/*
 * Copyright (c) 2001-2011 Marc Alexander Lehmann <schmorp@schmorp.de>
 *
 * Redistribution and use in source and binary forms, with or without modifica-
 * tion, are permitted provided that the following conditions are met:
 *
 *   1.  Redistributions of source code must retain the above copyright notice,
 *       this list of conditions and the following disclaimer.
 *
 *   2.  Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
 * CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO
 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
 * CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
 * ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Alternatively, the contents of this file may be used under the terms of
 * the GNU General Public License ("GPL") version 2 or any later version,
 * in which case the provisions of the GPL are applicable instead of
 * the above. If you wish to allow the use of your version of this file
 * only under the terms of the GPL and not to allow others to use your
 * version of this file under the BSD license, indicate your decision
 * by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL. If you do not delete the
 * provisions above, a recipient may use your version of this file under
 * either the BSD or the GPL.
 *
 * This library is modelled strictly after Ralf S. Engelschalls article at
 * http://www.gnu.org/software/pth/rse-pmt.ps. So most of the credit must
 * go to Ralf S. Engelschall <rse@engelschall.com>.
 */

#include "coro.h"

#include <stddef.h>
#include <string.h>

/*****************************************************************************/
/* ucontext/setjmp/asm backends                                              */
/*****************************************************************************/
#if CORO_UCONTEXT || CORO_SJLJ || CORO_LOSER || CORO_LINUX || CORO_IRIX || CORO_ASM

# if CORO_UCONTEXT
#  include <stddef.h>
# endif

# if !defined(STACK_ADJUST_PTR)
#  if __sgi
/* IRIX is decidedly NON-unix */
#   define STACK_ADJUST_PTR(sp,ss) ((char *)(sp) + (ss) - 8)
#   define STACK_ADJUST_SIZE(sp,ss) ((ss) - 8)
#  elif (__i386__ && CORO_LINUX) || (_M_IX86 && CORO_LOSER)
#   define STACK_ADJUST_PTR(sp,ss) ((char *)(sp) + (ss))
#   define STACK_ADJUST_SIZE(sp,ss) (ss)
#  elif (__amd64__ && CORO_LINUX) || ((_M_AMD64 || _M_IA64) && CORO_LOSER)
#   define STACK_ADJUST_PTR(sp,ss) ((char *)(sp) + (ss) - 8)
#   define STACK_ADJUST_SIZE(sp,ss) (ss)
#  else
#   define STACK_ADJUST_PTR(sp,ss) (sp)
#   define STACK_ADJUST_SIZE(sp,ss) (ss)
#  endif
# endif

# include <stdlib.h>

# if CORO_SJLJ
#  include <stdio.h>
#  include <signal.h>
#  include <unistd.h>
# endif

static coro_func coro_init_func;
static void *coro_init_arg;
static coro_context *new_coro, *create_coro;

static void
coro_init (void)
{
  volatile coro_func func = coro_init_func;
  volatile void *arg = coro_init_arg;

  coro_transfer (new_coro, create_coro);

#if __GCC_HAVE_DWARF2_CFI_ASM && __amd64
  /*asm (".cfi_startproc");*/
  /*asm (".cfi_undefined rip");*/
#endif

  func ((void *)arg);

#if __GCC_HAVE_DWARF2_CFI_ASM && __amd64
  /*asm (".cfi_endproc");*/
#endif

  /* the new coro returned. bad. just abort() for now */
  abort ();
}

# if CORO_SJLJ

static volatile int trampoline_done;

/* trampoline signal handler */
static void
trampoline (int sig)
{
  if (coro_setjmp (new_coro->env))
    coro_init (); /* start it */
  else
    trampoline_done = 1;
}

# endif

# if CORO_ASM

  #if __arm__ && \
      (defined __ARM_ARCH_7__  || defined __ARM_ARCH_7A__ \
    || defined __ARM_ARCH_7R__ || defined __ARM_ARCH_7M__ \
    || __ARM_ARCH == 7)
    #define CORO_ARM 1
  #endif

  #if _WIN32 || __CYGWIN__
    #define CORO_WIN_TIB 1
  #endif

  asm (
       "\t.text\n"
       #if _WIN32 || __CYGWIN__
       "\t.globl _coro_transfer\n"
       "_coro_transfer:\n"
       #else
       "\t.globl coro_transfer\n"
       "coro_transfer:\n"
       #endif
       /* windows, of course, gives a shit on the amd64 ABI and uses different registers */
       /* http://blogs.msdn.com/freik/archive/2005/03/17/398200.aspx */
       #if __amd64

         #if _WIN32 || __CYGWIN__
           #define NUM_SAVED 29
           "\tsubq $168, %rsp\t" /* one dummy qword to improve alignment */
           "\tmovaps %xmm6, (%rsp)\n"
           "\tmovaps %xmm7, 16(%rsp)\n"
           "\tmovaps %xmm8, 32(%rsp)\n"
           "\tmovaps %xmm9, 48(%rsp)\n"
           "\tmovaps %xmm10, 64(%rsp)\n"
           "\tmovaps %xmm11, 80(%rsp)\n"
           "\tmovaps %xmm12, 96(%rsp)\n"
           "\tmovaps %xmm13, 112(%rsp)\n"
           "\tmovaps %xmm14, 128(%rsp)\n"
           "\tmovaps %xmm15, 144(%rsp)\n"
           "\tpushq %rsi\n"
           "\tpushq %rdi\n"
           "\tpushq %rbp\n"
           "\tpushq %rbx\n"
           "\tpushq %r12\n"
           "\tpushq %r13\n"
           "\tpushq %r14\n"
           "\tpushq %r15\n"
           #if CORO_WIN_TIB
             "\tpushq %fs:0x0\n"
             "\tpushq %fs:0x8\n"
             "\tpushq %fs:0xc\n"
           #endif
           "\tmovq %rsp, (%rcx)\n"
           "\tmovq (%rdx), %rsp\n"
           #if CORO_WIN_TIB
             "\tpopq %fs:0xc\n"
             "\tpopq %fs:0x8\n"
             "\tpopq %fs:0x0\n"
           #endif
           "\tpopq %r15\n"
           "\tpopq %r14\n"
           "\tpopq %r13\n"
           "\tpopq %r12\n"
           "\tpopq %rbx\n"
           "\tpopq %rbp\n"
           "\tpopq %rdi\n"
           "\tpopq %rsi\n"
           "\tmovaps (%rsp), %xmm6\n"
           "\tmovaps 16(%rsp), %xmm7\n"
           "\tmovaps 32(%rsp), %xmm8\n"
           "\tmovaps 48(%rsp), %xmm9\n"
           "\tmovaps 64(%rsp), %xmm10\n"
           "\tmovaps 80(%rsp), %xmm11\n"
           "\tmovaps 96(%rsp), %xmm12\n"
           "\tmovaps 112(%rsp), %xmm13\n"
           "\tmovaps 128(%rsp), %xmm14\n"
           "\tmovaps 144(%rsp), %xmm15\n"
           "\taddq $168, %rsp\n"
         #else
           #define NUM_SAVED 6
           "\tpushq %rbp\n"
           "\tpushq %rbx\n"
           "\tpushq %r12\n"
           "\tpushq %r13\n"
           "\tpushq %r14\n"
           "\tpushq %r15\n"
           "\tmovq %rsp, (%rdi)\n"
           "\tmovq (%rsi), %rsp\n"
           "\tpopq %r15\n"
           "\tpopq %r14\n"
           "\tpopq %r13\n"
           "\tpopq %r12\n"
           "\tpopq %rbx\n"
           "\tpopq %rbp\n"
         #endif
         "\tpopq %rcx\n"
         "\tjmpq *%rcx\n"

       #elif __i386__

         #define NUM_SAVED 4
         "\tpushl %ebp\n"
         "\tpushl %ebx\n"
         "\tpushl %esi\n"
         "\tpushl %edi\n"
         #if CORO_WIN_TIB
           #undef NUM_SAVED
           #define NUM_SAVED 7
           "\tpushl %fs:0\n"
           "\tpushl %fs:4\n"
           "\tpushl %fs:8\n"
         #endif
         "\tmovl %esp, (%eax)\n"
         "\tmovl (%edx), %esp\n"
         #if CORO_WIN_TIB
           "\tpopl %fs:8\n"
           "\tpopl %fs:4\n"
           "\tpopl %fs:0\n"
         #endif
         "\tpopl %edi\n"
         "\tpopl %esi\n"
         "\tpopl %ebx\n"
         "\tpopl %ebp\n"
         "\tpopl %ecx\n"
         "\tjmpl *%ecx\n"

       #elif CORO_ARM /* untested, what about thumb, neon, iwmmxt? */

         #if __ARM_PCS_VFP
           "\tvpush {d8-d15}\n"
           #define NUM_SAVED (9 + 8 * 2)
         #else
           #define NUM_SAVED 9
         #endif
         "\tpush {r4-r11,lr}\n"
         "\tstr sp, [r0]\n"
         "\tldr sp, [r1]\n"
         "\tpop {r4-r11,lr}\n"
         #if __ARM_PCS_VFP
           "\tvpop {d8-d15}\n"
         #endif
         "\tmov r15, lr\n"

       #elif __mips__ && 0 /* untested, 32 bit only */

        #define NUM_SAVED (12 + 8 * 2)
         /* TODO: n64/o64, lw=>ld */

         "\t.set    nomips16\n"
         "\t.frame  $sp,112,$31\n"
         #if __mips_soft_float
           "\taddiu   $sp,$sp,-44\n"
         #else
           "\taddiu   $sp,$sp,-112\n"
           "\ts.d     $f30,88($sp)\n"
           "\ts.d     $f28,80($sp)\n"
           "\ts.d     $f26,72($sp)\n"
           "\ts.d     $f24,64($sp)\n"
           "\ts.d     $f22,56($sp)\n"
           "\ts.d     $f20,48($sp)\n"
         #endif
         "\tsw      $28,40($sp)\n"
         "\tsw      $31,36($sp)\n"
         "\tsw      $fp,32($sp)\n"
         "\tsw      $23,28($sp)\n"
         "\tsw      $22,24($sp)\n"
         "\tsw      $21,20($sp)\n"
         "\tsw      $20,16($sp)\n"
         "\tsw      $19,12($sp)\n"
         "\tsw      $18,8($sp)\n"
         "\tsw      $17,4($sp)\n"
         "\tsw      $16,0($sp)\n"
         "\tsw      $sp,0($4)\n"
         "\tlw      $sp,0($5)\n"
         #if !__mips_soft_float
           "\tl.d     $f30,88($sp)\n"
           "\tl.d     $f28,80($sp)\n"
           "\tl.d     $f26,72($sp)\n"
           "\tl.d     $f24,64($sp)\n"
           "\tl.d     $f22,56($sp)\n"
           "\tl.d     $f20,48($sp)\n"
         #endif
         "\tlw      $28,40($sp)\n"
         "\tlw      $31,36($sp)\n"
         "\tlw      $fp,32($sp)\n"
         "\tlw      $23,28($sp)\n"
         "\tlw      $22,24($sp)\n"
         "\tlw      $21,20($sp)\n"
         "\tlw      $20,16($sp)\n"
         "\tlw      $19,12($sp)\n"
         "\tlw      $18,8($sp)\n"
         "\tlw      $17,4($sp)\n"
         "\tlw      $16,0($sp)\n"
         "\tj       $31\n"
         #if __mips_soft_float
           "\taddiu   $sp,$sp,44\n"
         #else
           "\taddiu   $sp,$sp,112\n"
         #endif

       #else
         #error unsupported architecture
       #endif
  );

# endif

void
coro_create (coro_context *ctx, coro_func coro, void *arg, void *sptr, size_t ssize)
{
  coro_context nctx;
# if CORO_SJLJ
  stack_t ostk, nstk;
  struct sigaction osa, nsa;
  sigset_t nsig, osig;
# endif

  if (!coro)
    return;

  coro_init_func = coro;
  coro_init_arg  = arg;

  new_coro    = ctx;
  create_coro = &nctx;

# if CORO_SJLJ
  /* we use SIGUSR2. first block it, then fiddle with it. */

  sigemptyset (&nsig);
  sigaddset (&nsig, SIGUSR2);
  sigprocmask (SIG_BLOCK, &nsig, &osig);

  nsa.sa_handler = trampoline;
  sigemptyset (&nsa.sa_mask);
  nsa.sa_flags = SA_ONSTACK;

  if (sigaction (SIGUSR2, &nsa, &osa))
    {
      perror ("sigaction");
      abort ();
    }

  /* set the new stack */
  nstk.ss_sp    = STACK_ADJUST_PTR (sptr, ssize); /* yes, some platforms (IRIX) get this wrong. */
  nstk.ss_size  = STACK_ADJUST_SIZE (sptr, ssize);
  nstk.ss_flags = 0;

  if (sigaltstack (&nstk, &ostk) < 0)
    {
      perror ("sigaltstack");
      abort ();
    }

  trampoline_done = 0;
  kill (getpid (), SIGUSR2);
  sigfillset (&nsig); sigdelset (&nsig, SIGUSR2);

  while (!trampoline_done)
    sigsuspend (&nsig);

  sigaltstack (0, &nstk);
  nstk.ss_flags = SS_DISABLE;
  if (sigaltstack (&nstk, 0) < 0)
    perror ("sigaltstack");

  sigaltstack (0, &nstk);
  if (~nstk.ss_flags & SS_DISABLE)
    abort ();

  if (~ostk.ss_flags & SS_DISABLE)
    sigaltstack (&ostk, 0);

  sigaction (SIGUSR2, &osa, 0);
  sigprocmask (SIG_SETMASK, &osig, 0);

# elif CORO_LOSER

  coro_setjmp (ctx->env);
  #if __CYGWIN__ && __i386__
    ctx->env[8]                        = (long)    coro_init;
    ctx->env[7]                        = (long)    ((char *)sptr + ssize)         - sizeof (long);
  #elif __CYGWIN__ && __x86_64__
    ctx->env[7]                        = (long)    coro_init;
    ctx->env[6]                        = (long)    ((char *)sptr + ssize)         - sizeof (long);
  #elif defined __MINGW32__
    ctx->env[5]                        = (long)    coro_init;
    ctx->env[4]                        = (long)    ((char *)sptr + ssize)         - sizeof (long);
  #elif defined _M_IX86
    ((_JUMP_BUFFER *)&ctx->env)->Eip   = (long)    coro_init;
    ((_JUMP_BUFFER *)&ctx->env)->Esp   = (long)    STACK_ADJUST_PTR (sptr, ssize) - sizeof (long);
  #elif defined _M_AMD64
    ((_JUMP_BUFFER *)&ctx->env)->Rip   = (__int64) coro_init;
    ((_JUMP_BUFFER *)&ctx->env)->Rsp   = (__int64) STACK_ADJUST_PTR (sptr, ssize) - sizeof (__int64);
  #elif defined _M_IA64
    ((_JUMP_BUFFER *)&ctx->env)->StIIP = (__int64) coro_init;
    ((_JUMP_BUFFER *)&ctx->env)->IntSp = (__int64) STACK_ADJUST_PTR (sptr, ssize) - sizeof (__int64);
  #else
    #error "microsoft libc or architecture not supported"
  #endif

# elif CORO_LINUX

  coro_setjmp (ctx->env);
  #if __GLIBC__ >= 2 && __GLIBC_MINOR__ >= 0 && defined (JB_PC) && defined (JB_SP)
    ctx->env[0].__jmpbuf[JB_PC]        = (long)    coro_init;
    ctx->env[0].__jmpbuf[JB_SP]        = (long)    STACK_ADJUST_PTR (sptr, ssize) - sizeof (long);
  #elif __GLIBC__ >= 2 && __GLIBC_MINOR__ >= 0 && defined (__mc68000__)
    ctx->env[0].__jmpbuf[0].__aregs[0] = (long int)coro_init;
    ctx->env[0].__jmpbuf[0].__sp       = (int *)   ((char *)sptr + ssize)         - sizeof (long);
  #elif defined (__GNU_LIBRARY__) && defined (__i386__)
    ctx->env[0].__jmpbuf[0].__pc       = (char *)  coro_init;
    ctx->env[0].__jmpbuf[0].__sp       = (void *)  ((char *)sptr + ssize)         - sizeof (long);
  #elif defined (__GNU_LIBRARY__) && defined (__x86_64__)
    ctx->env[0].__jmpbuf[JB_PC]        = (long)    coro_init;
    ctx->env[0].__jmpbuf[0].__sp       = (void *)  ((char *)sptr + ssize)         - sizeof (long);
  #else
    #error "linux libc or architecture not supported"
  #endif

# elif CORO_IRIX

  coro_setjmp (ctx->env, 0);
  ctx->env[JB_PC]                      = (__uint64_t)coro_init;
  ctx->env[JB_SP]                      = (__uint64_t)STACK_ADJUST_PTR (sptr, ssize) - sizeof (long);

# elif CORO_ASM

  #if __i386__ || __x86_64__
    ctx->sp = (void **)(ssize + (char *)sptr);
    *--ctx->sp = (void *)abort; /* needed for alignment only */
    *--ctx->sp = (void *)coro_init;
    #if CORO_WIN_TIB
      *--ctx->sp = 0;                    /* ExceptionList */
      *--ctx->sp = (char *)sptr + ssize; /* StackBase */
      *--ctx->sp = sptr;                 /* StackLimit */
    #endif
  #elif CORO_ARM
    /* return address stored in lr register, don't push anything */
  #else
    #error unsupported architecture
  #endif

  ctx->sp -= NUM_SAVED;
  memset (ctx->sp, 0, sizeof (*ctx->sp) * NUM_SAVED);

  #if __i386__ || __x86_64__
    /* done already */
  #elif CORO_ARM
    ctx->sp[0] = coro; /* r4 */
    ctx->sp[1] = arg;  /* r5 */
    ctx->sp[8] = (char *)coro_init; /* lr */
  #else
    #error unsupported architecture
  #endif

# elif CORO_UCONTEXT

  getcontext (&(ctx->uc));

  ctx->uc.uc_link           =  0;
  ctx->uc.uc_stack.ss_sp    = sptr;
  ctx->uc.uc_stack.ss_size  = (size_t)ssize;
  ctx->uc.uc_stack.ss_flags = 0;

  makecontext (&(ctx->uc), (void (*)())coro_init, 0);

# endif

  coro_transfer (create_coro, new_coro);
}

/*****************************************************************************/
/* pthread backend                                                           */
/*****************************************************************************/
#elif CORO_PTHREAD

/* this mutex will be locked by the running coroutine */
pthread_mutex_t coro_mutex = PTHREAD_MUTEX_INITIALIZER;

struct coro_init_args
{
  coro_func func;
  void *arg;
  coro_context *self, *main;
};

static void *
coro_init (void *args_)
{
  struct coro_init_args *args = (struct coro_init_args *)args_;
  coro_func func = args->func;
  void *arg = args->arg;

  coro_transfer (args->self, args->main);
  func (arg);

  return 0;
}

void
coro_transfer (coro_context *prev, coro_context *next)
{
  pthread_mutex_lock (&coro_mutex);

  next->flags = 1;
  pthread_cond_signal (&next->cv);

  prev->flags = 0;

  while (!prev->flags)
    pthread_cond_wait (&prev->cv, &coro_mutex);

  if (prev->flags == 2)
    {
      pthread_mutex_unlock (&coro_mutex);
      pthread_cond_destroy (&prev->cv);
      pthread_detach (pthread_self ());
      pthread_exit (0);
    }

  pthread_mutex_unlock (&coro_mutex);
}

void
coro_create (coro_context *ctx, coro_func coro, void *arg, void *sptr, size_t ssize)
{
  static coro_context nctx;
  static int once;

  if (!once)
    {
      once = 1;

      pthread_cond_init (&nctx.cv, 0);
    }

  pthread_cond_init (&ctx->cv, 0);

  if (coro)
    {
      pthread_attr_t attr;
      struct coro_init_args args;
      pthread_t id;

      args.func = coro;
      args.arg  = arg;
      args.self = ctx;
      args.main = &nctx;

      pthread_attr_init (&attr);
#if __UCLIBC__
      /* exists, but is borked */
      /*pthread_attr_setstacksize (&attr, (size_t)ssize);*/
#elif __CYGWIN__
      /* POSIX, not here */
      pthread_attr_setstacksize (&attr, (size_t)ssize);
#else
      pthread_attr_setstack (&attr, sptr, (size_t)ssize);
#endif
      pthread_attr_setscope (&attr, PTHREAD_SCOPE_PROCESS);
      pthread_create (&id, &attr, coro_init, &args);

      coro_transfer (args.main, args.self);
    }
}

void
coro_destroy (coro_context *ctx)
{
  pthread_mutex_lock (&coro_mutex);
  ctx->flags = 2;
  pthread_cond_signal (&ctx->cv);
  pthread_mutex_unlock (&coro_mutex);
}

/*****************************************************************************/
/* fiber backend                                                             */
/*****************************************************************************/
#elif CORO_FIBER

#define WIN32_LEAN_AND_MEAN
#if _WIN32_WINNT < 0x0400
  #undef _WIN32_WINNT
  #define _WIN32_WINNT 0x0400
#endif
#include <windows.h>

VOID CALLBACK
coro_init (PVOID arg)
{
  coro_context *ctx = (coro_context *)arg;

  ctx->coro (ctx->arg);
}

void
coro_transfer (coro_context *prev, coro_context *next)
{
  if (!prev->fiber)
    {
      prev->fiber = GetCurrentFiber ();

      if (prev->fiber == 0 || prev->fiber == (void *)0x1e00)
        prev->fiber = ConvertThreadToFiber (0);
    }

  SwitchToFiber (next->fiber);
}

void
coro_create (coro_context *ctx, coro_func coro, void *arg, void *sptr, size_t ssize)
{
  ctx->fiber = 0;
  ctx->coro  = coro;
  ctx->arg   = arg;

  if (!coro)
    return;

  ctx->fiber = CreateFiber (ssize, coro_init, ctx);
}

void
coro_destroy (coro_context *ctx)
{
  DeleteFiber (ctx->fiber);
}

#else
  #error unsupported backend
#endif

/*****************************************************************************/
/* stack management                                                          */
/*****************************************************************************/
#if CORO_STACKALLOC

#include <stdlib.h>

#ifndef _WIN32
# include <unistd.h>
#endif

#if CORO_USE_VALGRIND
# include <valgrind/valgrind.h>
#endif

#if _POSIX_MAPPED_FILES
# include <sys/mman.h>
# define CORO_MMAP 1
# ifndef MAP_ANONYMOUS
#  ifdef MAP_ANON
#   define MAP_ANONYMOUS MAP_ANON
#  else
#   undef CORO_MMAP
#  endif
# endif
# include <limits.h>
#else
# undef CORO_MMAP
#endif

#if _POSIX_MEMORY_PROTECTION
# ifndef CORO_GUARDPAGES
#  define CORO_GUARDPAGES 4
# endif
#else
# undef CORO_GUARDPAGES
#endif

#if !CORO_MMAP
# undef CORO_GUARDPAGES
#endif

#if !__i386__ && !__x86_64__ && !__powerpc__ && !__arm__ && !__aarch64__ && !__m68k__ && !__alpha__ && !__mips__ && !__sparc64__
# undef CORO_GUARDPAGES
#endif

#ifndef CORO_GUARDPAGES
# define CORO_GUARDPAGES 0
#endif

#if !PAGESIZE
  #if !CORO_MMAP
    #define PAGESIZE 4096
  #else
    static size_t
    coro_pagesize (void)
    {
      static size_t pagesize;

      if (!pagesize)
        pagesize = sysconf (_SC_PAGESIZE);

      return pagesize;
    }

    #define PAGESIZE coro_pagesize ()
  #endif
#endif

int
coro_stack_alloc (struct coro_stack *stack, unsigned int size)
{
  if (!size)
    size = 256 * 1024;

  stack->sptr = 0;
  stack->ssze = ((size_t)size * sizeof (void *) + PAGESIZE - 1) / PAGESIZE * PAGESIZE;

#if CORO_FIBER

  stack->sptr = (void *)stack;
  return 1;

#else

  size_t ssze = stack->ssze + CORO_GUARDPAGES * PAGESIZE;
  void *base;

  #if CORO_MMAP
    /* mmap supposedly does allocate-on-write for us */
    base = mmap (0, ssze, PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);

    if (base == (void *)-1)
      {
        /* some systems don't let us have executable heap */
        /* we assume they won't need executable stack in that case */
        base = mmap (0, ssze, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);

        if (base == (void *)-1)
          return 0;
      }

    #if CORO_GUARDPAGES
      mprotect (base, CORO_GUARDPAGES * PAGESIZE, PROT_NONE);
    #endif

    base = (void*)((char *)base + CORO_GUARDPAGES * PAGESIZE);
  #else
    base = malloc (ssze);
    if (!base)
      return 0;
  #endif

  #if CORO_USE_VALGRIND
    stack->valgrind_id = VALGRIND_STACK_REGISTER ((char *)base, ((char *)base) + ssze - CORO_GUARDPAGES * PAGESIZE);
  #endif

  stack->sptr = base;
  return 1;

#endif
}

void
coro_stack_free (struct coro_stack *stack)
{
#if CORO_FIBER
  /* nop */
#else
  #if CORO_USE_VALGRIND
    VALGRIND_STACK_DEREGISTER (stack->valgrind_id);
  #endif

  #if CORO_MMAP
    if (stack->sptr)
      munmap ((void*)((char *)stack->sptr - CORO_GUARDPAGES * PAGESIZE),
              stack->ssze                 + CORO_GUARDPAGES * PAGESIZE);
  #else
    free (stack->sptr);
  #endif
#endif
}

#endif
