*
- * r0 = decompressed kernel length
- * r1-r3 = unused
- * r4 = kernel execution address
- * r5 = decompressed kernel start
- * r7 = architecture ID
- * r8 = atags pointer
- * r9-r12,r14 = corrupted
- */
- add r1, r5, r0 @ end of decompressed kernel
- adr r2, reloc_start
- ldr r3, LC1
- add r3, r2, r3
-1: ldmia r2!, {r9 - r12, r14} @ copy relocation code
- stmia r1!, {r9 - r12, r14}
- ldmia r2!, {r9 - r12, r14}
- stmia r1!, {r9 - r12, r14}
- cmp r2, r3
- blo 1b
- mov sp, r1
- add sp, sp, #128 @ relocate the stack
-
bl cache_clean_flush
- ARM( add pc, r5, r0 ) @ call relocation code
- THUMB( add r12, r5, r0 )
- THUMB( mov pc, r12 ) @ call relocation code
-
-/*
- * We're not in danger of overwriting ourselves. Do this the simple way.
- *
- * r4 = kernel execution address
- * r7 = architecture ID
- */
-wont_overwrite: mov r0, r4
- mov r3, r7
- bl decompress_kernel
- b call_kernel
+ bl cache_off
+ mov r0, #0 @ must be zero
+ mov r1, r7 @ restore architecture number
+ mov r2, r8 @ restore atags pointer
+ mov pc, r4 @ call kernel
.align 2
.type LC0, #object
@@ -323,11 +342,11 @@ LC0: .word LC0 @ r1
.word __bss_start @ r2
.word _end @ r3
.word _start @ r5
- .word _image_size @ r6
+ .word _edata @ r6
+ .word _image_size @ r9
.word _got_start @ r11
.word _got_end @ ip
.word user_stack_end @ sp
-LC1: .word reloc_end - reloc_start
.size LC0, . - LC0
#ifdef CONFIG_ARCH_RPC
@@ -353,7 +372,7 @@ params: ldr r0, =0x10000100 @ params_phys for RPC
* On exit,
* r0, r1, r2, r3, r9, r10, r12 corrupted
* This routine must preserve:
- * r4, r5, r6, r7, r8
+ * r4, r7, r8
*/
.align 5
cache_on: mov r3, #8 @ cache_on function
@@ -551,43 +570,6 @@ __common_mmu_cache_on:
#endif
/*
- * All code following this line is relocatable. It is relocated by
- * the above code to the end of the decompressed kernel image and
- * executed there. During this time, we have no stacks.
- *
- * r0 = decompressed kernel length
- * r1-r3 = unused
- * r4 = kernel execution address
- * r5 = decompressed kernel start
- * r7 = architecture ID
- * r8 = atags pointer
- * r9-r12,r14 = corrupted
- */
- .align 5
-reloc_start: add r9, r5, r0
- sub r9, r9, #128 @ do not copy the stack
- debug_reloc_start
- mov r1, r4
-1:
- .rept 4
- ldmia r5!, {r0, r2, r3, r10 - r12, r14} @ relocate kernel
- stmia r1!, {r0, r2, r3, r10 - r12, r14}
- .endr
-
- cmp r5, r9
- blo 1b
- mov sp, r1
- add sp, sp, #128 @ relocate the stack
- debug_reloc_end
-
-call_kernel: bl cache_clean_flush
- bl cache_off
- mov r0, #0 @ must be zero
- mov r1, r7 @ restore architecture number
- mov r2, r8 @ restore atags pointer
- mov pc, r4 @ call kernel
-
-/*
* Here follow the relocatable cache support functions for the
* various processors. This is a generic hook for locating an
* entry and jumping to an instruction at the specified offset
@@ -791,7 +773,7 @@ proc_types:
* On exit,
* r0, r1, r2, r3, r9, r12 corrupted
* This routine must preserve:
- * r4, r6, r7
+ * r4, r7, r8
*/
.align 5
cache_off: mov r3, #12 @ cache_off function
@@ -866,7 +848,7 @@ __armv3_mmu_cache_off:
* On exit,
* r1, r2, r3, r9, r10, r11, r12 corrupted
* This routine must preserve:
- * r0, r4, r5, r6, r7
+ * r4, r6, r7, r8
*/
.align 5
cache_clean_flush:
@@ -1088,7 +1070,6 @@ memdump: mov r12, r0
#endif
.ltorg
-reloc_end:
.align
.section ".stack", "aw", %nobits
--
1.7.4
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