tracepoint: Have tracepoints created with DECLARE_TRACE() have _tp suffix

Most tracepoints in the kernel are created with TRACE_EVENT(). The
TRACE_EVENT() macro (and DECLARE_EVENT_CLASS() and DEFINE_EVENT() where in
reality, TRACE_EVENT() is just a helper macro that calls those other two
macros), will create not only a tracepoint (the function trace_<event>()
used in the kernel), it also exposes the tracepoint to user space along
with defining what fields will be saved by that tracepoint.

There are a few places that tracepoints are created in the kernel that are
not exposed to userspace via tracefs. They can only be accessed from code
within the kernel. These tracepoints are created with DEFINE_TRACE()

Most of these tracepoints end with "_tp". This is useful as when the
developer sees that, they know that the tracepoint is for in-kernel only
(meaning it can only be accessed inside the kernel, either directly by the
kernel or indirectly via modules and BPF programs) and is not exposed to
user space.

Instead of making this only a process to add "_tp", enforce it by making
the DECLARE_TRACE() append the "_tp" suffix to the tracepoint. This
requires adding DECLARE_TRACE_EVENT() macros for the TRACE_EVENT() macro
to use that keeps the original name.

Link: https://lore.kernel.org/all/[email protected]/

Cc: netdev <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Juri Lelli <[email protected]>
Cc: Breno Leitao <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: Gabriele Monaco <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Link: https://lore.kernel.org/[email protected]
Acked-by: Mathieu Desnoyers <[email protected]>
Acked-by: Andrii Nakryiko <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

Author: rostedt

Documentation/trace/tracepoints.rst

@@ -71,7 +71,7 @@ In subsys/file.c (where the tracing statement must be added)::
 	void somefct(void)
 	{
 		...
-		trace_subsys_eventname(arg, task);
+		trace_subsys_eventname_tp(arg, task);
 		...
 	}
 
@@ -129,12 +129,12 @@ within an if statement with the following::
 		for (i = 0; i < count; i++)
 			tot += calculate_nuggets();
 
-		trace_foo_bar(tot);
+		trace_foo_bar_tp(tot);
 	}
 
-All trace_<tracepoint>() calls have a matching trace_<tracepoint>_enabled()
+All trace_<tracepoint>_tp() calls have a matching trace_<tracepoint>_enabled()
 function defined that returns true if the tracepoint is enabled and
-false otherwise. The trace_<tracepoint>() should always be within the
+false otherwise. The trace_<tracepoint>_tp() should always be within the
 block of the if (trace_<tracepoint>_enabled()) to prevent races between
 the tracepoint being enabled and the check being seen.
 
@@ -143,7 +143,10 @@ the static_key of the tracepoint to allow the if statement to be implemented
 with jump labels and avoid conditional branches.
 
 .. note:: The convenience macro TRACE_EVENT provides an alternative way to
-      define tracepoints. Check http://lwn.net/Articles/379903,
+      define tracepoints. Note, DECLARE_TRACE(foo) creates a function
+      "trace_foo_tp()" whereas TRACE_EVENT(foo) creates a function
+      "trace_foo()", and also exposes the tracepoint as a trace event in
+      /sys/kernel/tracing/events directory.  Check http://lwn.net/Articles/379903,
       http://lwn.net/Articles/381064 and http://lwn.net/Articles/383362
       for a series of articles with more details.
 
@@ -159,7 +162,9 @@ In a C file::
 
 	void do_trace_foo_bar_wrapper(args)
 	{
-		trace_foo_bar(args);
+		trace_foo_bar_tp(args); // for tracepoints created via DECLARE_TRACE
+					//   or
+		trace_foo_bar(args);    // for tracepoints created via TRACE_EVENT
 	}
 
 In the header file::

include/linux/tracepoint.h

@@ -464,16 +464,30 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
 #endif
 
 #define DECLARE_TRACE(name, proto, args)				\
-	__DECLARE_TRACE(name, PARAMS(proto), PARAMS(args),		\
+	__DECLARE_TRACE(name##_tp, PARAMS(proto), PARAMS(args),		\
 			cpu_online(raw_smp_processor_id()),		\
 			PARAMS(void *__data, proto))
 
 #define DECLARE_TRACE_CONDITION(name, proto, args, cond)		\
-	__DECLARE_TRACE(name, PARAMS(proto), PARAMS(args),		\
+	__DECLARE_TRACE(name##_tp, PARAMS(proto), PARAMS(args),		\
 			cpu_online(raw_smp_processor_id()) && (PARAMS(cond)), \
 			PARAMS(void *__data, proto))
 
 #define DECLARE_TRACE_SYSCALL(name, proto, args)			\
+	__DECLARE_TRACE_SYSCALL(name##_tp, PARAMS(proto), PARAMS(args),	\
+				PARAMS(void *__data, proto))
+
+#define DECLARE_TRACE_EVENT(name, proto, args)				\
+	__DECLARE_TRACE(name, PARAMS(proto), PARAMS(args),		\
+			cpu_online(raw_smp_processor_id()),		\
+			PARAMS(void *__data, proto))
+
+#define DECLARE_TRACE_EVENT_CONDITION(name, proto, args, cond)		\
+	__DECLARE_TRACE(name, PARAMS(proto), PARAMS(args),		\
+			cpu_online(raw_smp_processor_id()) && (PARAMS(cond)), \
+			PARAMS(void *__data, proto))
+
+#define DECLARE_TRACE_EVENT_SYSCALL(name, proto, args)			\
 	__DECLARE_TRACE_SYSCALL(name, PARAMS(proto), PARAMS(args),	\
 				PARAMS(void *__data, proto))
 
@@ -591,32 +605,32 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
 
 #define DECLARE_EVENT_CLASS(name, proto, args, tstruct, assign, print)
 #define DEFINE_EVENT(template, name, proto, args)		\
-	DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
+	DECLARE_TRACE_EVENT(name, PARAMS(proto), PARAMS(args))
 #define DEFINE_EVENT_FN(template, name, proto, args, reg, unreg)\
-	DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
+	DECLARE_TRACE_EVENT(name, PARAMS(proto), PARAMS(args))
 #define DEFINE_EVENT_PRINT(template, name, proto, args, print)	\
-	DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
+	DECLARE_TRACE_EVENT(name, PARAMS(proto), PARAMS(args))
 #define DEFINE_EVENT_CONDITION(template, name, proto,		\
 			       args, cond)			\
-	DECLARE_TRACE_CONDITION(name, PARAMS(proto),		\
+	DECLARE_TRACE_EVENT_CONDITION(name, PARAMS(proto),	\
 				PARAMS(args), PARAMS(cond))
 
 #define TRACE_EVENT(name, proto, args, struct, assign, print)	\
-	DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
+	DECLARE_TRACE_EVENT(name, PARAMS(proto), PARAMS(args))
 #define TRACE_EVENT_FN(name, proto, args, struct,		\
 		assign, print, reg, unreg)			\
-	DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
-#define TRACE_EVENT_FN_COND(name, proto, args, cond, struct,		\
+	DECLARE_TRACE_EVENT(name, PARAMS(proto), PARAMS(args))
+#define TRACE_EVENT_FN_COND(name, proto, args, cond, struct,	\
 		assign, print, reg, unreg)			\
-	DECLARE_TRACE_CONDITION(name, PARAMS(proto),	\
+	DECLARE_TRACE_EVENT_CONDITION(name, PARAMS(proto),	\
 			PARAMS(args), PARAMS(cond))
 #define TRACE_EVENT_CONDITION(name, proto, args, cond,		\
 			      struct, assign, print)		\
-	DECLARE_TRACE_CONDITION(name, PARAMS(proto),		\
+	DECLARE_TRACE_EVENT_CONDITION(name, PARAMS(proto),	\
 				PARAMS(args), PARAMS(cond))
 #define TRACE_EVENT_SYSCALL(name, proto, args, struct, assign,	\
 			    print, reg, unreg)			\
-	DECLARE_TRACE_SYSCALL(name, PARAMS(proto), PARAMS(args))
+	DECLARE_TRACE_EVENT_SYSCALL(name, PARAMS(proto), PARAMS(args))
 
 #define TRACE_EVENT_FLAGS(event, flag)
 

include/trace/bpf_probe.h

@@ -119,14 +119,14 @@ static inline void bpf_test_buffer_##call(void)				\
 
 #undef DECLARE_TRACE
 #define DECLARE_TRACE(call, proto, args)				\
-	__BPF_DECLARE_TRACE(call, PARAMS(proto), PARAMS(args))		\
-	__DEFINE_EVENT(call, call, PARAMS(proto), PARAMS(args), 0)
+	__BPF_DECLARE_TRACE(call##_tp, PARAMS(proto), PARAMS(args))		\
+	__DEFINE_EVENT(call##_tp, call##_tp, PARAMS(proto), PARAMS(args), 0)
 
 #undef DECLARE_TRACE_WRITABLE
 #define DECLARE_TRACE_WRITABLE(call, proto, args, size) \
 	__CHECK_WRITABLE_BUF_SIZE(call, PARAMS(proto), PARAMS(args), size) \
-	__BPF_DECLARE_TRACE(call, PARAMS(proto), PARAMS(args)) \
-	__DEFINE_EVENT(call, call, PARAMS(proto), PARAMS(args), size)
+	__BPF_DECLARE_TRACE(call##_tp, PARAMS(proto), PARAMS(args)) \
+	__DEFINE_EVENT(call##_tp, call##_tp, PARAMS(proto), PARAMS(args), size)
 
 #include TRACE_INCLUDE(TRACE_INCLUDE_FILE)
 

include/trace/define_trace.h

@@ -74,10 +74,18 @@
 
 #undef DECLARE_TRACE
 #define DECLARE_TRACE(name, proto, args)	\
-	DEFINE_TRACE(name, PARAMS(proto), PARAMS(args))
+	DEFINE_TRACE(name##_tp, PARAMS(proto), PARAMS(args))
 
 #undef DECLARE_TRACE_CONDITION
 #define DECLARE_TRACE_CONDITION(name, proto, args, cond)	\
+	DEFINE_TRACE(name##_tp, PARAMS(proto), PARAMS(args))
+
+#undef DECLARE_TRACE_EVENT
+#define DECLARE_TRACE_EVENT(name, proto, args)	\
+	DEFINE_TRACE(name, PARAMS(proto), PARAMS(args))
+
+#undef DECLARE_TRACE_EVENT_CONDITION
+#define DECLARE_TRACE_EVENT_CONDITION(name, proto, args, cond)	\
 	DEFINE_TRACE(name, PARAMS(proto), PARAMS(args))
 
 /* If requested, create helpers for calling these tracepoints from Rust. */
@@ -115,6 +123,11 @@
 #undef DECLARE_TRACE_CONDITION
 #define DECLARE_TRACE_CONDITION(name, proto, args, cond)
 
+#undef DECLARE_TRACE_EVENT
+#define DECLARE_TRACE_EVENT(name, proto, args)
+#undef DECLARE_TRACE_EVENT_CONDITION
+#define DECLARE_TRACE_EVENT_CONDITION(name, proto, args, cond)
+
 #ifdef TRACEPOINTS_ENABLED
 #include <trace/trace_events.h>
 #include <trace/perf.h>
@@ -136,6 +149,8 @@
 #undef TRACE_HEADER_MULTI_READ
 #undef DECLARE_TRACE
 #undef DECLARE_TRACE_CONDITION
+#undef DECLARE_TRACE_EVENT
+#undef DECLARE_TRACE_EVENT_CONDITION
 
 /* Only undef what we defined in this file */
 #ifdef UNDEF_TRACE_INCLUDE_FILE

include/trace/events/sched.h

@@ -773,64 +773,64 @@ TRACE_EVENT(sched_wake_idle_without_ipi,
  *
  * Postfixed with _tp to make them easily identifiable in the code.
  */
-DECLARE_TRACE(pelt_cfs_tp,
+DECLARE_TRACE(pelt_cfs,
 	TP_PROTO(struct cfs_rq *cfs_rq),
 	TP_ARGS(cfs_rq));
 
-DECLARE_TRACE(pelt_rt_tp,
+DECLARE_TRACE(pelt_rt,
 	TP_PROTO(struct rq *rq),
 	TP_ARGS(rq));
 
-DECLARE_TRACE(pelt_dl_tp,
+DECLARE_TRACE(pelt_dl,
 	TP_PROTO(struct rq *rq),
 	TP_ARGS(rq));
 
-DECLARE_TRACE(pelt_hw_tp,
+DECLARE_TRACE(pelt_hw,
 	TP_PROTO(struct rq *rq),
 	TP_ARGS(rq));
 
-DECLARE_TRACE(pelt_irq_tp,
+DECLARE_TRACE(pelt_irq,
 	TP_PROTO(struct rq *rq),
 	TP_ARGS(rq));
 
-DECLARE_TRACE(pelt_se_tp,
+DECLARE_TRACE(pelt_se,
 	TP_PROTO(struct sched_entity *se),
 	TP_ARGS(se));
 
-DECLARE_TRACE(sched_cpu_capacity_tp,
+DECLARE_TRACE(sched_cpu_capacity,
 	TP_PROTO(struct rq *rq),
 	TP_ARGS(rq));
 
-DECLARE_TRACE(sched_overutilized_tp,
+DECLARE_TRACE(sched_overutilized,
 	TP_PROTO(struct root_domain *rd, bool overutilized),
 	TP_ARGS(rd, overutilized));
 
-DECLARE_TRACE(sched_util_est_cfs_tp,
+DECLARE_TRACE(sched_util_est_cfs,
 	TP_PROTO(struct cfs_rq *cfs_rq),
 	TP_ARGS(cfs_rq));
 
-DECLARE_TRACE(sched_util_est_se_tp,
+DECLARE_TRACE(sched_util_est_se,
 	TP_PROTO(struct sched_entity *se),
 	TP_ARGS(se));
 
-DECLARE_TRACE(sched_update_nr_running_tp,
+DECLARE_TRACE(sched_update_nr_running,
 	TP_PROTO(struct rq *rq, int change),
 	TP_ARGS(rq, change));
 
-DECLARE_TRACE(sched_compute_energy_tp,
+DECLARE_TRACE(sched_compute_energy,
 	TP_PROTO(struct task_struct *p, int dst_cpu, unsigned long energy,
 		 unsigned long max_util, unsigned long busy_time),
 	TP_ARGS(p, dst_cpu, energy, max_util, busy_time));
 
-DECLARE_TRACE(sched_entry_tp,
+DECLARE_TRACE(sched_entry,
 	TP_PROTO(bool preempt, unsigned long ip),
 	TP_ARGS(preempt, ip));
 
-DECLARE_TRACE(sched_exit_tp,
+DECLARE_TRACE(sched_exit,
 	TP_PROTO(bool is_switch, unsigned long ip),
 	TP_ARGS(is_switch, ip));
 
-DECLARE_TRACE_CONDITION(sched_set_state_tp,
+DECLARE_TRACE_CONDITION(sched_set_state,
 	TP_PROTO(struct task_struct *tsk, int state),
 	TP_ARGS(tsk, state),
 	TP_CONDITION(!!(tsk->__state) != !!state));

include/trace/events/tcp.h

@@ -259,7 +259,7 @@ TRACE_EVENT(tcp_retransmit_synack,
 		  __entry->saddr_v6, __entry->daddr_v6)
 );
 
-DECLARE_TRACE(tcp_cwnd_reduction_tp,
+DECLARE_TRACE(tcp_cwnd_reduction,
 	TP_PROTO(const struct sock *sk, int newly_acked_sacked,
 		 int newly_lost, int flag),
 	TP_ARGS(sk, newly_acked_sacked, newly_lost, flag)

tools/testing/selftests/bpf/progs/raw_tp_null.c

@@ -10,7 +10,7 @@ char _license[] SEC("license") = "GPL";
 int tid;
 int i;
 
-SEC("tp_btf/bpf_testmod_test_raw_tp_null")
+SEC("tp_btf/bpf_testmod_test_raw_tp_null_tp")
 int BPF_PROG(test_raw_tp_null, struct sk_buff *skb)
 {
 	struct task_struct *task = bpf_get_current_task_btf();

tools/testing/selftests/bpf/progs/raw_tp_null_fail.c

@@ -8,7 +8,7 @@
 char _license[] SEC("license") = "GPL";
 
 /* Ensure module parameter has PTR_MAYBE_NULL */
-SEC("tp_btf/bpf_testmod_test_raw_tp_null")
+SEC("tp_btf/bpf_testmod_test_raw_tp_null_tp")
 __failure __msg("R1 invalid mem access 'trusted_ptr_or_null_'")
 int test_raw_tp_null_bpf_testmod_test_raw_tp_null_arg_1(void *ctx) {
     asm volatile("r1 = *(u64 *)(r1 +0); r1 = *(u64 *)(r1 +0);" ::: __clobber_all);

tools/testing/selftests/bpf/progs/test_module_attach.c

@@ -19,7 +19,7 @@ int BPF_PROG(handle_raw_tp,
 
 __u32 raw_tp_bare_write_sz = 0;
 
-SEC("raw_tp/bpf_testmod_test_write_bare")
+SEC("raw_tp/bpf_testmod_test_write_bare_tp")
 int BPF_PROG(handle_raw_tp_bare,
 	     struct task_struct *task, struct bpf_testmod_test_write_ctx *write_ctx)
 {
@@ -31,7 +31,7 @@ int raw_tp_writable_bare_in_val = 0;
 int raw_tp_writable_bare_early_ret = 0;
 int raw_tp_writable_bare_out_val = 0;
 
-SEC("raw_tp.w/bpf_testmod_test_writable_bare")
+SEC("raw_tp.w/bpf_testmod_test_writable_bare_tp")
 int BPF_PROG(handle_raw_tp_writable_bare,
 	     struct bpf_testmod_test_writable_ctx *writable)
 {

tools/testing/selftests/bpf/progs/test_tp_btf_nullable.c

@@ -6,14 +6,14 @@
 #include "../test_kmods/bpf_testmod.h"
 #include "bpf_misc.h"
 
-SEC("tp_btf/bpf_testmod_test_nullable_bare")
+SEC("tp_btf/bpf_testmod_test_nullable_bare_tp")
 __failure __msg("R1 invalid mem access 'trusted_ptr_or_null_'")
 int BPF_PROG(handle_tp_btf_nullable_bare1, struct bpf_testmod_test_read_ctx *nullable_ctx)
 {
 	return nullable_ctx->len;
 }
 
-SEC("tp_btf/bpf_testmod_test_nullable_bare")
+SEC("tp_btf/bpf_testmod_test_nullable_bare_tp")
 int BPF_PROG(handle_tp_btf_nullable_bare2, struct bpf_testmod_test_read_ctx *nullable_ctx)
 {
 	if (nullable_ctx)