文章目录

• 一、用户虚拟地址空间组成
• 二、内存描述符 mm_struct 结构体源码

一、用户虚拟地址空间组成

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" 用户虚拟地址空间 " 包括以下区域 :

① 代码段

② 数据段

③ 未初始化数据段

④ 动态库 代码段 , 数据段 , 未初始化数据段 ;

⑤ 堆内存 : 通过 malloc brk vmalloc 等函数 申请的 动态分配 的内存 ;

⑥ 栈内存 : 存放 局部变量 和 函数调用栈 ;

⑦ 内存映射区 : 将 文件 通过 mmap 函数 映射到 " 虚拟地址空间 " 的 " 内存映射区 " ;

⑧ 环境变量与参数 : 在 栈底 存放着程序运行的 环境变量 与 参数配置 信息 ;

二、内存描述符 mm_struct 结构体源码

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在 Linux 内核中 , 使用 " 内存描述符 " mm_struct 结构体 代表 " 用户虚拟地址内存空间 " ,

mm_struct 结构体 在 Linux 源码 linux-4.12\include\linux\mm_types.h#359 位置 ;

mm_struct 结构体源码如下 :

struct mm_struct {struct vm_area_struct *mmap; /* list of VMAs */struct rb_root mm_rb;u32 vmacache_seqnum; /* per-thread vmacache */ #ifdef CONFIG_MMUunsigned long (*get_unmapped_area) (struct file *filp,unsigned long addr, unsigned long len,unsigned long pgoff, unsigned long flags); #endifunsigned 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; #endifunsigned long task_size; /* size of task vm space */unsigned long highest_vm_end; /* highest vma end address */pgd_t * pgd;/*** @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;/*** @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;atomic_long_t nr_ptes; /* PTE page table pages */ #if CONFIG_PGTABLE_LEVELS > 2atomic_long_t nr_pmds; /* PMD page table pages */ #endifint map_count; /* number of VMAs */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 */unsigned long locked_vm; /* Pages that have PG_mlocked set */unsigned long pinned_vm; /* Refcount permanently increased */unsigned long data_vm; /* VM_WRITE & ~VM_SHARED & ~VM_STACK */unsigned long exec_vm; /* VM_EXEC & ~VM_WRITE & ~VM_STACK */unsigned long stack_vm; /* VM_STACK */unsigned long def_flags;unsigned long start_code, end_code, start_data, end_data;unsigned long start_brk, brk, start_stack;unsigned long arg_start, arg_end, env_start, env_end;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_AIOspinlock_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; #endifstruct user_namespace *user_ns;/* store ref to file /proc/<pid>/exe symlink points to */struct file __rcu *exe_file; #ifdef CONFIG_MMU_NOTIFIERstruct mmu_notifier_mm *mmu_notifier_mm; #endif #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKSpgtable_t pmd_huge_pte; /* protected by page_table_lock */ #endif #ifdef CONFIG_CPUMASK_OFFSTACKstruct 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 #if defined(CONFIG_NUMA_BALANCING) || defined(CONFIG_COMPACTION)/** 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.*/bool tlb_flush_pending; #endifstruct uprobes_state uprobes_state; #ifdef CONFIG_HUGETLB_PAGEatomic_long_t hugetlb_usage; #endifstruct work_struct async_put_work; };

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