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From: "jay+ggcc@jp-hosting.net" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/104713] gcc does not reject -march=i686 -fcf-protection
Date: Mon, 20 Mar 2023 08:42:37 +0000 [thread overview]
Message-ID: <bug-104713-4-UYq4Xw2klq@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-104713-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104713
James Addison <jay+ggcc@jp-hosting.net> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jay+ggcc@jp-hosting.net
--- Comment #5 from James Addison <jay+ggcc@jp-hosting.net> ---
Adrian wrote:
> To support the Geode in OLPC, the toolchain definition of i686 does include CMOV but it does not include multi-byte NOPs.
...
> Sorry for being unclear, this is the historical reason why the binutils/gcc definition of i686 does not include multi-byte NOPs.
Jakub wrote:
> Just build for those as -march=i586. preventing -fcf-protection with -march=i686 would be a really bad idea, that would basically prevent all of CET protection for 32-bit code, i686 is what is used as the supported lowest common denominator of 32-bit code.
Could the findings indicate that there are two bugs here?
- The Geode LX target capable of supporting fcf-protection but GCC-11
currently rejects that architecture and flag combination (in the
potentially-buggy code[1] that Adrian refers to)
- Multi-byte NOPs are emitted for architecture i686 by GCC-11, despite some
CPUs within that architecture lacking[2] support
Also potentially relevant is bug 41989.
[1] -
https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/config/i386/i386-options.cc;h=805539364108eee07f5bda527acd6f39f3f7bf95;hb=HEAD#l2929
[2] - https://bugzilla.redhat.com/show_bug.cgi?id=579838#c32
next prev parent reply other threads:[~2023-03-20 8:42 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-28 10:15 [Bug target/104713] New: " bunk at stusta dot de
2022-02-28 10:25 ` [Bug target/104713] " pinskia at gcc dot gnu.org
2022-02-28 10:36 ` bunk at stusta dot de
2022-02-28 11:02 ` jakub at gcc dot gnu.org
2022-02-28 11:42 ` bunk at stusta dot de
2023-03-20 8:42 ` jay+ggcc@jp-hosting.net [this message]
2023-03-20 9:01 ` bunk at stusta dot de
2023-03-20 11:20 ` jay+ggcc@jp-hosting.net
2023-03-23 16:37 ` jay+ggcc@jp-hosting.net
2023-03-24 10:15 ` jay+ggcc@jp-hosting.net
2023-05-16 11:48 ` jay+ggcc@jp-hosting.net
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