linux-kernel - Re: [PATCH] alloc_tag: introduce Kconfig option for default compressed profiling

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <72pac6pkjebt6xo7engiuuu7r3zr7fu6fh6bj77f22m7gslxgr@3gjawofplas2>
Date: Wed, 16 Apr 2025 14:41:50 -0700
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Suren Baghdasaryan <surenb@...gle.com>
Cc: Usama Arif <usamaarif642@...il.com>, 
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org, hannes@...xchg.org, 
	linux-kernel@...r.kernel.org, kernel-team@...a.com
Subject: Re: [PATCH] alloc_tag: introduce Kconfig option for default
 compressed profiling

On Wed, Apr 16, 2025 at 02:08:31PM -0700, Suren Baghdasaryan wrote:
> On Wed, Apr 16, 2025 at 11:06 AM Usama Arif <usamaarif642@...il.com> wrote:
> >
> > With this Kconfig option enabled, the kernel stores allocation tag references
> > in the page flags by default.
> >
> > There are 2 reasons to introduce this:
> > - As mentioned in [1], compressed tags dont have system memory overhead
> > and much lower performance overhead. It would be preferrable to have this as
> > the default option, and to be able to switch it at compile time. Another
> > option is to just declare the static key as true by default?
> > - As compressed option is the best one, it doesn't make sense to have to
> > change both defconfig and command line options to enable memory
> > allocation profiling. Changing commandline across a large number of services
> > can result in signifcant work, which shouldn't be needed if the kernel
> > defconfig needs to be changed anyways.
> 
> The reason tag compression is not the default option is because it
> works only if there are enough free bits in the page flags to store a
> tag index. If you configure it to use page flags and your build does
> not have enough free bits, the profiling will be disabled (see
> alloc_tag_sec_init()).

Is it possible to fail the build in that case i.e. check the page flags
availability at build time?