64 lines
1.2 KiB
ArmAsm
64 lines
1.2 KiB
ArmAsm
//
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// Payload launcher stub.
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//
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.globl _start
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.section ".text"
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_start:
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// First, we'll need to move ourselves _out_ of the target area.
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// We'll copy down into the IRAM.
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ldr r0, =INTERMEZZO_RELOCATED_ADDRESS
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ldr r1, =post_relocation
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ldr r2, =intermezzo_end
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sub r2, r2, r1
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bl copy
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// Jump to the start of RAM, which should now contain the post-relocation code.
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ldr r0, =INTERMEZZO_RELOCATED_ADDRESS
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bx r0
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.align 4
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post_relocation:
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// Next, we'll copy our payload down to the appropriate relocaiton address.
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ldr r0, =RELOCATION_TARGET
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ldr r1, =PAYLOAD_START_ADDR
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ldr r2, =BEFORE_SPRAY_LENGTH
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bl copy
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ldr r0, =RELOCATION_TARGET
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ldr r1, =BEFORE_SPRAY_LENGTH
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add r0, r0, r1
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ldr r1, =STACK_SPRAY_END
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ldr r2, =AFTER_SPRAY_LENGTH
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bl copy
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// Finally, jump into the relocated target.
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ldr r0, =ENTRY_POINT_ADDRESS
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bx r0
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//
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// Simple block copy.
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// r0 = destination address
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// r1 = source address
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// r2 = length in bytes
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// Destroys r0-r3.
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//
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copy:
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// Copy the word...
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ldr r3, [r1], #4
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str r3, [r0], #4
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// And continue while we have words left to copy.
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subs r2, r2, #4
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bne copy
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// Once we're done, return.
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bx lr
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