src/libthread/NetBSD-386-asm.s - plan9 - Git at Google

 .globl _tas
 _tas:
 	movl $0xCAFEBABE, %eax
 	movl 4(%esp), %ecx
 	xchgl %eax, 0(%ecx)
 	ret
	.globl _tas
	_tas:
	movl $0xCAFEBABE, %eax
	movl 4(%esp), %ecx
	xchgl %eax, 0(%ecx)
	ret