linux-kernel - Re: [RFC] x86/mm/dump_pagetables: Allow dumping pagetables by pid

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Message-ID: <ca8d4f94-a106-dc56-893d-d32d43beed85@intel.com>
Date:   Sat, 10 Sep 2022 16:09:55 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     lizhe.67@...edance.com, dave.hansen@...ux.intel.com,
        luto@...nel.org, peterz@...radead.org
Cc:     linux-kernel@...r.kernel.org, lizefan.x@...edance.com,
        yuanzhu@...edance.com
Subject: Re: [RFC] x86/mm/dump_pagetables: Allow dumping pagetables by pid

On 8/4/22 00:04, lizhe.67@...edance.com wrote:
> In current kernel we can only dump a user task's pagetable
> by task itself. Sometimes we need to inspect the page table
> attributes of different memory maps to user space to meet
> the relevant development and debugging requirements. This
> patch helps us to make our works easier. It add two file
> named 'pid' and 'pid_pgtable_show'. We can use 'pid' to
> input the task we want to inspect and get pagetable info
> from 'pid_pgtable_show'.
> 
> User space can use file 'pid' and 'pid_pgtable_show' as follows.
> ====
> $ echo $pid > /sys/kernel/debug/page_tables/pid
> $ cat /sys/kernel/debug/page_tables/pid_pgtable_show

This seems a wee bit silly considering that we have /proc.  It's also
impossible to have an ABI like this work if multiple processes are
trying to dump different pids.

Are there any other per-process things in debugfs where folks have done
something similar?