内存比较导致系统停止
发布时间:2020-12-16 09:45:28 所属栏目:百科 来源:网络整理
导读:我正在研究内核模块,我需要比较两个缓冲区以确定它们是否相同.我正在使用 Linux内核中定义的memcmp函数来执行此操作.我的第一个缓冲区是这样的: cache_buffer = (unsigned char *)vmalloc(4097);cache_buffer[4096] = '/0'; 第二个缓冲区来自使用page_addre
我正在研究内核模块,我需要比较两个缓冲区以确定它们是否相同.我正在使用
Linux内核中定义的memcmp函数来执行此操作.我的第一个缓冲区是这样的:
cache_buffer = (unsigned char *)vmalloc(4097); cache_buffer[4096] = '/0'; 第二个缓冲区来自使用page_address()函数的页面. page = bio_page(bio); kmap(page); write_buffer = (char *)page_address(page); kunmap(page); 我已经预先打印了两个缓冲区的内容,不仅打印正确,而且它们也有相同的内容.接下来,我这样做: result = memcmp(write_buffer,cache_buffer,2048); // only comparing up to 2048 positions 这导致内核冻结,我无法弄清楚原因.我检查了memcmp的实现,没有看到任何会导致冻结的东西.谁能提出一个原因? 这是memcmp实现: int memcmp(const void *cs,const void *ct,size_t count) { const unsigned char *su1,*su2; int res = 0; for (su1 = cs,su2 = ct; 0 < count; ++su1,++su2,count--) if ((res = *su1 - *su2) != 0) break; return res; } 编辑:导致冻结的功能是memcmp.当我评论它时,一切都有效.另外,当我做memcmp时如下 memcmp(write_buffer,write_buffer,2048); //comparing two write_buffers 一切都运作良好.只有当我将cache_buffer抛入混合时才会出现错误.此外,上面是我的实际代码的简化.这是整个功能: static int compare_data(sector_t location,struct bio * bio,struct cache_c * dmc) { struct dm_io_region where; unsigned long bits; int segno; struct bio_vec * bvec; struct page * page; unsigned char * cache_data; char * temp_data; char * write_data; int result,length,i; cache_data = (unsigned char *)vmalloc((dmc->block_size * 512) + 1); where.bdev = dmc->cache_dev->bdev; where.count = dmc->block_size; where.sector = location << dmc->block_shift; printk(KERN_DEBUG "place: %llun",where.sector); dm_io_sync_vm(1,&where,READ,cache_data,&bits,dmc); length = 0; bio_for_each_segment(bvec,bio,segno) { if(segno == 0) { page = bio_page(bio); kmap(page); write_data = (char *)page_address(page); //kunmap(page); length += bvec->bv_len; } else { page = bio_page(bio); kmap(page); temp_data = strcat(write_data,(char *)page_address(page)); //kunmap(page); write_data = temp_data; length += bvec->bv_len; } } printk(KERN_INFO "length: %un",length); cache_data[dmc->block_size * 512] = ' '; for(i = 0; i < 2048; i++) { printk("%c",write_data[i]); } printk("n"); for(i = 0; i < 2048; i++) { printk("%c",cache_data[i]); } printk("n"); result = memcmp(write_data,length); return result; } 编辑#2:对不起伙计们.问题不在于memcmp.这是memcmp的结果.当它返回正数或负数时,调用我的函数的函数将使用一些指针,其中一个未初始化.我不知道为什么我之前没有意识到这一点.感谢您尽力帮助! 解决方法
我不是内核专家,但我认为你需要在进行比较时保留这个内存映射?换句话说,在memcmp完成之前不要调用kunmap.我认为之前调用它会导致write_buffer指向不再映射的页面.
把你的代码放在另一个问题中,这是对增量的粗略尝试.仍然需要一些清理,我敢肯定: static int compare_data(sector_t location,struct cache_c * dmc) { struct dm_io_region where; unsigned long bits; int segno; struct bio_vec * bvec; struct page * page; unsigned char * cache_data; char * temp_data; char * write_data; int length,i; int result = 0; size_t position = 0; size_t max_size = (dmc->block_size * 512) + 1; cache_data = (unsigned char *)vmalloc(max_size); where.bdev = dmc->cache_dev->bdev; where.count = dmc->block_size; where.sector = location << dmc->block_shift; printk(KERN_DEBUG "place: %llun",where.sector); dm_io_sync_vm(1,dmc); bio_for_each_segment(bvec,segno) { // Map the page into memory page = bio_page(bio); write_data = (char *)kmap(page); length = bvec->bv_len; // Make sure we don't go past the end if(position >= max_size) break; if(position + length > max_size) length = max_size - position; // Compare the data result = memcmp(write_data,cache_data + position,length); position += length; kunmap(page); // If the memory is not equal,bail out now and return the result if(result != 0) break; } cache_data[dmc->block_size * 512] = ' '; return result; } (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |