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From: Nick Desaulniers <ndesaulniers@google.com>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
	<x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Arnd Bergmann <arnd@arndb.de>, Jann Horn <jannh@google.com>,
	Randy Dunlap <rdunlap@infradead.org>
Subject: Re: [PATCH 00/22] x86, objtool: several fixes/improvements
Date: Fri, 27 Sep 2019 13:24:50 -0700	[thread overview]
Message-ID: <CAKwvOdmXbkprvi5FO2aic__JQh7z4NmU6MV_iqcnfu5G7T=9Xg@mail.gmail.com> (raw)
In-Reply-To: <CAKwvOdn8_NENF8_cxizrD-PYN_t11px+51WKtkAUa2Q-vH68yw@mail.gmail.com>

On Thu, Jul 18, 2019 at 3:26 PM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> On Tue, Jul 16, 2019 at 4:17 PM Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> >
> > > > > 2) There's also an issue in clang where a large switch table had a bunch
> > > > >    of unused (bad) entries.  It's not a code correctness issue, but
> > > > >    hopefully it can get fixed in clang anyway.  See patch 20/22 for more
> > > > >    details.
> > >
> > > Thanks for the report, let's follow up on steps for me to reproduce.
> >
> > Just to clarify, there are two clang issues.  Both of them were reported
> > originally by Arnd, IIRC.
> >
> > 1) The one described above and in patch 20, where the switch table is
> >    mostly unused entries.  Not a real bug, but it's a bit sloppy and
> >    wasteful, and objtool doesn't know how to interpret it.
>
> Thanks for the concise reports.  Will follow up on these in:
> https://github.com/ClangBuiltLinux/linux/issues/611

Following up on this one; in one of the test cases we determined that
the default destination of an exhaustive switch wasn't getting cleaned
up properly, and is being fixed in:
https://reviews.llvm.org/D68131
https://bugs.llvm.org/show_bug.cgi?id=43129
I'm not sure that was the precise issue you described, or if there's
more than one bug here, but hopefully it will help.

>
> >
> > 2) The bug with the noreturn call site having a different stack size
> >    depending on which code path was taken.
>
> and:
> https://github.com/ClangBuiltLinux/linux/issues/612
-- 
Thanks,
~Nick Desaulniers

      reply	other threads:[~2019-09-27 20:25 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-15  0:36 [PATCH 00/22] x86, objtool: several fixes/improvements Josh Poimboeuf
2019-07-15  0:36 ` [PATCH 01/22] x86/paravirt: Fix callee-saved function ELF sizes Josh Poimboeuf
2019-07-15  4:58   ` Juergen Gross
2019-07-15 12:43     ` Josh Poimboeuf
2019-07-15  0:36 ` [PATCH 02/22] x86/kvm: Fix fastop function ELF metadata Josh Poimboeuf
2019-07-15  9:05   ` Paolo Bonzini
2019-07-15  0:36 ` [PATCH 03/22] x86/kvm: Fix frame pointer usage in vmx_vmenter() Josh Poimboeuf
2019-07-15  9:04   ` Paolo Bonzini
2019-07-15 12:37     ` Josh Poimboeuf
2019-07-15 13:03       ` Paolo Bonzini
2019-07-15 13:35         ` Josh Poimboeuf
2019-07-15 18:17           ` Paolo Bonzini
2019-07-15  0:36 ` [PATCH 04/22] x86/kvm: Don't call kvm_spurious_fault() from .fixup Josh Poimboeuf
2019-07-15  9:07   ` Paolo Bonzini
2019-07-15 12:40     ` Josh Poimboeuf
2019-07-15 13:05       ` Paolo Bonzini
2019-07-15 13:25         ` Josh Poimboeuf
2019-07-15 18:16           ` Paolo Bonzini
2019-07-15  0:37 ` [PATCH 05/22] x86/entry: Fix thunk function ELF sizes Josh Poimboeuf
2019-07-15  0:37 ` [PATCH 06/22] x86/head/64: Annotate start_cpu0() as non-callable Josh Poimboeuf
2019-07-15  0:37 ` [PATCH 07/22] x86/uaccess: Remove ELF function annotation from copy_user_handle_tail() Josh Poimboeuf
2019-07-16 18:16   ` Nick Desaulniers
2019-07-16 18:51     ` Peter Zijlstra
2019-07-15  0:37 ` [PATCH 08/22] x86/uaccess: Don't leak AC flag into fentry from mcsafe_handle_tail() Josh Poimboeuf
2019-07-15  0:37 ` [PATCH 09/22] x86/uaccess: Remove redundant CLACs in getuser/putuser error paths Josh Poimboeuf
2019-07-15  0:37 ` [PATCH 10/22] bpf: Disable GCC -fgcse optimization for ___bpf_prog_run() Josh Poimboeuf
2019-07-16 18:15   ` Nick Desaulniers
2019-07-16 23:02     ` Josh Poimboeuf
2019-07-15  0:37 ` [PATCH 11/22] objtool: Add mcsafe_handle_tail() to the uaccess safe list Josh Poimboeuf
2019-07-15  0:37 ` [PATCH 12/22] objtool: Track original function across branches Josh Poimboeuf
2019-07-15  0:37 ` [PATCH 13/22] objtool: Refactor function alias logic Josh Poimboeuf
2019-07-15  0:37 ` [PATCH 14/22] objtool: Warn on zero-length functions Josh Poimboeuf
2019-07-15  0:37 ` [PATCH 15/22] objtool: Change dead_end_function() to return boolean Josh Poimboeuf
2019-07-15  0:37 ` [PATCH 16/22] objtool: Do frame pointer check before dead end check Josh Poimboeuf
2019-07-15  0:37 ` [PATCH 17/22] objtool: Refactor sibling call detection logic Josh Poimboeuf
2019-07-15  0:37 ` [PATCH 18/22] objtool: Refactor jump table code Josh Poimboeuf
2019-07-15  9:38   ` Peter Zijlstra
2019-07-15  0:37 ` [PATCH 19/22] objtool: Support repeated uses of the same C jump table Josh Poimboeuf
2019-07-15  0:37 ` [PATCH 20/22] objtool: Fix seg fault on bad switch table entry Josh Poimboeuf
2019-07-15 17:24   ` Nick Desaulniers
2019-07-15 17:29     ` Josh Poimboeuf
2019-07-18 23:02       ` Nick Desaulniers
2019-07-15  0:37 ` [PATCH 21/22] objtool: convert insn type to enum Josh Poimboeuf
2019-07-15  0:37 ` [PATCH 22/22] objtool: Support conditional retpolines Josh Poimboeuf
2019-07-15  9:52 ` [PATCH 00/22] x86, objtool: several fixes/improvements Peter Zijlstra
2019-07-15 19:38 ` Josh Poimboeuf
2019-07-15 21:45   ` Nick Desaulniers
2019-07-16 23:17     ` Josh Poimboeuf
2019-07-18 22:26       ` Nick Desaulniers
2019-09-27 20:24         ` Nick Desaulniers [this message]

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