Debug macro for Linux kernel Debug Method summary

The kernel debug macro described in this article is a static debugging method, which is triggered oops by the debug macro to print out the function call stack information.

1) bug_on View the stack contents of the BUG, and actively manufacture the Oops

Linux bug_on,warn_on are used for debugging, such as

#define BUG_ON (condition) do {/

if (unlikely ((condition)!=0))/

BUG (); /

} while (0)

If you feel that the condition is a bug, you can add this debug information to view the corresponding stack contents

The specific bug_on final call __bug

__bug

{

* (int*) 0=0;

}

In order to address illegal access, such as calling bug_on (1) in your driver, DMESG will appear similar to the following information:

[19.360000] Unable to handle kernel NULL pointer dereference at virtual Address 00000000

[19.360000] PGD = c0004000

[19.360000] [00000000] *pgd=00000000

The procedure for calling a function is

Fault.c

__do_kernel_fault--------[19.360000] Unable to handle kernel NULL pointer dereference at virtual Address 00000000

Traps.c

Die--->__die--->__show_regs/dump_mem

2) warn_on call dump_stack print stack information, does not oops

#define WARN_ON (condition) do{/

if (unlikely ((condition)! = 0)) {/

PRINTK ("Badness in%s at%s:%d\n", __function__, __file__, __line__);

Dump_stack ();

}

}while (0)

3) build_bug_on compile debug Macro

#define BUILD_BUG_ON (condition) (void) sizeof (char[1-2*!! (condition)]))

BUILD_BUG_ON macros in the condition if True will be an error. Assuming the condition is true, the build_bug_on changes to: (void) sizeof (char[-1]), which is difficult to understand because char[-1] is inherently illegal. The result is a compilation error.

Example:

#define CONDITION 0

static int __init main_init (void)

{

PRINTK ("in%s function\n", __func__);

BUILD_BUG_ON (condition);/*if the macro "Confition" is not zero, and the program can isn't compiled to success. The build_bug_on used for the BUILD of program*/

WARN_ON (!condition);/*if the macro "Confition" is not zero, there would dump the SATCK information for this program. So the warn_on used for Debugof program*/

BUG_ON (condition); /*IF the macro "Confition" is not zero, the kernel would occur an Oops Errro "unable to handle kernel NULL pointer derefere NCE at virtual Address 00000000 ". So the bug_on used for ending the BUG program*/

return 0;

}

Debug macro for Linux kernel Debug Method summary