linux内存管理之用户态内存管理

分配一个新的线性区

do_mmap    =>ret = do_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);        =>len = PAGE_ALIGN(len);        =>addr = get_unmapped_area(file, addr, len, pgoff, flags);//找到一个空闲的线性区            =>get_area = current->mm->get_unmapped_area;            =>addr = get_area(file, addr, len, pgoff, flags);//mm->get_unmapped_area = arch_get_unmapped_area;                =>addr = PAGE_ALIGN(addr);                =>vma = find_vma(mm, addr);                    =>注意，vma && vma->vm_end > addr 的优先级是 > 更高，可以理解成 (vma && (vma->vm_end > addr))                    =>通过红黑树查找                full_search:                    for (vma = find_vma(mm, addr); ; vma = vma->vm_next)        =>error = security_file_mmap(file, reqprot, prot, flags, addr, 0);            =>security_ops->file_mmap (file, reqprot, prot, flags, addr, addr_only);                =>mmap_region(file, addr, len, flags, vm_flags, pgoff, accountable);            =>vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);            =>vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);            vma->vm_mm = mm;            vma->vm_start = addr;            vma->vm_end = addr + len;            vma->vm_flags = vm_flags;            vma->vm_page_prot = protection_map[vm_flags &                        (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)];            vma->vm_pgoff = pgoff;            addr = vma->vm_start;            pgoff = vma->vm_pgoff;            vm_flags = vma->vm_flags;            =>make_pages_present(addr, addr + len);                =>vma = find_vma(current->mm, addr);                =>ret = get_user_pages(current, current->mm, addr, len, write, 0, NULL, NULL);

分配了线性区之后只是空头支票，没有干货，当访问内存的时候的时候要走入缺页中断
另外一个与分配线性区类似的是malloc，调用do_brk

do_brk    =>if (security_vm_enough_memory(len >> PAGE_SHIFT)) //len >> PAGE_SHIFT 把len转换成pages作为参数，        =>security_ops->vm_enough_memory(current->mm, pages);            =>selinux_vm_enough_memory                =>__vm_enough_memory//判断物理内存是否够用，是否能申请下len大小的空间，这个函数貌似很有用，后续好好研究一下    =>vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);    =>vma->vm_mm = mm;    vma->vm_start = addr;    vma->vm_end = addr + len;    vma->vm_pgoff = pgoff;    vma->vm_flags = flags;    vma->vm_page_prot = protection_map[flags & (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)];    =>vma_link(mm, vma, prev, rb_link, rb_parent);    =>make_pages_present(addr, addr + len);

参考文章
linux底层内存管理–用户空间的分级分配系统以及懒惰的含义
http://blog.csdn.net/liuyuanqing2010/article/details/6680443

linux内存管理之sys_brk实现分析 和 Linux内核分析之缺页中断
http://blog.csdn.net/sadamoo/article/category/1334891