chmemcore.c

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/*
    ChibiOS - Copyright (C) 2006-2026 Giovanni Di Sirio.
 
    This file is part of ChibiOS.
 
    ChibiOS is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation version 3 of the License.
 
    ChibiOS is distributed 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 General Public License for more details.
 
    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/
 
/**
 * @file    oslib/src/chmemcore.c
 * @brief   Core memory manager code.
 *
 * @addtogroup oslib_memcore
 * @details Core Memory Manager related APIs and services.
 *          <h2>Operation mode</h2>
 *          The core memory manager is a simplified allocator that only
 *          allows to allocate memory blocks without the possibility to
 *          free them.<br>
 *          This allocator is meant as a memory blocks provider for the
 *          other allocators such as:
 *          - C-Runtime allocator (through a compiler specific adapter module).
 *          - Heap allocator (see @ref oslib_memheaps).
 *          - Memory pools allocator (see @ref oslib_mempools).
 *          .
 *          By having a centralized memory provider the various allocators
 *          can coexist and share the main memory.<br>
 *          This allocator, alone, is also useful for very simple
 *          applications that just require a simple way to get memory
 *          blocks.
 * @pre     In order to use the core memory manager APIs the @p CH_CFG_USE_MEMCORE
 *          option must be enabled in @p chconf.h.
 * @note    Compatible with RT and NIL.
 * @{
 */
 
#include "ch.h"
 
#if (CH_CFG_USE_MEMCORE == TRUE) || defined(__DOXYGEN__)
 
/*===========================================================================*/
/* Module exported variables.                                                */
/*===========================================================================*/
 
/**
 * @brief   Memory core descriptor.
 */
memcore_t ch_memcore;
 
/*===========================================================================*/
/* Module local types.                                                       */
/*===========================================================================*/
 
/*===========================================================================*/
/* Module local variables.                                                   */
/*===========================================================================*/
 
/*===========================================================================*/
/* Module local functions.                                                   */
/*===========================================================================*/
 
/*===========================================================================*/
/* Module exported functions.                                                */
/*===========================================================================*/
 
/**
 * @brief   Low level memory manager initialization.
 *
 * @notapi
 */
void __core_init(void) {
#if CH_CFG_MEMCORE_SIZE == 0
  extern uint8_t __heap_base__[];
  extern uint8_t __heap_end__[];
 
  /*lint -save -e9033 [10.8] Required cast operations.*/
  ch_memcore.basemem = __heap_base__;
  ch_memcore.topmem  = __heap_end__;
  /*lint restore*/
#else
  static uint8_t static_heap[CH_CFG_MEMCORE_SIZE];
 
  ch_memcore.basemem = &static_heap[0];
  ch_memcore.topmem  = &static_heap[CH_CFG_MEMCORE_SIZE];
#endif
}
 
/**
 * @brief   Allocates a memory block starting from the lowest address upward.
 * @details This function allocates a block of @p offset + @p size bytes. The
 *          returned pointer has @p offset bytes before its address and
 *          @p size bytes after.
 *
 * @param[in] size      the size of the block to be allocated.
 * @param[in] align     desired memory alignment
 * @param[in] offset    aligned pointer offset
 * @return              A pointer to the allocated memory block.
 * @retval NULL         allocation failed, core memory exhausted.
 *
 * @iclass
 */
void *chCoreAllocFromBaseI(size_t size, unsigned align, size_t offset) {
  uintptr_t base, top, p, next;
 
  chDbgCheckClassI();
  chDbgCheck(MEM_IS_VALID_ALIGNMENT(align));
 
  /*lint -save -e9033 [10.8] Required cast operations.*/
  base = (uintptr_t)ch_memcore.basemem;
  top  = (uintptr_t)ch_memcore.topmem;
  /*lint -restore*/
 
  /* Integer-space pre-check: offset alone must fit in available space to
     avoid forming an out-of-range value before the alignment step.*/
  if (offset > (top - base)) {
    return NULL;
  }
 
  /* All remaining arithmetic stays in integer space; no pointer is formed
     until the bounds are verified.*/
  p    = MEM_ALIGN_NEXT(base + offset, align);
  next = p + size;
 
  /* Considering also the case where there is numeric overflow.*/
  if ((next > top) || (next < base)) {
    return NULL;
  }
 
  /*lint -save -e9033 [10.8] Required cast operations.*/
  ch_memcore.basemem = (uint8_t *)next;
  /*lint -restore*/
 
  return (void *)p;
}
 
/**
 * @brief   Allocates a memory block starting from the top address downward.
 * @details This function allocates a block of @p offset + @p size bytes. The
 *          returned pointer has @p offset bytes before its address and
 *          @p size bytes after.
 *
 * @param[in] size      the size of the block to be allocated.
 * @param[in] align     desired memory alignment
 * @param[in] offset    aligned pointer offset
 * @return              A pointer to the allocated memory block.
 * @retval NULL         allocation failed, core memory exhausted.
 *
 * @iclass
 */
void *chCoreAllocFromTopI(size_t size, unsigned align, size_t offset) {
  uintptr_t base, top, p, prev;
 
  chDbgCheckClassI();
  chDbgCheck(MEM_IS_VALID_ALIGNMENT(align));
 
  /*lint -save -e9033 [10.8] Required cast operations.*/
  base = (uintptr_t)ch_memcore.basemem;
  top  = (uintptr_t)ch_memcore.topmem;
  /*lint -restore*/
 
  /* Integer-space pre-check: size alone must fit in available space to
     avoid forming an out-of-range value before the alignment step.*/
  if (size > (top - base)) {
    return NULL;
  }
 
  /* All remaining arithmetic stays in integer space; no pointer is formed
     until the bounds are verified.*/
  p    = MEM_ALIGN_PREV(top - size, align);
  prev = p - offset;
 
  /* Considering also the case where there is numeric overflow.*/
  if ((prev < base) || (prev > top)) {
    return NULL;
  }
 
  /*lint -save -e9033 [10.8] Required cast operations.*/
  ch_memcore.topmem = (uint8_t *)prev;
  /*lint -restore*/
 
  return (void *)p;
}
 
/**
 * @brief   Allocates a memory block starting from the lowest address upward.
 * @details This function allocates a block of @p offset + @p size bytes. The
 *          returned pointer has @p offset bytes before its address and
 *          @p size bytes after.
 *
 * @param[in] size      the size of the block to be allocated.
 * @param[in] align     desired memory alignment
 * @param[in] offset    aligned pointer offset
 * @return              A pointer to the allocated memory block.
 * @retval NULL         allocation failed, core memory exhausted.
 *
 * @api
 */
void *chCoreAllocFromBase(size_t size, unsigned align, size_t offset) {
  void *p;
 
  chSysLock();
  p = chCoreAllocFromBaseI(size, align, offset);
  chSysUnlock();
 
  return p;
}
 
/**
 * @brief   Allocates a memory block starting from the top address downward.
 * @details This function allocates a block of @p offset + @p size bytes. The
 *          returned pointer has @p offset bytes before its address and
 *          @p size bytes after.
 *
 * @param[in] size      the size of the block to be allocated.
 * @param[in] align     desired memory alignment
 * @param[in] offset    aligned pointer offset
 * @return              A pointer to the allocated memory block.
 * @retval NULL         allocation failed, core memory exhausted.
 *
 * @api
 */
void *chCoreAllocFromTop(size_t size, unsigned align, size_t offset) {
  void *p;
 
  chSysLock();
  p = chCoreAllocFromTopI(size, align, offset);
  chSysUnlock();
 
  return p;
}
 
/**
 * @brief   Core memory status.
 *
 * @return              The size, in bytes, of the free core memory.
 *
 * @xclass
 */
size_t chCoreGetStatusX(void) {
 
  /*lint -save -e9033 [10.8] The cast is safe.*/
  return (size_t)(ch_memcore.topmem - ch_memcore.basemem);
  /*lint -restore*/
}
#endif /* CH_CFG_USE_MEMCORE == TRUE */
 
/** @} */