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 /*
  *  sbrk.c
  *
  * Authorship
  * ----------
  * This software was created by
  *     Till Straumann <strauman@slac.stanford.edu>, 2002,
  *        Stanford Linear Accelerator Center, Stanford University.
  *
  * Acknowledgement of sponsorship
  * ------------------------------
  * This software was produced by
  *     the Stanford Linear Accelerator Center, Stanford University,
  *        under Contract DE-AC03-76SFO0515 with the Department of Energy.
  *
  * Government disclaimer of liability
  * ----------------------------------
  * Neither the United States nor the United States Department of Energy,
  * nor any of their employees, makes any warranty, express or implied, or
  * assumes any legal liability or responsibility for the accuracy,
  * completeness, or usefulness of any data, apparatus, product, or process
  * disclosed, or represents that its use would not infringe privately owned
  * rights.
  *
  * Stanford disclaimer of liability
  * --------------------------------
  * Stanford University makes no representations or warranties, express or
  * implied, nor assumes any liability for the use of this software.
  *
  * Stanford disclaimer of copyright
  * --------------------------------
  * Stanford University, owner of the copyright, hereby disclaims its
  * copyright and all other rights in this software.  Hence, anyone may
  * freely use it for any purpose without restriction.
  *
  * Maintenance of notices
  * ----------------------
  * In the interest of clarity regarding the origin and status of this
  * SLAC software, this and all the preceding Stanford University notices
  * are to remain affixed to any copy or derivative of this software made
  * or distributed by the recipient and are to be affixed to any copy of
  * software made or distributed by the recipient that contains a copy or
  * derivative of this software.
  *
  * ------------------ SLAC Software Notices, Set 4 OTT.002a, 2004 FEB 03
  */
 
 /*
  *  Hack around the 32bit powerpc 32M problem:
  *
  *  GCC by default uses relative branches which can not jump
  *  farther than 32M. Hence all program text is confined to
  *  a single 32M segment.
  *  This hack gives the RTEMS malloc region all memory below
  *  32M at startup. Only when this region is exhausted will sbrk
  *  add more memory. Loading modules may fail at that point, hence
  *  the user is expected to load all modules at startup _prior_
  *  to malloc()ing lots of memory...
  *
  *  NOTE: it would probably be better to have a separate region
  *        for module code.
  */
 
 #include <errno.h>
 #include <unistd.h>
 
 #include <bsp.h>
 #include <bsp/bootcard.h>
 
 #include <rtems/sysinit.h>
 
 #ifdef CONFIGURE_MALLOC_BSP_SUPPORTS_SBRK
 
 #define INVALID_REMAINING_START ((uintptr_t) -1)
 
 static uintptr_t remaining_start = INVALID_REMAINING_START;
 static uintptr_t remaining_size = 0;
 
 /* App. may provide a value by defining the BSP_sbrk_policy
  * variable.
  *
  *  (-1) -> give all memory to the heap at initialization time
  *  > 0  -> value used as sbrk amount; initially give 32M
  *    0  -> limit memory effectively to 32M.
  *
  */
 extern uintptr_t        BSP_sbrk_policy[] __attribute__((weak));
 
 #define LIMIT_32M  0x02000000
 
 /**
  * @brief Gives the BSP a chance to reduce the work area size with sbrk()
  * adding more later.
  *
  * bsp_sbrk_init() may reduce the work area size passed in. The routine
  * returns the 'sbrk_amount' to be used when extending the heap.  Note that
  * the return value may be zero.
  *
  * In case the @a mem area size is altered, then the remaining size of the
  * @a mem area must be greater than or equal to @a min_size.
  */
 static ptrdiff_t bsp_sbrk_init(const Memory_Information *mem, uintptr_t min_size)
 {
   uintptr_t         rval = 0;
   uintptr_t         policy;
   uintptr_t         remaining_end;
   Memory_Area      *area;
 
   area = &mem->areas[ 0 ];
   remaining_start = (uintptr_t) _Memory_Get_free_begin(area);
   remaining_size  = _Memory_Get_free_size(area);
   remaining_end   = (uintptr_t) _Memory_Get_end(area);
 
   if (remaining_start < LIMIT_32M &&
       remaining_end > LIMIT_32M &&
       min_size <= LIMIT_32M - remaining_start) {
     /* clip at LIMIT_32M */
     rval = remaining_end - LIMIT_32M;
     _Memory_Set_end(area, (void *) (LIMIT_32M - remaining_start));
     remaining_start = LIMIT_32M;
     remaining_size  = rval;
   }
 
   policy = (0 == BSP_sbrk_policy[0] ? (uintptr_t)(-1) : BSP_sbrk_policy[0]);
   switch ( policy ) {
       case (uintptr_t)(-1):
         _Memory_Set_end(area, (const char *) _Memory_Get_end(area) + rval);
         remaining_start = (uintptr_t) _Memory_Get_end(area);
         remaining_size  = 0;
       break;
 
       case 0:
         remaining_size = 0;
       break;
 
       default:
         if ( rval > policy )
           rval = policy;
       break;
   }
 
   return (ptrdiff_t) (rval <= PTRDIFF_MAX ? rval : rval / 2);
 }
 
 void *sbrk(ptrdiff_t incr)
 {
   void *rval=(void*)-1;
 
   if ( remaining_start != INVALID_REMAINING_START && incr <= remaining_size) {
     remaining_size-=incr;
     rval = (void *) remaining_start;
     remaining_start += incr;
   }
 
   /*
    * sbrk() is a Legacy POSIX method which means it is no longer part of the
    * POSIX standard. Historically, it was required to set errno to ENOMEM if
    * the extension failed. This implementation does not do that for two
    * reasons. First, this method is only called from the RTEMS malloc()
    * implementation and does not expect errno to be set when -1 is returned.
    * Second, setting errno implicitly pulls in some of the newlib reentrancy
    * support. Not setting errno avoids this method forcing that support
    * into every application for every BSP that uses this method.
    */
 
   #ifdef DEBUG
     printk("************* SBRK 0x%08x (ret 0x%08x) **********\n", incr, rval);
   #endif
   return rval;
 }
 
 static void bsp_sbrk_initialize(void)
 {
   uintptr_t overhead = _Heap_Area_overhead(CPU_HEAP_ALIGNMENT);
   uintptr_t work_space_size = rtems_configuration_get_work_space_size();
   ptrdiff_t sbrk_amount = bsp_sbrk_init(
     _Memory_Get(),
     work_space_size
       + overhead
       + (rtems_configuration_get_unified_work_area() ? 0 : overhead)
   );
 
   rtems_heap_set_sbrk_amount(sbrk_amount);
 }
 
 RTEMS_SYSINIT_ITEM(
   bsp_sbrk_initialize,
   RTEMS_SYSINIT_SBRK,
   RTEMS_SYSINIT_ORDER_MIDDLE
 );
 
 #endif /* CONFIGURE_MALLOC_BSP_SUPPORTS_SBRK */

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