From: Segher Boessenkool <segher@kernel.crashing.org>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Alexandre Chartre <alexandre.chartre@oracle.com>,
kbuild-all@lists.01.org,
clang-built-linux <clang-built-linux@googlegroups.com>,
linux-toolchains@vger.kernel.org,
kernel test robot <lkp@intel.com>,
Arvind Sankar <nivedita@alum.mit.edu>,
Ard Biesheuvel <ardb@kernel.org>,
Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
Peter Zijlstra <peterz@infradead.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Kees Cook <keescook@chromium.org>
Subject: Re: [RFC][PATCH 21/24] x86/entry: Disable stack-protector for IST entry C handlers
Date: Fri, 13 Nov 2020 18:43:18 -0600 [thread overview]
Message-ID: <20201114004318.GY2672@gate.crashing.org> (raw)
In-Reply-To: <CAKwvOdk8ewY1nOA2ji6yoZcOOYDX7OKqmbZYuMAnCFV=9t0VNA@mail.gmail.com>
On Fri, Nov 13, 2020 at 04:11:41PM -0800, Nick Desaulniers wrote:
> On Fri, Nov 13, 2020 at 3:49 PM Segher Boessenkool
> <segher@kernel.crashing.org> wrote:
> > On Fri, Nov 13, 2020 at 10:59:26AM -0800, Nick Desaulniers wrote:
> > > The `optimize` attribute is both non-portable across toolchains (hence
> > > this warning)
> >
> > Like *all* GCC extensions.
> >
> > > and a little quirky in GCC.
> >
> > How so? Don't spread FUD please, say what *is* wrong, then people can
> > decide for themselves whether they want it or not.
>
> Spread FUD? Ard literally sent TO YOU:
> https://lore.kernel.org/lkml/CAMj1kXHxX+u5-cN0v3SLdqZTSiKsWsFOvc2SC5=-ScaUZOu8Ng@mail.gmail.com/,
> and it was referenced again in
> https://lore.kernel.org/lkml/20201028081123.GT2628@hirez.programming.kicks-ass.net/.
>
> Was it FUD when Ard sent it to you?
He didn't say "this option is a little quirky". He simply quoted our
wiki entry for it, which says "use this only for debugging" (just like
the user documentation btw). The FAQ also goes on to explain the
attribute is very hard to use, it is not obvious at all what flags you
can and cannot set, it's a user interface disaster. It explains what is
bad with it, it doesn't just say "ooh I don't understand it, do not use
it". (It does say "no one really understands it, do not use it", there
is that ;-) )
Segher
next prev parent reply other threads:[~2020-11-14 0:50 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-09 14:44 [RFC][PATCH 00/24] x86/pti: Defer CR3 switch to C code Alexandre Chartre
2020-11-09 14:44 ` [RFC][PATCH 01/24] x86/syscall: Add wrapper for invoking syscall function Alexandre Chartre
2020-11-09 14:44 ` [RFC][PATCH 02/24] x86/entry: Update asm_call_on_stack to support more function arguments Alexandre Chartre
2020-11-09 14:44 ` [RFC][PATCH 03/24] x86/entry: Consolidate IST entry from userspace Alexandre Chartre
2020-11-09 14:44 ` [RFC][PATCH 04/24] x86/sev-es: Define a setup stack function for the VC idtentry Alexandre Chartre
2020-11-09 14:44 ` [RFC][PATCH 05/24] x86/entry: Implement ret_from_fork body with C code Alexandre Chartre
2020-11-10 16:24 ` kernel test robot
2020-11-15 21:26 ` kernel test robot
2020-11-15 21:34 ` kernel test robot
2020-11-09 14:44 ` [RFC][PATCH 06/24] x86/pti: Provide C variants of PTI switch CR3 macros Alexandre Chartre
2020-11-09 14:44 ` [RFC][PATCH 07/24] x86/entry: Fill ESPFIX stack using C code Alexandre Chartre
2020-11-10 16:52 ` kernel test robot
2020-11-09 14:44 ` [RFC][PATCH 08/24] x86/entry: Add C version of SWAPGS and SWAPGS_UNSAFE_STACK Alexandre Chartre
2020-11-09 19:55 ` Alexandre Chartre
2020-11-09 14:44 ` [RFC][PATCH 09/24] x86/entry: Add C version of paranoid_entry/exit Alexandre Chartre
2020-11-10 18:40 ` kernel test robot
2020-11-09 14:44 ` [RFC][PATCH 10/24] x86/pti: Introduce per-task PTI trampoline stack Alexandre Chartre
2020-11-09 14:44 ` [RFC][PATCH 11/24] x86/pti: Function to clone page-table entries from a specified mm Alexandre Chartre
2020-11-09 14:44 ` [RFC][PATCH 12/24] x86/pti: Function to map per-cpu page-table entry Alexandre Chartre
2020-11-09 14:44 ` [RFC][PATCH 13/24] x86/pti: Extend PTI user mappings Alexandre Chartre
2020-11-09 19:56 ` Alexandre Chartre
2020-11-10 23:39 ` Andy Lutomirski
2020-11-11 8:55 ` Alexandre Chartre
2020-11-13 8:48 ` kernel test robot
2020-11-09 14:44 ` [RFC][PATCH 14/24] x86/pti: Use PTI stack instead of trampoline stack Alexandre Chartre
2020-11-09 14:44 ` [RFC][PATCH 15/24] x86/pti: Execute syscall functions on the kernel stack Alexandre Chartre
2020-11-09 14:44 ` [RFC][PATCH 16/24] x86/pti: Execute IDT handlers " Alexandre Chartre
2020-11-09 14:44 ` [RFC][PATCH 17/24] x86/pti: Execute IDT handlers with error code " Alexandre Chartre
2020-11-09 14:44 ` [RFC][PATCH 18/24] x86/pti: Execute system vector handlers " Alexandre Chartre
2020-11-09 14:44 ` [RFC][PATCH 19/24] x86/pti: Execute page fault handler " Alexandre Chartre
2020-11-09 14:44 ` [RFC][PATCH 20/24] x86/pti: Execute NMI " Alexandre Chartre
2020-11-09 14:44 ` [RFC][PATCH 21/24] x86/entry: Disable stack-protector for IST entry C handlers Alexandre Chartre
2020-11-13 7:58 ` kernel test robot
2020-11-13 18:59 ` Nick Desaulniers
2020-11-13 18:59 ` Nick Desaulniers
2020-11-13 19:39 ` Alexandre Chartre
2020-11-13 19:39 ` Alexandre Chartre
2020-11-13 19:45 ` Nick Desaulniers
2020-11-13 19:45 ` Nick Desaulniers
2020-11-13 23:47 ` Segher Boessenkool
2020-11-14 0:01 ` Miguel Ojeda
2020-11-14 0:01 ` Miguel Ojeda
2020-11-14 0:26 ` Segher Boessenkool
2020-11-14 1:58 ` Miguel Ojeda
2020-11-14 1:58 ` Miguel Ojeda
2020-11-14 10:20 ` Ard Biesheuvel
2020-11-14 10:20 ` Ard Biesheuvel
2020-11-25 19:56 ` Kees Cook
2020-11-25 19:56 ` Kees Cook
2020-11-25 23:00 ` Segher Boessenkool
2020-11-26 6:40 ` Ard Biesheuvel
2020-11-26 6:40 ` Ard Biesheuvel
2020-11-26 20:22 ` Segher Boessenkool
2020-11-26 21:05 ` Arvind Sankar
2020-11-26 21:05 ` Arvind Sankar
2020-11-26 22:00 ` Ard Biesheuvel
2020-11-26 22:00 ` Ard Biesheuvel
2020-11-14 0:11 ` Nick Desaulniers
2020-11-14 0:11 ` Nick Desaulniers
2020-11-14 0:43 ` Segher Boessenkool [this message]
2020-11-14 0:48 ` Nick Desaulniers
2020-11-14 0:48 ` Nick Desaulniers
2020-11-09 14:44 ` [RFC][PATCH 22/24] x86/entry: Defer paranoid entry/exit to C code Alexandre Chartre
2020-11-15 22:51 ` kernel test robot
2020-11-09 14:44 ` [RFC][PATCH 23/24] x86/entry: Remove paranoid_entry and paranoid_exit Alexandre Chartre
2020-11-09 14:44 ` [RFC][PATCH 24/24] x86/pti: Defer CR3 switch to C code for non-IST and syscall entries Alexandre Chartre
2020-11-09 19:35 ` [RFC][PATCH 00/24] x86/pti: Defer CR3 switch to C code Dave Hansen
2020-11-09 19:53 ` Alexandre Chartre
-- strict thread matches above, loose matches on Subject: below --
2020-11-09 11:22 Alexandre Chartre
2020-11-09 11:23 ` [RFC][PATCH 21/24] x86/entry: Disable stack-protector for IST entry C handlers Alexandre Chartre
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