perf/ftrace: Add recursion protection to the ftrace callback

If a ftrace callback does not supply its own recursion protection and
does not set the RECURSION_SAFE flag in its ftrace_ops, then ftrace will
make a helper trampoline to do so before calling the callback instead of
just calling the callback directly.

The default for ftrace_ops is going to change. It will expect that handlers
provide their own recursion protection, unless its ftrace_ops states
otherwise.

Link: https://lkml.kernel.org/r/20201028115613.444477858@goodmis.org
Link: https://lkml.kernel.org/r/20201106023547.466892083@goodmis.org
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh  Poimboeuf <jpoimboe@redhat.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Miroslav Benes <mbenes@suse.cz>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
index 643e0b1..fd58d83 100644 (file)
--- a/kernel/trace/trace_event_perf.c
+++ b/kernel/trace/trace_event_perf.c
@@ -439,10 +439,15 @@ perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip,
        struct hlist_head head;
        struct pt_regs regs;
        int rctx;
+       int bit;
 
        if ((unsigned long)ops->private != smp_processor_id())
                return;
 
+       bit = ftrace_test_recursion_trylock();
+       if (bit < 0)
+               return;
+
        event = container_of(ops, struct perf_event, ftrace_ops);
 
        /*
@@ -463,13 +468,15 @@ perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip,
 
        entry = perf_trace_buf_alloc(ENTRY_SIZE, NULL, &rctx);
        if (!entry)
-               return;
+               goto out;
 
        entry->ip = ip;
        entry->parent_ip = parent_ip;
        perf_trace_buf_submit(entry, ENTRY_SIZE, rctx, TRACE_FN,
                              1, &regs, &head, NULL);
 
+out:
+       ftrace_test_recursion_unlock(bit);
 #undef ENTRY_SIZE
 }