Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH v3 16/16] objtool,x86: Rewrite retpoline thunk calls
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Nick Desaulniers <ndesaulniers@google.com>,
        =?UTF-8?B?RsSBbmctcnXDrCBTw7JuZw==?= <maskray@google.com>,
        Josh Poimboeuf <jpoimboe@redhat.com>, lma@semihalf.com,
        Guenter Roeck <groeck@google.com>,
        Juergen Gross <jgross@suse.com>, lb@semihalf.com,
        LKML <linux-kernel@vger.kernel.org>, mbenes@suse.com,
        =?UTF-8?Q?Rados=c5=82aw_Biernacki?= <rad@semihalf.com>,
        upstream@semihalf.com,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@kernel.org>,
        clang-built-linux <clang-built-linux@googlegroups.com>,
        Sami Tolvanen <samitolvanen@google.com>
References: <20210604235046.w3hazgcpsg4oefex@google.com>
 <YLtUO/thYUp2wU7k@hirez.programming.kicks-ass.net>
 <CAFP8O3+ggR8N-ffsaYSMPX7s2XgrzzTQQjOgCwUe9smyos-waA@mail.gmail.com>
 <YL3RQCJGIw9835Y1@hirez.programming.kicks-ass.net>
 <YL3lQ5QdNV2qwLR/@hirez.programming.kicks-ass.net>
 <YL3q1qFO9QIRL/BA@hirez.programming.kicks-ass.net>
 <CAKwvOdkuJBwZRigeqdZGevPF9WHyrC5pBAsz6_tWdXAc-wO+1A@mail.gmail.com>
 <e351ac97-4038-61b5-b373-63698a787fc1@kernel.org>
 <YL+nb235rIfEdye0@hirez.programming.kicks-ass.net>
 <de1a21c0-f20a-cde5-016e-4b8ca92eafa9@kernel.org>
 <YL+0MO/1Ra1tnzhT@hirez.programming.kicks-ass.net>
From:   Nathan Chancellor <nathan@kernel.org>
Message-ID: <5dd58dce-c3a7-39e5-8959-b858de95b72c@kernel.org>
Date:   Tue, 8 Jun 2021 11:49:47 -0700
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101
 Thunderbird/78.11.0
MIME-Version: 1.0
In-Reply-To: <YL+0MO/1Ra1tnzhT@hirez.programming.kicks-ass.net>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 6/8/2021 11:17 AM, Peter Zijlstra wrote:
> On Tue, Jun 08, 2021 at 10:29:56AM -0700, Nathan Chancellor wrote:
>> Unfortunately, this is the VM provided by the Windows Subsystem for Linux so
>> examining it is nigh-impossible :/ I am considering bisecting the transforms
>> that objtool does to try and figure out the one that causes the machine to
>> fail to boot or try to reproduce in a different hypervisor, unless you have
>> any other ideas.
> 
> Does breaking Windows earn points similar to breaking the binary
> drivers? :-) :-)

:)

> The below should kill this latest transform and would quickly confirm if
> the that is causing your problem. If that's not it, what was your last
> known working version?

Yes, that diff gets me back to booting. I will see if I can figure out 
the exact rewrite that blows everything up.

> diff --git a/tools/objtool/check.c b/tools/objtool/check.c
> index e5947fbb9e7a..d0f231b9c5a1 100644
> --- a/tools/objtool/check.c
> +++ b/tools/objtool/check.c
> @@ -1857,10 +1857,10 @@ static int decode_sections(struct objtool_file *file)
>   	 * Must be after add_special_section_alts(), since this will emit
>   	 * alternatives. Must be after add_{jump,call}_destination(), since
>   	 * those create the call insn lists.
> -	 */
>   	ret = arch_rewrite_retpolines(file);
>   	if (ret)
>   		return ret;
> +	 */
>   
>   	return 0;
>   }
> 

Cheers,
Nathan