Oops error location method in ARM kernel

The error log information is as follows:

 1 Unable to handle kernel NULL pointer dereference at virtual address 00000014
 2 pgd = c0004000
 3 [00000014] *pgd=00000000
 4 Internal error: Oops: 5 [#1] PREEMPT SMP ARM
 5 Modules linked in:
 6 CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.10.45 #125
 7 task: dc078000 ti: dc05a000 task.ti: dc05a000
 8 PC is at at24c02_probe+0x78/0xa0
 9 LR is at wake_up_klogd+0x84/0xac
10 pc : [<c03e27c0>]    lr : [<c002d9b0>]    psr: 40000113
11 sp : dc05bdb8  ip : dc05bcc0  fp : dc05bdd4
12 r10: c0a20a80  r9 : 0000009e  r8 : c03e2748
13 r7 : 00000000  r6 : c08ccee4  r5 : c08ccf00  r4 : c075dbbc
14 r3 : 00000000  r2 : 00000001  r1 : 20000193  r0 : 00000020
15 Flags: nZcv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment kernel
16 Control: 10c5387d  Table: 1000404a  DAC: 00000015
17 Process swapper/0 (pid: 1, stack limit = 0xdc05a238)

1) According to the log information, the value of PC is   PC is at at24c02_ probe+0x78/0xa0;

  at24c02_ Probe: the function indicating the error;

0x78: indicates the offset position of the Error statement in the error function;

0xa0: AT24C02_ The size of probe function

2)   Use arm none Linux gnueabi GCC nm command to find the function AT24C02_ The linear address of probe in the kernel (you can also find it in the system. Map file)

  arm-none-linux-gnueabi-gcc-nm vmlinux | grep at24c02_ probe

(vmlinux is an uncompressed image file, which is in the compilation folder of the kernel.)

The results are as follows

1 c03e2748 t at24c02_probe

Description AT24C02_ The initial linear address of probe function in kernel is 0xc03e2748;

3) According to the deviation value of 0x78, using the arm none Linux gnueabi objdump command, the disassembly of address c03e2748-c03e27ff is displayed (estimated approximate range)

  arm-none-linux-gnueabi-objdump -S vmlinux –start-address=0xc03e2748 –stop-address=0xc03e27ff >/tmp/file

Deviation value + starting address of function = 0x78 + 0xc03e2748 = 0xc03e27c0 (it can also be obtained from PC value of log)

The errors found in the file file are as follows:

1  c03e27b8:       e59f0020        ldr     r0, [pc, #32]   ; c03e27e0 <at24c02_probe+0x98>
2  56 c03e27bc:       eb0c86de        bl      c070433c <printk>
3  57     printk("The i2c device id data is %d\n", id->driver_data);
4  58 c03e27c0:       e5971014        ldr     r1, [r7, #20]
5  59 c03e27c4:       e59f0018        ldr     r0, [pc, #24]   ; c03e27e4 <at24c02_probe+0x9c>
6  60 c03e27c8:       eb0c86db        bl      c070433c <printk>

We can see that the wrong statement is: printk (“the I2C device ID data is% D/N”, ID – & gt; driver_ data);

Another method:  
You can directly obtain the following information through the addr2line command:

Execute the following command under the compiled source code folder to show which line of code of that function has problems,  
    arm-none-linux-gnueabi-addr2line -e vmlinux   c03e27c0

/opt/Sourcery_CodeBench_for_ARM_Embedded/bin/arm-none-linux-gnueabi-addr2line -e vmlinux c03e27c0

Note: please make sure that cross_ Compile is compiled with the same prefix as you, such as arm none Linux gnueabi – above. You must compile with this prefix, otherwise the calculated line number may deviate greatly.

Read More: