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From: Ingo Molnar <mingo@kernel.org>
To: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Petr Mladek <pmladek@suse.cz>,
	"David S. Miller" <davem@davemloft.net>,
	Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>,
	Ananth NMavinakayanahalli <ananth@in.ibm.com>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Jiri Kosina <jkosina@suse.cz>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] kprobes/x86: Use 5-byte NOP when the code might be modified by ftrace
Date: Fri, 20 Feb 2015 13:52:23 +0100	[thread overview]
Message-ID: <20150220125223.GA28882@gmail.com> (raw)
In-Reply-To: <54E72ABA.8050804@hitachi.com>


* Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> wrote:

> (2015/02/20 19:26), Ingo Molnar wrote:
> > 
> > * Petr Mladek <pmladek@suse.cz> wrote:
> > 
> >> can_probe() checks if the given address points to the 
> >> beginning of an instruction. It analyzes all the 
> >> instructions from the beginning of the function until the 
> >> given address. The code might be modified by another 
> >> Kprobe. In this case, the current code is read into a 
> >> buffer, int3 breakpoint is replaced by the saved opcode 
> >> in the buffer, and can_probe() analyzes the buffer 
> >> instead.
> >>
> >> [...]
> > 
> > Had to drop this patch due to build failures on 32-bit x86:
> > 
> > arch/x86/kernel/kprobes/core.c:258:40: error: ‘MCOUNT_INSN_SIZE’ undeclared (first use in this function)
> 
> Oops, MCOUNT_INSN_SIZE actually depends on 
> CONFIG_FUNCTION_TRACER... I think we can use 5 instead of 
> that since we are copying NOP_ATOMIC5.

Or just make the define more widely available? It's not 
like the size changes from disabling the function tracer.

Thanks,

	Ingo

  reply	other threads:[~2015-02-20 12:52 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-02-02 17:48 [PATCH v2] kprobes/x86: Use 5-byte NOP when the code might be modified by ftrace Petr Mladek
2015-02-03  7:41 ` Masami Hiramatsu
2015-02-03 11:38   ` Petr Mladek
2015-02-03 11:52     ` Masami Hiramatsu
2015-02-03 12:00     ` Petr Mladek
2015-02-18 21:22     ` Ingo Molnar
2015-02-20 10:16       ` Petr Mladek
2015-02-20 10:16         ` [PATCH 1/2] " Petr Mladek
2015-02-20 10:26           ` Ingo Molnar
2015-02-20 12:38             ` Masami Hiramatsu
2015-02-20 12:52               ` Ingo Molnar [this message]
2015-02-20 13:25                 ` Masami Hiramatsu
2015-02-20 13:34                 ` Petr Mladek
2015-02-20 10:16         ` [PATCH 2/2] kprobes/x86: Check for invalid ftrace location in __recover_probed_insn() Petr Mladek
2015-02-20 10:19           ` Ingo Molnar

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