From: Sami Tolvanen <samitolvanen@google.com>
To: kernel test robot <oliver.sang@intel.com>,
Steven Rostedt <rostedt@goodmis.org>,
Peter Zijlstra <peterz@infradead.org>
Cc: Kees Cook <keescook@chromium.org>,
LKML <linux-kernel@vger.kernel.org>,
lkp@lists.01.org, kernel test robot <lkp@intel.com>
Subject: Re: [x86, build] 6dafca9780: WARNING:at_arch/x86/kernel/ftrace.c:#ftrace_verify_code
Date: Mon, 1 Mar 2021 14:14:51 -0800 [thread overview]
Message-ID: <CABCJKuc8H83b_8_Ccp+Cb7O9x5oEu6sPNq63sjGcAJcgiwy0bw@mail.gmail.com> (raw)
In-Reply-To: <20210301074027.GD12822@xsang-OptiPlex-9020>
On Sun, Feb 28, 2021 at 11:25 PM kernel test robot
<oliver.sang@intel.com> wrote:
>
>
> Greeting,
>
> FYI, we noticed the following commit (built with clang-13):
>
> commit: 6dafca97803309c3cb5148d449bfa711e41ddef2 ("x86, build: use objtool mcount")
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
Thanks for the report, I'm able to reproduce the warning.
> [ 4.764496] ------------[ ftrace bug ]------------
> [ 4.764847] ftrace failed to modify
> [ 4.764852] do_sys_open (kbuild/src/consumer/fs/open.c:1186)
> [ 4.765483] actual: 0f:1f:44:00:00
> [ 4.765784] Setting ftrace call site to call ftrace function
> [ 4.766193] ftrace record flags: 50000001
> [ 4.766490] (1) R
> [ 4.766490] expected tramp: ffffffff81037af0
> [ 4.766959] ------------[ cut here ]------------
Basically, the problem is that ftrace_replace_code() expects to find
ideal_nops[NOP_ATOMIC5] here, which in this case is 66:66:66:66:90,
while objtool has replaced the __fentry__ call with 0f:1f:44:00:00.
As ideal_nops changes depending on kernel config and hardware, when
CC_USING_NOP_MCOUNT is defined we could either change
ftrace_nop_replace() to always use P6_NOP5, or skip
ftrace_verify_code() in ftrace_replace_code() for
FTRACE_UPDATE_MAKE_CALL.
Steven, Peter, any thoughts?
Sami
WARNING: multiple messages have this Message-ID (diff)
From: Sami Tolvanen <samitolvanen@google.com>
To: lkp@lists.01.org
Subject: Re: [x86, build] 6dafca9780: WARNING:at_arch/x86/kernel/ftrace.c:#ftrace_verify_code
Date: Mon, 01 Mar 2021 14:14:51 -0800 [thread overview]
Message-ID: <CABCJKuc8H83b_8_Ccp+Cb7O9x5oEu6sPNq63sjGcAJcgiwy0bw@mail.gmail.com> (raw)
In-Reply-To: <20210301074027.GD12822@xsang-OptiPlex-9020>
[-- Attachment #1: Type: text/plain, Size: 1357 bytes --]
On Sun, Feb 28, 2021 at 11:25 PM kernel test robot
<oliver.sang@intel.com> wrote:
>
>
> Greeting,
>
> FYI, we noticed the following commit (built with clang-13):
>
> commit: 6dafca97803309c3cb5148d449bfa711e41ddef2 ("x86, build: use objtool mcount")
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
Thanks for the report, I'm able to reproduce the warning.
> [ 4.764496] ------------[ ftrace bug ]------------
> [ 4.764847] ftrace failed to modify
> [ 4.764852] do_sys_open (kbuild/src/consumer/fs/open.c:1186)
> [ 4.765483] actual: 0f:1f:44:00:00
> [ 4.765784] Setting ftrace call site to call ftrace function
> [ 4.766193] ftrace record flags: 50000001
> [ 4.766490] (1) R
> [ 4.766490] expected tramp: ffffffff81037af0
> [ 4.766959] ------------[ cut here ]------------
Basically, the problem is that ftrace_replace_code() expects to find
ideal_nops[NOP_ATOMIC5] here, which in this case is 66:66:66:66:90,
while objtool has replaced the __fentry__ call with 0f:1f:44:00:00.
As ideal_nops changes depending on kernel config and hardware, when
CC_USING_NOP_MCOUNT is defined we could either change
ftrace_nop_replace() to always use P6_NOP5, or skip
ftrace_verify_code() in ftrace_replace_code() for
FTRACE_UPDATE_MAKE_CALL.
Steven, Peter, any thoughts?
Sami
next prev parent reply other threads:[~2021-03-02 7:11 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-01 7:40 [x86, build] 6dafca9780: WARNING:at_arch/x86/kernel/ftrace.c:#ftrace_verify_code kernel test robot
2021-03-01 7:40 ` kernel test robot
2021-03-01 22:14 ` Sami Tolvanen [this message]
2021-03-01 22:14 ` Sami Tolvanen
2021-03-01 23:45 ` Steven Rostedt
2021-03-01 23:45 ` Steven Rostedt
2021-03-02 0:03 ` Sami Tolvanen
2021-03-02 0:03 ` Sami Tolvanen
2021-03-02 1:15 ` Steven Rostedt
2021-03-02 1:15 ` Steven Rostedt
2021-03-02 2:40 ` Sami Tolvanen
2021-03-02 2:40 ` Sami Tolvanen
2021-03-02 2:47 ` Steven Rostedt
2021-03-02 2:47 ` Steven Rostedt
2021-03-02 3:23 ` Sami Tolvanen
2021-03-02 3:23 ` Sami Tolvanen
2021-03-02 9:19 ` Peter Zijlstra
2021-03-02 9:19 ` Peter Zijlstra
2021-03-02 15:58 ` Steven Rostedt
2021-03-02 15:58 ` Steven Rostedt
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