clone

pub fn clone() callconv(.naked) u64

File

Code

pub fn clone() callconv(.naked) u64 {
    // __clone(func, stack, flags, arg, ptid, tls, ctid)
    //         i0,   i1,    i2,    i3,  i4,   i5,  sp
    //
    // syscall(SYS_clone, flags, stack, ptid, tls, ctid)
    //         g1         o0,    o1,    o2,   o3,  o4
    asm volatile (
        \\ save %%sp, -192, %%sp
        \\
        \\ // clone() on SPARC can fail with EFAULT if %%sp points to uncommitted memory, so flush
        \\ // all register windows up to this point to ensure that the kernel has enough committed
        \\ // memory for its stack frame.
        \\ save %%sp, -192, %%sp
        \\ flushw
        \\ restore
        \\
        \\ # Save the func pointer and the arg pointer
        \\ mov %%i0, %%g2
        \\ mov %%i3, %%g3
        \\
        \\ # Shuffle the arguments
        \\ mov 217, %%g1 // SYS_clone
        \\ mov %%i2, %%o0
        \\
        \\ # Align, and add some extra space for the initial frame
        \\ and %%i1, -16, %%i1
        \\ sub %%i1, 192 + 2047, %%o1
        \\
        \\ mov %%i4, %%o2
        \\ mov %%i5, %%o3
        \\ ldx [%%fp + 176 + 2047], %%o4
        \\ t 0x6d
        \\ bcs,pn %%xcc, 1f
        \\  nop
        \\ # The child pid is returned in o0 while o1 tells if this
        \\ # process is the child (=1) or the parent (=0).
        \\ brnz %%o1, 2f
        \\  nop
        \\
        \\ # Parent process, return the child pid
        \\ mov %%o0, %%i0
        \\ ret
        \\  restore
        \\
        \\1:
        \\ # The syscall failed
        \\ sub %%g0, %%o0, %%i0
        \\ ret
        \\  restore
        \\
        \\2:
        \\ # Child process
    );
    if (builtin.unwind_tables != .none or !builtin.strip_debug_info) asm volatile (
        \\ .cfi_undefined %%i7
    );
    asm volatile (
        \\ mov %%g0, %%fp
        \\ mov %%g0, %%i7
        \\
        \\ # call func(arg)
        \\ call %%g2
        \\  mov %%g3, %%o0
        \\ # Exit
        \\ mov 1, %%g1 // SYS_exit
        \\ t 0x6d
    );
}