clone

pub fn clone() callconv(.naked) u32

File

Code

pub fn clone() callconv(.naked) u32 {
    // __clone(func, stack, flags, arg, ptid, tls, ctid)
    //         3,    4,     5,     6,   7,    8,   9
    //
    // syscall(SYS_clone, flags, stack, ptid, tls, ctid)
    //         0          3,     4,     5,    6,   7
    asm volatile (
        \\ # store non-volatile regs r29, r30 on stack in order to put our
        \\ # start func and its arg there
        \\ stwu 29, -16(1)
        \\ stw 30, 4(1)
        \\
        \\ # save r3 (func) into r29, and r6(arg) into r30
        \\ mr 29, 3
        \\ mr 30, 6
        \\
        \\ # create initial stack frame for new thread
        \\ clrrwi 4, 4, 4
        \\ li 0, 0
        \\ stwu 0, -16(4)
        \\
        \\ #move c into first arg
        \\ mr 3, 5
        \\ #mr 4, 4
        \\ mr 5, 7
        \\ mr 6, 8
        \\ mr 7, 9
        \\
        \\ # move syscall number into r0
        \\ li 0, 120 # SYS_clone
        \\
        \\ sc
        \\
        \\ # check for syscall error
        \\ bns+ 1f # jump to label 1 if no summary overflow.
        \\ #else
        \\ neg 3, 3 #negate the result (errno)
        \\ 1:
        \\ # compare sc result with 0
        \\ cmpwi cr7, 3, 0
        \\
        \\ # if not 0, restore stack and return
        \\ beq cr7, 2f
        \\ lwz 29, 0(1)
        \\ lwz 30, 4(1)
        \\ addi 1, 1, 16
        \\ blr
        \\
        \\ #else: we're the child
        \\ 2:
    );
    if (builtin.unwind_tables != .none or !builtin.strip_debug_info) asm volatile (
        \\ .cfi_undefined lr
    );
    asm volatile (
        \\ li 31, 0
        \\ mtlr 0
        \\
        \\ #call funcptr: move arg (d) into r3
        \\ mr 3, 30
        \\ #move r29 (funcptr) into CTR reg
        \\ mtctr 29
        \\ # call CTR reg
        \\ bctrl
        \\ # mov SYS_exit into r0 (the exit param is already in r3)
        \\ li 0, 1
        \\ sc
    );
}