Martin Michelsen
151 lines
4.1 KiB
ArmAsm
151 lines
4.1 KiB
ArmAsm
# This function is required for loading DOLs. If it's not present, newserv can't
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# serve DOL files to GameCube clients.
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.meta index=E2
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entry_ptr:
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reloc0:
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.offsetof start
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start:
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disable_interrupts:
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mfmsr r3
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rlwinm r3, r3, 0, 17, 15
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mtmsr r3
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bl get_current_addr
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dol_base_ptr:
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.zero
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get_current_addr:
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mflr r31
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# TODO: It'd be nice to be able to use an expression for the immediate value
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# here - something like (dol_base_ptr - start), for example
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subi r31, r31, 0x10 # r31 = base of data to copy to low memory (start label)
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# If this code is not running from low memory (80001800-80003000), then copy
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# it there and branch to it
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lis r3, 0x8000
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ori r3, r3, 0x3000
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cmp r31, r3
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blt run_dol
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copy_code_to_low_memory:
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bl get_end_ptr
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sub r30, r3, r31 # r30 = size of code to copy (for cache flushing later)
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subi r5, r3, 4 # r5 = end ptr
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subi r4, r31, 4
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lis r3, 0x8000
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ori r3, r3, 0x17FC
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copy_code_to_low_memory__again:
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lwzu r0, [r4 + 4]
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stwu [r3 + 4], r0
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cmp r4, r5
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bne copy_code_to_low_memory__again
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# Flush the data cache and clear the instruction cache before running the
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# moved code
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lis r3, 0x8000
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ori r3, r3, 0x1800
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mr r4, r30
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mtlr r3
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b flush_cached_code_writes
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run_dol:
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lwz r30, [r31 + 0x10] # r30 = data base ptr
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# Decompress the file first. If the compressed size is zero, then skip this
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# step (the file is not compressed). The header consists of two fields:
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# compressed size followed by decompressed size.
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lwz r6, [r30]
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cmplwi r6, 0
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beq run_dol__not_compressed
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lwz r5, [r30 + 4]
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addi r4, r30, 8 # Compressed data immediately follows the 2 header fields
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sub r3, r30, r5 # Decompress to immediately before the compressed data
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mr r30, r3 # Save DOL header pointer for after decompression
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bl prs_decompress
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b run_dol__decompressed
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run_dol__not_compressed:
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addi r30, r30, 8
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run_dol__decompressed:
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# DOL files are very simple: they have up to 7 text sections, up to 11 data
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# sections, and a BSS section and an entrypoint. No imports or other fancy
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# things to do - we just have to move a bunch of bytes around.
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mr r29, r30 # r29 = DOL header iterator
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addi r28, r29, 0x48 # r28 = DOL header iterator end value
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run_dol__move_section:
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lwz r4, [r29] # r4 = file offset of section data
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add r4, r4, r30 # r4 = address of section data
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lwz r3, [r29 + 0x48] # r3 = dest address of section data
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lwz r5, [r29 + 0x90] # r5 = number of bytes to move
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cmplwi r5, 0 # If size is 0, skip the section entirely
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beq skip_section
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subi r3, r3, 1
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subi r4, r4, 1
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add r5, r4, r5 # r5 = source end pointer
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run_dol__move_section_data__again:
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# TODO: We probably should implement memmove-like semantics here, in case the
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# DOL loads at an unusually late address. This is probably very rare.
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lbzu r0, [r4 + 1]
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stbu [r3 + 1], r0
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cmp r4, r5
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bne run_dol__move_section_data__again
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# Flush the data cache and invalidate the instruction cache after copying the
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# section data. Technically we don't have to do this for data sections, but
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# I'm lazy and it doesn't take too long.
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lwz r3, [r29 + 0x48] # r3 = dest address of section data
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lwz r4, [r29 + 0x90] # r4 = size of section data
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bl flush_cached_code_writes
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skip_section:
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# Move to the next section
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addi r29, r29, 4
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cmp r29, r28
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bne run_dol__move_section
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run_dol__zero_bss:
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lwz r3, [r30 + 0xD8] # r3 = BSS address
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lwz r4, [r30 + 0xDC] # r4 = BSS size
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cmplwi r4, 0
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beq run_dol__skip_zero_bss
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add r4, r3, r4 # r4 = BSS end address
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subi r3, r3, 1
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li r0, 0
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run_dol__zero_bss__again:
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stbu [r3 + 1], r0
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cmp r3, r4
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bne run_dol__zero_bss__again
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run_dol__skip_zero_bss:
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run_dol__go_to_entrypoint:
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lwz r0, [r30 + 0xE0] # r30 = entrypoint
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mtctr r0
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bctr
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flush_cached_code_writes:
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.include FlushCachedCode
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blr
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prs_decompress:
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.include PRSDecompress
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return_end_ptr:
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mflr r3
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bctr
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get_end_ptr:
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mflr r0
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mtctr r0
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bl return_end_ptr
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