/* Copyright (C) 1992, the Florida State University
   Distributed by the Florida State University under the terms of the
   GNU Library General Public License.

This file is part of Pthreads.

Pthreads is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public
License as published by the Free Software Foundation (version 2).

Pthreads is distributed "AS IS" in the hope that it will be
useful, but WITHOUT ANY WARRANTY; without even the implied
warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
See the GNU Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with Pthreads; see the file COPYING.  If not, write
to the Free Software Foundation, 675 Mass Ave, Cambridge,
MA 02139, USA.

Report problems and direct all questions to:

  pthreads-bugs@ada.cs.fsu.edu

  @(#)stack.c	2.2 5/31/94

*/

/*
 * Thread stack allocation.
 * This handles all stack allocation including defined policies.
 */

#include "pthread_internals.h"
#include <sys/resource.h>

#ifndef STAND_ALONE
#include <sys/mman.h>
#endif

extern char *pthread_get_sp();
extern int *pthread_get_fp();
void pthread_set_sp();
void pthread_set_fp();

#ifdef STACK_CHECK
int pthread_page_size;
#elif STAND_ALONE
int pthread_page_size = 8192;
#endif

#if STACK_CHECK && SIGNAL_STACK
#ifdef SOLARIS
#include <sys/frame.h>
#else !SOLARIS
#include <sparc/frame.h>
#endif !SOLARIS

extern KERNEL_STACK pthread_tempstack;
static struct frame f;
static int fp_offset = (int)&f.fr_savfp - (int)&f;
static int fp_index = ((int)&f.fr_savfp - (int)&f) / sizeof(int);
#endif

#ifdef STACK_CHECK
#ifdef SIGNAL_STACK
#define NUM_PAGES 3
#else !SIGNAL_STACK
#define NUM_PAGES 1
#endif !SIGNAL_STACK
#else !STACK_CHECK
#define NUM_PAGES -1
#endif !STACK_CHECK

/*------------------------------------------------------------*/
/*
 * pthread_stack_init - initialize the main thread's stack
 */
void pthread_stack_init(p)
pthread_t p;
{
  struct rlimit rlim;
  
#ifdef STACK_CHECK
  pthread_page_size = (int) GETPAGESIZE(_SC_PAGESIZE);
#endif

  /*
   * Stack size of the main thread is the stack size of the process
   */
#ifdef STAND_ALONE
  p->attr.stacksize = 150*SA(MINFRAME);
#else
  if (getrlimit(RLIMIT_STACK, &rlim) != 0) {
    perror("getrlimit");
    pthread_process_exit(1);
  }
  p->attr.stacksize = rlim.rlim_cur;
#endif

  /*
   * dummy stack base which can be freed
   */
  p->stack_base = (char *) malloc(sizeof(int));
#ifdef STACK_CHECK
  pthread_lock_stack(p);
#endif STACK_CHECK
}

#ifdef STACK_CHECK
/*------------------------------------------------------------*/
/*
 * pthread_lock_stack - lock memory page on stack
 * lock page at lower bound of stack to cause segmentation violation
 * when stack overflows
 */
int pthread_lock_stack(p)
pthread_t p;
{
  SIGSTACK_T ss;
#ifndef SVR4

  ss.ss_sp = (char *) SA((int) pthread_tempstack_top - STACK_OFFSET);
  CLR_SS_ONSTACK;
  if (SIGSTACK(&ss, (SIGSTACK_T *) NULL)) {
#ifdef DEBUG
    fprintf(stderr,
	    "Pthreads: Could not specify signal stack, errno %d\n", errno);
#endif DEBUG
    return(-1);
  }
#endif !SVR4

  if (p->state & T_MAIN ||
      !mprotect((caddr_t) PA(p->stack_base),
		NUM_PAGES * pthread_page_size,
		PROT_NONE)) {
#ifdef SIGNAL_STACK
    p->state |= T_LOCKED;
#endif
    return (0);
  }
#ifdef DEBUG
    fprintf(stderr,
	    "Pthreads: Could not lock stack, errno %d\n", errno);
#endif DEBUG
  return (-1);
}

/*------------------------------------------------------------*/
/*
 * pthread_unlock_all_stack - unlock all pages of stack, called at thread
 *                    termination.
 */
int pthread_unlock_all_stack(p)
pthread_t p;
{
  if (p->state & T_MAIN)
    return(0);
  else
    return mprotect((caddr_t) PA(p->stack_base), 
		    NUM_PAGES * pthread_page_size,
		    PROT_READ | PROT_WRITE);
}

#ifdef SIGNAL_STACK
/*------------------------------------------------------------*/
/*
 * pthread_unlock_stack - unlock memory pages on stack if overflow occurs
 */
int pthread_unlock_stack(p)
pthread_t p;
{
  if (p->state & T_MAIN ||
      !mprotect((caddr_t) PA(p->stack_base)+pthread_page_size,
		(NUM_PAGES-1) * pthread_page_size, 
		PROT_READ | PROT_WRITE)) {
    p->state &= ~T_LOCKED;
    return (0);
  }
  return (-1);
}
#endif
#endif

/*------------------------------------------------------------*/
/*
 * pthread_alloc_stack - allocate stack space on heap for a thread
 * Stacks are deallocated when the thread has returned and is detached.
 * In case, SIGNAL_STACK is defined, 2 extra pages are allocated and
 * locked to detect stack overflow condition. These pages are unlocked to
 * allow the stack overflow handling.
 */
int pthread_alloc_stack(p)
pthread_t p;
{
#ifndef _POSIX_THREAD_ATTR_STACKSIZE
  p->attr.stacksize = DEFAULT_STACKSIZE;
#endif

  p->stack_base = (char *) malloc(p->attr.stacksize + PTHREAD_BODY_OFFSET
#ifdef STACK_CHECK
				  + pthread_page_size * (NUM_PAGES+1)
#endif STACK_CHECK
				  );
  
  if ((int) p->stack_base == NULL) {
#ifdef DEBUG
    fprintf(stderr, "\n*** Out of space for thread stacks. ***\n");
    fflush(stderr);
#endif
    return(FALSE);
  }
  
#ifdef STACK_CHECK
  if (pthread_lock_stack(p))
    return(FALSE);
#endif

  return(TRUE);
}

#if defined(STACK_CHECK) && defined(SIGNAL_STACK)
/*------------------------------------------------------------*/
/*
 * switch_stacks - Flushes the windows and copies the stack frames from signal 
 *   stack to thread's stack and then sets the frame pointer links correctly for
 *   thread's stack and then finally switches to thread's stack.
 */

void switch_stacks(oldsp)
int oldsp;
{
  char *sp = pthread_get_sp();
  int *fp = pthread_get_fp();
  int size = (char *) SA((int) pthread_tempstack_top) - sp;
  int *target = (int *)(oldsp - size);
  int *user_fp = target;

  pthread_ST_FLUSH_WINDOWS();
  memcpy(target, sp, size);

  do {
    user_fp[fp_index] = (int)user_fp + (int)((char *)fp - sp);
    user_fp = (int *)user_fp[fp_index];
    sp = (char *)fp;
    fp = (int *)fp[fp_index];
  } while (fp && ((char *)fp < ((char *) SA((int) pthread_tempstack_top))));

  user_fp[fp_index] = oldsp;
  pthread_set_fp(target[fp_index]);
  pthread_set_sp(target);
}
/*------------------------------------------------------------*/
#endif

#ifdef STAND_ALONE

/*------------------------------------------------------------*/
/*
 * sbrk - change segment size (for heap allocation)
 */

int sbrk(incr)
     int incr;
{
  extern char heap_start;
  int old;
  
  if ((cur_heap + incr) < ((int)(&heap_start) + HEAP_SIZE)) {
    old = cur_heap;
    cur_heap += incr;
    return old;
  }
  else {
    set_errno(ENOMEM);
    return (-1);
  }
}

#endif STAND_ALONE