/* 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__)
#if defined(__i386__)
#define NEEDX86MAKECONTEXT
#define NEEDSWAPCONTEXT
#elif defined(__x86_64__)
#define NEEDAMD64MAKECONTEXT
#define NEEDSWAPCONTEXT
#endif
#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)
        *(int*)0 = 0;
    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 NEEDSWAPCONTEXT
int swapcontext(ucontext_t *oucp, const ucontext_t *ucp)
{
    if(getcontext(oucp) == 0) {
        setcontext(ucp);
    }

    return 0;
}
#endif

