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| 关键词： page file mmap operations nopage ext write vma dentry ops |
do_execve ->open_exec->dentry_open .... f->f_dentry = dentry; .... f->f_op = fops_get(inode->i_fop); .... 设置f->f_dentry和f->f_op,我们考察执行ext2的情景，因此f_op将是ext2_file_operations ->search_binary_handler->load_elf_binary->elf_map->do_mmap->do_mmap_pgoff .... vma->vm_file = file; get_file(file); error = file->f_op->mmap(file, vma); .... 设置vm_file,执行f_op->mmap,在ext2_file_operations中的mmap是generic_file_mmap,在generic_file_mmap中主要是设置vma->vm_ops = ops,绝大多数情况下ops是file_private_mmap static struct vm_operations_struct file_private_mmap = { nopage: filemap_nopage, }; 执行do_mmap时，如果是代码段，一般只允许读和执行，如果是数据段，一般允许读和写,但是vma->vm_page_prot中只设置有可读和可执行位(没有深入研究) sys_execve做完映射后就退出了.当调度到该进程时并执行代码时,立即产生page fault，依次do_page_fault->handle_mm_fault->handle_pte_fault->do_no_page ... new_page = vma->vm_ops->nopage(vma, address & PAGE_MASK, (vma->vm_flags & VM_SHARED)?0:write_access); ... 从前面知道,此处将调用filemap_nopage(基本所有这类的情景都执行这个函数) filemap_nopage->page_cache_read ..... page = page_cache_alloc(); if (!page) return -ENOMEM; if (!add_to_page_cache_unique(page, mapping, offset, hash)) { int error = mapping->a_ops->readpage(file, page); page_cache_release(page); return error; } .... 此处分配一空闲页,然后读入该页,由于是ext2,应此此处的a_ops是 struct address_space_operations ext2_aops = { readpage: ext2_readpage, writepage: ext2_writepage, sync_page: block_sync_page, prepare_write: ext2_prepare_write, commit_write: generic_commit_write, bmap: ext2_bmap }; |
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