fgraph: Get ftrace recursion lock in function_graph_enter

Get the ftrace recursion lock in the generic function_graph_enter()
instead of each architecture code.
This changes all function_graph tracer callbacks running in
non-preemptive state. On x86 and powerpc, this is by default, but
on the other architecutres, this will be new.

Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Florent Revest <revest@chromium.org>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: bpf <bpf@vger.kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Alan Maguire <alan.maguire@oracle.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Naveen N Rao <naveen@kernel.org>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/173379653720.973433.18438622234884980494.stgit@devnote2
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

arch/powerpc/kernel/trace/ftrace.c

@@ -658,22 +658,16 @@ void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
 		       struct ftrace_ops *op, struct ftrace_regs *fregs)
 {
 	unsigned long sp = arch_ftrace_regs(fregs)->regs.gpr[1];
-	int bit;
 
 	if (unlikely(ftrace_graph_is_dead()))
 		goto out;
 
 	if (unlikely(atomic_read(&current->tracing_graph_pause)))
 		goto out;
 
-	bit = ftrace_test_recursion_trylock(ip, parent_ip);
-	if (bit < 0)
-		goto out;
-
 	if (!function_graph_enter(parent_ip, ip, 0, (unsigned long *)sp))
 		parent_ip = ppc_function_entry(return_to_handler);
 
-	ftrace_test_recursion_unlock(bit);
 out:
 	arch_ftrace_regs(fregs)->regs.link = parent_ip;
 }

arch/powerpc/kernel/trace/ftrace_64_pg.c

@@ -790,24 +790,18 @@ static unsigned long
 __prepare_ftrace_return(unsigned long parent, unsigned long ip, unsigned long sp)
 {
 	unsigned long return_hooker;
-	int bit;
 
 	if (unlikely(ftrace_graph_is_dead()))
 		goto out;
 
 	if (unlikely(atomic_read(&current->tracing_graph_pause)))
 		goto out;
 
-	bit = ftrace_test_recursion_trylock(ip, parent);
-	if (bit < 0)
-		goto out;
-
 	return_hooker = ppc_function_entry(return_to_handler);
 
 	if (!function_graph_enter(parent, ip, 0, (unsigned long *)sp))
 		parent = return_hooker;
 
-	ftrace_test_recursion_unlock(bit);
 out:
 	return parent;
 }

arch/x86/kernel/ftrace.c

@@ -615,7 +615,6 @@ void prepare_ftrace_return(unsigned long ip, unsigned long *parent,
 			   unsigned long frame_pointer)
 {
 	unsigned long return_hooker = (unsigned long)&return_to_handler;
-	int bit;
 
 	/*
 	 * When resuming from suspend-to-ram, this function can be indirectly
@@ -635,14 +634,8 @@ void prepare_ftrace_return(unsigned long ip, unsigned long *parent,
 	if (unlikely(atomic_read(&current->tracing_graph_pause)))
 		return;
 
-	bit = ftrace_test_recursion_trylock(ip, *parent);
-	if (bit < 0)
-		return;
-
 	if (!function_graph_enter(*parent, ip, frame_pointer, parent))
 		*parent = return_hooker;
-
-	ftrace_test_recursion_unlock(bit);
 }
 
 #ifdef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS

kernel/trace/fgraph.c

@@ -650,8 +650,13 @@ int function_graph_enter(unsigned long ret, unsigned long func,
 	struct ftrace_graph_ent trace;
 	unsigned long bitmap = 0;
 	int offset;
+	int bit;
 	int i;
 
+	bit = ftrace_test_recursion_trylock(func, ret);
+	if (bit < 0)
+		return -EBUSY;
+
 	trace.func = func;
 	trace.depth = ++current->curr_ret_depth;
 
@@ -697,12 +702,13 @@ int function_graph_enter(unsigned long ret, unsigned long func,
 	 * flag, set that bit always.
 	 */
 	set_bitmap(current, offset, bitmap | BIT(0));
-
+	ftrace_test_recursion_unlock(bit);
 	return 0;
  out_ret:
 	current->curr_ret_stack -= FGRAPH_FRAME_OFFSET + 1;
  out:
 	current->curr_ret_depth--;
+	ftrace_test_recursion_unlock(bit);
 	return -EBUSY;
 }