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

     /*-
      * SPDX-License-Identifier: BSD-3-Clause
      *
      * Copyright (c) 1987, 1993
      *      The Regents of the University of California.
      * Copyright (c) 2005, 2009 Robert N. M. Watson
      * All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      @(#)malloc.h    8.5 (Berkeley) 5/3/95
     * $FreeBSD: releng/12.0/sys/sys/malloc.h 340401 2018-11-13 18:21:47Z markj $
     */
    
    #ifndef _SYS_MALLOC_H_
    #define _SYS_MALLOC_H_
    
    #include <sys/param.h>
    #ifdef _KERNEL
    #include <sys/systm.h>
    #endif
    #include <sys/queue.h>
    #include <sys/_lock.h>
    #include <sys/_mutex.h>
    #include <machine/_limits.h>
    
    #define MINALLOCSIZE    UMA_SMALLEST_UNIT
    
    /*
     * Flags to memory allocation functions.
     */
    #define M_NOWAIT        0x0001          /* do not block */
    #define M_WAITOK        0x0002          /* ok to block */
    #define M_ZERO          0x0100          /* bzero the allocation */
    #define M_NOVM          0x0200          /* don't ask VM for pages */
    #define M_USE_RESERVE   0x0400          /* can alloc out of reserve memory */
    #define M_NODUMP        0x0800          /* don't dump pages in this allocation */
    #define M_FIRSTFIT      0x1000          /* Only for vmem, fast fit. */
    #define M_BESTFIT       0x2000          /* Only for vmem, low fragmentation. */
    #define M_EXEC          0x4000          /* allocate executable space. */
    
    #define M_MAGIC         877983977       /* time when first defined :-) */
    
    /*
     * Two malloc type structures are present: malloc_type, which is used by a
     * type owner to declare the type, and malloc_type_internal, which holds
     * malloc-owned statistics and other ABI-sensitive fields, such as the set of
     * malloc statistics indexed by the compile-time MAXCPU constant.
     * Applications should avoid introducing dependence on the allocator private
     * data layout and size.
     *
     * The malloc_type ks_next field is protected by malloc_mtx.  Other fields in
     * malloc_type are static after initialization so unsynchronized.
     *
     * Statistics in malloc_type_stats are written only when holding a critical
     * section and running on the CPU associated with the index into the stat
     * array, but read lock-free resulting in possible (minor) races, which the
     * monitoring app should take into account.
     */
    struct malloc_type_stats {
            uint64_t        mts_memalloced; /* Bytes allocated on CPU. */
            uint64_t        mts_memfreed;   /* Bytes freed on CPU. */
            uint64_t        mts_numallocs;  /* Number of allocates on CPU. */
            uint64_t        mts_numfrees;   /* number of frees on CPU. */
            uint64_t        mts_size;       /* Bitmask of sizes allocated on CPU. */
            uint64_t        _mts_reserved1; /* Reserved field. */
            uint64_t        _mts_reserved2; /* Reserved field. */
            uint64_t        _mts_reserved3; /* Reserved field. */
    };
    
    /*
     * Index definitions for the mti_probes[] array.
     */
    #define DTMALLOC_PROBE_MALLOC           0
    #define DTMALLOC_PROBE_FREE             1
    #define DTMALLOC_PROBE_MAX              2
    
   struct malloc_type_internal {
           uint32_t        mti_probes[DTMALLOC_PROBE_MAX];
                                           /* DTrace probe ID array. */
           u_char          mti_zone;
           struct malloc_type_stats        *mti_stats;
   };
   
   /*
    * Public data structure describing a malloc type.  Private data is hung off
    * of ks_handle to avoid encoding internal malloc(9) data structures in
    * modules, which will statically allocate struct malloc_type.
    */
   struct malloc_type {
           struct malloc_type *ks_next;    /* Next in global chain. */
           u_long           ks_magic;      /* Detect programmer error. */
           const char      *ks_shortdesc;  /* Printable type name. */
           void            *ks_handle;     /* Priv. data, was lo_class. */
   };
   
   /*
    * Statistics structure headers for user space.  The kern.malloc sysctl
    * exposes a structure stream consisting of a stream header, then a series of
    * malloc type headers and statistics structures (quantity maxcpus).  For
    * convenience, the kernel will provide the current value of maxcpus at the
    * head of the stream.
    */
   #define MALLOC_TYPE_STREAM_VERSION      0x00000001
   struct malloc_type_stream_header {
           uint32_t        mtsh_version;   /* Stream format version. */
           uint32_t        mtsh_maxcpus;   /* Value of MAXCPU for stream. */
           uint32_t        mtsh_count;     /* Number of records. */
           uint32_t        _mtsh_pad;      /* Pad/reserved field. */
   };
   
   #define MALLOC_MAX_NAME 32
   struct malloc_type_header {
           char                            mth_name[MALLOC_MAX_NAME];
   };
   
   #ifdef _KERNEL
   #define MALLOC_DEFINE(type, shortdesc, longdesc)                        \
           struct malloc_type type[1] = {                                  \
                   { NULL, M_MAGIC, shortdesc, NULL }                      \
           };                                                              \
           SYSINIT(type##_init, SI_SUB_KMEM, SI_ORDER_THIRD, malloc_init,  \
               type);                                                      \
           SYSUNINIT(type##_uninit, SI_SUB_KMEM, SI_ORDER_ANY,             \
               malloc_uninit, type)
   
   #define MALLOC_DECLARE(type) \
           extern struct malloc_type type[1]
   
   MALLOC_DECLARE(M_CACHE);
   MALLOC_DECLARE(M_DEVBUF);
   MALLOC_DECLARE(M_TEMP);
   
   /*
    * XXX this should be declared in <sys/uio.h>, but that tends to fail
    * because <sys/uio.h> is included in a header before the source file
    * has a chance to include <sys/malloc.h> to get MALLOC_DECLARE() defined.
    */
   MALLOC_DECLARE(M_IOV);
   
   struct domainset;
   extern struct mtx malloc_mtx;
   
   /*
    * Function type used when iterating over the list of malloc types.
    */
   typedef void malloc_type_list_func_t(struct malloc_type *, void *);
   
   void    contigfree(void *addr, unsigned long size, struct malloc_type *type);
   void    *contigmalloc(unsigned long size, struct malloc_type *type, int flags,
               vm_paddr_t low, vm_paddr_t high, unsigned long alignment,
               vm_paddr_t boundary) __malloc_like __result_use_check
               __alloc_size(1) __alloc_align(6);
   void    *contigmalloc_domainset(unsigned long size, struct malloc_type *type,
               struct domainset *ds, int flags, vm_paddr_t low, vm_paddr_t high,
               unsigned long alignment, vm_paddr_t boundary)
               __malloc_like __result_use_check __alloc_size(1) __alloc_align(6);
   void    free(void *addr, struct malloc_type *type);
   void    free_domain(void *addr, struct malloc_type *type);
   void    *malloc(size_t size, struct malloc_type *type, int flags) __malloc_like
               __result_use_check __alloc_size(1);
   /*
    * Try to optimize malloc(..., ..., M_ZERO) allocations by doing zeroing in
    * place if the size is known at compilation time.
    *
    * Passing the flag down requires malloc to blindly zero the entire object.
    * In practice a lot of the zeroing can be avoided if most of the object
    * gets explicitly initialized after the allocation. Letting the compiler
    * zero in place gives it the opportunity to take advantage of this state.
    *
    * Note that the operation is only applicable if both flags and size are
    * known at compilation time. If M_ZERO is passed but M_WAITOK is not, the
    * allocation can fail and a NULL check is needed. However, if M_WAITOK is
    * passed we know the allocation must succeed and the check can be elided.
    *
    *      _malloc_item = malloc(_size, type, (flags) &~ M_ZERO);
    *      if (((flags) & M_WAITOK) != 0 || _malloc_item != NULL)
    *              bzero(_malloc_item, _size);
    *
    * If the flag is set, the compiler knows the left side is always true,
    * therefore the entire statement is true and the callsite is:
    *
    *      _malloc_item = malloc(_size, type, (flags) &~ M_ZERO);
    *      bzero(_malloc_item, _size);
    *
    * If the flag is not set, the compiler knows the left size is always false
    * and the NULL check is needed, therefore the callsite is:
    *
    *      _malloc_item = malloc(_size, type, (flags) &~ M_ZERO);
    *      if (_malloc_item != NULL)
    *              bzero(_malloc_item, _size);                     
    *
    * The implementation is a macro because of what appears to be a clang 6 bug:
    * an inline function variant ended up being compiled to a mere malloc call
    * regardless of argument. gcc generates expected code (like the above).
    */
   #define malloc(size, type, flags) ({                                    \
           void *_malloc_item;                                             \
           size_t _size = (size);                                          \
           if (__builtin_constant_p(size) && __builtin_constant_p(flags) &&\
               ((flags) & M_ZERO) != 0) {                                  \
                   _malloc_item = malloc(_size, type, (flags) &~ M_ZERO);  \
                   if (((flags) & M_WAITOK) != 0 ||                        \
                       __predict_true(_malloc_item != NULL))               \
                           bzero(_malloc_item, _size);                     \
           } else {                                                        \
                   _malloc_item = malloc(_size, type, flags);              \
           }                                                               \
           _malloc_item;                                                   \
   })
   
   void    *malloc_domainset(size_t size, struct malloc_type *type,
               struct domainset *ds, int flags) __malloc_like __result_use_check
               __alloc_size(1);
   void    *mallocarray(size_t nmemb, size_t size, struct malloc_type *type,
               int flags) __malloc_like __result_use_check
               __alloc_size2(1, 2);
   void    malloc_init(void *);
   int     malloc_last_fail(void);
   void    malloc_type_allocated(struct malloc_type *type, unsigned long size);
   void    malloc_type_freed(struct malloc_type *type, unsigned long size);
   void    malloc_type_list(malloc_type_list_func_t *, void *);
   void    malloc_uninit(void *);
   void    *realloc(void *addr, size_t size, struct malloc_type *type, int flags)
               __result_use_check __alloc_size(2);
   void    *reallocf(void *addr, size_t size, struct malloc_type *type, int flags)
               __result_use_check __alloc_size(2);
   
   struct malloc_type *malloc_desc2type(const char *desc);
   
   /*
    * This is sqrt(SIZE_MAX+1), as s1*s2 <= SIZE_MAX
    * if both s1 < MUL_NO_OVERFLOW and s2 < MUL_NO_OVERFLOW
    */
   #define MUL_NO_OVERFLOW         (1UL << (sizeof(size_t) * 8 / 2))
   static inline bool
   WOULD_OVERFLOW(size_t nmemb, size_t size)
   {
   
           return ((nmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
               nmemb > 0 && __SIZE_T_MAX / nmemb < size);
   }
   #undef MUL_NO_OVERFLOW
   #endif /* _KERNEL */
   
   #endif /* !_SYS_MALLOC_H_ */

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