Commit a363d27c authored by Mathieu Desnoyers's avatar Mathieu Desnoyers Committed by Steven Rostedt (Google)
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tracing: Allow system call tracepoints to handle page faults 

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.

Cc: Michael Jeanson <mjeanson@efficios.com>
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>
Link: https://lore.kernel.org/20241009010718.2050182-6-mathieu.desnoyers@efficios.com


Signed-off-by: default avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 4aadde89

include/linux/tracepoint.h

+16 −2
Original line number Diff line number Diff line
@@ -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>
@@ -107,6 +108,7 @@ void for_each_tracepoint_in_module(struct module *mod, 
#ifdef CONFIG_TRACEPOINTS

static inline void tracepoint_synchronize_unregister(void)

{

	synchronize_rcu_tasks_trace();

	synchronize_rcu();

}

#else
@@ -196,6 +198,12 @@ 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.

 *

 * With @syscall=0, the tracepoint callback array dereference is

 * protected by disabling preemption.

 * With @syscall=1, the tracepoint callback array dereference is

 * protected by Tasks Trace RCU, which allows probes to handle page

 * faults.

 */

#define __DO_TRACE(name, args, cond, syscall)				\

	do {								\
@@ -204,10 +212,16 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p) 
		if (!(cond))						\

			return;						\

									\

		if (syscall)						\

			rcu_read_lock_trace();				\

		else							\

			preempt_disable_notrace();			\

									\

		__DO_TRACE_CALL(name, TP_ARGS(args));			\

									\

		if (syscall)						\

			rcu_read_unlock_trace();			\

		else							\

			preempt_enable_notrace();			\

	} while (0)

init/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -1985,6 +1985,7 @@ config BINDGEN_VERSION_TEXT 
#

config TRACEPOINTS

	bool

	select TASKS_TRACE_RCU



source "kernel/Kconfig.kexec"