linux-kernel - Re: [PATCH v3 13/35] lib: add allocation tagging support for memory allocation profiling

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Date: Tue, 13 Feb 2024 17:47:33 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Kees Cook <keescook@...omium.org>
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Subject: Re: [PATCH v3 13/35] lib: add allocation tagging support for memory
 allocation profiling

On Tue, 13 Feb 2024 14:38:16 -0800
Kees Cook <keescook@...omium.org> wrote:

> > > Save yourself a cycle of "rework the whole fs interface only to have
> > > someone else tell you no" and put it in debugfs, not sysfs.  Wrangling
> > > with debugfs is easier than all the macro-happy sysfs stuff; you don't
> > > have to integrate with the "device" model; and there is no 'one value
> > > per file' rule.  
> > 
> > Thanks for the input. This file used to be in debugfs but reviewers
> > felt it belonged in /proc if it's to be used in production
> > environments. Some distros (like Android) disable debugfs in
> > production.  
> 
> FWIW, I agree debugfs is not right. If others feel it's right in /proc,
> I certainly won't NAK -- it's just been that we've traditionally been
> trying to avoid continuing to pollute the top-level /proc and instead
> associate new things with something in /sys.

You can create your own file system, but I would suggest using kernfs for it ;-)

If you look in /sys/kernel/ you'll see a bunch of kernel file systems already there:

 ~# mount |grep kernel
 securityfs on /sys/kernel/security type securityfs (rw,nosuid,nodev,noexec,relatime)
 debugfs on /sys/kernel/debug type debugfs (rw,nosuid,nodev,noexec,relatime)
 tracefs on /sys/kernel/tracing type tracefs (rw,nosuid,nodev,noexec,relatime)
 configfs on /sys/kernel/config type configfs (rw,nosuid,nodev,noexec,relatime)

-- Steve