Use Tasks Trace RCU to protect iteration of system call enter/exit
tracepoint probes to allow those probes to handle page faults.
In preparation for this change, all tracers registering to system call
enter/exit tracepoints should expect those to be called with preemption
enabled.
This allows tracers to fault-in userspace system call arguments such as
path strings within their probe callbacks.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoy...@efficios.com>
Cc: Michael Jeanson <mjean...@efficios.com>
Cc: Steven Rostedt <rost...@goodmis.org>
Cc: Masami Hiramatsu <mhira...@kernel.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Alexei Starovoitov <a...@kernel.org>
Cc: Yonghong Song <y...@fb.com>
Cc: Paul E. McKenney <paul...@kernel.org>
Cc: Ingo Molnar <mi...@redhat.com>
Cc: Arnaldo Carvalho de Melo <a...@kernel.org>
Cc: Mark Rutland <mark.rutl...@arm.com>
Cc: Alexander Shishkin <alexander.shish...@linux.intel.com>
Cc: Namhyung Kim <namhy...@kernel.org>
Cc: Andrii Nakryiko <andrii.nakry...@gmail.com>
Cc: b...@vger.kernel.org
Cc: Joel Fernandes <j...@joelfernandes.org>
---
include/linux/tracepoint.h | 25 +++++++++++++++++--------
init/Kconfig | 1 +
2 files changed, 18 insertions(+), 8 deletions(-)
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 2e4b4952bba2..106e951896c2 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -17,6 +17,7 @@
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/rcupdate.h>
+#include <linux/rcupdate_trace.h>
#include <linux/tracepoint-defs.h>
#include <linux/static_call.h>
@@ -89,6 +90,7 @@ int unregister_tracepoint_module_notifier(struct
notifier_block *nb)
#ifdef CONFIG_TRACEPOINTS
static inline void tracepoint_synchronize_unregister(void)
{
+ synchronize_rcu_tasks_trace();
synchronize_srcu(&tracepoint_srcu);
synchronize_rcu();
}
@@ -191,7 +193,7 @@ static inline struct tracepoint
*tracepoint_ptr_deref(tracepoint_ptr_t *p)
* it_func[0] is never NULL because there is at least one element in the array
* when the array itself is non NULL.
*/
-#define __DO_TRACE(name, args, cond, rcuidle) \
+#define __DO_TRACE(name, args, cond, rcuidle, syscall) \
do { \
int __maybe_unused __idx = 0; \
\
@@ -202,8 +204,12 @@ static inline struct tracepoint
*tracepoint_ptr_deref(tracepoint_ptr_t *p)
"Bad RCU usage for tracepoint")) \
return; \
\
- /* keep srcu and sched-rcu usage consistent */ \
- preempt_disable_notrace(); \
+ if (syscall) { \
+ rcu_read_lock_trace(); \
+ } else { \
+ /* keep srcu and sched-rcu usage consistent */ \
+ preempt_disable_notrace(); \
+ } \
\
/* \
* For rcuidle callers, use srcu since sched-rcu \
@@ -221,7 +227,10 @@ static inline struct tracepoint
*tracepoint_ptr_deref(tracepoint_ptr_t *p)
srcu_read_unlock_notrace(&tracepoint_srcu, __idx);\
} \
\
- preempt_enable_notrace(); \
+ if (syscall) \
+ rcu_read_unlock_trace(); \
+ else \
+ preempt_enable_notrace(); \
} while (0)
#ifndef MODULE
@@ -231,7 +240,7 @@ static inline struct tracepoint
*tracepoint_ptr_deref(tracepoint_ptr_t *p)
if (static_key_false(&__tracepoint_##name.key)) \
__DO_TRACE(name, \
TP_ARGS(args), \
- TP_CONDITION(cond), 1); \
+ TP_CONDITION(cond), 1, 0); \
}
#else
#define __DECLARE_TRACE_RCU(name, proto, args, cond)
@@ -275,7 +284,7 @@ static inline struct tracepoint
*tracepoint_ptr_deref(tracepoint_ptr_t *p)
if (static_key_false(&__tracepoint_##name.key)) \
__DO_TRACE(name, \
TP_ARGS(args), \
- TP_CONDITION(cond), 0); \
+ TP_CONDITION(cond), 0, 0); \
if (IS_ENABLED(CONFIG_LOCKDEP) && (cond)) { \
WARN_ONCE(!rcu_is_watching(), \
"RCU not watching for tracepoint"); \
@@ -286,7 +295,7 @@ static inline struct tracepoint
*tracepoint_ptr_deref(tracepoint_ptr_t *p)
if (static_key_false(&__tracepoint_##name.key)) \
__DO_TRACE(name, \
TP_ARGS(args), \
- TP_CONDITION(cond), 1); \
+ TP_CONDITION(cond), 1, 0); \
} \
static inline int \
register_trace_##name(void (*probe)(data_proto), void *data) \
@@ -309,7 +318,7 @@ static inline struct tracepoint
*tracepoint_ptr_deref(tracepoint_ptr_t *p)
if (static_key_false(&__tracepoint_##name.key)) \
__DO_TRACE(name, \
TP_ARGS(args), \
- TP_CONDITION(cond), 0); \
+ TP_CONDITION(cond), 0, 1); \
if (IS_ENABLED(CONFIG_LOCKDEP) && (cond)) { \
WARN_ONCE(!rcu_is_watching(), \
"RCU not watching for tracepoint"); \
diff --git a/init/Kconfig b/init/Kconfig
index 5783a0b87517..72e13ee73c43 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1936,6 +1936,7 @@ config BINDGEN_VERSION_TEXT
#
config TRACEPOINTS
bool
+ select TASKS_TRACE_RCU
source "kernel/Kconfig.kexec"
--
2.39.2
