[PATCH 5/8] tracing: Allow system call tracepoints to handle page faults
From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: 2024-09-09 20:17:19
Also in:
bpf, lkml
Subsystem:
the rest, tracing · Maintainers:
Linus Torvalds, Steven Rostedt, Masami Hiramatsu
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 <redacted> 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 <redacted> 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 <redacted> Cc: bpf@vger.kernel.org Cc: Joel Fernandes <redacted> --- 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"
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2.39.2