Martin Michelsen
90 lines
2.0 KiB
ArmAsm
90 lines
2.0 KiB
ArmAsm
start:
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mflr r7
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# If this patch has already been run, then the opcode that led here will
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# not be bctrl (4E800421). In that case, do nothing.
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lis r3, 0x4E80
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ori r3, r3, 0x0421
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lwz r4, [r7 - 4]
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cmp r3, r4
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beq apply_patch
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blr
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apply_patch:
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bl patch_end
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.offsetof patch
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.offsetof patch_end
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patch:
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mfctr r6
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mr r3, r6
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li r4, 0x7C00
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.include FlushCachedCode-GC
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mtctr r6
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bctr
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patch_end:
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mflr r4
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addi r4, r4, 8
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lwz r3, [r4 - 8]
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lwz r5, [r4 - 4]
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sub r5, r5, r3
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# At this point:
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# r4 = address of patch label
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# r5 = patch size in bytes
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# r7 = saved LR
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# Find a spot in the interrupt handlers with enough memory for the patch
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lis r3, 0x8000
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ori r3, r3, 0x0200
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sub r3, r3, r5
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check_location:
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rlwinm r0, r5, 30, 2, 31
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mtctr r0 # ctr = patch size in words
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subi r8, r3, 4
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check_location_next_word:
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lwzu r0, [r8 + 4]
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cmpwi r0, 0
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beq check_location_word_ok
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addi r3, r3, 0x0100
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rlwinm r0, r3, 0, 16, 31
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cmpwi r0, 0x1800
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blt check_location
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# No suitable location was found - return null
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li r3, 0
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mtlr r7
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blr
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check_location_word_ok:
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bdnz check_location_next_word
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location_ok:
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mr r6, r3
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# Now:
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# r3 = destination location
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# r4 = patch src data
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# r5 = patch size in bytes
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# r6 = destination location
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# r7 = saved LR
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.include CopyCode-GC
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setup_branch:
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# Replace the bctrl opcode that led to this call with a bl opcode that
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# leads to the copied patch code
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subi r3, r7, 4
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sub r4, r6, r3
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rlwinm r4, r4, 0, 6, 31
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oris r4, r4, 0x4800
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ori r4, r4, 0x0001
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stw [r3], r4
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dcbst r0, r3
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sync
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icbi r0, r3
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isync
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# Return the address that the patch was copied to
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mr r3, r6
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mtlr r7
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blr
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