Linux內存泄漏調試

背景

循環壓力測試驅動某個模塊功能時,會出現alloc不到memory情況

工具

利用Linux自帶的工具(kmemleak),進行調試

怎樣編譯出工具

配置config,默認配置如下:

CONFIG_DEBUG_KMEMLEAK=y
CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE=4000
CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y

修改後:

CONFIG_DEBUG_KMEMLEAK=y
CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE=10000
CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=n

• 1.CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF配置爲n,表示默認編譯kmemleak模塊

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

	#ifdef CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF //關掉此宏
        if (!kmemleak_skip_disable) {
                kmemleak_early_log = 0;
                kmemleak_disable();//這個會關掉kmemleak功能
                return;
        }
	#endif

• 2.如果CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE不修改的話,在初始化的時候會默認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;
        }
		//這裏會判斷log size是不是大於4000,如果不是,則disable
        if (crt_early_log >= ARRAY_SIZE(early_log)) {
                crt_early_log++;
                kmemleak_disable();
                return;
        }
		...
	}

• 3.上面代碼在kernel/msm-4.9/mm/kmemleak.c文件中

配置好並且編譯kernel後,開始調試

• 查看目錄/sys/kernel/debug下有沒有kmemleak文件?有則配置成功,沒有請重新配置
• 抓取kernel log, cat /dev/kmsg | grep kmemleak
• 開啓掃描echo scan=on > /sys/kernel/debug/kmemleak
• 等待一會後看看log中是否會有kmemleak,再同步cat /sys/kernel/debug/kmemleak
• 我這邊有故意alloc memory後沒有釋放,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

• 每調用proc_reg_read後就會出現4K的內存泄漏,如果調用n次可想而知.

以此記錄