linux-kernel - [patch V4 part 1 33/36] x86,tracing: Robustify ftrace_nmi

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Date:   Tue, 05 May 2020 15:16:35 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, "Paul E. McKenney" <paulmck@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Brian Gerst <brgerst@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Will Deacon <will@...nel.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>
Subject: [patch V4 part 1 33/36] x86,tracing: Robustify ftrace_nmi_enter()

From: Peter Zijlstra <peterz@...radead.org>

  ftrace_nmi_enter()
     trace_hwlat_callback()
       trace_clock_local()
         sched_clock()
           paravirt_sched_clock()
           native_sched_clock()

All must not be traced or kprobed, it will be called from do_debug()
before the kprobe handler.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 arch/x86/include/asm/paravirt.h |    2 +-
 arch/x86/kernel/tsc.c           |    4 ++--
 include/linux/ftrace_irq.h      |    4 ++--
 kernel/trace/trace_clock.c      |    3 ++-
 kernel/trace/trace_hwlat.c      |    2 +-
 5 files changed, 8 insertions(+), 7 deletions(-)

--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -17,7 +17,7 @@
 #include <linux/cpumask.h>
 #include <asm/frame.h>
 
-static inline unsigned long long paravirt_sched_clock(void)
+static __always_inline unsigned long long paravirt_sched_clock(void)
 {
 	return PVOP_CALL0(unsigned long long, time.sched_clock);
 }
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -207,7 +207,7 @@ static void __init cyc2ns_init_secondary
 /*
  * Scheduler clock - returns current time in nanosec units.
  */
-u64 native_sched_clock(void)
+noinstr u64 native_sched_clock(void)
 {
 	if (static_branch_likely(&__use_tsc)) {
 		u64 tsc_now = rdtsc();
@@ -240,7 +240,7 @@ u64 native_sched_clock_from_tsc(u64 tsc)
 /* We need to define a real function for sched_clock, to override the
    weak default version */
 #ifdef CONFIG_PARAVIRT
-unsigned long long sched_clock(void)
+noinstr unsigned long long sched_clock(void)
 {
 	return paravirt_sched_clock();
 }
--- a/include/linux/ftrace_irq.h
+++ b/include/linux/ftrace_irq.h
@@ -7,7 +7,7 @@ extern bool trace_hwlat_callback_enabled
 extern void trace_hwlat_callback(bool enter);
 #endif
 
-static inline void ftrace_nmi_enter(void)
+static __always_inline void ftrace_nmi_enter(void)
 {
 #ifdef CONFIG_HWLAT_TRACER
 	if (trace_hwlat_callback_enabled)
@@ -15,7 +15,7 @@ static inline void ftrace_nmi_enter(void
 #endif
 }
 
-static inline void ftrace_nmi_exit(void)
+static __always_inline void ftrace_nmi_exit(void)
 {
 #ifdef CONFIG_HWLAT_TRACER
 	if (trace_hwlat_callback_enabled)
--- a/kernel/trace/trace_clock.c
+++ b/kernel/trace/trace_clock.c
@@ -22,6 +22,7 @@
 #include <linux/sched/clock.h>
 #include <linux/ktime.h>
 #include <linux/trace_clock.h>
+#include <linux/kprobes.h>
 
 /*
  * trace_clock_local(): the simplest and least coherent tracing clock.
@@ -29,7 +30,7 @@
  * Useful for tracing that does not cross to other CPUs nor
  * does it go through idle events.
  */
-u64 notrace trace_clock_local(void)
+u64 noinstr trace_clock_local(void)
 {
 	u64 clock;
 
--- a/kernel/trace/trace_hwlat.c
+++ b/kernel/trace/trace_hwlat.c
@@ -139,7 +139,7 @@ static void trace_hwlat_sample(struct hw
 #define init_time(a, b)	(a = b)
 #define time_u64(a)	a
 
-void trace_hwlat_callback(bool enter)
+noinstr void trace_hwlat_callback(bool enter)
 {
 	if (smp_processor_id() != nmi_cpu)
 		return;