struct mm_struct {

    struct vm_area_struct * mmap;        /* [内存区域]链表 */

    struct rb_root mm_rb;               /* [内存区域]红黑树 */

    struct vm_area_struct * mmap_cache;    /* 近期一次訪问的[内存区域] */

    unsigned long (*get_unmapped_area) (struct file *filp,

                unsigned long addr, unsigned long len,

                unsigned long pgoff, unsigned long flags);  /* 获取指定区间内一个还未映射的地址。出错时返回错误码 */

    void (*unmap_area) (struct mm_struct *mm, unsigned long addr);  /* 取消地址 addr 的映射 */

    unsigned long mmap_base;        /* 地址空间中能够用来映射的首地址 */

    unsigned long task_size;        /* 进程的虚拟地址空间大小 */

    unsigned long cached_hole_size;     /* 假设不空的话，就是 free_area_cache 后最大的空洞 */

    unsigned long free_area_cache;        /* 地址空间的第一个空洞 */

    pgd_t * pgd;                        /* 页全局文件夹 */

    atomic_t mm_users;            /* 使用地址空间的用户数 */

    atomic_t mm_count;            /* 实际使用地址空间的计数， (users count as 1) */

    int map_count;                /* [内存区域]个数 */

    struct rw_semaphore mmap_sem;   /* 内存区域信号量 */

    spinlock_t page_table_lock;        /* 页表锁 */

    struct list_head mmlist;        /* 全部地址空间形成的链表 */

    /* Special counters, in some configurations protected by the

     * page_table_lock, in other configurations by being atomic.

     */

    mm_counter_t _file_rss;

    mm_counter_t _anon_rss;

    unsigned long hiwater_rss;    /* High-watermark of RSS usage */

    unsigned long hiwater_vm;    /* High-water virtual memory usage */

    unsigned long total_vm, locked_vm, shared_vm, exec_vm;

    unsigned long stack_vm, reserved_vm, def_flags, nr_ptes;

    unsigned long start_code, end_code, start_data, end_data; /* 代码段，数据段的開始和结束地址 */

    unsigned long start_brk, brk, start_stack; /* 堆的首地址，尾地址，进程栈首地址 */

    unsigned long arg_start, arg_end, env_start, env_end; /* 命令行參数，环境变量首地址，尾地址 */

    unsigned long saved_auxv[AT_VECTOR_SIZE]; /* for /proc/PID/auxv */

    struct linux_binfmt *binfmt;

    cpumask_t cpu_vm_mask;

    /* Architecture-specific MM context */

    mm_context_t context;

    /* Swap token stuff */

    /*

     * Last value of global fault stamp as seen by this process.

     * In other words, this value gives an indication of how long

     * it has been since this task got the token.

     * Look at mm/thrash.c

     */

    unsigned int faultstamp;

    unsigned int token_priority;

    unsigned int last_interval;

    unsigned long flags; /* Must use atomic bitops to access the bits */

    struct core_state *core_state; /* coredumping support */

#ifdef CONFIG_AIO

    spinlock_t        ioctx_lock;

    struct hlist_head    ioctx_list;

#endif

#ifdef CONFIG_MM_OWNER

    /*

     * "owner" points to a task that is regarded as the canonical

     * user/owner of this mm. All of the following must be true in

     * order for it to be changed:

     *

     * current == mm->owner

     * current->mm != mm

     * new_owner->mm == mm

     * new_owner->alloc_lock is held

     */

    struct task_struct *owner;

#endif

#ifdef CONFIG_PROC_FS

    /* store ref to file /proc/<pid>/exe symlink points to */

    struct file *exe_file;

    unsigned long num_exe_file_vmas;

#endif

#ifdef CONFIG_MMU_NOTIFIER

    struct mmu_notifier_mm *mmu_notifier_mm;

#endif

};

#define allocate_mm()    (kmem_cache_alloc(mm_cachep, GFP_KERNEL))

#define free_mm(mm)    (kmem_cache_free(mm_cachep, (mm)))

# cat /proc/slabinfo | grep mm_struct

mm_struct             35     45   1408    5    2 : tunables   24   12    8 : slabdata      9      9      0

cat /proc/<PID>/maps

或者

pmap PID

struct vm_area_struct {

    struct mm_struct * vm_mm;    /* 相关的 mm_struct 结构体 */

    unsigned long vm_start;        /* 内存区域首地址 */

    unsigned long vm_end;        /* 内存区域尾地址 */

    /* linked list of VM areas per task, sorted by address */

    struct vm_area_struct *vm_next, *vm_prev;  /* VMA链表 */

    pgprot_t vm_page_prot;        /* 訪问控制权限 */

    unsigned long vm_flags;        /* 标志 */

    struct rb_node vm_rb;       /* 树上的VMA节点 */

    /*

     * For areas with an address space and backing store,

     * linkage into the address_space->i_mmap prio tree, or

     * linkage to the list of like vmas hanging off its node, or

     * linkage of vma in the address_space->i_mmap_nonlinear list.

     */

    union {

        struct {

            struct list_head list;

            void *parent;    /* aligns with prio_tree_node parent */

            struct vm_area_struct *head;

        } vm_set;

        struct raw_prio_tree_node prio_tree_node;

    } shared;

    /*

     * A file's MAP_PRIVATE vma can be in both i_mmap tree and anon_vma

     * list, after a COW of one of the file pages.    A MAP_SHARED vma

     * can only be in the i_mmap tree.  An anonymous MAP_PRIVATE, stack

     * or brk vma (with NULL file) can only be in an anon_vma list.

     */

    struct list_head anon_vma_node;    /* Serialized by anon_vma->lock */

    struct anon_vma *anon_vma;    /* Serialized by page_table_lock */

    /* Function pointers to deal with this struct. */

    const struct vm_operations_struct *vm_ops;

    /* Information about our backing store: */

    unsigned long vm_pgoff;        /* Offset (within vm_file) in PAGE_SIZE

                       units, *not* PAGE_CACHE_SIZE */

    struct file * vm_file;        /* File we map to (can be NULL). */

    void * vm_private_data;        /* was vm_pte (shared mem) */

    unsigned long vm_truncate_count;/* truncate_count or restart_addr */

#ifndef CONFIG_MMU

    struct vm_region *vm_region;    /* NOMMU mapping region */

#endif

#ifdef CONFIG_NUMA

    struct mempolicy *vm_policy;    /* NUMA policy for the VMA */

#endif

};

/*

 * These are the virtual MM functions - opening of an area, closing and

 * unmapping it (needed to keep files on disk up-to-date etc), pointer

 * to the functions called when a no-page or a wp-page exception occurs.

 */

struct vm_operations_struct {

    void (*open)(struct vm_area_struct * area);  /* 指定内存区域增加到一个地址空间时，该函数被调用 */

    void (*close)(struct vm_area_struct * area); /* 指定内存区域从一个地址空间删除时，该函数被调用 */

    int (*fault)(struct vm_area_struct *vma, struct vm_fault *vmf); /* 当没有出如今物理页面中的内存被訪问时，该函数被调用 */

    /* 当一个之前仅仅读的页面变为可写时，该函数被调用，

     * 假设此函数出错，将导致一个 SIGBUS 信号 */

    int (*page_mkwrite)(struct vm_area_struct *vma, struct vm_fault *vmf);

    /* 当 get_user_pages() 调用失败时, 该函数被 access_process_vm() 函数调用 */

    int (*access)(struct vm_area_struct *vma, unsigned long addr,

              void *buf, int len, int write);

#ifdef CONFIG_NUMA

    /*

     * set_policy() op must add a reference to any non-NULL @new mempolicy

     * to hold the policy upon return.  Caller should pass NULL @new to

     * remove a policy and fall back to surrounding context--i.e. do not

     * install a MPOL_DEFAULT policy, nor the task or system default

     * mempolicy.

     */

    int (*set_policy)(struct vm_area_struct *vma, struct mempolicy *new);

    /*

     * get_policy() op must add reference [mpol_get()] to any policy at

     * (vma,addr) marked as MPOL_SHARED.  The shared policy infrastructure

     * in mm/mempolicy.c will do this automatically.

     * get_policy() must NOT add a ref if the policy at (vma,addr) is not

     * marked as MPOL_SHARED. vma policies are protected by the mmap_sem.

     * If no [shared/vma] mempolicy exists at the addr, get_policy() op

     * must return NULL--i.e., do not "fallback" to task or system default

     * policy.

     */

    struct mempolicy *(*get_policy)(struct vm_area_struct *vma,

                    unsigned long addr);

    int (*migrate)(struct vm_area_struct *vma, const nodemask_t *from,

        const nodemask_t *to, unsigned long flags);

#endif

};

/* Look up the first VMA which satisfies  addr < vm_end,  NULL if none. */

extern struct vm_area_struct * find_vma(struct mm_struct * mm, unsigned long addr);

extern struct vm_area_struct * find_vma_prev(struct mm_struct * mm, unsigned long addr,

                         struct vm_area_struct **pprev);

/* Look up the first VMA which intersects the interval start_addr..end_addr-1,

   NULL if none.  Assume start_addr < end_addr. */

static inline struct vm_area_struct * find_vma_intersection(struct mm_struct * mm, unsigned long start_addr, unsigned long end_addr)

{

    struct vm_area_struct * vma = find_vma(mm,start_addr);

    if (vma && end_addr <= vma->vm_start)

        vma = NULL;

    return vma;

}

static inline unsigned long do_mmap(struct file *file, unsigned long addr,

    unsigned long len, unsigned long prot,

    unsigned long flag, unsigned long offset)

{

    unsigned long ret = -EINVAL;

    if ((offset + PAGE_ALIGN(len)) < offset)

        goto out;

    if (!(offset & ~PAGE_MASK))

        ret = do_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);

out:

    return ret;

}

extern int do_munmap(struct mm_struct *, unsigned long, size_t);

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