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From: Roland McGrath <roland@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
	Ingo Molnar <mingo@elte.hu>, Steven Rostedt <rostedt@goodmis.org>,
	Arnaldo Carvalho de Melo <acme@infradead.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
	Christoph Hellwig <hch@infradead.org>,
	Andi Kleen <andi@firstfloor.org>, Oleg Nesterov <oleg@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	SystemTap <systemtap@sources.redhat.com>,
	Jim Keniston <jkenisto@linux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
	LKML <linux-kernel@vger.kernel.org>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: [RFC] [PATCH 2.6.37-rc5-tip 13/20] 13: x86: x86 specific probe handling
Date: Fri, 28 Jan 2011 10:23:11 -0800 (PST)	[thread overview]
Message-ID: <20110128182311.B9D57180996@magilla.sf.frob.com> (raw)
In-Reply-To: Peter Zijlstra's message of  Friday, 28 January 2011 09:36:38 +0100 <1296203798.15234.249.camel@laptop>

> And reset the hardware back to block step when done, and provide the
> actual break blockstep would have.

Oh, sure, that too.  If you're that ambitious, then the place to start
first is with plain single-step working right.  When TF was already set
(either via user_enable_single_step, so TIF_SINGLESTEP is set, or just from
user mode, so it and TIF_FORCED_TF are not set, but TF is in the user
state's eflags) and you hit a uprobe, then after servicing the uprobe and
stepping over the copied original instruction and restoring the PC to where
it should be, you should let the trap turn into a SIGTRAP as normal rather
than swallowing it.

To support block-step correctly, you have to do something more clever.
If block-step was enabled (TIF_BLOCKSTEP set), then you need to figure
out which of two things is the right one to do.  If the copied original
instruction uprobes just single-stepped over is one that would trigger
block-step, then you should treat it as if plain single-step were
enabled, i.e. let that SIGTRAP go as above.  If not, then you should
swallow the signal, re-enable block-step and set TF (i.e. do the work of
user_enable_block_step) before resuming.  You have to decide which case
it is based on instruction analysis.  If it's a control-flow instruction
(including the syscall instructions), then it would trigger block-step.
IIRC a conditional branch instruction triggers it only if the branch is
taken (check the book), so you have to notice that too.


Thanks,
Roland

  reply	other threads:[~2011-01-28 18:23 UTC|newest]

Thread overview: 116+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-12-16  9:57 [RFC] [PATCH 2.6.37-rc5-tip 0/20] 0: Inode based uprobes Srikar Dronamraju
2010-12-16  9:57 ` [RFC] [PATCH 2.6.37-rc5-tip 1/20] 1: mm: Move replace_page() / write_protect_page() to mm/memory.c Srikar Dronamraju
2010-12-16  9:57 ` [RFC] [PATCH 2.6.37-rc5-tip 2/20] 2: X86 specific breakpoint definitions Srikar Dronamraju
2010-12-16  9:57 ` [RFC] [PATCH 2.6.37-rc5-tip 3/20] 3: uprobes: Breakground page replacement Srikar Dronamraju
2010-12-16  9:58 ` [RFC] [PATCH 2.6.37-rc5-tip 4/20] 4: uprobes: Adding and remove a uprobe in a rb tree Srikar Dronamraju
2011-01-25 12:15   ` Peter Zijlstra
2011-01-26  8:37     ` Srikar Dronamraju
2011-01-26  8:37       ` Srikar Dronamraju
2011-01-25 12:15   ` Peter Zijlstra
2011-01-26  8:41     ` Srikar Dronamraju
2011-01-26 10:13       ` Peter Zijlstra
2011-01-25 12:15   ` Peter Zijlstra
2011-01-26  8:38     ` Srikar Dronamraju
2011-01-25 13:56   ` Peter Zijlstra
2011-01-26  8:45     ` Srikar Dronamraju
2011-01-26 10:14       ` Peter Zijlstra
2011-01-26 15:18         ` Srikar Dronamraju
2011-01-26 15:33           ` Peter Zijlstra
2010-12-16  9:58 ` [RFC] [PATCH 2.6.37-rc5-tip 5/20] 5: Uprobes: register/unregister probes Srikar Dronamraju
2011-01-25 12:15   ` Peter Zijlstra
2011-01-26  7:55     ` Srikar Dronamraju
2011-01-26  7:55       ` Srikar Dronamraju
2011-01-26 10:11       ` Peter Zijlstra
2011-01-26 10:11         ` Peter Zijlstra
2011-01-26 15:30         ` Srikar Dronamraju
2011-01-26 15:30           ` Srikar Dronamraju
2011-01-26 15:45           ` Peter Zijlstra
2011-01-26 15:45             ` Peter Zijlstra
2011-01-26 16:56             ` Srikar Dronamraju
2011-01-26 16:56               ` Srikar Dronamraju
2011-01-26 17:12               ` Peter Zijlstra
2011-01-26 17:12                 ` Peter Zijlstra
2011-01-27 10:01                 ` Srikar Dronamraju
2011-01-27 10:01                   ` Srikar Dronamraju
2011-01-27 10:23                   ` Peter Zijlstra
2011-01-27 10:23                     ` Peter Zijlstra
2011-01-27 10:25                     ` Srikar Dronamraju
2011-01-27 10:25                       ` Srikar Dronamraju
2011-01-27 10:41                       ` Peter Zijlstra
2011-01-27 10:41                         ` Peter Zijlstra
2011-01-27 10:29                   ` Peter Zijlstra
2011-01-27 10:29                     ` Peter Zijlstra
2011-01-25 12:15   ` Peter Zijlstra
2011-01-26  7:47     ` Srikar Dronamraju
2011-01-26  7:47       ` Srikar Dronamraju
2011-01-26 10:10       ` Peter Zijlstra
2011-01-26 10:10         ` Peter Zijlstra
2010-12-16  9:58 ` [RFC] [PATCH 2.6.37-rc5-tip 6/20] 6: x86: analyze instruction and determine fixups Srikar Dronamraju
2010-12-16  9:58 ` [RFC] [PATCH 2.6.37-rc5-tip 7/20] 7: uprobes: store/restore original instruction Srikar Dronamraju
2011-01-25 12:15   ` Peter Zijlstra
2010-12-16  9:58 ` [RFC] [PATCH 2.6.37-rc5-tip 8/20] 8: uprobes: mmap and fork hooks Srikar Dronamraju
2011-01-25 12:15   ` Peter Zijlstra
2011-01-26  9:03     ` Srikar Dronamraju
2011-01-26  9:03       ` Srikar Dronamraju
2011-01-26 10:20       ` Peter Zijlstra
2011-01-26 10:20         ` Peter Zijlstra
2011-01-26 14:59         ` Srikar Dronamraju
2011-01-26 14:59           ` Srikar Dronamraju
2011-01-26 15:16           ` Peter Zijlstra
2011-01-26 15:16             ` Peter Zijlstra
2011-01-26 16:30             ` Srikar Dronamraju
2011-01-26 16:30               ` Srikar Dronamraju
2011-01-25 12:15   ` Peter Zijlstra
2011-01-25 20:05     ` Steven Rostedt
2011-01-26  9:06       ` Srikar Dronamraju
2011-01-27 17:03         ` Steven Rostedt
2011-01-28  4:53           ` Srikar Dronamraju
2011-01-28 13:57             ` Steven Rostedt
2011-01-28 14:28               ` Steven Rostedt
2011-01-28 14:46                 ` Srikar Dronamraju
2011-01-28 15:02                   ` Steven Rostedt
2011-01-26 15:09     ` Srikar Dronamraju
2011-01-26 15:09       ` Srikar Dronamraju
2011-01-26 15:20       ` Peter Zijlstra
2011-01-26 15:20         ` Peter Zijlstra
2010-12-16  9:58 ` [RFC] [PATCH 2.6.37-rc5-tip 9/20] 9: x86: architecture specific task information Srikar Dronamraju
2010-12-16  9:59 ` [RFC] [PATCH 2.6.37-rc5-tip 10/20] 10: uprobes: task specific information Srikar Dronamraju
2011-01-25 13:56   ` Peter Zijlstra
2011-01-25 18:38     ` Josh Stone
2011-01-25 18:55       ` Roland McGrath
2011-01-25 19:56       ` Peter Zijlstra
2010-12-16  9:59 ` [RFC] [PATCH 2.6.37-rc5-tip 11/20] 11: uprobes: slot allocation for uprobes Srikar Dronamraju
2011-01-25 13:56   ` Peter Zijlstra
2010-12-16  9:59 ` [RFC] [PATCH 2.6.37-rc5-tip 12/20] 12: uprobes: get the breakpoint address Srikar Dronamraju
2011-01-25 13:56   ` Peter Zijlstra
2010-12-16  9:59 ` [RFC] [PATCH 2.6.37-rc5-tip 13/20] 13: x86: x86 specific probe handling Srikar Dronamraju
2011-01-25 13:56   ` Peter Zijlstra
2011-01-27  9:40     ` Srikar Dronamraju
2011-01-27 10:22       ` Peter Zijlstra
2011-01-27 19:11         ` Roland McGrath
2011-01-28  4:57           ` Srikar Dronamraju
2011-01-28  6:23             ` Roland McGrath
2011-01-28  8:36               ` Peter Zijlstra
2011-01-28 18:23                 ` Roland McGrath [this message]
2010-12-16  9:59 ` [RFC] [PATCH 2.6.37-rc5-tip 14/20] 14: uprobes: Handing int3 and singlestep exception Srikar Dronamraju
2011-01-25 13:56   ` Peter Zijlstra
2011-01-25 13:56   ` Peter Zijlstra
2011-01-26  8:52     ` Srikar Dronamraju
2011-01-26  8:52       ` Srikar Dronamraju
2011-01-26 10:17       ` Peter Zijlstra
2011-01-26 10:17         ` Peter Zijlstra
2011-01-26 15:14         ` Srikar Dronamraju
2011-01-26 15:14           ` Srikar Dronamraju
2011-01-26 15:29           ` Peter Zijlstra
2011-01-26 15:29             ` Peter Zijlstra
2010-12-16 10:00 ` [RFC] [PATCH 2.6.37-rc5-tip 15/20] 15: x86: uprobes exception notifier for x86 Srikar Dronamraju
2010-12-16 10:00 ` [RFC] [PATCH 2.6.37-rc5-tip 16/20] 16: uprobes: register a notifier for uprobes Srikar Dronamraju
2011-01-25 13:56   ` Peter Zijlstra
2011-01-27  6:50     ` Srikar Dronamraju
2010-12-16 10:00 ` [RFC] [PATCH 2.6.37-rc5-tip 17/20] 17: uprobes: filter chain Srikar Dronamraju
2010-12-16 10:00 ` [RFC] [PATCH 2.6.37-rc5-tip 18/20] 18: uprobes: commonly used filters Srikar Dronamraju
2010-12-17 19:32   ` Valdis.Kletnieks
2010-12-18  3:04     ` Srikar Dronamraju
2010-12-16 10:00 ` [RFC] [PATCH 2.6.37-rc5-tip 19/20] 19: tracing: Extract out common code for kprobes/uprobes traceevents Srikar Dronamraju
2010-12-16 10:01 ` [RFC] [PATCH 2.6.37-rc5-tip 20/20] 20: tracing: uprobes trace_event interface Srikar Dronamraju
2010-12-16 10:07 ` [RFC] [PATCH 2.6.37-rc5-tip 0/20] 0: Inode based uprobes Srikar Dronamraju

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