From: Kees Cook <keescook@chromium.org> To: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Josh Poimboeuf <jpoimboe@redhat.com>, Rasmus Villemoes <linux@rasmusvillemoes.dk>, "Gustavo A. R. Silva" <gustavo@embeddedor.com>, "Tobin C. Harding" <me@tobin.cc>, Steven Rostedt <rostedt@goodmis.org>, Jonathan Corbet <corbet@lwn.net>, Chris Mason <clm@fb.com>, Josef Bacik <jbacik@fb.com>, David Sterba <dsterba@suse.com>, "David S. Miller" <davem@davemloft.net>, Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>, Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>, Ingo Molnar <mingo@kernel.org>, Peter Zijlstra <peterz@infradead.org>, Thomas Gleixner <tglx@linutronix.de>, Masahiro Yamada <yamada.masahiro@socionext.com>, Borislav Petkov <bp@suse.de>, Randy Dunlap <rdunlap@infradead.org>, Ian Abbott <abbotti@mev.co.uk>, Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>, Petr Mladek <pmladek@suse.com>, Andy Shevchenko <andriy.shevchenko@linux.intel.com>, Pantelis Antoniou <pantelis.antoniou@konsulko.com>, Linux Btrfs <linux-btrfs@vger.kernel.org>, Network Development <netdev@vger.kernel.org>, Kernel Hardening <kernel-hardening@lists.openwall.com> Subject: Re: [PATCH v3] kernel.h: Skip single-eval logic on literals in min()/max() Date: Fri, 9 Mar 2018 17:30:15 -0800 [thread overview] Message-ID: <CAGXu5j+D=zs8AMb969dhH05GmKPuBxKPcAs89KfKzVf47faL1g@mail.gmail.com> (raw) In-Reply-To: <CA+55aFwbO2vUsjWzAwB6SZ65RM4r3P0+2JvyMHn=ry0CgWCBgA@mail.gmail.com> On Fri, Mar 9, 2018 at 4:38 PM, Linus Torvalds <torvalds@linux-foundation.org> wrote: > On Fri, Mar 9, 2018 at 4:32 PM, Andrew Morton <akpm@linux-foundation.org> wrote: >> >> I wonder which gcc versions actually accept Kees's addition. Ah, my old nemesis, gcc 4.4.4. *sob* > Note that we already do have this pattern, as seen by: > > git grep -2 __builtin_choose_expr | grep -2 __builtin_constant_p > > which show drivers/pinctrl/intel/pinctrl-intel.h, so the pattern > already exists current kernels and _works_ - it apparently just > doesn't work in slightly more complicated cases. Fun. Yeah, so all the PIN_GROUP() callers have either a literal or an array name for that argument, so the argument to __builtin_constant_p() isn't complex. git grep '\bPIN_GROUP\b' | egrep -v '(1|2|3|true|false)\)' > It's one reason why I wondered if simplifying the expression to have > just that single __builtin_constant_p() might not end up working.. Yeah, it seems like it doesn't bail out as "false" for complex expressions given to __builtin_constant_p(). If no magic solution, then which of these? - go back to my original "multi-eval max only for constants" macro (meh) - add gcc version checks around this and similarly for -Wvla in the future (eww) - raise gcc version (yikes) -Kees -- Kees Cook Pixel Security<div class="gmail_extra"><br><div class="gmail_quote">On Fri, Mar 9, 2018 at 4:38 PM, Linus Torvalds <span dir="ltr"><<a href="mailto:torvalds@linux-foundation.org" target="_blank">torvalds@linux-foundation.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">On Fri, Mar 9, 2018 at 4:32 PM, Andrew Morton <<a href="mailto:akpm@linux-foundation.org">akpm@linux-foundation.org</a>> wrote:<br> ><br> > I wonder which gcc versions actually accept Kees's addition.<br> <br> </span>Note that we already do have this pattern, as seen by:<br> <br> git grep -2 __builtin_choose_expr | grep -2 __builtin_constant_p<br> <br> which show drivers/pinctrl/intel/pinctrl-<wbr>intel.h, so the pattern<br> already exists current kernels and _works_ - it apparently just<br> doesn't work in slightly more complicated cases.<br> <br> It's one reason why I wondered if simplifying the expression to have<br> just that single __builtin_constant_p() might not end up working..<br> <span class="HOEnZb"><font color="#888888"><br> Linus<br> </font></span></blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature" data-smartmail="gmail_signature">Kees Cook<br>Pixel Security</div> </div>
WARNING: multiple messages have this Message-ID (diff)
From: Kees Cook <keescook@chromium.org> To: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Josh Poimboeuf <jpoimboe@redhat.com>, Rasmus Villemoes <linux@rasmusvillemoes.dk>, "Gustavo A. R. Silva" <gustavo@embeddedor.com>, "Tobin C. Harding" <me@tobin.cc>, Steven Rostedt <rostedt@goodmis.org>, Jonathan Corbet <corbet@lwn.net>, Chris Mason <clm@fb.com>, Josef Bacik <jbacik@fb.com>, David Sterba <dsterba@suse.com>, "David S. Miller" <davem@davemloft.net>, Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>, Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>, Ingo Molnar <mingo@kernel.org>, Peter Zijlstra <peterz@infradead.org>, Thomas Gleixner <tglx@linutronix.de>, Masahiro Yamada <yamada.masahiro@socionext.com>, Borislav Petkov <bp@suse.de>, Randy Dunlap <rdunl Subject: Re: [PATCH v3] kernel.h: Skip single-eval logic on literals in min()/max() Date: Fri, 9 Mar 2018 17:30:15 -0800 [thread overview] Message-ID: <CAGXu5j+D=zs8AMb969dhH05GmKPuBxKPcAs89KfKzVf47faL1g@mail.gmail.com> (raw) In-Reply-To: <CA+55aFwbO2vUsjWzAwB6SZ65RM4r3P0+2JvyMHn=ry0CgWCBgA@mail.gmail.com> On Fri, Mar 9, 2018 at 4:38 PM, Linus Torvalds <torvalds@linux-foundation.org> wrote: > On Fri, Mar 9, 2018 at 4:32 PM, Andrew Morton <akpm@linux-foundation.org> wrote: >> >> I wonder which gcc versions actually accept Kees's addition. Ah, my old nemesis, gcc 4.4.4. *sob* > Note that we already do have this pattern, as seen by: > > git grep -2 __builtin_choose_expr | grep -2 __builtin_constant_p > > which show drivers/pinctrl/intel/pinctrl-intel.h, so the pattern > already exists current kernels and _works_ - it apparently just > doesn't work in slightly more complicated cases. Fun. Yeah, so all the PIN_GROUP() callers have either a literal or an array name for that argument, so the argument to __builtin_constant_p() isn't complex. git grep '\bPIN_GROUP\b' | egrep -v '(1|2|3|true|false)\)' > It's one reason why I wondered if simplifying the expression to have > just that single __builtin_constant_p() might not end up working.. Yeah, it seems like it doesn't bail out as "false" for complex expressions given to __builtin_constant_p(). If no magic solution, then which of these? - go back to my original "multi-eval max only for constants" macro (meh) - add gcc version checks around this and similarly for -Wvla in the future (eww) - raise gcc version (yikes) -Kees -- Kees Cook Pixel Security<div class="gmail_extra"><br><div class="gmail_quote">On Fri, Mar 9, 2018 at 4:38 PM, Linus Torvalds <span dir="ltr"><<a href="mailto:torvalds@linux-foundation.org" target="_blank">torvalds@linux-foundation.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">On Fri, Mar 9, 2018 at 4:32 PM, Andrew Morton <<a href="mailto:akpm@linux-foundation.org">akpm@linux-foundation.org</a>> wrote:<br> ><br> > I wonder which gcc versions actually accept Kees's addition.<br> <br> </span>Note that we already do have this pattern, as seen by:<br> <br> git grep -2 __builtin_choose_expr | grep -2 __builtin_constant_p<br> <br> which show drivers/pinctrl/intel/pinctrl-<wbr>intel.h, so the pattern<br> already exists current kernels and _works_ - it apparently just<br> doesn't work in slightly more complicated cases.<br> <br> It's one reason why I wondered if simplifying the expression to have<br> just that single __builtin_constant_p() might not end up working..<br> <span class="HOEnZb"><font color="#888888"><br> Linus<br> </font></span></blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature" data-smartmail="gmail_signature">Kees Cook<br>Pixel Security</div> </div>
next prev parent reply other threads:[~2018-03-10 1:30 UTC|newest] Thread overview: 85+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-03-09 20:05 [PATCH v3] kernel.h: Skip single-eval logic on literals in min()/max() Kees Cook 2018-03-09 20:05 ` Kees Cook 2018-03-09 21:10 ` Linus Torvalds 2018-03-09 21:10 ` Linus Torvalds 2018-03-09 21:47 ` Kees Cook 2018-03-09 21:47 ` Kees Cook 2018-03-11 22:46 ` Tobin C. Harding 2018-03-11 22:46 ` Tobin C. Harding 2018-03-11 22:46 ` Tobin C. Harding 2018-03-13 13:31 ` David Laight 2018-03-13 13:31 ` David Laight 2018-03-10 0:07 ` Andrew Morton 2018-03-10 0:07 ` Andrew Morton 2018-03-10 0:28 ` Linus Torvalds 2018-03-10 0:28 ` Linus Torvalds 2018-03-10 0:32 ` Andrew Morton 2018-03-10 0:32 ` Andrew Morton 2018-03-10 0:38 ` Linus Torvalds 2018-03-10 0:38 ` Linus Torvalds 2018-03-10 1:30 ` Kees Cook [this message] 2018-03-10 1:30 ` Kees Cook 2018-03-10 1:31 ` Kees Cook 2018-03-10 1:31 ` Kees Cook 2018-03-10 2:37 ` Linus Torvalds 2018-03-10 2:37 ` Linus Torvalds 2018-03-12 22:55 ` Andrew Morton 2018-03-12 22:55 ` Andrew Morton 2018-03-12 23:57 ` Linus Torvalds 2018-03-12 23:57 ` Linus Torvalds 2018-03-13 4:28 ` Kees Cook 2018-03-13 4:28 ` Kees Cook 2018-03-13 21:02 ` Andrew Morton 2018-03-13 21:02 ` Andrew Morton 2018-03-13 22:14 ` Kees Cook 2018-03-13 22:14 ` Kees Cook 2018-03-14 11:35 ` David Laight 2018-03-14 11:35 ` David Laight 2018-03-10 3:11 ` Randy Dunlap 2018-03-10 3:11 ` Randy Dunlap 2018-03-10 6:10 ` Miguel Ojeda 2018-03-10 6:10 ` Miguel Ojeda 2018-03-10 7:03 ` Miguel Ojeda 2018-03-10 7:03 ` Miguel Ojeda 2018-03-10 16:04 ` Linus Torvalds 2018-03-10 16:04 ` Linus Torvalds 2018-03-10 15:33 ` Kees Cook 2018-03-10 15:33 ` Kees Cook 2018-03-10 16:11 ` Linus Torvalds 2018-03-10 16:11 ` Linus Torvalds 2018-03-10 16:30 ` Linus Torvalds 2018-03-10 16:30 ` Linus Torvalds 2018-03-10 17:34 ` Miguel Ojeda 2018-03-10 17:34 ` Miguel Ojeda 2018-03-10 17:51 ` Linus Torvalds 2018-03-10 17:51 ` Linus Torvalds 2018-03-10 19:08 ` Miguel Ojeda 2018-03-10 19:08 ` Miguel Ojeda 2018-03-11 11:05 ` Ingo Molnar 2018-03-11 11:05 ` Ingo Molnar 2018-03-11 18:23 ` Linus Torvalds 2018-03-11 18:23 ` Linus Torvalds 2018-03-10 2:34 [PATCH 0/3] tracing: Rewrite the function filter code Steven Rostedt 2018-03-10 2:34 ` [PATCH 1/3] tracing: Combine enum and arrays into single macro in " Steven Rostedt 2018-03-12 10:31 ` Masami Hiramatsu 2018-03-10 2:34 ` [PATCH 2/3] tracing: Clean up and document pred_funcs_##type creation and use Steven Rostedt 2018-03-12 13:42 ` Masami Hiramatsu 2018-03-10 2:34 ` [PATCH 3/3] tracing: Rewrite filter logic to be simpler and faster Steven Rostedt 2018-03-10 3:10 ` Steven Rostedt 2018-03-10 3:10 ` Steven Rostedt 2018-03-10 3:15 ` Steven Rostedt 2018-03-10 3:15 ` Steven Rostedt 2018-03-10 3:22 ` Steven Rostedt 2018-03-10 3:22 ` Steven Rostedt 2018-03-10 3:18 ` Steven Rostedt 2018-03-12 12:42 ` Jiri Olsa 2018-03-12 18:38 ` Steven Rostedt 2018-03-12 15:10 ` Jiri Olsa 2018-03-12 18:40 ` Steven Rostedt 2018-03-12 18:54 ` Jiri Olsa 2018-03-12 19:10 ` Steven Rostedt 2018-03-12 23:52 ` Steven Rostedt 2018-03-13 10:14 ` Jiri Olsa 2018-03-13 14:12 ` Steven Rostedt 2018-03-13 14:27 ` Jiri Olsa 2018-03-11 19:54 ` [PATCH 0/3] tracing: Rewrite the function filter code Jiri Olsa
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