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Date: Sun, 28 Feb 2016 07:57:29 +0100
From: Ingo Molnar <mingo@kernel.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        linux-kernel@vger.kernel.org, live-patching@vger.kernel.org,
        Michal Marek <mmarek@suse.cz>, Peter Zijlstra <peterz@infradead.org>,
        Andy Lutomirski <luto@kernel.org>, Borislav Petkov <bp@alien8.de>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andi Kleen <andi@firstfloor.org>, Pedro Alves <palves@redhat.com>,
        Namhyung Kim <namhyung@gmail.com>,
        Bernd Petrovitsch <bernd@petrovitsch.priv.at>,
        Chris J Arges <chris.j.arges@canonical.com>,
        Andrew Morton <akpm@linux-foundation.org>, Jiri Slaby <jslaby@suse.cz>,
        Arnaldo Carvalho de Melo <acme@kernel.org>
Subject: Re: [PATCH v18 0/9] Compile-time stack metadata validation
Message-ID: <20160228065729.GB20796@gmail.com>
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Another thing I've noticed are _thousands_ of these warnings:

objtool: kernel/sched/core.o: preempt_schedule_irq()+0x20: function has unreachable instruction
objtool: kernel/sched/core.o: preempt_schedule_irq()+0x27: function has unreachable instruction
objtool: kernel/sched/core.o: preempt_schedule_irq()+0x2c: function has unreachable instruction
objtool: kernel/sched/core.o: preempt_schedule_irq()+0x33: function has unreachable instruction
objtool: net/ceph/pagevec.o: ceph_put_page_vector()+0x171: function has unreachable instruction
objtool: net/ceph/pagevec.o: ceph_put_page_vector()+0x178: function has unreachable instruction
objtool: net/ceph/pagevec.o: ceph_put_page_vector()+0x17d: function has unreachable instruction
objtool: net/ceph/pagevec.o: ceph_put_page_vector()+0x184: function has unreachable instruction
objtool: net/ceph/pagevec.o: ceph_get_direct_page_vector()+0xe2: function has unreachable instruction
objtool: net/ceph/pagevec.o: ceph_get_direct_page_vector()+0xe9: function has unreachable instruction
objtool: net/ceph/pagevec.o: ceph_get_direct_page_vector()+0xee: function has unreachable instruction
objtool: net/ceph/pagevec.o: ceph_get_direct_page_vector()+0xf5: function has unreachable instruction
objtool: net/ceph/pagevec.o: zero_user_segment()+0x120: function has unreachable instruction
objtool: net/ceph/pagevec.o: zero_user_segment()+0x127: function has unreachable instruction
objtool: net/ceph/pagevec.o: zero_user_segment()+0x12c: function has unreachable instruction
objtool: net/ceph/pagevec.o: zero_user_segment()+0x133: function has unreachable instruction

that's on an x86-64 allyesconfig kernel, with objtool merged to tip:master, using 
GCC 4.9.2:

  gcc version 4.9.2 20150212 (Red Hat 4.9.2-6) (GCC) 

Also, please prefix such warnings with the standard compiler prefix, something 
like this:

	kernel/sched/core.c: warning: objtool: preempt_schedule_irq()+0x20: function has unreachable instruction

so that scripts/tools monitoring new build warnings can pick them up 
automatically?

Thanks,

	Ingo