On 2018-04-20 16:08, valdis.kletnieks@vt.edu wrote:
On Fri, 20 Apr 2018 23:39:10 +0800, Yubin Ruan said:
On 2018-04-19 13:28, valdis.kletnieks@vt.edu wrote:
On Thu, 19 Apr 2018 16:58:40 +0800, sizel said:
How can I disable compile optimization in kernel for friendly debugging, Thanks
First off, there are parts of the kernel that *WILL* explode if you try to build with -O0 - in particular, any code that expects static inlines to be treated as part of the unit they are inlined into for the purposes of __builtin_return_address() and similar.
Can you elaborate more on that?
grep for __builtin_return_address. Look where it's used. What does it return if it's inlined? What does it return if it's called as not inlined?
For a simple example, consider this code from lib/smp_processor_id.c: in function check_preemption_disabled():
printk(KERN_ERR "BUG: using %s%s() in preemptible [%08x] code: %s/%d\n", what1, what2, preempt_count() - 1, current->comm, current->pid);
printk("caller is %pS\n", __builtin_return_address(0)); dump_stack();
If __builtin_return_address is not inlined, that call points at the printk() call. If it *is* inlined, it points at the return point in the function that called check_preemption_disabled().
Thanks! I tested it and found that __builtin_return_addres's behavior is indeed as you described.
From this, I have a related question, can I treat __builtin_return_address() as a "builtin" stack unwinder (but only check for return addresses, or, where a function is called).
Yubin