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From: peterz@infradead.org (Peter Zijlstra)
Subject: [RFC][PATCH 1/2] x86: Allow breakpoints to emulate call functions
Date: Tue, 7 May 2019 15:32:00 +0200	[thread overview]
Message-ID: <20190507133200.GP2623@hirez.programming.kicks-ass.net> (raw)
Message-ID: <20190507133200.ii9O7q8LjrS3cxnlOcZQkUCebEgoBlqnUMpvSeSDRzg@z> (raw)
In-Reply-To: <f55e3c951aee4b5686201aaf282cc62b@AcuMS.aculab.com>

On Tue, May 07, 2019@12:57:15PM +0000, David Laight wrote:

> > Only the INT3 thing needs 'the gap', but the far bigger change here is
> > that kernel frames now have a complete pt_regs set and all sorts of
> > horrible crap can go away.
> 
> I'm not doubting that generating the 'five register' interrupt stack frame
> for faults in kernel space makes life simpler just suggesting that the
> 'emulated call' can be done by emulating the 'iret' rather than generating
> a gap in the stack.

The thing you suggested doesn't actually work, INT3 can nest.

> > For 32bit 'the gap' happens naturally when building a 5 entry frame. Yes
> > it is possible to build a 5 entry frame on top of the old 3 entry one,
> > but why bother...
> 
> Presumably there is 'horrid' code to generate the gap in 64bit mode?
> (less horrid than 32bit, but still horrid?)
> Or does it copy the entire pt_regs into a local stack frame and use
> that for the iret?

It's in the patch you replied to; it is so small you might have
overlooked it. It simply pushes another copy on top of what was already
there.

> I've just tried to parse the pseudo code for IRET in the intel docs.
> Does anyone find that readable?

No; it's abysmal.

> I wonder if you can force 32bit mode to do a stack switch 'iret'
> by doing something like a far jump to a different %cs ?

I don't think that'll work.

  parent reply	other threads:[~2019-05-07 13:32 UTC|newest]

Thread overview: 204+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20190501202830.347656894@goodmis.org>
2019-05-01 20:28 ` [RFC][PATCH 1/2] x86: Allow breakpoints to emulate call functions rostedt
2019-05-01 20:28   ` Steven Rostedt
2019-05-02  3:24   ` rostedt
2019-05-02  3:24     ` Steven Rostedt
2019-05-02 16:21     ` peterz
2019-05-02 16:21       ` Peter Zijlstra
2019-05-02 16:29       ` peterz
2019-05-02 16:29         ` Peter Zijlstra
2019-05-02 18:02       ` torvalds
2019-05-02 18:02         ` Linus Torvalds
2019-05-02 18:18         ` peterz
2019-05-02 18:18           ` Peter Zijlstra
2019-05-02 18:30           ` peterz
2019-05-02 18:30             ` Peter Zijlstra
2019-05-02 18:43           ` torvalds
2019-05-02 18:43             ` Linus Torvalds
2019-05-02 19:28             ` jikos
2019-05-02 19:28               ` Jiri Kosina
2019-05-02 20:25               ` luto
2019-05-02 20:25                 ` Andy Lutomirski
2019-05-02 20:21             ` peterz
2019-05-02 20:21               ` Peter Zijlstra
2019-05-02 20:49               ` torvalds
2019-05-02 20:49                 ` Linus Torvalds
2019-05-02 21:32                 ` peterz
2019-05-02 21:32                   ` Peter Zijlstra
2019-05-03 19:24                 ` rostedt
2019-05-03 19:24                   ` Steven Rostedt
2019-05-03 21:46                   ` torvalds
2019-05-03 21:46                     ` Linus Torvalds
2019-05-03 22:49                     ` rostedt
2019-05-03 22:49                       ` Steven Rostedt
2019-05-03 23:07                       ` torvalds
2019-05-03 23:07                         ` Linus Torvalds
2019-05-04  4:17                         ` rostedt
2019-05-04  4:17                           ` Steven Rostedt
     [not found]                           ` <CAHk-=wiuSFbv_rELND-BLWcP0GSZ0yF=xOAEcf61GE3bU9d=yg@mail.gmail.com>
2019-05-04 18:59                             ` torvalds
2019-05-04 18:59                               ` Linus Torvalds
2019-05-04 20:12                               ` luto
2019-05-04 20:12                                 ` Andy Lutomirski
2019-05-04 20:28                                 ` torvalds
2019-05-04 20:28                                   ` Linus Torvalds
2019-05-04 20:36                                 ` torvalds
2019-05-04 20:36                                   ` Linus Torvalds
2019-05-03 22:55                     ` luto
2019-05-03 22:55                       ` Andy Lutomirski
2019-05-03 23:16                       ` torvalds
2019-05-03 23:16                         ` Linus Torvalds
2019-05-03 23:32                         ` luto
2019-05-03 23:32                           ` Andy Lutomirski
2019-05-02 22:52               ` rostedt
2019-05-02 22:52                 ` Steven Rostedt
2019-05-02 23:31                 ` rostedt
2019-05-02 23:31                   ` Steven Rostedt
2019-05-02 23:50                   ` rostedt
2019-05-02 23:50                     ` Steven Rostedt
2019-05-03  1:51                     ` [RFC][PATCH 1/2 v2] " rostedt
2019-05-03  1:51                       ` Steven Rostedt
2019-05-03  9:29                     ` [RFC][PATCH 1/2] " peterz
2019-05-03  9:29                       ` Peter Zijlstra
2019-05-03 13:22                       ` rostedt
2019-05-03 13:22                         ` Steven Rostedt
2019-05-03 16:20                         ` luto
2019-05-03 16:20                           ` Andy Lutomirski
2019-05-03 16:31                           ` rostedt
2019-05-03 16:31                             ` Steven Rostedt
2019-05-03 16:35                             ` peterz
2019-05-03 16:35                               ` Peter Zijlstra
2019-05-03 16:44                               ` luto
2019-05-03 16:44                                 ` Andy Lutomirski
2019-05-03 16:49                                 ` rostedt
2019-05-03 16:49                                   ` Steven Rostedt
2019-05-03 16:32                           ` peterz
2019-05-03 16:32                             ` Peter Zijlstra
2019-05-03 18:57                           ` torvalds
2019-05-03 18:57                             ` Linus Torvalds
2019-05-06  8:19                             ` peterz
2019-05-06  8:19                               ` Peter Zijlstra
2019-05-06 13:56                               ` rostedt
2019-05-06 13:56                                 ` Steven Rostedt
2019-05-06 16:17                                 ` torvalds
2019-05-06 16:17                                   ` Linus Torvalds
2019-05-06 16:19                                   ` torvalds
2019-05-06 16:19                                     ` Linus Torvalds
2019-05-06 17:06                                   ` rostedt
2019-05-06 17:06                                     ` Steven Rostedt
2019-05-06 18:06                                     ` torvalds
2019-05-06 18:06                                       ` Linus Torvalds
2019-05-06 18:57                                       ` rostedt
2019-05-06 18:57                                         ` Steven Rostedt
2019-05-06 19:46                                         ` torvalds
2019-05-06 19:46                                           ` Linus Torvalds
2019-05-06 20:29                                           ` rostedt
2019-05-06 20:29                                             ` Steven Rostedt
2019-05-06 20:42                                             ` torvalds
2019-05-06 20:42                                               ` Linus Torvalds
2019-05-06 20:44                                               ` torvalds
2019-05-06 20:44                                                 ` Linus Torvalds
2019-05-06 21:45                                               ` rostedt
2019-05-06 21:45                                                 ` Steven Rostedt
2019-05-06 22:06                                                 ` torvalds
2019-05-06 22:06                                                   ` Linus Torvalds
2019-05-06 22:31                                                   ` torvalds
2019-05-06 22:31                                                     ` Linus Torvalds
2019-05-07  0:10                                                     ` rostedt
2019-05-07  0:10                                                       ` Steven Rostedt
2019-05-07  1:06                                                       ` torvalds
2019-05-07  1:06                                                         ` Linus Torvalds
2019-05-07  1:04                                                   ` rostedt
2019-05-07  1:04                                                     ` Steven Rostedt
2019-05-07  1:34                                                     ` rostedt
2019-05-07  1:34                                                       ` Steven Rostedt
2019-05-07  1:34                                                     ` torvalds
2019-05-07  1:34                                                       ` Linus Torvalds
2019-05-07  1:53                                                       ` rostedt
2019-05-07  1:53                                                         ` Steven Rostedt
2019-05-07  2:22                                                         ` torvalds
2019-05-07  2:22                                                           ` Linus Torvalds
2019-05-07  2:58                                                           ` rostedt
2019-05-07  2:58                                                             ` Steven Rostedt
2019-05-07  3:05                                                             ` torvalds
2019-05-07  3:05                                                               ` Linus Torvalds
2019-05-07  3:21                                                               ` rostedt
2019-05-07  3:21                                                                 ` Steven Rostedt
2019-05-07  3:28                                                                 ` torvalds
2019-05-07  3:28                                                                   ` Linus Torvalds
2019-05-07 14:54                                                                   ` torvalds
2019-05-07 14:54                                                                     ` Linus Torvalds
2019-05-07 15:12                                                                     ` rostedt
2019-05-07 15:12                                                                       ` Steven Rostedt
2019-05-07 15:25                                                                       ` rostedt
2019-05-07 15:25                                                                         ` Steven Rostedt
2019-05-07 16:25                                                                         ` rostedt
2019-05-07 16:25                                                                           ` Steven Rostedt
2019-05-07 15:31                                                                       ` torvalds
2019-05-07 15:31                                                                         ` Linus Torvalds
2019-05-07 15:45                                                                         ` rostedt
2019-05-07 15:45                                                                           ` Steven Rostedt
2019-05-07 16:34                                                                         ` peterz
2019-05-07 16:34                                                                           ` Peter Zijlstra
2019-05-07 17:08                                                                           ` torvalds
2019-05-07 17:08                                                                             ` Linus Torvalds
2019-05-07 17:21                                                                             ` jpoimboe
2019-05-07 17:21                                                                               ` Josh Poimboeuf
2019-05-07 21:24                                                                               ` rostedt
2019-05-07 21:24                                                                                 ` Steven Rostedt
2019-05-08  4:50                                                                                 ` torvalds
2019-05-08  4:50                                                                                   ` Linus Torvalds
2019-05-08 16:37                                                                                   ` rostedt
2019-05-08 16:37                                                                                     ` Steven Rostedt
2019-05-07 17:38                                                                             ` peterz
2019-05-07 17:38                                                                               ` Peter Zijlstra
2019-05-07  9:51                                                           ` peterz
2019-05-07  9:51                                                             ` Peter Zijlstra
2019-05-07 14:48                                                           ` luto
2019-05-07 14:48                                                             ` Andy Lutomirski
2019-05-07 14:57                                                             ` torvalds
2019-05-07 14:57                                                               ` Linus Torvalds
2019-05-07 14:13                                                 ` mhiramat
2019-05-07 14:13                                                   ` Masami Hiramatsu
2019-05-07 17:15                                                   ` mhiramat
2019-05-07 17:15                                                     ` Masami Hiramatsu
2019-05-06 14:22                               ` peterz
2019-05-06 14:22                                 ` Peter Zijlstra
2019-05-07  8:57                               ` peterz
2019-05-07  8:57                                 ` Peter Zijlstra
2019-05-07  9:18                                 ` David.Laight
2019-05-07  9:18                                   ` David Laight
2019-05-07 11:30                                   ` peterz
2019-05-07 11:30                                     ` Peter Zijlstra
2019-05-07 12:57                                     ` David.Laight
2019-05-07 12:57                                       ` David Laight
2019-05-07 13:14                                       ` rostedt
2019-05-07 13:14                                         ` Steven Rostedt
2019-05-07 14:50                                         ` David.Laight
2019-05-07 14:50                                           ` David Laight
2019-05-07 14:57                                           ` rostedt
2019-05-07 14:57                                             ` Steven Rostedt
2019-05-07 15:46                                             ` David.Laight
2019-05-07 15:46                                               ` David Laight
2019-05-07 13:32                                       ` peterz [this message]
2019-05-07 13:32                                         ` Peter Zijlstra
2019-05-07  9:27                                 ` peterz
2019-05-07  9:27                                   ` Peter Zijlstra
2019-05-07 12:27                                   ` rostedt
2019-05-07 12:27                                     ` Steven Rostedt
2019-05-07 12:41                                     ` peterz
2019-05-07 12:41                                       ` Peter Zijlstra
2019-05-07 12:54                                       ` rostedt
2019-05-07 12:54                                         ` Steven Rostedt
2019-05-07 17:22                                         ` masami.hiramatsu
2019-05-07 17:22                                           ` Masami Hiramatsu
2019-05-07 14:28                                 ` peterz
2019-05-07 14:28                                   ` Peter Zijlstra
2019-05-02 20:48         ` rostedt
2019-05-02 20:48           ` Steven Rostedt
2019-05-06 15:14         ` jpoimboe
2019-05-06 15:14           ` Josh Poimboeuf
2019-05-01 20:28 ` [RFC][PATCH 2/2] ftrace/x86: Emulate call function while updating in breakpoint handler rostedt
2019-05-01 20:28   ` Steven Rostedt
2019-05-03 10:22 ` [RFC][PATCH 1.5/2] x86: Add int3_emulate_call() selftest peterz
2019-05-03 10:22   ` Peter Zijlstra
2019-05-03 18:46   ` rostedt
2019-05-03 18:46     ` Steven Rostedt

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