From: Nathan Chancellor <natechancellor@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>,
clang-built-linux <clang-built-linux@googlegroups.com>,
x86@kernel.org, Arnd Bergmann <arnd@arndb.de>,
Sedat Dilek <sedat.dilek@gmail.com>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH] objtool: Improve UACCESS coverage
Date: Wed, 24 Jul 2019 09:54:46 -0700 [thread overview]
Message-ID: <20190724165446.GA110233@archlinux-threadripper> (raw)
In-Reply-To: <20190724164821.GB31425@hirez.programming.kicks-ass.net>
On Wed, Jul 24, 2019 at 06:48:21PM +0200, Peter Zijlstra wrote:
> On Wed, Jul 24, 2019 at 04:10:40PM +0200, Peter Zijlstra wrote:
> > And that most certainly should trigger...
> >
> > Let me gdb that objtool thing.
>
> ---
> Subject: objtool: Improve UACCESS coverage
>
> A clang build reported an (obvious) double CLAC while a GCC build did
> not; it turns out we only re-visit instructions if the first visit was
> with AC=0. If OTOH the first visit was with AC=1, we completely ignore
> any subsequent visit, even when it has AC=0.
>
> Fix this by using a visited mask, instead of boolean and (explicitly)
> mark the AC state.
>
> $ ./objtool check -b --no-fp --retpoline --uaccess ../../defconfig-build/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o
> ../../defconfig-build/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: .altinstr_replacement+0x22: redundant UACCESS disable
> ../../defconfig-build/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: eb_copy_relocations.isra.34()+0xea: (alt)
> ../../defconfig-build/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: .altinstr_replacement+0xffffffffffffffff: (branch)
> ../../defconfig-build/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: eb_copy_relocations.isra.34()+0xd9: (alt)
> ../../defconfig-build/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: eb_copy_relocations.isra.34()+0xb2: (branch)
> ../../defconfig-build/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: eb_copy_relocations.isra.34()+0x39: (branch)
> ../../defconfig-build/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: eb_copy_relocations.isra.34()+0x0: <=== (func)
>
> Reported-by: Josh Poimboeuf <jpoimboe@redhat.com>
> Reported-by: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
This doesn't regress clang and I see the warning on GCC now too.
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
next prev parent reply other threads:[~2019-07-24 16:54 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-18 20:40 x86 - clang / objtool status Thomas Gleixner
2019-07-18 20:58 ` Nathan Chancellor
2019-07-19 6:39 ` Thomas Gleixner
2019-07-19 7:00 ` Arnd Bergmann
2019-07-19 7:03 ` Nathan Chancellor
2019-07-24 16:57 ` Nick Desaulniers
2019-07-18 22:42 ` Nick Desaulniers
2019-07-19 6:44 ` Thomas Gleixner
2019-07-19 11:37 ` Sedat Dilek
2019-07-19 13:48 ` Sedat Dilek
2019-07-22 15:40 ` Sedat Dilek
2019-07-25 6:17 ` Sedat Dilek
2019-07-24 2:43 ` Josh Poimboeuf
2019-07-24 7:47 ` Peter Zijlstra
2019-07-24 12:37 ` Josh Poimboeuf
2019-07-24 12:55 ` Josh Poimboeuf
2019-07-24 13:35 ` Peter Zijlstra
2019-07-24 14:05 ` Josh Poimboeuf
2019-07-24 14:10 ` Peter Zijlstra
2019-07-24 16:48 ` [PATCH] objtool: Improve UACCESS coverage Peter Zijlstra
2019-07-24 16:54 ` Nathan Chancellor [this message]
2019-07-24 16:55 ` Nick Desaulniers
2019-07-24 18:30 ` Sedat Dilek
2019-07-24 18:32 ` Sedat Dilek
2019-07-24 16:52 ` x86 - clang / objtool status Peter Zijlstra
2019-07-24 17:22 ` Nick Desaulniers
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