kernel - 如何理解这个 dmesg 错误信息？

Question

这个问题已经有答案了:

How to understand this dmesg error message? (1 个回答)

已关闭 7 年前。

我编写了这个简单的模块来处理设备并调用其一些电源管理方法，例如 .suspend和.resume 。在初始化时，模块简单地查找特定设备并尝试调用其方法。

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/pci.h>

static int __init mfps_driver_init(void){

struct pci_dev    *dev      = NULL;
struct pci_driver *driver   = NULL;
struct device     *device   = NULL;

dev = pci_get_device(0x8086, 0x15a2, NULL);

if((dev == NULL) || (dev == 0)){

    printk(KERN_INFO "LEONZO: NOTHING FOUND SIZE %ld\n", sizeof(dev));

} else {

    driver = dev->driver;

    printk(KERN_INFO "LEONZO: I FOUND THE DEVICE OF THE SIZE %ld\n", sizeof(dev));
    printk(KERN_INFO "LEONZO: HERE IS ITS DRIVER NAME %s\n", driver->name);

    *device = dev->dev;

    device_lock(device);

    device_unlock(device);
}

return 0;

}

static void __exit mfps_driver_exit(void){

}


module_init(mfps_driver_init);
module_exit(mfps_driver_exit);

代码编译成功。但是当我加载模块时，我遇到了一个内核错误:

sudo insmod MyFirstPowerState.ko

dmesg 显示以下输出

[   59.545180] MyFirstPowerState: module license 'unspecified' taints   kernel. 
[   59.545183] Disabling lock debugging due to kernel taint
[   59.546010] LEONZO: I FOUND THE DEVICE OF THE SIZE 8
[   59.546012] LEONZO: HERE IS ITS DRIVER NAME e1000e
[   59.546013] LEONZO: CALLING IT SUSPEND METHOD
[   59.546021] BUG: unable to handle kernel NULL pointer dereference         at           (null)
[   59.546051] IP: [<ffffffffc011907e>] mfps_driver_init+0x7e/0x1000         [MyFirstPowerState]
[   59.546077] PGD 0 
[   59.546085] Oops: 0002 [#1] SMP 
[   59.546097] Modules linked in: MyFirstPowerState(POE+) xt_CHECKSUM arc4 iwlmvm mac80211 snd_hda_codec_hdmi snd_hda_codec_realtek iwlwifi snd_hda_codec_generic rtsx_pci_ms memstick cfg80211 nf_conntrack_netbios_ns nf_conntrack_broadcast ipt_MASQUERADE nf_nat_masquerade_ipv4 xt_tcpudp ip6t_REJECT nf_reject_ipv6 ipt_REJECT nf_reject_ipv4 xt_conntrack ebtable_nat ebtable_broute bridge stp llc ebtable_filter ebtables ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_mangle ip6table_security ip6table_raw ip6table_filter ip6_tables iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle iptable_security iptable_raw iptable_filter ip_tables x_tables dm_crypt hp_wmi sparse_keymap intel_rapl iosf_mbi x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm crct10dif_pclmul dm_multipath crc32_pclmul scsi_dh aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper cryptd joydev serio_raw lpc_ich uvcvideo snd_seq_midi snd_seq_midi_event snd_rawmidi snd_hda_intel snd_hda_controller snd_hda_codec videobuf2_vmalloc snd_hwdep shpchp snd_pcm videobuf2_memops videobuf2_core v4l2_common snd_seq e1000e(OE) i915_bpo ptp mei_me pps_core mei videodev media snd_seq_device intel_ips snd_timer drm_kms_helper drm btusb snd i2c_algo_bit soundcore 8250_fintek hp_accel lis3lv02d input_polldev tpm_infineon hp_wireless mac_hid parport_pc ppdev lp parport rfcomm bnep bluetooth binfmt_misc btrfs xor raid6_pq dm_mirror dm_region_hash dm_log uas usb_storage hid_generic usbhid hid rtsx_pci_sdmmc ahci psmouse libahci rtsx_pci wmi video
[   59.546577] CPU: 1 PID: 4180 Comm: insmod Tainted: P           OE   3.19.0-51-generic #58~14.04.1-Ubuntu
[   59.546613] Hardware name: Hewlett-Packard HP EliteBook 840 G2/2216, BIOS M71 Ver. 01.05 03/26/2015
[   59.546648] task: ffff880241a7b110 ti: ffff880242f68000 task.ti: ffff880242f68000
[   59.546678] RIP: 0010:[<ffffffffc011907e>]  [<ffffffffc011907e>] mfps_driver_init+0x7e/0x1000 [MyFirstPowerState]
[   59.546720] RSP: 0018:ffff880242f6bd18  EFLAGS: 00010246
[   59.546741] RAX: 0000000000000000 RBX: ffff880245b4d000 RCX: 00000000000000ae
[   59.546772] RDX: 0000000000000000 RSI: ffff880245b4d098 RDI: 0000000000000000
[   59.546807] RBP: ffff880242f6bd28 R08: 000000000000000a R09: 0000000000000000
[   59.546839] R10: 0000000000000d53 R11: ffff880242f6b9de R12: ffffffffc06a8000
[   59.546868] R13: 0000000000000000 R14: ffffffffc0119000 R15: ffff880242f6bef8
[   59.546900] FS:  00007f8787aa6740(0000) GS:ffff88024f440000(0000) knlGS:0000000000000000
[   59.546921] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   59.546936] CR2: 0000000000000000 CR3: 0000000244393000 CR4: 00000000003407e0
[   59.546955] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   59.546978] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[   59.547006] Stack:
[   59.547014]  ffffffff81c1d060 ffff880204cd3280 ffff880242f6bda8 ffffffff81002144
[   59.547046]  0000000000000001 0000000000000002 ffff8801f8ddc4c0 0000000000000001
[   59.547079]  ffff880242f6bd88 ffffffff811cef19 ffffffff810f7aac 0000000000000018
[   59.547114] Call Trace:
[   59.547131]  [<ffffffff81002144>] do_one_initcall+0xd4/0x210
[   59.547162]  [<ffffffff811cef19>] ? kmem_cache_alloc_trace+0x199/0x220
[   59.547194]  [<ffffffff810f7aac>] ? load_module+0x164c/0x1cc0
[   59.547222]  [<ffffffff810f7ae5>] load_module+0x1685/0x1cc0
[   59.547247]  [<ffffffff810f3380>] ? store_uevent+0x40/0x40
[   59.547274]  [<ffffffff810f8296>] SyS_finit_module+0x86/0xb0
[   59.547298]  [<ffffffff817b788d>] system_call_fastpath+0x16/0x1b
[   59.547314] Code: c7 80 c0 4b c0 31 c0 e8 19 14 69 c1 48 c7 c7 a8 c0  4b c0 31 c0 e8 0b 14 69 c1 31 c0 48 8d b3 98 00 00 00 b9 ae 00 00 00 48 89 c7 <f3> a5 bf 60 00 00 00 e8 26 c7 69 c1 bf 60 00 00 00 e8 ac c5 69 
[   59.547393] RIP  [<ffffffffc011907e>] mfps_driver_init+0x7e/0x1000 [MyFirstPowerState]
[   59.547416]  RSP <ffff880242f6bd18>
[   59.547425] CR2: 0000000000000000
[   59.554577] ---[ end trace 42e3b1c73677cdfa ]---

我还注意到，因此无法删除该模块:

sudo rmmod MyFirstPowerState.ko 
rmmod: ERROR: Module MyFirstPowerState is in use

知道这段代码的含义以及如何纠正错误吗？

Answer 1

您的代码遇到的具体问题在以下语句中:

*device = dev->dev;

device 变量用 NULL 初始化。您试图写入此变量指向的地址，这会导致 NULL 指针取消引用。