/* Copyright (c) 2005-2006 Russ Cox, MIT; see COPYRIGHT */

#include "taskimpl.h"

#if defined(__APPLE__) && defined(__i386__)
#define NEEDX86MAKECONTEXT
#define NEEDSWAPCONTEXT
#endif

#if defined(__APPLE__) && !defined(__i386__)
#define NEEDPOWERMAKECONTEXT
#define NEEDSWAPCONTEXT
#endif

#if defined(__FreeBSD__) && defined(__i386__) && __FreeBSD__ < 5
#define NEEDX86MAKECONTEXT
#define NEEDSWAPCONTEXT
#endif

#if defined(__OpenBSD__) && defined(__i386__)
#define NEEDX86MAKECONTEXT
#define NEEDSWAPCONTEXT
#endif

#if defined(__linux__) && defined(__arm__)
#define NEEDSWAPCONTEXT
#define NEEDARMMAKECONTEXT
#endif

#ifdef NEEDPOWERMAKECONTEXT
void
makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
{
	ulong *sp, *tos;
	va_list arg;

	tos = (ulong*)ucp->uc_stack.ss_sp+ucp->uc_stack.ss_size/sizeof(ulong);
	sp = tos - 16;	
	ucp->mc.pc = (long)func;
	ucp->mc.sp = (long)sp;
	va_start(arg, argc);
	ucp->mc.r3 = va_arg(arg, long);
	va_end(arg);
}
#endif

#ifdef NEEDX86MAKECONTEXT
void
makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
{
	int *sp;

	sp = (int*)ucp->uc_stack.ss_sp+ucp->uc_stack.ss_size/4;
	sp -= argc;
	sp = (void*)((uintptr_t)sp - (uintptr_t)sp%16);	/* 16-align for OS X */
	memmove(sp, &argc+1, argc*sizeof(int));

	*--sp = 0;		/* return address */
	ucp->uc_mcontext.mc_eip = (long)func;
	ucp->uc_mcontext.mc_esp = (int)sp;
}
#endif

#ifdef NEEDARMMAKECONTEXT
void
makecontext(ucontext_t *uc, void (*fn)(void), int argc, ...)
{
	int i, *sp;
	va_list arg;
	
	sp = (int*)uc->uc_stack.ss_sp+uc->uc_stack.ss_size/4;
	va_start(arg, argc);
	for(i=0; i<4 && i<argc; i++)
		uc->uc_mcontext.gregs[i] = va_arg(arg, uint);
	va_end(arg);
	uc->uc_mcontext.gregs[13] = (uint)sp;
	uc->uc_mcontext.gregs[14] = (uint)fn;
}
#endif

#ifdef NEEDSWAPCONTEXT
int
swapcontext(ucontext_t *oucp, const ucontext_t *ucp)
{
	if(getcontext(oucp) == 0)
		setcontext(ucp);
	return 0;
}
#endif