mirror of https://github.com/flysand7/ciabatta.git
55 lines
1.3 KiB
NASM
55 lines
1.3 KiB
NASM
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bits 64
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section .text
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global ld_stack_trampoline
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; DESCRIPTION:
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; This function copies the current stack down from RSP to the top of the stack
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; into a memory region provided in parameter
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; After the stack has been copied, we jump into ld_stage3_entry
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; PARAMS:
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; RDI (u64) - dst stack base
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; RSI (u64) - src stack base
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; RDX (u64) - dst stack size
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; RCX (u64) - src stack size
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; R8 (u64) - function to call
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; R9 (u64) - param to pass to function
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; RETURNS:
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; guess what, it doesn't
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ld_stack_trampoline:
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; Calculate the amount of memory we need to move to the new stack
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add rcx, rsi
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sub rcx, rsp
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; Calculate the base of the source memory
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mov rsi, rsp
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; Check to see if the amount we're about to move is less than dst stack size
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cmp rcx, rdx
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jl .continue
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xor rdi, rdi
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mov rsi, r9
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mov rax, r8
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call rax
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.continue:
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; Save rsi, rdi, rcx on stack
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push rsi
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push rdi
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push rcx
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; copy stack
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shr rcx, 3
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rep movsq
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; get back our regs
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pop rcx
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pop rdi
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pop rsi
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; We copied the stack at this point, lets switch
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add rsp, rdi
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sub rsp, rsi
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add rsp, rdx
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sub rsp, rcx
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; We should have the new stack now, which is an exact copy of the old stack
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and rsp, -16
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mov rdi, 1
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mov rsi, r9
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mov rax, r8
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call rax
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