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 e1a4179144a136fd5126fdb688c5d2431e71ef23..52ca2093831cc7b5010c6e180661937537cf5e69 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 31675b209db2a6303e32a52663d9a4f0c61e40dc..2baaf77165372a3b3637b817bb81c056ca603558 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)