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

#include "taskimpl.h"

#if defined(__APPLE__)
#if defined(__i386__)
#define NEEDX86MAKECONTEXT
#define NEEDSWAPCONTEXT
#elif defined(__x86_64__)
#define NEEDAMD64MAKECONTEXT
#define NEEDSWAPCONTEXT
#else
#define NEEDPOWERMAKECONTEXT
#define NEEDSWAPCONTEXT
#endif
#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 NEEDAMD64MAKECONTEXT
void makecontext(ucontext_t* ucp, void (*func)(void), int argc, ...) {
	long* sp;
	va_list va;

	memset(&ucp->uc_mcontext, 0, sizeof ucp->uc_mcontext);
	if (argc != 2)
		__builtin_trap();
	va_start(va, argc);
	ucp->uc_mcontext.mc_rdi = va_arg(va, int);
	ucp->uc_mcontext.mc_rsi = va_arg(va, int);
	va_end(va);
	sp = (long*)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size / sizeof(long);
	sp -= argc;
	sp = (void*)((uintptr_t)sp - (uintptr_t)sp % 16); /* 16-align for OS X */
	*--sp = 0; /* return address */
	ucp->uc_mcontext.mc_rip = (long)func;
	ucp->uc_mcontext.mc_rsp = (long)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
