Date: Tue, 7 Nov 2017 17:44:13 -0500 From: Steven Rostedt <rostedt@...dmis.org> To: Linus Torvalds <torvalds@...ux-foundation.org> Cc: Kees Cook <keescook@...omium.org>, "Tobin C. Harding" <me@...in.cc>, "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>, Andy Lutomirski <luto@...nel.org>, Joe Perches <joe@...ches.com>, Network Development <netdev@...r.kernel.org>, David Miller <davem@...emloft.net>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, "Jason A. Donenfeld" <Jason@...c4.com>, "Theodore Ts'o" <tytso@....edu>, Paolo Bonzini <pbonzini@...hat.com>, Tycho Andersen <tycho@...ker.com>, "Roberts, William C" <william.c.roberts@...el.com>, Tejun Heo <tj@...nel.org>, Jordan Glover <Golden_Miller83@...tonmail.ch>, Greg KH <gregkh@...uxfoundation.org>, Petr Mladek <pmladek@...e.com>, Ian Campbell <ijc@...lion.org.uk>, Sergey Senozhatsky <sergey.senozhatsky@...il.com>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <wilal.deacon@....com>, Chris Fries <cfries@...gle.com>, Dave Weinstein <olorin@...gle.com>, Daniel Micay <danielmicay@...il.com>, Djalal Harouni <tixxdz@...il.com>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Peter Zijlstra <peterz@...radead.org> Subject: Re: [PATCH v3] scripts: add leaking_addresses.pl On Tue, 7 Nov 2017 13:44:01 -0800 Linus Torvalds <torvalds@...ux-foundation.org> wrote: > > Looking other places that stand out, it seems like > > /proc/lockdep_chains and /proc/lockdep (CONFIG_LOCKDEP=y) has a ton of > > %p usage. It's unclear to me if a hash is sufficient for meaningful > > debugging there? > > Maybe not, but that is also _so_ esoteric that I suspect the right fix > is to just make it root-only readable. Also note, I don't believe anyone should be running a LOCKDEP configured kernel in a production (secured) environment. As it adds quite a bit of overhead. It's something you run on test environments to make sure it doesn't detect any possible deadlocks. > > I've never used it, we should check with people who have. I get the > feeling that this is purely for PeterZ debugging. I've used it. But then again, I also debug lockdep ;-) > > The very first commit that introduced that code actually has a > > (FIXME: should go into debugfs) > > so I suspect it never should have been user-readable to begin with. I > guess it makes some things easier, but it really is *very* different > from things like profiling. Want me to whip up a patch to move the file? -- Steve > > Profiling you often *cannot* do as root - some things you profile > really shouldn't be run as root, and might even refuse to do so. So > requiring you to be root just to get a kernel profile is very bad. > > But looking at lockdep stats? Yeah, 'sudo' isn't so big of a deal. > >
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