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From: Josh Poimboeuf <jpoimboe@redhat.com>
To: damian <damian.tometzki@icloud.com>
Cc: peterz@infradead.org, linux-kernel@vger.kernel.org
Subject: Re: Kernel build with gcc 8 a lot of warnings
Date: Sun, 6 May 2018 23:54:53 -0500	[thread overview]
Message-ID: <20180507045453.leou4zypnlcck4vr@treble> (raw)
In-Reply-To: <20180505192112.GA18728@zrhn9910b>

On Sat, May 05, 2018 at 09:21:12PM +0200, damian wrote:
> Helllo together,
> 
> Hello everybody,
> 
> is something special to note when kernel build with gcc 8? I receive various warnings from the objtool:
> With GCC 7 works all fine.
> 
> kernel/cgroup/cgroup.o: warning: objtool: parse_cgroup_root_flags()+0x40: sibling call from callable instruction with modified stack frame
> kernel/cgroup/cgroup.o: warning: objtool: cgroup_addrm_files()+0x2a3: sibling call from callable instruction with modified stack frame
> kernel/cgroup/cgroup.o: warning: objtool: cgroup_apply_control_enable()+0x20b: sibling call from callable instruction with modified stack frame
> kernel/cgroup/cgroup.o: warning: objtool: rebind_subsystems()+0x296: sibling call from callable instruction with modified stack frame
> kernel/cgroup/cgroup.o: warning: objtool: cgroup_sk_alloc_disable()+0x10: sibling call from callable instruction with modified stack frame
> kernel/cgroup/cgroup.o: warning: objtool: parse_cgroup_root_flags.cold.45()+0xa: call without frame pointer save/setup
> kernel/cgroup/cgroup.o: warning: objtool: cgroup_addrm_files.cold.46()+0x17: call without frame pointer save/setup
> kernel/cgroup/cgroup.o: warning: objtool: cgroup_apply_control_enable.cold.47()+0x24: call without frame pointer save/setup
> kernel/cgroup/cgroup.o: warning: objtool: rebind_subsystems.cold.48()+0x10: call without frame pointer save/setup
> kernel/cgroup/cgroup.o: warning: objtool: cgroup_sk_alloc_disable.cold.49()+0x7: call without frame pointer save/setup
>   CC      kernel/cgroup/stat.o
>   CC [M]  arch/x86/kvm/../../../virt/kvm/kvm_main.o
> arch/x86/kernel/acpi/boot.o: warning: objtool: acpi_register_lapic()+0x10: sibling call from callable instruction with modified stack frame
> arch/x86/kernel/acpi/boot.o: warning: objtool: acpi_map_cpu()+0x2c: sibling call from callable instruction with modified stack frame
> arch/x86/kernel/acpi/boot.o: warning: objtool: acpi_register_lapic.cold.6()+0x7: call without frame pointer save/setup
> arch/x86/kernel/acpi/boot.o: warning: objtool: acpi_map_cpu.cold.7()+0x7: call without frame pointer save/setup

Thanks, this is a known issue with GCC 8 that I haven't gotten a chance
to fix yet.  They're related to the fact that GCC 8 is splitting out
'unlikely' code into 'cold' subfunctions in .text.unlikely.

I've got some old patches that fix it.  Now that GCC 8 is out, I'll need
get the patches dusted off and cleaned up for merging.

-- 
Josh

  reply	other threads:[~2018-05-07  4:55 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-05 19:21 Kernel build with gcc 8 a lot of warnings damian
2018-05-07  4:54 ` Josh Poimboeuf [this message]
2018-05-07 10:57   ` damian
2018-05-08  5:51   ` Greg KH
2018-05-08  5:58     ` Greg KH
2018-05-08 13:34     ` Josh Poimboeuf
2018-05-08 14:25       ` Greg KH
2018-05-08 14:32         ` Josh Poimboeuf
2018-05-09  3:46           ` Josh Poimboeuf
2018-05-09  7:35             ` damian
2018-05-09 15:23               ` Josh Poimboeuf
2018-05-09 19:15                 ` damian
2018-05-09 14:27 ` David Laight
2018-05-09 14:54   ` Josh Poimboeuf

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