54 lines
1.5 KiB
ArmAsm
54 lines
1.5 KiB
ArmAsm
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format elf64
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section '.text' executable
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; x64sysvcall int sysv_x64fastcall(void* addr, int numArgs, long args1, args2, args3, args4)
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;
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; Calls Microsoft x64 ABI functions under System V AMD64 ABI.
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;
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; This function can handle ONLY up to FOUR arguments.
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; numArgs is in fact unused.
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;
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; Input: (void* rdi, int rsi, long rdx, rcx, r8, r9)
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; Output: int rax
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; Clobbers: flags
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public sysv_x64fastcall
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sysv_x64fastcall:
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sub rsp, 4*8 ; reserve the 4*8 bytes of shadow space
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; So, before we start, let's make a chart!
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;
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; | SysVx64 | MSx64 |
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; ----+---------------+---------------+
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; RAX | Return Value | Return Value |
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; RBX | Callee Saved | Callee Saved |
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; RCX | Argument 4 | Argument 1 |
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; RDX | Argument 3 | Argument 2 |
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; RSI | Argument 2 | Callee Saved |
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; RDI | Argument 1 | Callee Saved |
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; RBP | Callee Saved | Callee Saved |
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; RSP | Stack Pointer | Stack Pointer |
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; R8 | Argument 5 | Argument 3 |
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; R9 | Argument 6 | Argument 4 |
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; R10 | Caller Saved | Caller Saved |
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; R11 | Caller Saved | Caller Saved |
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; R12 | Callee Saved | Callee Saved |
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; R13 | Callee Saved | Callee Saved |
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; R14 | Callee Saved | Callee Saved |
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; R15 | Callee Saved | Callee Saved |
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;
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; To sum up, all we need to do is:
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; - RCX = RDX; RDX = RCX; and that's it!
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; Other stuff correspond quite well actually.
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mov rax, rcx
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mov rcx, rdx
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mov rdx, rax
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call rdi
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add rsp, 4*8 ; pop the shadow space
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ret
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