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arm-uboot: Make self-relocatable to allow loading at any address

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This commit is contained in:
Vladimir Serbinenko 2016-02-19 00:43:36 +01:00
parent 5bcb7d394c
commit 86ef66d977
7 changed files with 305 additions and 87 deletions
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60
grub-core/kern/arm/uboot/startup.S
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@ -55,10 +55,6 @@ FUNCTION(_start)
VARIABLE(grub_total_module_size)
.long 0
VARIABLE(grub_uboot_machine_type)
.long 0
VARIABLE(grub_uboot_boot_data)
.long 0
VARIABLE(grub_modbase)
.long 0
bss_start_ptr:
@ -66,29 +62,66 @@ bss_start_ptr:
end_ptr:
.long EXT_C(_end)
@ Memory map at start:
@ * text+data
@ * list relocations
@ * modules
@ Before we enter C, we need to apply the relocations
@ and get following map:
@ * text+data
@ * BSS (cleared)
@ * stack
@ * modules
@
@ To make things easier we ensure
@ that BSS+stack is larger than list of relocations
@ by increasing stack if necessarry.
@ This allows us to always unconditionally copy backwards
@ Currently list of relocations is ~5K and stack is set
@ to be at least 256K
FUNCTION(codestart)
@ Store context: Machine ID, atags/dtb, ...
@ U-Boot API signature is stored on the U-Boot heap
@ Stack pointer used as start address for signature probing
mov r12, sp
adr sp, entry_state
push {r4-r12,lr} @ store U-Boot context (sp in r12)
push {r1-r12,lr} @ store U-Boot context (sp in r12)
str r1, EXT_C(grub_uboot_machine_type)
str r2, EXT_C(grub_uboot_boot_data)
@ Modules have been stored as a blob in BSS,
@ they need to be manually relocated to _end
adr r1, _start
ldr r0, bss_start_ptr @ src
add r0, r0, r1
add r0, r0, #(GRUB_KERNEL_MACHINE_MOD_ALIGN - 1)
mvn r2, #(GRUB_KERNEL_MACHINE_MOD_ALIGN - 1)
and r0, r0, r2
1:
ldr r3, [r0], #4 @load next offset
@ both -2 and -1 are treated the same as we have only one type of relocs
@ -2 means "end of this type of relocs" and -1 means "end of all relocs"
add r2, r3, #2
cmp r2, #1
bls reloc_done
@ Adjust next offset
ldr r2, [r3, r1]
add r2, r2, r1
str r2, [r3, r1]
b 1b
reloc_done:
@ Modules have been stored as a blob
@ they need to be manually relocated to _end
add r0, r0, #(GRUB_KERNEL_MACHINE_MOD_ALIGN - 1)
mvn r1, #(GRUB_KERNEL_MACHINE_MOD_ALIGN - 1)
and r0, r0, r1
and r0, r0, r1 @ src = aligned end of relocations
ldr r1, end_ptr @ dst = End of BSS
ldr r2, grub_total_module_size @ blob size
add r1, r1, #GRUB_KERNEL_MACHINE_STACK_SIZE
and r1, r1, #~0x7 @ Ensure 8-byte alignment
sub sp, r1, #8
add r1, r1, #1024
@ -157,6 +190,11 @@ FUNCTION(grub_uboot_return)
.align 3
@ U-boot context stack space
entry_state_end:
VARIABLE(grub_uboot_machine_type)
.long 0 @ r1
VARIABLE(grub_uboot_boot_data)
.long 0 @ r2
.long 0 @ r3
.long 0 @ r4
.long 0 @ r5
.long 0 @ r6