From: Steven Rostedt <rostedt@goodmis.org>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Nicolai Stange <nstange@suse.de>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, Josh Poimboeuf <jpoimboe@redhat.com>,
Jiri Kosina <jikos@kernel.org>, Miroslav Benes <mbenes@suse.cz>,
Petr Mladek <pmladek@suse.com>,
Joe Lawrence <joe.lawrence@redhat.com>,
Shuah Khan <shuah@kernel.org>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Tim Chen <tim.c.chen@linux.intel.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Mimi Zohar <zohar@linux.ibm.com>, Juergen Gross <jgross@suse.com>,
Nick Desaulniers <ndesaulniers@google.com>,
Nayna Jain <nayna@linux.ibm.com>,
Masahiro Yamada <yamada.masahiro@socionext.com>,
Andy Lutomirski <luto@kernel.org>, Joerg Roedel <jroedel@suse.de>,
linux-kernel@vger.kernel.org, live-patching@vger.kernel.org,
linux-kselftest@vger.kernel.org
Subject: Re: [PATCH 1/4] x86/thread_info: introduce ->ftrace_int3_stack member
Date: Sun, 28 Apr 2019 13:51:43 -0400 [thread overview]
Message-ID: <20190428135143.09d35bb6@oasis.local.home> (raw)
In-Reply-To: <F6268634-96D3-4267-B739-6D375FAB26A8@amacapital.net>
On Sun, 28 Apr 2019 10:41:10 -0700
Andy Lutomirski <luto@amacapital.net> wrote:
> > Note that at any given point
> > in time, there can be at most four such call insn emulations pending:
> > namely at most one per "process", "irq", "softirq" and "nmi" context.
> >
>
> That’s quite an assumption. I think your list should also contain
> exception, exceptions nested inside that exception, and machine
> check, at the very least. I’m also wondering why irq and softirq are
> treated separately.
4 has usually been the context count we choose. But I guess in theory,
if we get exceptions then I could potentially be more.
As for irq vs softirq, an interrupt can preempt a softirq. Interrupts
are enabled while softirqs are running. When sofirqs run, softirqs are
disabled to prevent nested softirqs. But interrupts are enabled again,
and another interrupt may come in while a softirq is executing.
>
> All this makes me think that one of the other solutions we came up
> with last time we discussed this might be better.
+100
Perhaps adding another slot into pt_regs that gets used by int3 to
store a slot to emulate a call on return?
-- Steve
WARNING: multiple messages have this Message-ID (diff)
From: rostedt at goodmis.org (Steven Rostedt)
Subject: [PATCH 1/4] x86/thread_info: introduce ->ftrace_int3_stack member
Date: Sun, 28 Apr 2019 13:51:43 -0400 [thread overview]
Message-ID: <20190428135143.09d35bb6@oasis.local.home> (raw)
In-Reply-To: <F6268634-96D3-4267-B739-6D375FAB26A8@amacapital.net>
On Sun, 28 Apr 2019 10:41:10 -0700
Andy Lutomirski <luto at amacapital.net> wrote:
> > Note that at any given point
> > in time, there can be at most four such call insn emulations pending:
> > namely at most one per "process", "irq", "softirq" and "nmi" context.
> >
>
> That’s quite an assumption. I think your list should also contain
> exception, exceptions nested inside that exception, and machine
> check, at the very least. I’m also wondering why irq and softirq are
> treated separately.
4 has usually been the context count we choose. But I guess in theory,
if we get exceptions then I could potentially be more.
As for irq vs softirq, an interrupt can preempt a softirq. Interrupts
are enabled while softirqs are running. When sofirqs run, softirqs are
disabled to prevent nested softirqs. But interrupts are enabled again,
and another interrupt may come in while a softirq is executing.
>
> All this makes me think that one of the other solutions we came up
> with last time we discussed this might be better.
+100
Perhaps adding another slot into pt_regs that gets used by int3 to
store a slot to emulate a call on return?
-- Steve
WARNING: multiple messages have this Message-ID (diff)
From: rostedt@goodmis.org (Steven Rostedt)
Subject: [PATCH 1/4] x86/thread_info: introduce ->ftrace_int3_stack member
Date: Sun, 28 Apr 2019 13:51:43 -0400 [thread overview]
Message-ID: <20190428135143.09d35bb6@oasis.local.home> (raw)
Message-ID: <20190428175143.FDJbfbtv0_j1a3ywAKvQEAOIX5t8Oq4A3uRkgsG0sAQ@z> (raw)
In-Reply-To: <F6268634-96D3-4267-B739-6D375FAB26A8@amacapital.net>
On Sun, 28 Apr 2019 10:41:10 -0700
Andy Lutomirski <luto@amacapital.net> wrote:
> > Note that at any given point
> > in time, there can be at most four such call insn emulations pending:
> > namely at most one per "process", "irq", "softirq" and "nmi" context.
> >
>
> That’s quite an assumption. I think your list should also contain
> exception, exceptions nested inside that exception, and machine
> check, at the very least. I’m also wondering why irq and softirq are
> treated separately.
4 has usually been the context count we choose. But I guess in theory,
if we get exceptions then I could potentially be more.
As for irq vs softirq, an interrupt can preempt a softirq. Interrupts
are enabled while softirqs are running. When sofirqs run, softirqs are
disabled to prevent nested softirqs. But interrupts are enabled again,
and another interrupt may come in while a softirq is executing.
>
> All this makes me think that one of the other solutions we came up
> with last time we discussed this might be better.
+100
Perhaps adding another slot into pt_regs that gets used by int3 to
store a slot to emulate a call on return?
-- Steve
next prev parent reply other threads:[~2019-04-28 17:51 UTC|newest]
Thread overview: 192+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-27 10:06 [PATCH 0/4] x86/ftrace: make ftrace_int3_handler() not to skip fops invocation Nicolai Stange
2019-04-27 10:06 ` Nicolai Stange
2019-04-27 10:06 ` nstange
2019-04-27 10:06 ` [PATCH 1/4] x86/thread_info: introduce ->ftrace_int3_stack member Nicolai Stange
2019-04-27 10:06 ` Nicolai Stange
2019-04-27 10:06 ` nstange
2019-04-28 17:41 ` Andy Lutomirski
2019-04-28 17:41 ` Andy Lutomirski
2019-04-28 17:41 ` luto
2019-04-28 17:51 ` Steven Rostedt [this message]
2019-04-28 17:51 ` Steven Rostedt
2019-04-28 17:51 ` rostedt
2019-04-28 18:08 ` Andy Lutomirski
2019-04-28 18:08 ` Andy Lutomirski
2019-04-28 18:08 ` luto
2019-04-28 19:43 ` Steven Rostedt
2019-04-28 19:43 ` Steven Rostedt
2019-04-28 19:43 ` rostedt
2019-04-28 20:56 ` Andy Lutomirski
2019-04-28 20:56 ` Andy Lutomirski
2019-04-28 20:56 ` luto
2019-04-28 21:22 ` Nicolai Stange
2019-04-28 21:22 ` Nicolai Stange
2019-04-28 21:22 ` nstange
2019-04-28 23:27 ` Andy Lutomirski
2019-04-28 23:27 ` Andy Lutomirski
2019-04-28 23:27 ` luto
2019-04-27 10:06 ` [PATCH 2/4] ftrace: drop 'static' qualifier from ftrace_ops_list_func() Nicolai Stange
2019-04-27 10:06 ` Nicolai Stange
2019-04-27 10:06 ` nstange
2019-04-27 10:06 ` [PATCH 3/4] x86/ftrace: make ftrace_int3_handler() not to skip fops invocation Nicolai Stange
2019-04-27 10:06 ` Nicolai Stange
2019-04-27 10:06 ` nstange
2019-04-27 10:26 ` Peter Zijlstra
2019-04-27 10:26 ` Peter Zijlstra
2019-04-27 10:26 ` peterz
2019-04-28 17:38 ` Steven Rostedt
2019-04-28 17:38 ` Steven Rostedt
2019-04-28 17:38 ` rostedt
2019-04-29 18:06 ` Linus Torvalds
2019-04-29 18:06 ` Linus Torvalds
2019-04-29 18:06 ` torvalds
2019-04-29 18:22 ` Linus Torvalds
2019-04-29 18:22 ` Linus Torvalds
2019-04-29 18:22 ` torvalds
2019-04-29 18:42 ` Andy Lutomirski
2019-04-29 18:42 ` Andy Lutomirski
2019-04-29 18:42 ` luto
[not found] ` <CAHk-=whtt4K2f0KPtG-4Pykh3FK8UBOjD8jhXCUKB5nWDj_YRA@mail.gmail.com>
2019-04-29 18:56 ` Andy Lutomirski
2019-04-29 18:56 ` Andy Lutomirski
2019-04-29 18:56 ` luto
[not found] ` <CAHk-=wgewK4eFhF3=0RNtk1KQjMANFH6oDE=8m=84RExn2gxhw@mail.gmail.com>
[not found] ` <CAHk-=whay7eN6+2gZjY-ybRbkbcqAmgrLwwszzHx8ws3c=S-MA@mail.gmail.com>
2019-04-29 19:24 ` Andy Lutomirski
2019-04-29 19:24 ` Andy Lutomirski
2019-04-29 19:24 ` luto
2019-04-29 20:07 ` Linus Torvalds
2019-04-29 20:07 ` Linus Torvalds
2019-04-29 20:07 ` torvalds
2019-04-30 13:56 ` Peter Zijlstra
2019-04-30 13:56 ` Peter Zijlstra
2019-04-30 13:56 ` peterz
2019-04-30 16:06 ` Linus Torvalds
2019-04-30 16:06 ` Linus Torvalds
2019-04-30 16:06 ` torvalds
2019-04-30 16:33 ` Andy Lutomirski
2019-04-30 16:33 ` Andy Lutomirski
2019-04-30 16:33 ` luto
2019-04-30 17:03 ` Steven Rostedt
2019-04-30 17:03 ` Steven Rostedt
2019-04-30 17:03 ` rostedt
2019-04-30 17:20 ` Steven Rostedt
2019-04-30 17:20 ` Steven Rostedt
2019-04-30 17:20 ` rostedt
2019-04-30 17:49 ` [RFC][PATCH] ftrace/x86: Emulate call function while updating in breakpoint handler Steven Rostedt
2019-04-30 17:49 ` Steven Rostedt
2019-04-30 17:49 ` rostedt
2019-04-30 18:33 ` Linus Torvalds
2019-04-30 18:33 ` Linus Torvalds
2019-04-30 18:33 ` torvalds
2019-04-30 19:00 ` Steven Rostedt
2019-04-30 19:00 ` Steven Rostedt
2019-04-30 19:00 ` rostedt
2019-04-30 21:08 ` Steven Rostedt
2019-04-30 21:08 ` Steven Rostedt
2019-04-30 21:08 ` rostedt
2019-05-01 13:11 ` Peter Zijlstra
2019-05-01 13:11 ` Peter Zijlstra
2019-05-01 13:11 ` peterz
2019-05-01 18:58 ` Steven Rostedt
2019-05-01 18:58 ` Steven Rostedt
2019-05-01 18:58 ` rostedt
2019-05-01 19:03 ` Peter Zijlstra
2019-05-01 19:03 ` Peter Zijlstra
2019-05-01 19:03 ` peterz
2019-05-01 19:03 ` Linus Torvalds
2019-05-01 19:03 ` Linus Torvalds
2019-05-01 19:03 ` torvalds
2019-05-01 19:13 ` Peter Zijlstra
2019-05-01 19:13 ` Peter Zijlstra
2019-05-01 19:13 ` peterz
2019-05-01 19:13 ` Steven Rostedt
2019-05-01 19:13 ` Steven Rostedt
2019-05-01 19:13 ` rostedt
2019-05-01 19:33 ` Jiri Kosina
2019-05-01 19:33 ` Jiri Kosina
2019-05-01 19:33 ` jikos
2019-05-01 19:41 ` Peter Zijlstra
2019-05-01 19:41 ` Peter Zijlstra
2019-05-01 19:41 ` peterz
2019-04-30 21:53 ` [RFC][PATCH v2] " Steven Rostedt
2019-04-30 21:53 ` Steven Rostedt
2019-04-30 21:53 ` rostedt
2019-05-01 1:35 ` Steven Rostedt
2019-05-01 1:35 ` Steven Rostedt
2019-05-01 1:35 ` rostedt
2019-05-01 1:58 ` Linus Torvalds
2019-05-01 1:58 ` Linus Torvalds
2019-05-01 1:58 ` torvalds
2019-05-01 8:26 ` Nicolai Stange
2019-05-01 8:26 ` Nicolai Stange
2019-05-01 8:26 ` nstange
2019-05-01 13:22 ` Steven Rostedt
2019-05-01 13:22 ` Steven Rostedt
2019-05-01 13:22 ` rostedt
2019-04-29 20:16 ` [PATCH 3/4] x86/ftrace: make ftrace_int3_handler() not to skip fops invocation Linus Torvalds
2019-04-29 20:16 ` Linus Torvalds
2019-04-29 20:16 ` torvalds
2019-04-29 22:08 ` Sean Christopherson
2019-04-29 22:08 ` Sean Christopherson
2019-04-29 22:08 ` sean.j.christopherson
2019-04-29 22:22 ` Linus Torvalds
2019-04-29 22:22 ` Linus Torvalds
2019-04-29 22:22 ` torvalds
2019-04-30 0:08 ` Sean Christopherson
2019-04-30 0:08 ` Sean Christopherson
2019-04-30 0:08 ` sean.j.christopherson
2019-04-30 0:45 ` Sean Christopherson
2019-04-30 0:45 ` Sean Christopherson
2019-04-30 0:45 ` sean.j.christopherson
2019-04-30 2:26 ` Linus Torvalds
2019-04-30 2:26 ` Linus Torvalds
2019-04-30 2:26 ` torvalds
2019-04-30 10:40 ` Peter Zijlstra
2019-04-30 10:40 ` Peter Zijlstra
2019-04-30 10:40 ` peterz
2019-04-30 11:17 ` Jiri Kosina
2019-04-30 11:17 ` Jiri Kosina
2019-04-30 11:17 ` jikos
2019-04-29 22:06 ` Linus Torvalds
2019-04-29 22:06 ` Linus Torvalds
2019-04-29 22:06 ` torvalds
2019-04-30 11:18 ` Peter Zijlstra
2019-04-30 11:18 ` Peter Zijlstra
2019-04-30 11:18 ` peterz
2019-04-29 18:52 ` Steven Rostedt
2019-04-29 18:52 ` Steven Rostedt
2019-04-29 18:52 ` rostedt
[not found] ` <CAHk-=wjm93jLtVxTX4HZs6K4k1Wqh3ujjmapqaYtcibVk_YnzQ@mail.gmail.com>
2019-04-29 19:07 ` Steven Rostedt
2019-04-29 19:07 ` Steven Rostedt
2019-04-29 19:07 ` rostedt
2019-04-29 20:06 ` Linus Torvalds
2019-04-29 20:06 ` Linus Torvalds
2019-04-29 20:06 ` torvalds
2019-04-29 20:20 ` Linus Torvalds
2019-04-29 20:20 ` Linus Torvalds
2019-04-29 20:20 ` torvalds
2019-04-29 20:30 ` Steven Rostedt
2019-04-29 20:30 ` Steven Rostedt
2019-04-29 20:30 ` rostedt
2019-04-29 21:38 ` Linus Torvalds
2019-04-29 21:38 ` Linus Torvalds
2019-04-29 21:38 ` torvalds
2019-04-29 22:07 ` Steven Rostedt
2019-04-29 22:07 ` Steven Rostedt
2019-04-29 22:07 ` rostedt
2019-04-30 9:24 ` Nicolai Stange
2019-04-30 9:24 ` Nicolai Stange
2019-04-30 9:24 ` nstange
2019-04-30 10:46 ` Peter Zijlstra
2019-04-30 10:46 ` Peter Zijlstra
2019-04-30 10:46 ` peterz
2019-04-30 13:44 ` Steven Rostedt
2019-04-30 13:44 ` Steven Rostedt
2019-04-30 13:44 ` rostedt
2019-04-30 14:20 ` Peter Zijlstra
2019-04-30 14:20 ` Peter Zijlstra
2019-04-30 14:20 ` peterz
2019-04-30 14:36 ` Steven Rostedt
2019-04-30 14:36 ` Steven Rostedt
2019-04-30 14:36 ` rostedt
2019-04-27 10:06 ` [PATCH 4/4] selftests/livepatch: add "ftrace a live patched function" test Nicolai Stange
2019-04-27 10:06 ` Nicolai Stange
2019-04-27 10:06 ` nstange
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