The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/sys/malloc.h

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    1 /*-
    2  * SPDX-License-Identifier: BSD-3-Clause
    3  *
    4  * Copyright (c) 1987, 1993
    5  *      The Regents of the University of California.
    6  * Copyright (c) 2005, 2009 Robert N. M. Watson
    7  * All rights reserved.
    8  *
    9  * Redistribution and use in source and binary forms, with or without
   10  * modification, are permitted provided that the following conditions
   11  * are met:
   12  * 1. Redistributions of source code must retain the above copyright
   13  *    notice, this list of conditions and the following disclaimer.
   14  * 2. Redistributions in binary form must reproduce the above copyright
   15  *    notice, this list of conditions and the following disclaimer in the
   16  *    documentation and/or other materials provided with the distribution.
   17  * 3. Neither the name of the University nor the names of its contributors
   18  *    may be used to endorse or promote products derived from this software
   19  *    without specific prior written permission.
   20  *
   21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   31  * SUCH DAMAGE.
   32  *
   33  *      @(#)malloc.h    8.5 (Berkeley) 5/3/95
   34  * $FreeBSD: stable/12/sys/sys/malloc.h 352397 2019-09-16 14:25:51Z andrew $
   35  */
   36 
   37 #ifndef _SYS_MALLOC_H_
   38 #define _SYS_MALLOC_H_
   39 
   40 #include <sys/param.h>
   41 #ifdef _KERNEL
   42 #include <sys/systm.h>
   43 #endif
   44 #include <sys/queue.h>
   45 #include <sys/_lock.h>
   46 #include <sys/_mutex.h>
   47 #include <machine/_limits.h>
   48 
   49 #define MINALLOCSIZE    UMA_SMALLEST_UNIT
   50 
   51 /*
   52  * Flags to memory allocation functions.
   53  */
   54 #define M_NOWAIT        0x0001          /* do not block */
   55 #define M_WAITOK        0x0002          /* ok to block */
   56 #define M_ZERO          0x0100          /* bzero the allocation */
   57 #define M_NOVM          0x0200          /* don't ask VM for pages */
   58 #define M_USE_RESERVE   0x0400          /* can alloc out of reserve memory */
   59 #define M_NODUMP        0x0800          /* don't dump pages in this allocation */
   60 #define M_FIRSTFIT      0x1000          /* only for vmem, fast fit */
   61 #define M_BESTFIT       0x2000          /* only for vmem, low fragmentation */
   62 #define M_EXEC          0x4000          /* allocate executable space */
   63 #define M_NEXTFIT       0x8000          /* only for vmem, follow cursor */
   64 
   65 #define M_MAGIC         877983977       /* time when first defined :-) */
   66 
   67 /*
   68  * Two malloc type structures are present: malloc_type, which is used by a
   69  * type owner to declare the type, and malloc_type_internal, which holds
   70  * malloc-owned statistics and other ABI-sensitive fields, such as the set of
   71  * malloc statistics indexed by the compile-time MAXCPU constant.
   72  * Applications should avoid introducing dependence on the allocator private
   73  * data layout and size.
   74  *
   75  * The malloc_type ks_next field is protected by malloc_mtx.  Other fields in
   76  * malloc_type are static after initialization so unsynchronized.
   77  *
   78  * Statistics in malloc_type_stats are written only when holding a critical
   79  * section and running on the CPU associated with the index into the stat
   80  * array, but read lock-free resulting in possible (minor) races, which the
   81  * monitoring app should take into account.
   82  */
   83 struct malloc_type_stats {
   84         uint64_t        mts_memalloced; /* Bytes allocated on CPU. */
   85         uint64_t        mts_memfreed;   /* Bytes freed on CPU. */
   86         uint64_t        mts_numallocs;  /* Number of allocates on CPU. */
   87         uint64_t        mts_numfrees;   /* number of frees on CPU. */
   88         uint64_t        mts_size;       /* Bitmask of sizes allocated on CPU. */
   89         uint64_t        _mts_reserved1; /* Reserved field. */
   90         uint64_t        _mts_reserved2; /* Reserved field. */
   91         uint64_t        _mts_reserved3; /* Reserved field. */
   92 };
   93 
   94 /*
   95  * Index definitions for the mti_probes[] array.
   96  */
   97 #define DTMALLOC_PROBE_MALLOC           0
   98 #define DTMALLOC_PROBE_FREE             1
   99 #define DTMALLOC_PROBE_MAX              2
  100 
  101 struct malloc_type_internal {
  102         uint32_t        mti_probes[DTMALLOC_PROBE_MAX];
  103                                         /* DTrace probe ID array. */
  104         u_char          mti_zone;
  105         struct malloc_type_stats        *mti_stats;
  106 };
  107 
  108 /*
  109  * Public data structure describing a malloc type.  Private data is hung off
  110  * of ks_handle to avoid encoding internal malloc(9) data structures in
  111  * modules, which will statically allocate struct malloc_type.
  112  */
  113 struct malloc_type {
  114         struct malloc_type *ks_next;    /* Next in global chain. */
  115         u_long           ks_magic;      /* Detect programmer error. */
  116         const char      *ks_shortdesc;  /* Printable type name. */
  117         void            *ks_handle;     /* Priv. data, was lo_class. */
  118 };
  119 
  120 /*
  121  * Statistics structure headers for user space.  The kern.malloc sysctl
  122  * exposes a structure stream consisting of a stream header, then a series of
  123  * malloc type headers and statistics structures (quantity maxcpus).  For
  124  * convenience, the kernel will provide the current value of maxcpus at the
  125  * head of the stream.
  126  */
  127 #define MALLOC_TYPE_STREAM_VERSION      0x00000001
  128 struct malloc_type_stream_header {
  129         uint32_t        mtsh_version;   /* Stream format version. */
  130         uint32_t        mtsh_maxcpus;   /* Value of MAXCPU for stream. */
  131         uint32_t        mtsh_count;     /* Number of records. */
  132         uint32_t        _mtsh_pad;      /* Pad/reserved field. */
  133 };
  134 
  135 #define MALLOC_MAX_NAME 32
  136 struct malloc_type_header {
  137         char                            mth_name[MALLOC_MAX_NAME];
  138 };
  139 
  140 #ifdef _KERNEL
  141 #define MALLOC_DEFINE(type, shortdesc, longdesc)                        \
  142         struct malloc_type type[1] = {                                  \
  143                 { NULL, M_MAGIC, shortdesc, NULL }                      \
  144         };                                                              \
  145         SYSINIT(type##_init, SI_SUB_KMEM, SI_ORDER_THIRD, malloc_init,  \
  146             type);                                                      \
  147         SYSUNINIT(type##_uninit, SI_SUB_KMEM, SI_ORDER_ANY,             \
  148             malloc_uninit, type)
  149 
  150 #define MALLOC_DECLARE(type) \
  151         extern struct malloc_type type[1]
  152 
  153 MALLOC_DECLARE(M_CACHE);
  154 MALLOC_DECLARE(M_DEVBUF);
  155 MALLOC_DECLARE(M_TEMP);
  156 
  157 /*
  158  * XXX this should be declared in <sys/uio.h>, but that tends to fail
  159  * because <sys/uio.h> is included in a header before the source file
  160  * has a chance to include <sys/malloc.h> to get MALLOC_DECLARE() defined.
  161  */
  162 MALLOC_DECLARE(M_IOV);
  163 
  164 struct domainset;
  165 extern struct mtx malloc_mtx;
  166 
  167 /*
  168  * Function type used when iterating over the list of malloc types.
  169  */
  170 typedef void malloc_type_list_func_t(struct malloc_type *, void *);
  171 
  172 void    contigfree(void *addr, unsigned long size, struct malloc_type *type);
  173 void    *contigmalloc(unsigned long size, struct malloc_type *type, int flags,
  174             vm_paddr_t low, vm_paddr_t high, unsigned long alignment,
  175             vm_paddr_t boundary) __malloc_like __result_use_check
  176             __alloc_size(1) __alloc_align(6);
  177 void    *contigmalloc_domainset(unsigned long size, struct malloc_type *type,
  178             struct domainset *ds, int flags, vm_paddr_t low, vm_paddr_t high,
  179             unsigned long alignment, vm_paddr_t boundary)
  180             __malloc_like __result_use_check __alloc_size(1) __alloc_align(7);
  181 void    free(void *addr, struct malloc_type *type);
  182 void    free_domain(void *addr, struct malloc_type *type);
  183 void    *malloc(size_t size, struct malloc_type *type, int flags) __malloc_like
  184             __result_use_check __alloc_size(1);
  185 /*
  186  * Try to optimize malloc(..., ..., M_ZERO) allocations by doing zeroing in
  187  * place if the size is known at compilation time.
  188  *
  189  * Passing the flag down requires malloc to blindly zero the entire object.
  190  * In practice a lot of the zeroing can be avoided if most of the object
  191  * gets explicitly initialized after the allocation. Letting the compiler
  192  * zero in place gives it the opportunity to take advantage of this state.
  193  *
  194  * Note that the operation is only applicable if both flags and size are
  195  * known at compilation time. If M_ZERO is passed but M_WAITOK is not, the
  196  * allocation can fail and a NULL check is needed. However, if M_WAITOK is
  197  * passed we know the allocation must succeed and the check can be elided.
  198  *
  199  *      _malloc_item = malloc(_size, type, (flags) &~ M_ZERO);
  200  *      if (((flags) & M_WAITOK) != 0 || _malloc_item != NULL)
  201  *              bzero(_malloc_item, _size);
  202  *
  203  * If the flag is set, the compiler knows the left side is always true,
  204  * therefore the entire statement is true and the callsite is:
  205  *
  206  *      _malloc_item = malloc(_size, type, (flags) &~ M_ZERO);
  207  *      bzero(_malloc_item, _size);
  208  *
  209  * If the flag is not set, the compiler knows the left size is always false
  210  * and the NULL check is needed, therefore the callsite is:
  211  *
  212  *      _malloc_item = malloc(_size, type, (flags) &~ M_ZERO);
  213  *      if (_malloc_item != NULL)
  214  *              bzero(_malloc_item, _size);                     
  215  *
  216  * The implementation is a macro because of what appears to be a clang 6 bug:
  217  * an inline function variant ended up being compiled to a mere malloc call
  218  * regardless of argument. gcc generates expected code (like the above).
  219  */
  220 #define malloc(size, type, flags) ({                                    \
  221         void *_malloc_item;                                             \
  222         size_t _size = (size);                                          \
  223         if (__builtin_constant_p(size) && __builtin_constant_p(flags) &&\
  224             ((flags) & M_ZERO) != 0) {                                  \
  225                 _malloc_item = malloc(_size, type, (flags) &~ M_ZERO);  \
  226                 if (((flags) & M_WAITOK) != 0 ||                        \
  227                     __predict_true(_malloc_item != NULL))               \
  228                         bzero(_malloc_item, _size);                     \
  229         } else {                                                        \
  230                 _malloc_item = malloc(_size, type, flags);              \
  231         }                                                               \
  232         _malloc_item;                                                   \
  233 })
  234 
  235 void    *malloc_domainset(size_t size, struct malloc_type *type,
  236             struct domainset *ds, int flags) __malloc_like __result_use_check
  237             __alloc_size(1);
  238 void    *mallocarray(size_t nmemb, size_t size, struct malloc_type *type,
  239             int flags) __malloc_like __result_use_check
  240             __alloc_size2(1, 2);
  241 void    malloc_init(void *);
  242 int     malloc_last_fail(void);
  243 void    malloc_type_allocated(struct malloc_type *type, unsigned long size);
  244 void    malloc_type_freed(struct malloc_type *type, unsigned long size);
  245 void    malloc_type_list(malloc_type_list_func_t *, void *);
  246 void    malloc_uninit(void *);
  247 void    *realloc(void *addr, size_t size, struct malloc_type *type, int flags)
  248             __result_use_check __alloc_size(2);
  249 void    *reallocf(void *addr, size_t size, struct malloc_type *type, int flags)
  250             __result_use_check __alloc_size(2);
  251 
  252 struct malloc_type *malloc_desc2type(const char *desc);
  253 
  254 /*
  255  * This is sqrt(SIZE_MAX+1), as s1*s2 <= SIZE_MAX
  256  * if both s1 < MUL_NO_OVERFLOW and s2 < MUL_NO_OVERFLOW
  257  */
  258 #define MUL_NO_OVERFLOW         (1UL << (sizeof(size_t) * 8 / 2))
  259 static inline bool
  260 WOULD_OVERFLOW(size_t nmemb, size_t size)
  261 {
  262 
  263         return ((nmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
  264             nmemb > 0 && __SIZE_T_MAX / nmemb < size);
  265 }
  266 #undef MUL_NO_OVERFLOW
  267 #endif /* _KERNEL */
  268 
  269 #endif /* !_SYS_MALLOC_H_ */

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