sysmem.c
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1 /**
2  ******************************************************************************
3  * @file sysmem.c
4  * @author Generated by STM32CubeIDE
5  * @brief STM32CubeIDE System Memory calls file
6  *
7  * For more information about which C functions
8  * need which of these lowlevel functions
9  * please consult the newlib libc manual
10  ******************************************************************************
11  * @attention
12  *
13  * <h2><center>&copy; Copyright (c) 2020 STMicroelectronics.
14  * All rights reserved.</center></h2>
15  *
16  * This software component is licensed by ST under BSD 3-Clause license,
17  * the "License"; You may not use this file except in compliance with the
18  * License. You may obtain a copy of the License at:
19  * opensource.org/licenses/BSD-3-Clause
20  *
21  ******************************************************************************
22  */
23 
24 /* Includes */
25 #include <errno.h>
26 #include <stddef.h>
27 #include <stdint.h>
28 
29 /**
30  * Pointer to the current high watermark of the heap usage
31  */
32 static uint8_t *__sbrk_heap_end = NULL;
33 
34 /**
35  * @brief _sbrk() allocates memory to the newlib heap and is used by malloc
36  * and others from the C library
37  *
38  * @verbatim
39  * ############################################################################
40  * # .data # .bss # newlib heap # MSP stack #
41  * # # # # Reserved by _Min_Stack_Size #
42  * ############################################################################
43  * ^-- RAM start ^-- _end _estack, RAM end --^
44  * @endverbatim
45  *
46  * This implementation starts allocating at the '_end' linker symbol
47  * The '_Min_Stack_Size' linker symbol reserves a memory for the MSP stack
48  * The implementation considers '_estack' linker symbol to be RAM end
49  * NOTE: If the MSP stack, at any point during execution, grows larger than the
50  * reserved size, please increase the '_Min_Stack_Size'.
51  *
52  * @param incr Memory size
53  * @return Pointer to allocated memory
54  */
55 void *_sbrk(ptrdiff_t incr)
56 {
57  extern uint8_t _end; /* Symbol defined in the linker script */
58  extern uint8_t _estack; /* Symbol defined in the linker script */
59  extern uint32_t _Min_Stack_Size; /* Symbol defined in the linker script */
60  const uint32_t stack_limit = (uint32_t)&_estack - (uint32_t)&_Min_Stack_Size;
61  const uint8_t *max_heap = (uint8_t *)stack_limit;
62  uint8_t *prev_heap_end;
63 
64  /* Initalize heap end at first call */
65  if (NULL == __sbrk_heap_end)
66  {
67  __sbrk_heap_end = &_end;
68  }
69 
70  /* Protect heap from growing into the reserved MSP stack */
71  if (__sbrk_heap_end + incr > max_heap)
72  {
73  errno = ENOMEM;
74  return (void *)-1;
75  }
76 
77  prev_heap_end = __sbrk_heap_end;
78  __sbrk_heap_end += incr;
79 
80  return (void *)prev_heap_end;
81 }
__sbrk_heap_end
static uint8_t * __sbrk_heap_end
Definition: sysmem.c:32
_sbrk
void * _sbrk(ptrdiff_t incr)
_sbrk() allocates memory to the newlib heap and is used by malloc and others from the C library
Definition: sysmem.c:55