Fix "symbol in discarded section" linker error for bpf probes

Summary:
Fixes gnu ld linker error where the nop code point injected by a bpf probe was being discarded at linking time. The bpf probe would add reference from the .notes section to this discared func location and a "(...) defined in discarded section (...) referenced in section .note.stapsdt" error would occur.

Previously tracked by github issue: (#84)

Reviewed By: mingtaoy

Differential Revision: D42998995

fbshipit-source-id: a2d1eb0c98823fc90b9886b98e7e5e671362af63

fizz/CMakeLists.txt

@@ -218,6 +218,7 @@ set(FIZZ_SOURCES
   client/EarlyDataRejectionPolicy.cpp
   tool/FizzCommandCommon.cpp
   util/FizzUtil.cpp
+  util/Tracing.cpp
 )
 
 add_library(fizz

fizz/client/AsyncFizzClient-inl.h

@@ -608,16 +608,14 @@ void AsyncFizzClientT<SM>::ActionMoveVisitor::operator()(
 template <typename SM>
 void AsyncFizzClientT<SM>::ActionMoveVisitor::operator()(
     SecretAvailable& secret) {
-  client_.secretAvailable(secret.secret);
-#if 0
-  FOLLY_SDT(
-      fizz,
-      fizz_secret_available,
+  fizz_probe_secret_available(
       secret.secret.secret.size(),
       secret.secret.secret.data(),
-      secret.secret.type,
+      KeyLogWriter::secretToNSSLabel(secret.secret.type)
+          .value_or(std::numeric_limits<KeyLogWriter::Label>::max()),
       client_.getClientRandom()->data());
-#endif
+
+  client_.secretAvailable(secret.secret);
 }
 
 template <typename SM>

fizz/client/AsyncFizzClient.h

@@ -15,8 +15,8 @@
 #include <fizz/client/FizzClientContext.h>
 #include <fizz/protocol/AsyncFizzBase.h>
 #include <fizz/protocol/Exporter.h>
+#include <fizz/util/Tracing.h>
 #include <folly/io/SocketOptionMap.h>
-#include <folly/tracing/StaticTracepoint.h>
 
 namespace fizz {
 namespace client {

fizz/server/AsyncFizzServer-inl.h

@@ -343,16 +343,13 @@ void AsyncFizzServerT<SM>::ActionMoveVisitor::operator()(
 template <typename SM>
 void AsyncFizzServerT<SM>::ActionMoveVisitor::operator()(
     SecretAvailable& secret) {
-#if 0
-  FOLLY_SDT(
-      fizz,
-      fizz_secret_available,
+  fizz_probe_secret_available(
       secret.secret.secret.size(),
       secret.secret.secret.data(),
       KeyLogWriter::secretToNSSLabel(secret.secret.type)
           .value_or(std::numeric_limits<KeyLogWriter::Label>::max()),
       server_.getClientRandom()->data());
-#endif
+
   server_.secretAvailable(secret.secret);
 }
 

fizz/server/AsyncFizzServer.h

@@ -13,8 +13,7 @@
 #include <fizz/server/FizzServer.h>
 #include <fizz/server/FizzServerContext.h>
 #include <fizz/server/ServerProtocol.h>
-#include <fizz/util/KeyLogWriter.h>
-#include <folly/tracing/StaticTracepoint.h>
+#include <fizz/util/Tracing.h>
 
 namespace fizz {
 namespace server {

fizz/util/Tracing.cpp

@@ -0,0 +1,21 @@
+#include <fizz/util/Tracing.h>
+#include <folly/tracing/StaticTracepoint.h>
+
+namespace fizz {
+extern "C" {
+void fizz_probe_secret_available(
+    long unsigned int secretSize,
+    unsigned char* secretData,
+    fizz::KeyLogWriter::Label nssLabel,
+    unsigned char* clientRandom) {
+  FOLLY_SDT(
+      fizz,
+      fizz_secret_available,
+      secretSize,
+      secretData,
+      nssLabel,
+      clientRandom);
+}
+}
+
+} // namespace fizz

fizz/util/Tracing.h

@@ -0,0 +1,22 @@
+/*
+ *  Copyright (c) 2023-present, Facebook, Inc.
+ *  All rights reserved.
+ *
+ *  This source code is licensed under the BSD-style license found in the
+ *  LICENSE file in the root directory of this source tree.
+ */
+
+#pragma once
+#include <fizz/util/KeyLogWriter.h>
+
+namespace fizz {
+
+extern "C" {
+void fizz_probe_secret_available(
+    long unsigned int secretSize,
+    unsigned char* secretData,
+    fizz::KeyLogWriter::Label nssLabel,
+    unsigned char* clientRandom);
+}
+
+} // namespace fizz