linux 内核态OOM内存泄漏memleak使用

1，配置，修改\kernel\arch\arm64\configs\rockchip_linux_defconfig，修改后查看.config.

lark@ubuntu:~/Public/rk356x-linux/rk356x-linux/kernel$ cat .config | grep -i kmemleak
CONFIG_HAVE_DEBUG_KMEMLEAK=y
CONFIG_DEBUG_KMEMLEAK=y
CONFIG_DEBUG_KMEMLEAK_MEM_POOL_SIZE=16000
# CONFIG_DEBUG_KMEMLEAK_TEST is not set
# CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF is not set
CONFIG_DEBUG_KMEMLEAK_AUTO_SCAN=y

配置参考：内核内存泄露检测器 — The Linux Kernel documentation

2，使用前先挂载debug文件系统

mount -t debugfs nodev /sys/kernel/debug/

root@ubuntu2004:/sys/kernel/debug# mount -t debugfs nodev /sys/kernel/debug/
mount: /sys/kernel/debug: nodev already mounted or mount point busy.

挂载失败后卸载重新挂载。

umount -t debugfs nodev /sys/kernel/debug/

清空信息

echo clear > /sys/kernel/debug/kmemleak

cat /sys/kernel/debug/kmemleak

直接扫描查看

echo scan > /sys/kernel/debug/kmemleak

再查看

cat /sys/kernel/debug/kmemleak

root@ubuntu2004:~# echo scan > /sys/kernel/debug/kmemleak
root@ubuntu2004:~# cat /sys/kernel/debug/kmemleak
unreferenced object 0xffffff8013b8ef80 (size 128):
comm "NetworkManager", pid 369, jiffies 4294879794 (age 84.547s)
hex dump (first 32 bytes):
50 4f 4c 4c 00 00 00 00 00 00 01 00 00 00 00 00 POLL............
ac 1a 28 13 80 ff ff ff 00 00 00 00 00 00 00 00 ..(.............
backtrace:
[<00000000607304f6>] __kmalloc_track_caller+0x208/0x40c
[<000000006d5ca9dd>] kvasprintf+0x90/0x120
[<000000009d2babac>] kasprintf+0x54/0x80
[<00000000fdf036ee>] phy_attached_info_irq+0x5c/0xa0
[<00000000031e1948>] phylink_bringup_phy+0xd8/0x370
[<00000000ff700461>] phylink_of_phy_connect+0xfc/0x120
[<00000000bbb6560e>] stmmac_open+0xa98/0xea0
[<00000000b38baf6a>] __dev_open+0x10c/0x18c
[<00000000f07defb8>] __dev_change_flags+0x164/0x1c0
[<00000000fe90a519>] dev_change_flags+0x28/0x64
[<00000000b86a7bf8>] do_setlink+0x224/0xda4
[<000000001d760f93>] __rtnl_newlink+0x50c/0x7d0
[<0000000022b7a662>] rtnl_newlink+0x54/0x80
[<0000000000f2f898>] rtnetlink_rcv_msg+0x120/0x35c
[<00000000b3efd0bb>] netlink_rcv_skb+0x60/0x12c
[<00000000bfaee2d8>] rtnetlink_rcv+0x1c/0x24

代码里面用到了kasprintf ，在这里看一下使用 kasprintf 时需要注意以下几点：

分配的内存位于内核空间，不能直接从用户空间访问。
分配的内存必须通过 kfree 函数来释放，以避免内存泄漏。
由于 kasprintf 可能会导致睡眠（如果内存紧张时可能需要等待内存分配），因此它不能在中断上下文或持有自旋锁时调用。

函数使用举例

#include <linux/kernel.h>
#include <linux/slab.h>

char *my_kasprintf_function(void)
{
gfp_t gfp = GFP_KERNEL;
char *my_string;

my_string = kasprintf(gfp, "The answer is %d", 42);
if (!my_string)
return NULL; // 分配失败

pr_info("%s\n", my_string); // 在内核日志中打印信息
kfree(my_string); // 释放分配的内存
return my_string;
}

再来看我程序中的代码

char *phy_attached_info_irq(struct phy_device *phydev)
{
   char *irq_str;
   char irq_num[8];

   switch(phydev->irq) {
   case PHY_POLL:
       irq_str = "POLL";
       break;
   case PHY_IGNORE_INTERRUPT:
       irq_str = "IGNORE";
       break;
   default:
       snprintf(irq_num, sizeof(irq_num), "%d", phydev->irq);
       irq_str = irq_num;
       break;
   }

   return kasprintf(GFP_KERNEL, "%s", irq_str);
}