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From: Peter Zijlstra <peterz@infradead.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
	mingo@kernel.org, paulus@samba.org, linux-kernel@vger.kernel.org,
	acme@ghostprotocols.net, seiji.aguchi@hds.com, jolsa@redhat.com,
	vincent.weaver@maine.edu, tglx@linutronix.de,
	hpa@linux.intel.com, linux-tip-commits@vger.kernel.org
Subject: [PATCH] x86: Further robustify CR2 handling vs tracing
Date: Thu, 6 Mar 2014 15:53:00 +0100
Message-ID: <20140306145300.GO9987@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20140306060215.2a78efc2@gandalf.local.home>

Subject: x86: Further robustify CR2 handling vs tracing
From: Peter Zijlstra <peterz@infradead.org>
Date: Wed, 5 Mar 2014 14:07:49 +0100

Building on commit 0ac09f9f8cd1 ("x86, trace: Fix CR2 corruption when
tracing page faults") this patch addresses another few issues:

 - Now that read_cr2() is lifted into trace_do_page_fault(), we should
   pass the address to trace_page_fault_entries() to avoid it
   re-reading a potentially changed cr2.

 - Put both trace_do_page_fault() and trace_page_fault_entries() under
   CONFIG_TRACING.

 - Mark both fault entry functions {,trace_}do_page_fault() as notrace
   to avoid getting __mcount or other function entry trace callbacks
   before we've observed CR2.

 - Mark __do_page_fault() as noinline to guarantee the function tracer
   does get to see the fault.

Cc: jolsa@redhat.com
Cc: vincent.weaver@maine.edu
Cc: tglx@linutronix.de
Cc: hpa@linux.intel.com
Cc: mingo@kernel.org
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
---
 arch/x86/mm/fault.c |   33 +++++++++++++++++++++++----------
 1 file changed, 23 insertions(+), 10 deletions(-)

--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1020,8 +1020,12 @@ static inline bool smap_violation(int er
  * This routine handles page faults.  It determines the address,
  * and the problem, and then passes it off to one of the appropriate
  * routines.
+ *
+ * This function must have noinline because both callers
+ * {,trace_}do_page_fault() have notrace on. Having this an actual function
+ * guarantees there's a function trace entry.
  */
-static void __kprobes
+static void __kprobes noinline
 __do_page_fault(struct pt_regs *regs, unsigned long error_code,
 		unsigned long address)
 {
@@ -1245,31 +1249,38 @@ __do_page_fault(struct pt_regs *regs, un
 	up_read(&mm->mmap_sem);
 }
 
-dotraplinkage void __kprobes
+dotraplinkage void __kprobes notrace
 do_page_fault(struct pt_regs *regs, unsigned long error_code)
 {
+	unsigned long address = read_cr2(); /* Get the faulting address */
 	enum ctx_state prev_state;
-	/* Get the faulting address: */
-	unsigned long address = read_cr2();
+
+	/*
+	 * We must have this function tagged with __kprobes, notrace and call
+	 * read_cr2() before calling anything else. To avoid calling any kind
+	 * of tracing machinery before we've observed the CR2 value.
+	 *
+	 * exception_{enter,exit}() contain all sorts of tracepoints.
+	 */
 
 	prev_state = exception_enter();
 	__do_page_fault(regs, error_code, address);
 	exception_exit(prev_state);
 }
 
-static void trace_page_fault_entries(struct pt_regs *regs,
+#ifdef CONFIG_TRACING
+static void trace_page_fault_entries(unsigned long address, struct pt_regs *regs,
 				     unsigned long error_code)
 {
 	if (user_mode(regs))
-		trace_page_fault_user(read_cr2(), regs, error_code);
+		trace_page_fault_user(address, regs, error_code);
 	else
-		trace_page_fault_kernel(read_cr2(), regs, error_code);
+		trace_page_fault_kernel(address, regs, error_code);
 }
 
-dotraplinkage void __kprobes
+dotraplinkage void __kprobes notrace
 trace_do_page_fault(struct pt_regs *regs, unsigned long error_code)
 {
-	enum ctx_state prev_state;
 	/*
 	 * The exception_enter and tracepoint processing could
 	 * trigger another page faults (user space callchain
@@ -1277,9 +1288,11 @@ trace_do_page_fault(struct pt_regs *regs
 	 * the faulting address now.
 	 */
 	unsigned long address = read_cr2();
+	enum ctx_state prev_state;
 
 	prev_state = exception_enter();
-	trace_page_fault_entries(regs, error_code);
+	trace_page_fault_entries(address, regs, error_code);
 	__do_page_fault(regs, error_code, address);
 	exception_exit(prev_state);
 }
+#endif /* CONFIG_TRACING */

  reply index

Thread overview: 115+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-02-28 15:33 [PATCH] x86 trace: Fix page fault tracing bug Jiri Olsa
2014-02-28 15:47 ` Peter Zijlstra
2014-02-28 16:05   ` [PATCHv2] " Jiri Olsa
2014-02-28 16:11     ` H. Peter Anvin
2014-02-28 16:23       ` Steven Rostedt
2014-02-28 16:15     ` Steven Rostedt
2014-03-05  0:03     ` [tip:x86/urgent] x86, trace: Fix CR2 corruption when tracing page faults tip-bot for Jiri Olsa
2014-03-05 11:14       ` Peter Zijlstra
2014-03-05 12:20         ` Steven Rostedt
2014-03-05 12:25           ` Peter Zijlstra
2014-03-05 12:33             ` Steven Rostedt
2014-03-05 12:54               ` Peter Zijlstra
2014-03-05 13:02                 ` Peter Zijlstra
2014-03-05 13:07                   ` Peter Zijlstra
2014-03-05 12:36             ` Peter Zijlstra
2014-03-05 13:00               ` Steven Rostedt
2014-03-05 13:08                 ` Peter Zijlstra
2014-03-05 21:37                   ` H. Peter Anvin
2014-03-06  8:40                     ` Peter Zijlstra
2014-03-06 11:02                       ` Steven Rostedt
2014-03-06 14:53                         ` Peter Zijlstra [this message]
2014-03-07 23:07                           ` [tip:x86/urgent] x86, trace: Further robustify CR2 handling vs tracing tip-bot for Peter Zijlstra
2014-02-28 15:47 ` [PATCH] x86 trace: Fix page fault tracing bug Jiri Olsa
2014-02-28 16:00   ` Steven Rostedt
2014-02-28 16:01 ` Steven Rostedt
  -- strict thread matches above, loose matches on Subject: below --
2014-02-21 20:25 perf_fuzzer causes reboot Vince Weaver
2014-02-21 22:13 ` perf_fuzzer compiled for x32 " Vince Weaver
2014-02-21 22:34   ` Vince Weaver
2014-02-22  4:50     ` Vince Weaver
2014-02-22  5:03       ` H. Peter Anvin
2014-02-22  6:26       ` H. Peter Anvin
2014-02-23  5:18         ` Vince Weaver
2014-02-23  5:24           ` H. Peter Anvin
2014-02-23  6:07           ` H. Peter Anvin
2014-02-23 14:05             ` Vince Weaver
2014-02-24  3:02               ` Vince Weaver
2014-02-24  5:22                 ` H. Peter Anvin
2014-02-24 15:35                   ` Vince Weaver
2014-02-24 16:34                     ` Vince Weaver
2014-02-24 16:47                       ` H. Peter Anvin
2014-02-24 17:10                         ` Vince Weaver
2014-02-24 17:25                           ` Peter Zijlstra
2014-02-24 17:32                             ` Vince Weaver
2014-02-24 17:40                               ` H. Peter Anvin
2014-02-24 18:00                                 ` Vince Weaver
2014-02-24 18:07                                   ` Vince Weaver
2014-02-24 18:34                                     ` H. Peter Anvin
2014-02-24 19:13                                       ` Steven Rostedt
2014-02-24 19:15                                         ` H. Peter Anvin
2014-02-24 19:30                                         ` Peter Zijlstra
2014-02-24 19:32                                           ` Steven Rostedt
2014-02-25  3:49                                           ` H. Peter Anvin
2014-02-25 14:07                                             ` Vince Weaver
2014-02-25 14:34                                               ` H. Peter Anvin
2014-02-25 14:43                                                 ` Steven Rostedt
2014-02-25 15:33                                                   ` Vince Weaver
2014-02-26 15:06                                                     ` Vince Weaver
2014-02-27 22:06                                                       ` Vince Weaver
2014-02-27 22:31                                                         ` Steven Rostedt
2014-02-27 22:52                                                           ` H. Peter Anvin
2014-02-27 23:30                                                             ` Steven Rostedt
2014-02-27 23:46                                                               ` H. Peter Anvin
2014-02-28  1:00                                                                 ` Vince Weaver
2014-02-28 20:34                                                                   ` Paul E. McKenney
2014-02-28 20:47                                                                     ` Steven Rostedt
2014-02-28 20:54                                                                       ` Peter Zijlstra
2014-02-28 21:17                                                                         ` Paul E. McKenney
2014-02-28 21:27                                                                           ` Peter Zijlstra
2014-02-28 21:51                                                                             ` Paul E. McKenney
2014-02-28 21:55                                                                               ` Peter Zijlstra
2014-02-28 22:05                                                                                 ` Steven Rostedt
2014-02-28 22:23                                                                                   ` Paul E. McKenney
2014-02-28  1:34                                                             ` Vince Weaver
2014-02-28  2:17                                                               ` H. Peter Anvin
2014-02-28  2:57                                                               ` Steven Rostedt
2014-02-28 11:11                                                                 ` Peter Zijlstra
2014-02-28 13:37                                                                   ` Steven Rostedt
2014-02-28 14:15                                                                 ` Vince Weaver
2014-02-28 14:23                                                                   ` Steven Rostedt
2014-02-28 15:07                                                                     ` Vince Weaver
2014-02-28 15:13                                                                       ` H. Peter Anvin
2014-02-28 15:40                                                                         ` Peter Zijlstra
2014-02-28 16:15                                                                           ` H. Peter Anvin
2014-02-28 16:29                                                                             ` Steven Rostedt
2014-02-28 19:33                                                                               ` [PATCH] x86: Rename copy_from_user_nmi() to copy_from_user_trace() Steven Rostedt
2014-02-28 20:46                                                                                 ` Peter Zijlstra
2014-02-28 20:51                                                                                   ` Steven Rostedt
2014-02-28 20:58                                                                                     ` Peter Zijlstra
2014-02-28 21:01                                                                                   ` Steven Rostedt
2014-02-28 21:17                                                                                     ` Peter Zijlstra
2014-02-28 20:56                                                                               ` perf_fuzzer compiled for x32 causes reboot Peter Zijlstra
2014-02-28 21:06                                                                                 ` Steven Rostedt
2014-03-01  9:16                                                                                   ` Ingo Molnar
2014-03-01  9:50                                                                                     ` Borislav Petkov
2014-03-01 16:50                                                                                       ` H. Peter Anvin
2014-03-04 23:05                                                                                         ` Borislav Petkov
2014-03-03  9:16                                                                                     ` Peter Zijlstra
2014-02-28 20:55                                                                             ` Peter Zijlstra
2014-02-28 15:20                                                                       ` Steven Rostedt
2014-02-28 15:30                                                                         ` Steven Rostedt
2014-02-28 20:38                                                                       ` H. Peter Anvin
2014-02-28 20:46                                                                         ` Steven Rostedt
2014-02-28 21:18                                                                         ` Vince Weaver
2014-02-28 21:30                                                                           ` Steven Rostedt
2014-02-28 23:34                                                                             ` Vince Weaver
2014-03-01  0:43                                                                               ` H. Peter Anvin
2014-03-01  3:36                                                                               ` Steven Rostedt
2014-03-01 16:24                                                                                 ` Andi Kleen
2014-03-02 15:34                                                                                   ` Vince Weaver
2014-03-02 16:02                                                                                 ` Vince Weaver
2014-02-28  9:39                                                           ` Peter Zijlstra
2014-02-24 17:40                               ` Peter Zijlstra
2014-02-24 17:41                               ` Vince Weaver
2014-02-24 17:42                                 ` H. Peter Anvin
2014-02-24 17:52                             ` H. Peter Anvin

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