ftrace: Add perf ksymbol events for ftrace trampolines

Symbols are needed for tools to describe instruction addresses. Pages
allocated for ftrace's purposes need symbols to be created for them.
Add such symbols to be visible via perf ksymbol events.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200512121922.8997-8-adrian.hunter@intel.com

diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index e1a4179..52ca209 100644 (file)
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -1051,7 +1051,7 @@ enum perf_record_ksymbol_type {
        PERF_RECORD_KSYMBOL_TYPE_BPF            = 1,
        /*
         * Out of line code such as kprobe-replaced instructions or optimized
-        * kprobes.
+        * kprobes or ftrace trampolines.
         */
        PERF_RECORD_KSYMBOL_TYPE_OOL            = 2,
        PERF_RECORD_KSYMBOL_TYPE_MAX            /* non-ABI */

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 31675b2..2baaf77 100644 (file)
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2790,8 +2790,13 @@ static void ftrace_remove_trampoline_from_kallsyms(struct ftrace_ops *ops)
 static void ftrace_trampoline_free(struct ftrace_ops *ops)
 {
        if (ops && (ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP) &&
-           ops->trampoline)
+           ops->trampoline) {
+               perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_OOL,
+                                  ops->trampoline, ops->trampoline_size,
+                                  true, FTRACE_TRAMPOLINE_SYM);
+               /* Remove from kallsyms after the perf events */
                ftrace_remove_trampoline_from_kallsyms(ops);
+       }
 
        arch_ftrace_trampoline_free(ops);
 }
@@ -6805,8 +6810,13 @@ static void ftrace_update_trampoline(struct ftrace_ops *ops)
 
        arch_ftrace_update_trampoline(ops);
        if (ops->trampoline && ops->trampoline != trampoline &&
-           (ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
+           (ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP)) {
+               /* Add to kallsyms before the perf events */
                ftrace_add_trampoline_to_kallsyms(ops);
+               perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_OOL,
+                                  ops->trampoline, ops->trampoline_size, false,
+                                  FTRACE_TRAMPOLINE_SYM);
+       }
 }
 
 void ftrace_init_trace_array(struct trace_array *tr)