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DvdGiessen/launcher.asm

Created January 10, 2019 23:26
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  1. DvdGiessen created this gist Jan 10, 2019.
    64 changes: 64 additions & 0 deletions launcher.asm
    View file
    Original file line number Diff line number Diff line change
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    extrn GetStartupInfoW: PROC
    extrn CreateProcessW: PROC
    extrn ExitProcess: PROC

    .data
    target word 2eh, 2eh, 5ch, 42h, 61h, 73h, 65h, 5ch, 42h, 69h, 6eh, 61h, 72h
    word 69h, 65h, 73h, 5ch, 57h, 69h, 6eh, 36h, 34h, 53h, 74h, 65h, 61h
    word 6dh, 5ch, 43h, 69h, 76h, 69h, 6ch, 69h, 7ah, 61h, 74h, 69h, 6fh
    word 6eh, 56h, 49h, 5fh, 44h, 58h, 31h, 32h, 2eh, 65h, 78h, 65h, 0
    ; ..\Base\Binaries\Win64Steam\CivilizationVI_DX12.exe as UTF-16

    .code
    main proc frame
    local startupInfo [104] :byte
    local processInfo [24] :byte
    ; set up stack base
    push rbp
    .pushreg rbp
    mov rbp, rsp
    .setframe rbp, 0
    ; reserve space on stack for structs + last 6 CreateProcessW arguments + shadow space
    sub rsp, 32 + 104 + 24 + 6 * 8 + 32
    .allocstack 32 + 104 + 24 + 6 * 8 + 32
    .endprolog

    ; get startupInfo for this process
    lea rcx, startupInfo
    call GetStartupInfoW
    ; write arguments for CreateProcessW to reserved space on stack
    lea rax, processInfo
    mov qword ptr [rsp + 72], rax ; lpProcessInformation
    lea rax, startupInfo
    mov qword ptr [rsp + 64], rax ; lpStartupInfo
    mov qword ptr [rsp + 56], 0 ; lpCurrentDirectory = NULL
    mov qword ptr [rsp + 48], 0 ; lpEnvironment = NULL
    mov qword ptr [rsp + 40], 0 ; dwCreationFlags = 0
    mov qword ptr [rsp + 32], 0 ; bInheritHandles = NULL
    ; first 4 arguments are passed via registers
    mov r9, 0 ; lpThreadAttributes = NULL
    mov r8, 0 ; lpProcessAttributes = NULL
    mov rdx, 0 ; lpCommandLine = NULL
    lea rcx, target ; lpApplicationName = target
    ; run target process using CreateProcessW
    call CreateProcessW
    ; exit this process
    mov rcx, rax ; uExitCode = returncode of CreateProcessW
    call ExitProcess ; explicitly exit, see https://stackoverflow.com/a/39907035
    ; never reached, but if you want to know: this is how we'd properly restore the stack
    add rsp, 32 + 104 + 24 + 6 * 8 + 32
    pop rbp
    ret 0

    align 4
    main endp

    end