What is Linux Oops? Parse error message

What is Linux Oops? To parse the error message, specific code examples are required

Introduction

Linux Oops refers to an error message output by the Linux kernel when a serious error occurs, similar to the blue screen error of Windows systems. When the Linux kernel encounters a serious error that cannot be handled, it will stop running and output an error log called Oops information. By analyzing this information, the problem can be located and debugged.

Oops information example

The following is a simple Linux Oops information example:

BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
IP: [<ffffffffa01f9f1a>] some_function 0x1a/0x40 [module_name]
PGD ​​7e0b067 PUD 7e0c067 PMD 0
Oops: 0000 [#1] SMP
Modules linked in: module_name
CPU: 0 PID: 1 Comm: init Not tainted 4.19.0-16-amd64 #1 Debian 4.19.181-1
Hardware name: VirtualBox VirtualBox, BIOS VirtualBox 12/01/2006
RIP: 0010:some_function 0x1a/0x40 [module_name]
RSP: 0018:ffffb3db003f3d8f
RAX: 0000000000000000 RBX: ffffabc656688000 RCX: 00000000000000000
RDX: 0000000000000000 RSI: ffffabc6566880f8 RDI: 0000000000000000
RBP: ffffb3db003f3d8f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000024 R11: 0000000000000003 R12: ffffabc6566880f8
R13: ffffabc6fad9d008 R14: 0000000000000000 R15: ffffabc656688000
FS: 0000000000000000(0000) GS:ffffabc6fac20000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000008 CR3: 0000001f23df6000 CR4: 00000000000706f0
Call Trace:
another_function 0x2b/0x60 [module_name]
init 0x1f/0x30

Parsing error message

1. BUG: Indicates that an error has occurred.
2. unable to handle kernel NULL pointer dereference at 0000000000000008: Indicates that the kernel cannot handle a null pointer dereference error.
3. IP: Indicates the instruction address where the error occurred.
4. PGD PUD ​​PMD: Describes the page table situation when an error occurs.
5. Oops: Indicates that this is an Oops message.
6. Modules linked in: Lists loaded modules.
7. CPU: Indicates the CPU number, process ID and process name where the error occurred.
8. RIP: Indicates the address and module of the instruction that caused the error.
9. Register information: Describes the values ​​of some CPU registers.
10. Call Trace: Shows the function call stack when the error occurred.

Sample Code

The following is a simple C code example that simulates the null pointer dereference error situation that triggers Oops:

#include <linux/ module.h>
#include <linux/init.h>

static int *ptr = NULL;

static int __init oops_example_init(void)
{
    int value;
    
    value = *ptr; // raises a null pointer dereference error
    
    return 0;
}

static void __exit oops_example_exit(void)
{
    printk(KERN_INFO "Exiting Oops Example Module
");
}

module_init(oops_example_init);
module_exit(oops_example_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Author");

Conclusion

Linux Oops information provides key information about serious errors in the kernel. By parsing Oops information and code samples, you can locate and solve the problem. When developing or debugging Linux kernel modules, it is very important to process Oops information in a timely manner to ensure the stability and reliability of the system.

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