// In any case, even if function has 0,1,2,3,4 args, there is reserved
	// but uninitialized "shadow space" for the first 4 args.
	// The values are in registers.
	MOVQ	CX, (16+0)(SP)
	MOVQ	DX, (16+8)(SP)
	MOVQ	R8, (16+16)(SP)
	MOVQ	R9, (16+24)(SP)
	// R8 = address of args vector
	LEAQ	(16+0)(SP), R8

	// remove return address from stack, we are not returning to callbackasm, but to its caller.
	MOVQ	0(SP), AX
	ADDQ	$8, SP

00000340  32 84 f9 b4 e1 89 08 8f  6a c2 2a 17 b9 f5 92 c8  |2.......j.*.....|
00000350  3a 97 62 98 b8 93 94 5d  a1 6b 05 17 56 5d 6e b5  |:.b....].k..V]n.|
00000360  d3 72 a6 06 77 b2 45 fe  2d 37 10 7e b8 16 16 f4  |.r..w.E.-7.~....|
00000370  70 86 56 a4 be 52 54 3e  90 7d 47 66 23 35 e9 a2  |p.V..RT>.}Gf#5..|
00000380  e9 4f 86 e2 a7 b9 20 b6  c8 9f 19 08 6b 73 93 86  |.O.... .....ks..|