Re: [PATCH 0/3][RESEND] add support for never printing hashed addresses

Tetsuo Handa
2021-02-10T17:08:50Z

On 2021/02/11 1:46, Steven Rostedt wrote:
> On Thu, 11 Feb 2021 01:39:41 +0900
> Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> wrote:
>
>> On 2021/02/11 1:18, Steven Rostedt wrote:
>>> The point of this exercise is to be able to debug the *same* kernel that
>>> someone is having issues with. And this is to facilitate that debugging.
>>
>> That's too difficult to use. If a problem is not reproducible, we will have
>> no choice but always specify "never hash pointers" command line option. If a
>> problem is reproducible, we can rebuild that kernel with "never hash pointers"
>> config option turned on.
>
> Now the question is, why do you need the unhashed pointer?

Because unhashed pointers might give some clue. We can rebuild the same kernel
using the same kernel config / compiler etc. and compare unhashed pointers with
addresses in System.map / kallsyms files without reproducing the problem.

>
> Currently, the instruction pointer is what is fine right? You get the
> a function and its offset. If there's something that is needed, perhaps we
> should look at how to fix that, instead of just unhashing all pointers by
> default.

I'm not refusing to use kernel command line options. I'm expecting that we can
also hardcode using kernel config options. Since boot-time switching via kernel
command line options makes the kernel behave differently, less boot-time
switching is better for avoiding unexpected problems (e.g. unintended LSM was
enabled).