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clone

m68k.clone
pub fn clone() callconv(.naked) u32

File

lib/std/os/linux/m68k.zig:112

Code

pub fn clone() callconv(.naked) u32 {
    // __clone(func, stack, flags, arg, ptid, tls, ctid)
    //         +4,   +8,    +12,   +16, +20,  +24, +28
    //
    // syscall(SYS_clone, flags, stack, ptid, ctid, tls)
    //         d0,        d1,    d2,    d3,   d4,   d5
    asm volatile (
        \\ // Save callee-saved registers.
        \\ movem.l %%d2-%%d5, -(%%sp) // sp -= 16
        \\
        \\ // Save func and arg.
        \\ move.l 16+4(%%sp), %%a0
        \\ move.l 16+16(%%sp), %%a1
        \\
        \\ // d0 = syscall(d0, d1, d2, d3, d4, d5)
        \\ move.l #120, %%d0 // SYS_clone
        \\ move.l 16+12(%%sp), %%d1
        \\ move.l 16+8(%%sp), %%d2
        \\ move.l 16+20(%%sp), %%d3
        \\ move.l 16+28(%%sp), %%d4
        \\ move.l 16+24(%%sp), %%d5
        \\ and.l #-4, %%d2 // Align the child stack pointer.
        \\ trap #0
        \\
        \\ // Are we in the parent or child?
        \\ tst.l %%d0
        \\ beq 1f
        \\ // Parent:
        \\
        \\ // Restore callee-saved registers and return.
        \\ movem.l (%%sp)+, %%d2-%%d5 // sp += 16
        \\ rts
        \\
        \\ // Child:
        \\1:
    );
    if (builtin.unwind_tables != .none or !builtin.strip_debug_info) asm volatile (
        \\ .cfi_undefined %%pc
    );
    asm volatile (
        \\ suba.l %%fp, %%fp
        \\
        \\ // d0 = func(a1)
        \\ move.l %%a1, -(%%sp)
        \\ jsr (%%a0)
        \\
        \\ // syscall(d0, d1)
        \\ move.l %%d0, %%d1
        \\ move.l #1, %%d0 // SYS_exit
        \\ trap #0
    );
}