释放分配内存的linux内核设备驱动模块

Question

我正在为linux内核模块编写代码，该模块分配空间并在其中存储一些数据，但是kmalloc分配发生在vfs的写函数中，因为我需要来自用户应用程序的缓冲区的大小，并且不能在写函数之外访问它。我应该把kfree()函数放在哪里？我不能将它放在清理下，因为每当我试图卸载模块时，它都会给我一个错误。

ssize_t hcsr04_write(struct file *filp, const char *buffer, size_t length, loff_t * offset)
{
        if (pulsecount < (5)){
            pulseptr[pulsecount] = kmalloc(sizeof(buffer),GFP_ATOMIC);
            sprintf (pulseptr[pulsecount],"%s",buffer);
            pulsecount++;
        }
        else{
            int j = 0;
            while (j<4){
                sprintf (pulseptr[j], "%s", (pulseptr[j+1]) ); // [5 , 20 , 30 , 70 , 50] ===> [20 , 30 , 70 , 50 , 50]
                j++;
            }
            sprintf (pulseptr[4],"%s",buffer);
        }       
    
}

这是我的写作功能。

static void __exit hcsr04_module_cleanup(void)
{
    //if (pulseptr!= {NULL,NULL,NULL,NULL,NULL}){
    kfree(pulseptr);
    printk(KERN_INFO "Dynamic memory freed successfully.");
    //}
    //pulseptr = {NULL,NULL,NULL,NULL,NULL};
    gpio_free( GPIO_OUT );
    gpio_free( GPIO_IN );
    hcsr04_lock = 0;
    cdev_del(&hcsr04_cdev);
    unregister_chrdev_region( hcsr04_dev, 1 );
    kobject_put( hcsr04_kobject );
}

这是清理功能。如果我使用这样的清理函数执行rmmod命令，就会得到以下错误：

[   93.294821] 8<--- cut here ---
[   93.297928] Unable to handle kernel paging request at virtual address bcf03574
[   93.305253] pgd = 3cdbb3d3
[   93.307993] [bcf03574] *pgd=00000000
[   93.311621] Internal error: Oops: 5 [#1] SMP ARM
[   93.316301] Modules linked in: hcsr04(O-) nfc bnep bluetooth ecdh_generic ecc ipv6 hello(PO) g_serial libcomposite udc_core brcmfmac brcmutil sha256_generic libsha256 vc4 cfg80211 bcm2835_codec(C) rfkill bcm2835_isp(C) bcm2835_v4l2(C) v4l2_mem2mem cec bcm2835_mmal_vchiq(C) videobuf2_dma_contig snd_soc_core videobuf2_vmalloc videobuf2_memops videobuf2_v4l2 snd_compress snd_pcm_dmaengine videobuf2_common snd_pcm videodev snd_timer mc snd raspberrypi_hwmon vc_sm_cma(C) uio_pdrv_genirq uio fixed
[   93.360563] CPU: 0 PID: 478 Comm: rmmod Tainted: P         C O      5.4.72-v7 #1
[   93.368060] Hardware name: BCM2835
[   93.371516] PC is at kfree+0x48/0x2bc
[   93.375235] LR is at hcsr04_module_cleanup+0x18/0xcac [hcsr04]
[   93.381148] pc : [<802fd004>]    lr : [<7f17a36c>]    psr: 20010013
[   93.387501] sp : b80abf08  ip : b80abf38  fp : b80abf34
[   93.392797] r10: 00000081  r9 : b80aa000  r8 : 801011c4
[   93.398095] r7 : 7f17a36c  r6 : 7e92dc38  r5 : 7f17c000  r4 : bcf03570
[   93.404713] r3 : bab24000  r2 : 00000024  r1 : 00000000  r0 : 7f17c000
[   93.411333] Flags: nzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
[   93.418568] Control: 10c5383d  Table: 38d5806a  DAC: 00000055
[   93.424394] Process rmmod (pid: 478, stack limit = 0x274b04e4)
[   93.430307] Stack: (0xb80abf08 to 0xb80ac000)
[   93.434728] bf00:                   801c8158 80989110 7f17c0c0 00000000 7e92dc38 00000081
[   93.443026] bf20: 801011c4 b80aa000 b80abf4c b80abf38 7f17a36c 802fcfc8 7f17c0c0 00000000
[   93.451324] bf40: b80abfa4 b80abf50 801ca940 7f17a360 72736368 00003430 00000000 80da6b10
[   93.459621] bf60: 80101068 7e92cbe8 00000000 801011c4 b80aa000 00000006 b80abfac b80abf88
[   93.467918] bf80: 80228294 8022938c 00000000 80e05f88 00000000 7e92de2c 00000000 b80abfa8
[   93.476216] bfa0: 80101000 801ca7e0 00000000 7e92de2c 01677694 00000800 6a0f1b00 7e92dbe4
[   93.484513] bfc0: 00000000 7e92de2c 7e92dc38 00000081 7e92df1f 7e92dc34 01677190 00000001
[   93.492811] bfe0: 004e1f70 7e92dbec 004c866f 76f37218 60010030 01677694 00000000 00000000
[   93.501100] Backtrace: 
[   93.503593] [<802fcfbc>] (kfree) from [<7f17a36c>] (hcsr04_module_cleanup+0x18/0xcac [hcsr04])
[   93.512331]  r9:b80aa000 r8:801011c4 r7:00000081 r6:7e92dc38 r5:00000000 r4:7f17c0c0
[   93.520195] [<7f17a354>] (hcsr04_module_cleanup [hcsr04]) from [<801ca940>] (sys_delete_module+0x16c/0x244)
[   93.530073]  r5:00000000 r4:7f17c0c0
[   93.533704] [<801ca7d4>] (sys_delete_module) from [<80101000>] (ret_fast_syscall+0x0/0x28)
[   93.542084] Exception stack(0xb80abfa8 to 0xb80abff0)
[   93.547209] bfa0:                   00000000 7e92de2c 01677694 00000800 6a0f1b00 7e92dbe4
[   93.555507] bfc0: 00000000 7e92de2c 7e92dc38 00000081 7e92df1f 7e92dc34 01677190 00000001
[   93.563801] bfe0: 004e1f70 7e92dbec 004c866f 76f37218
[   93.568922]  r5:7e92de2c r4:00000000
[   93.572549] Code: e3a02024 e5933000 e1a04624 e0243492 (e5943004) 
[   93.578730] ---[ end trace cff8773499967501 ]---

一旦我注释掉kfree，错误就消失了。

Answer 1

我意识到我做错了什么。我应该做kfree(pulseptr)，其中0可以是我所分配的内存位置的索引数。