On Thu, May 21, 2020 at 09:27:35AM -0400, Prarit Bhargava wrote:
On 5/21/20 9:18 AM, Jiri Benc wrote:
> On Thu, 21 May 2020 08:31:56 -0400, Prarit Bhargava wrote:
>> We've used it (heavily might I add) to debug the kernel. It's a
convenient
>> place for a quick kernel module.
>
> Now I'm curious. How does such module help debugging the kernel?
>
> I'm not saying you're wrong. I'm just saying I can't think of
anything.
> Probably just me not being imaginative enough. More details would be
> appreciated. It might come handy one time.
>
Well it's literally everything from dumping random values to confirming
alignment of structs to debugging.
What I'm doing today is attempting to break the Intel Split Lock detector by running
for (cpu = 0; cpu < nr_cpu_ids; cpu++) {
c = &cpu_data(cpu);
printk("data for cpu %d\n", cpu);
for (i = 0; i < (NCAPINTS + NBUGINTS * 32); i++) {
cpu_has(c, i);
}
}
in a tight loop. Unfortunately that doesn't seem to kick it. I suspect that
the cpuinfo_x86 struct is magically aligned atm :(.
I guess I could keep the dummy-module in it's own tree but that's just a PITA
when I have to quickly debug something. Let's keep it in the tree where it's
always been ;)
I remember using this module quite alot, and it was very helpful. I have to ask
though, does systemtap offer the same level of functionality at this point for
most of the debugging we need to do?
Neil
P.
> Thanks,
>
> Jiri
>
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