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.desnoyers@efficios.com>
Cc: Michael Jeanson <mjeanson@efficios.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Yonghong Song <yhs@fb.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: bpf@vger.kernel.org
Cc: Joel Fernandes <joel@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 b2cfe6a9097c..005ede3b1afa 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -18,6 +18,7 @@
#include <linux/types.h>
#include <linux/cpumask.h>
#include <linux/rcupdate.h>
+#include <linux/rcupdate_trace.h>
#include <linux/tracepoint-defs.h>
#include <linux/static_call.h>
@@ -90,6 +91,7 @@ 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();
}
@@ -192,7 +194,7 @@ 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; \
\
@@ -203,8 +205,12 @@ 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 \
@@ -222,7 +228,10 @@ 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
@@ -232,7 +241,7 @@ 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)
@@ -276,7 +285,7 @@ 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"); \
@@ -287,7 +296,7 @@ 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) \
@@ -310,7 +319,7 @@ 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 d8a971b804d3..c854b2887e7f 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1937,6 +1937,7 @@ config BINDGEN_VERSION_TEXT
#
config TRACEPOINTS
bool
+ select TASKS_TRACE_RCU
source "kernel/Kconfig.kexec"
--
2.39.2