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aarch64: make the microkit loader relocatable
This allows a microkit image to be loaded anywhere in memory at which point it will relocate itself to the LOADER_LINK_ADDRESS. These changes are based on the elfloader from seL4/seL4_tools. Changes include: * crt0.s was changed to crt0.S and compiled with gcc to pass in LINK_ADDRESS * memmove and memcpy implementations were added * loader_data was changed to include a size field. This is the size of loader_data, the list of regions, and the regions themselves. These also need to be relocated to ensure that everything works correctly Signed-off-by: Alwin Joshy <[email protected]>
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/* | ||
* Copyright 2021, Breakaway Consulting Pty. Ltd. | ||
* | ||
* SPDX-License-Identifier: BSD-2-Clause | ||
*/ | ||
.extern main | ||
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.section ".text.start" | ||
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.global _start; | ||
.type _start, %function; | ||
_start: | ||
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mrs x0, mpidr_el1 | ||
and x0, x0,#0xFF // Check processor id | ||
cbz x0, master // Hang for all non-primary CPU | ||
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proc_hang: | ||
wfe | ||
b proc_hang | ||
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master: | ||
adrp x1, _stack | ||
add x1, x1, #0xff0 | ||
mov sp, x1 | ||
/* May not have been loaded in the right location. | ||
* Try and move ourselves so we're in the right place | ||
*/ | ||
bl fixup_image_base | ||
cmp x0, #1 | ||
beq 1f | ||
/* Otherwise, jump to the start of the new elf-loader */ | ||
br x0 | ||
1: | ||
b main | ||
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fixup_image_base: | ||
stp x29, x30, [sp, #-16]! | ||
mov x29, sp | ||
/* Check if the image is already at the correct location */ | ||
ldr x0, =LINK_ADDRESS | ||
adr x1, _start | ||
cmp x0, x1 | ||
beq image_ok | ||
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/* Sanity check: We don't want to overwrite ourselves! We assume that | ||
* everything between _start (src_start) and _bss_end (src_end) is important (i.e. | ||
* something that might be run while relocating) but allow overlap for | ||
* things after _bss_end i.e. the loader_data. | ||
*/ | ||
adrp x2, _bss_end | ||
add x2, x2, #:lo12:_bss_end | ||
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/* The loader_data is directly after _bss_end, with the first | ||
* value being the loader_data struct. The first field of this | ||
* struct is the size of the loader_data region, so we add | ||
* this to _bss_end to get the real end of the image | ||
*/ | ||
ldr x3, [x2] | ||
add x2, x2, x3 | ||
sub x2, x2, x1 | ||
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adrp x3, _bss_end | ||
add x3, x3, #:lo12:_bss_end | ||
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add x4, x0, x2 /* dst_end */ | ||
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/* At this point: | ||
* x0: dst_start (LINK_ADDRESS) | ||
* x1: src_start (_start) | ||
* x2: image_size | ||
* x3: src_end (_bss_end) | ||
* x4: dst_end (LINK_ADDRESS + image_size) | ||
*/ | ||
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/* check: if (dst_end >= src_start && dst_end < src_end) { abort } */ | ||
cmp x4, x1 | ||
blt 1f | ||
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cmp x4, x3 | ||
bge 1f | ||
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b cant_reloc | ||
1: | ||
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/* check: if (dst_start >= src_start && dest_start < src_end) { abort } */ | ||
cmp x0, x1 | ||
blt 2f | ||
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cmp x0, x3 | ||
bge 2f | ||
cant_reloc: | ||
b abort | ||
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2: | ||
/* x0 = desired image base */ | ||
/* x1 = current image base */ | ||
/* x2 = image size */ | ||
bl memmove | ||
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/* x0 = dest, save it to a callee-saved register while we invalidate icache */ | ||
mov x19, x0 | ||
bl flush_dcache | ||
bl invalidate_icache | ||
mov x0, x19 | ||
b 1f | ||
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image_ok: | ||
/* Already in the right place, keep booting */ | ||
mov x0, #1 | ||
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1: | ||
ldp x29, x30, [sp], #16 | ||
ret |
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