From 1da2dcf30d8172e424d57a01a2c24f84df8ea719 Mon Sep 17 00:00:00 2001
From: Nick Richardson <richardsonnick@meta.com>
Date: Fri, 10 Feb 2023 09:22:13 -0800
Subject: [PATCH] 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: (https://github.com/facebookincubator/fizz/issues/84)

Reviewed By: mingtaoy

Differential Revision: D42998995

fbshipit-source-id: a2d1eb0c98823fc90b9886b98e7e5e671362af63
---
 fizz/CMakeLists.txt               |  1 +
 fizz/client/AsyncFizzClient-inl.h | 12 +++++-------
 fizz/client/AsyncFizzClient.h     |  2 +-
 fizz/server/AsyncFizzServer-inl.h |  7 ++-----
 fizz/server/AsyncFizzServer.h     |  3 +--
 fizz/util/Tracing.cpp             | 21 +++++++++++++++++++++
 fizz/util/Tracing.h               | 22 ++++++++++++++++++++++
 7 files changed, 53 insertions(+), 15 deletions(-)
 create mode 100644 fizz/util/Tracing.cpp
 create mode 100644 fizz/util/Tracing.h

diff --git a/fizz/CMakeLists.txt b/fizz/CMakeLists.txt
index 5c8a575bf05..21179a35898 100644
--- a/fizz/CMakeLists.txt
+++ b/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
diff --git a/fizz/client/AsyncFizzClient-inl.h b/fizz/client/AsyncFizzClient-inl.h
index d1dc6d803fc..75301a22432 100644
--- a/fizz/client/AsyncFizzClient-inl.h
+++ b/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>
diff --git a/fizz/client/AsyncFizzClient.h b/fizz/client/AsyncFizzClient.h
index fae048c9c61..f113a40576a 100644
--- a/fizz/client/AsyncFizzClient.h
+++ b/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 {
diff --git a/fizz/server/AsyncFizzServer-inl.h b/fizz/server/AsyncFizzServer-inl.h
index d3f3d13b1a5..86666e6c4dc 100644
--- a/fizz/server/AsyncFizzServer-inl.h
+++ b/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);
 }
 
diff --git a/fizz/server/AsyncFizzServer.h b/fizz/server/AsyncFizzServer.h
index a63426ba6a9..0ea9b57f0b5 100644
--- a/fizz/server/AsyncFizzServer.h
+++ b/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 {
diff --git a/fizz/util/Tracing.cpp b/fizz/util/Tracing.cpp
new file mode 100644
index 00000000000..fd22535d6fa
--- /dev/null
+++ b/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
diff --git a/fizz/util/Tracing.h b/fizz/util/Tracing.h
new file mode 100644
index 00000000000..2275a4cde0b
--- /dev/null
+++ b/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