struct mm_struct { struct vm_area_struct *mmap; /* list of VMAs */ //指向VMA對象的鏈表頭 struct rb_root mm_rb; //指向VMA對象的紅黑樹的根 u64 vmacache_seqnum; /* per-thread vmacache */#ifdef CONFIG_MMU unsigned long (*get_unmapped_area) (struct file *filp, unsigned long addr, unsigned long len, unsigned long pgoff, unsigned long flags); // 在進程地址空間中搜索有效線性地址區間的方法#endif unsigned long mmap_base; /* base of mmap area */ unsigned long mmap_legacy_base; /* base of mmap area in bottom-up allocations */#ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES /* Base adresses for compatible mmap() */ unsigned long mmap_compat_base; unsigned long mmap_compat_legacy_base;#endif unsigned long task_size; /* size of task vm space */ unsigned long highest_vm_end; /* highest vma end address */ pgd_t * pgd; //指向頁全局目錄 /** * @mm_users: The number of users including userspace. * * Use mmget()/mmget_not_zero()/mmput() to modify. When this drops * to 0 (i.e. when the task exits and there are no other temporary * reference holders), we also release a reference on @mm_count * (which may then free the &struct mm_struct if @mm_count also * drops to 0). */ atomic_t mm_users; //使用計數器 /** * @mm_count: The number of references to &struct mm_struct * (@mm_users count as 1). * * Use mmgrab()/mmdrop() to modify. When this drops to 0, the * &struct mm_struct is freed. */ atomic_t mm_count; //使用計數器 atomic_long_t nr_ptes; /* PTE page table pages */ //進程頁表數#if CONFIG_PGTABLE_LEVELS > 2 atomic_long_t nr_pmds; /* PMD page table pages */#endif int map_count; /* number of VMAs */ //VMA的個數 spinlock_t page_table_lock; /* Protects page tables and some counters */ struct rw_semaphore mmap_sem; struct list_head mmlist; /* List of maybe swapped mm's. These are globally strung * together off init_mm.mmlist, and are protected * by mmlist_lock */ unsigned long hiwater_rss; /* High-watermark of RSS usage */ unsigned long hiwater_vm; /* High-water virtual memory usage */ unsigned long total_vm; /* Total pages mapped */ //進程地址空間的頁數 unsigned long locked_vm; /* Pages that have PG_mlocked set */ //鎖住的頁數，不能換出 unsigned long pinned_vm; /* Refcount permanently increased */ unsigned long data_vm; /* VM_WRITE & ~VM_SHARED & ~VM_STACK */ //數據段內存的頁數 unsigned long exec_vm; /* VM_EXEC & ~VM_WRITE & ~VM_STACK */ //可執行內存映射的頁數 unsigned long stack_vm; /* VM_STACK */ //用戶態堆棧的頁數 unsigned long def_flags; unsigned long start_code, end_code, start_data, end_data; //代碼段，數據段等的地址 unsigned long start_brk, brk, start_stack; //堆棧段的地址，start_stack表示用戶態堆棧的起始地址，brk為堆的當前最后地址 unsigned long arg_start, arg_end, env_start, env_end; //命令行參數的地址，環境變量的地址 unsigned long saved_auxv[AT_VECTOR_SIZE]; /* for /proc/PID/auxv */ /* * Special counters, in some configurations protected by the * page_table_lock, in other configurations by being atomic. */ struct mm_rss_stat rss_stat; struct linux_binfmt *binfmt; cpumask_var_t cpu_vm_mask_var; /* Architecture-specific MM context */ mm_context_t context; unsigned long flags; /* Must use atomic bitops to access the bits */ struct core_state *core_state; /* coredumping support */#ifdef CONFIG_MEMBARRIER atomic_t membarrier_state;#endif#ifdef CONFIG_AIO spinlock_t ioctx_lock; struct kioctx_table __rcu *ioctx_table;#endif#ifdef CONFIG_MEMCG /* * "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 __rcu *owner;#endif struct user_namespace *user_ns; /* store ref to file /proc//exe symlink points to */ struct file __rcu *exe_file;#ifdef CONFIG_MMU_NOTIFIER struct mmu_notifier_mm *mmu_notifier_mm;#endif#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS pgtable_t pmd_huge_pte; /* protected by page_table_lock */#endif#ifdef CONFIG_CPUMASK_OFFSTACK struct cpumask cpumask_allocation;#endif#ifdef CONFIG_NUMA_BALANCING /* * numa_next_scan is the next time that the PTEs will be marked * pte_numa. NUMA hinting faults will gather statistics and migrate * pages to new nodes if necessary. */ unsigned long numa_next_scan; /* Restart point for scanning and setting pte_numa */ unsigned long numa_scan_offset; /* numa_scan_seq prevents two threads setting pte_numa */ int numa_scan_seq;#endif /* * An operation with batched TLB flushing is going on. Anything that * can move process memory needs to flush the TLB when moving a * PROT_NONE or PROT_NUMA mapped page. */ atomic_t tlb_flush_pending;#ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH /* See flush_tlb_batched_pending() */ bool tlb_flush_batched;#endif struct uprobes_state uprobes_state;#ifdef CONFIG_HUGETLB_PAGE atomic_long_t hugetlb_usage;#endif struct work_struct async_put_work;#if IS_ENABLED(CONFIG_HMM) /* HMM needs to track a few things per mm */ struct hmm *hmm;#endif} __randomize_layout;
/* * This struct defines a memory VMM memory area. There is one of these * per VM-area/task. A VM area is any part of the process virtual memory * space that has a special rule for the page-fault handlers (ie a shared * library, the executable area etc). */struct vm_area_struct { /* The first cache line has the info for VMA tree walking. */ unsigned long vm_start; /* Our start address within vm_mm. */ //起始地址 unsigned long vm_end; /* The first byte after our end address within vm_mm. */ //結束地址，區間中不包含結束地址 /* linked list of VM areas per task, sorted by address */ //按起始地址排序的鏈表 struct vm_area_struct *vm_next, *vm_prev; struct rb_node vm_rb; //紅黑樹節點 /* * Largest free memory gap in bytes to the left of this VMA. * Either between this VMA and vma->vm_prev, or between one of the * VMAs below us in the VMA rbtree and its ->vm_prev. This helps * get_unmapped_area find a free area of the right size. */ unsigned long rb_subtree_gap; /* Second cache line starts here. */ struct mm_struct *vm_mm; /* The address space we belong to. */ pgprot_t vm_page_prot; /* Access permissions of this VMA. */ unsigned long vm_flags; /* Flags, see mm.h. */ /* * For areas with an address space and backing store, * linkage into the address_space->i_mmap interval tree. */ struct { struct rb_node rb; unsigned long rb_subtree_last; } 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_chain; /* Serialized by mmap_sem & * page_table_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 */ struct file * vm_file; /* File we map to (can be NULL). */ //指向文件的一個打開實例 void * vm_private_data; /* was vm_pte (shared mem) */ atomic_long_t swap_readahead_info;#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 struct vm_userfaultfd_ctx vm_userfaultfd_ctx;} __randomize_layout;
關系圖來了：
是不是有點眼熟？這個跟內核中的vmap機制很類似。
宏觀的看一下進程地址空間中的各個VMA：
針對VMA的操作，有如下接口：
/* VMA的查找 *//* 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); //查找第一個滿足addr < vm_end的VMA塊extern struct vm_area_struct * find_vma_prev(struct mm_struct * mm, unsigned long addr, struct vm_area_struct **pprev); //與find_vma功能類似，不同之處在于還會返回VMA鏈接的前一個VMA； static inline struct vm_area_struct * find_vma_intersection(struct mm_struct * mm, unsigned long start_addr, unsigned long end_addr); //查找與start_addr~end_addr區域有交集的VMA /* VMA的插入 */ extern int insert_vm_struct(struct mm_struct *, struct vm_area_struct *); //插入VMA到紅黑樹中和鏈表中 /* VMA的合并 */ extern struct vm_area_struct *vma_merge(struct mm_struct *, struct vm_area_struct *prev, unsigned long addr, unsigned long end, unsigned long vm_flags, struct anon_vma *, struct file *, pgoff_t, struct mempolicy *, struct vm_userfaultfd_ctx); //將VMA與附近的VMA進行融合操作 /* VMA的拆分 */ extern int split_vma(struct mm_struct *, struct vm_area_struct *, unsigned long addr, int new_below); //將VMA以addr為界線分成兩個VMA
#define PROT_READ 0x1 /* page can be read */#define PROT_WRITE 0x2 /* page can be written */#define PROT_EXEC 0x4 /* page can be executed */#define PROT_SEM 0x8 /* page may be used for atomic ops */#define PROT_NONE 0x0 /* page can not be accessed */#define PROT_GROWSDOWN 0x01000000 /* mprotect flag: extend change to start of growsdown vma */#define PROT_GROWSUP 0x02000000 /* mprotect flag: extend change to end of growsup vma */#define MAP_SHARED 0x01 /* Share changes */#define MAP_PRIVATE 0x02 /* Changes are private */#define MAP_TYPE 0x0f /* Mask for type of mapping */#define MAP_FIXED 0x10 /* Interpret addr exactly */#define MAP_ANONYMOUS 0x20 /* don't use a file */#define MAP_GROWSDOWN 0x0100 /* stack-like segment */#define MAP_DENYWRITE 0x0800 /* ETXTBSY */#define MAP_EXECUTABLE 0x1000 /* mark it as an executable */#define MAP_LOCKED 0x2000 /* pages are locked */#define MAP_NORESERVE 0x4000 /* don't check for reservations */#define MAP_POPULATE 0x8000 /* populate (prefault) pagetables */#define MAP_NONBLOCK 0x10000 /* do not block on IO */#define MAP_STACK 0x20000 /* give out an address that is best suited for process/thread stacks */#define MAP_HUGETLB 0x40000 /* create a huge page mapping */
