summaryrefslogtreecommitdiff
path: root/libc/stdlib/malloc/malloc.h
blob: aa41870b914738ad1a8f85af15f95ab60eb12437 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
/*
 * libc/stdlib/malloc/malloc.h -- small malloc implementation
 *
 *  Copyright (C) 2002  NEC Corporation
 *  Copyright (C) 2002  Miles Bader <miles@gnu.org>
 *
 * This file is subject to the terms and conditions of the GNU Lesser
 * General Public License.  See the file COPYING.LIB in the main
 * directory of this archive for more details.
 *
 * Written by Miles Bader <miles@gnu.org>
 */

/* The alignment we guarantee for malloc return values.  We prefer this
   to be at least sizeof (size_t) bytes because (a) we have to allocate
   that many bytes for the header anyway and (b) guaranteeing word
   alignment can be a significant win on targets like m68k and Coldfire,
   where __alignof__(double) == 2.  */
#define MALLOC_ALIGNMENT \
  (__alignof__ (double) > sizeof (size_t) ? __alignof__ (double) : sizeof (size_t))

/* The system pagesize... */
#define MALLOC_PAGE_SIZE	sysconf(_SC_PAGESIZE)

/* The minimum size of block we request from the the system to extend the
   heap for small allocations (we may request a bigger block if necessary to
   satisfy a particularly big request).  */
#define MALLOC_HEAP_EXTEND_SIZE	MALLOC_PAGE_SIZE

/* When a heap free-area grows above this size, try to unmap it, releasing
   the memory back to the system.  */
#define MALLOC_UNMAP_THRESHOLD	(8*MALLOC_PAGE_SIZE)
/* When unmapping a free-area, retain this many bytes if it's the only one,
   to avoid completely emptying the heap.  This is only a heuristic -- the
   existance of another free area, even if it's smaller than
   MALLOC_MIN_SIZE, will cause us not to reserve anything.  */
#define MALLOC_MIN_SIZE		(2*MALLOC_PAGE_SIZE)

/* When realloc shrinks an allocation, it only does so if more than this
   many bytes will be freed; it must at at least HEAP_MIN_SIZE.  Larger
   values increase speed (by reducing heap fragmentation) at the expense of
   space.  */
#define MALLOC_REALLOC_MIN_FREE_SIZE  (HEAP_MIN_SIZE + 16)


/* For systems with an MMU, use sbrk to map/unmap memory for the malloc
   heap, instead of mmap/munmap.  This is a tradeoff -- sbrk is faster than
   mmap/munmap, and guarantees contiguous allocation, but is also less
   flexible, and causes the heap to only be shrinkable from the end.  */
#ifdef __ARCH_USE_MMU__
# define MALLOC_USE_SBRK
#endif


/* The current implementation of munmap in uClinux doesn't work correctly:
   it requires that ever call to munmap exactly match a corresponding call
   to mmap (that is, it doesn't allow you to unmap only part of a
   previously allocated block, or to unmap two contiguous blocks with a
   single call to munmap).  This behavior is broken, and uClinux should be
   fixed; however, until it is, we add code to work around the problem in
   malloc.  */
#ifdef __UCLIBC_UCLINUX_BROKEN_MUNMAP__

/* A structure recording a block of memory mmapped by malloc.  */
struct malloc_mmb
{
  void *mem;			/* the mmapped block */
  size_t size;			/* its size */
  struct malloc_mmb *next;
};

/* A list of all malloc_mmb structures describing blocks that malloc has
   mmapped, ordered by the block address.  */
extern struct malloc_mmb *__malloc_mmapped_blocks;

/* A heap used for allocating malloc_mmb structures.  We could allocate
   them from the main heap, but that tends to cause heap fragmentation in
   annoying ways.  */
extern struct heap_free_area *__malloc_mmb_heap;

/* Define MALLOC_MMB_DEBUGGING to cause malloc to emit debugging info about
   about mmap block allocation/freeing by the `uclinux broken munmap' code
   to stderr, when the variable __malloc_mmb_debug is set to true. */
#ifdef MALLOC_MMB_DEBUGGING
# include <stdio.h>

extern int __malloc_mmb_debug;
# define MALLOC_MMB_DEBUG(indent, fmt, args...)				      \
   (__malloc_mmb_debug ? __malloc_debug_printf (indent, fmt , ##args) : 0)
# define MALLOC_MMB_DEBUG_INDENT(indent)				      \
   (__malloc_mmb_debug ? __malloc_debug_indent (indent) : 0)
# ifndef MALLOC_DEBUGGING
#  define MALLOC_DEBUGGING
# endif
#else /* !MALLOC_MMB_DEBUGGING */
# define MALLOC_MMB_DEBUG(fmt, args...) (void)0
# define MALLOC_MMB_DEBUG_INDENT(indent) (void)0
#endif /* MALLOC_MMB_DEBUGGING */

#endif /* __UCLIBC_UCLINUX_BROKEN_MUNMAP__ */


/* The size of a malloc allocation is stored in a size_t word
   MALLOC_HEADER_SIZE bytes prior to the start address of the allocation:

     +--------+---------+-------------------+
     | SIZE   |(unused) | allocation  ...   |
     +--------+---------+-------------------+
     ^ BASE             ^ ADDR
     ^ ADDR - MALLOC_HEADER_SIZE
*/

/* The amount of extra space used by the malloc header.  */
#define MALLOC_HEADER_SIZE			\
  (MALLOC_ALIGNMENT < sizeof (size_t)		\
   ? sizeof (size_t)				\
   : MALLOC_ALIGNMENT)

/* Set up the malloc header, and return the user address of a malloc block. */
#define MALLOC_SETUP(base, size)  \
  (MALLOC_SET_SIZE (base, size), (void *)((char *)base + MALLOC_HEADER_SIZE))
/* Set the size of a malloc allocation, given the base address.  */
#define MALLOC_SET_SIZE(base, size)	(*(size_t *)(base) = (size))

/* Return base-address of a malloc allocation, given the user address.  */
#define MALLOC_BASE(addr)	((void *)((char *)addr - MALLOC_HEADER_SIZE))
/* Return the size of a malloc allocation, given the user address.  */
#define MALLOC_SIZE(addr)	(*(size_t *)MALLOC_BASE(addr))

#include <bits/uClibc_mutex.h>

#ifdef __UCLIBC_HAS_THREADS__
# define MALLOC_USE_LOCKING
#endif

#ifdef MALLOC_USE_SBRK
/* This lock is used to serialize uses of the `sbrk' function (in both
   malloc and free, sbrk may be used several times in succession, and
   things will break if these multiple calls are interleaved with another
   thread's use of sbrk!).  */
__UCLIBC_MUTEX_EXTERN(__malloc_sbrk_lock);
#  define __malloc_lock_sbrk()	__UCLIBC_MUTEX_LOCK_CANCEL_UNSAFE (__malloc_sbrk_lock)
#  define __malloc_unlock_sbrk() __UCLIBC_MUTEX_UNLOCK_CANCEL_UNSAFE (__malloc_sbrk_lock)
#else
# define __malloc_lock_sbrk()	(void)0
# define __malloc_unlock_sbrk()	(void)0
#endif /* MALLOC_USE_SBRK */

/* Define MALLOC_DEBUGGING to cause malloc to emit debugging info to stderr
   when the variable __malloc_debug is set to true. */
#ifdef MALLOC_DEBUGGING

extern void __malloc_debug_init (void) attribute_hidden;

/* The number of spaces in a malloc debug indent level.  */
#define MALLOC_DEBUG_INDENT_SIZE 3

extern int __malloc_debug attribute_hidden, __malloc_check attribute_hidden;

# define MALLOC_DEBUG(indent, fmt, args...)				      \
   (__malloc_debug ? __malloc_debug_printf (indent, fmt , ##args) : 0)
# define MALLOC_DEBUG_INDENT(indent)					      \
   (__malloc_debug ? __malloc_debug_indent (indent) : 0)

extern int __malloc_debug_cur_indent attribute_hidden;

/* Print FMT and args indented at the current debug print level, followed
   by a newline, and change the level by INDENT.  */
extern void __malloc_debug_printf (int indent, const char *fmt, ...) attribute_hidden;

/* Change the current debug print level by INDENT, and return the value.  */
#define __malloc_debug_indent(indent) (__malloc_debug_cur_indent += indent)

/* Set the current debug print level to LEVEL.  */
#define __malloc_debug_set_indent(level) (__malloc_debug_cur_indent = level)

#else /* !MALLOC_DEBUGGING */
# define MALLOC_DEBUG(fmt, args...) (void)0
# define MALLOC_DEBUG_INDENT(indent) (void)0
#endif /* MALLOC_DEBUGGING */


/* Return SZ rounded down to POWER_OF_2_SIZE (which must be power of 2).  */
#define MALLOC_ROUND_DOWN(sz, power_of_2_size)  \
  ((sz) & ~(power_of_2_size - 1))
/* Return SZ rounded to POWER_OF_2_SIZE (which must be power of 2).  */
#define MALLOC_ROUND_UP(sz, power_of_2_size)				\
  MALLOC_ROUND_DOWN ((sz) + (power_of_2_size - 1), (power_of_2_size))

/* Return SZ rounded down to a multiple MALLOC_PAGE_SIZE.  */
#define MALLOC_ROUND_DOWN_TO_PAGE_SIZE(sz)  \
  MALLOC_ROUND_DOWN (sz, MALLOC_PAGE_SIZE)
/* Return SZ rounded up to a multiple MALLOC_PAGE_SIZE.  */
#define MALLOC_ROUND_UP_TO_PAGE_SIZE(sz)  \
  MALLOC_ROUND_UP (sz, MALLOC_PAGE_SIZE)


/* The malloc heap.  */
extern struct heap_free_area *__malloc_heap attribute_hidden;
#ifdef __UCLIBC_HAS_THREADS__
__UCLIBC_MUTEX_EXTERN(__malloc_heap_lock)
# ifndef __LINUXTHREADS_OLD__
	attribute_hidden
# endif
	;
# ifdef __UCLIBC_UCLINUX_BROKEN_MUNMAP__
__UCLIBC_MUTEX_EXTERN(__malloc_mmb_heap_lock)
#  ifndef __LINUXTHREADS_OLD__
	attribute_hidden
#  endif
	;
# endif
#endif