Linux内存泄漏调试

背景

循环压力测试驱动某个模块功能时,会出现alloc不到memory情况

工具

利用Linux自带的工具(kmemleak),进行调试

怎样编译出工具

配置config,默认配置如下:

CONFIG_DEBUG_KMEMLEAK=y
CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE=4000
CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y

修改后:

CONFIG_DEBUG_KMEMLEAK=y
CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE=10000
CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=n

• 1.CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF配置为n,表示默认编译kmemleak模块

	void __init kmemleak_init(void)
	{
        int i;
        unsigned long flags;

	#ifdef CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF //关掉此宏
        if (!kmemleak_skip_disable) {
                kmemleak_early_log = 0;
                kmemleak_disable();//这个会关掉kmemleak功能
                return;
        }
	#endif

• 2.如果CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE不修改的话,在初始化的时候会默认disable

	static void __init log_early(int op_type, const void *ptr, size_t size,
                             int min_count)
	{
        unsigned long flags;
        struct early_log *log;

        if (kmemleak_error) {
                /* kmemleak stopped recording, just count the requests */
                crt_early_log++;
                return;
        }
		//这里会判断log size是不是大于4000,如果不是,则disable
        if (crt_early_log >= ARRAY_SIZE(early_log)) {
                crt_early_log++;
                kmemleak_disable();
                return;
        }
		...
	}

• 3.上面代码在kernel/msm-4.9/mm/kmemleak.c文件中

配置好并且编译kernel后,开始调试

• 查看目录/sys/kernel/debug下有没有kmemleak文件?有则配置成功,没有请重新配置
• 抓取kernel log, cat /dev/kmsg | grep kmemleak
• 开启扫描echo scan=on > /sys/kernel/debug/kmemleak
• 等待一会后看看log中是否会有kmemleak,再同步cat /sys/kernel/debug/kmemleak
• 我这边有故意alloc memory后没有释放,cat log如下:

	unreferenced object 0xffffffdf0aebd900 (size 4096):
  	comm "cat", pid 10908, jiffies 4295008846 (age 822.560s)
  	hex dump (first 32 bytes):
    1c d9 eb 0a df ff ff ff 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 01 00 00 00 2f 73 64 63  ............/sdc
  	backtrace:
    [<ffffff95e8637b64>] kmem_cache_alloc+0x1dc/0x2d8
    [<ffffff95e865b844>] getname_kernel+0x3c/0x104
    [<ffffff95e8e07900>] himax_vendor_read+0x64/0x300
    [<ffffff95e86c46bc>] proc_reg_read+0x88/0xf4
    [<ffffff95e8649cbc>] vfs_read+0x98/0x178
    [<ffffff95e864b360>] SyS_read+0x60/0xc0
    [<ffffff95e8483770>] el0_svc_naked+0x24/0x28
    [<ffffffffffffffff>] 0xffffffffffffffff

• 每调用proc_reg_read后就会出现4K的内存泄漏,如果调用n次可想而知.

以此记录