From 62a2d7f199996ef8cb16e08854edb44445db8d67 Mon Sep 17 00:00:00 2001
From: Daniel Xu <dxu@dxuuu.xyz>
Date: Wed, 14 Oct 2020 17:09:46 -0700
Subject: [PATCH 2/2] Detect 7 arg bpf_attach_uprobe() API

The 7th arg allows us to specify the usdt semaphore location.
---
 cmake/FindLibBcc.cmake | 11 +++++++++++
 src/CMakeLists.txt     |  3 +++
 src/attached_probe.cpp | 42 ++++++++++++++++++++++++++++++++++--------
 src/main.cpp           |  6 ++++++
 tests/CMakeLists.txt   |  3 +++
 5 files changed, 57 insertions(+), 8 deletions(-)

diff --git a/cmake/FindLibBcc.cmake b/cmake/FindLibBcc.cmake
index ec21627..76ab3b3 100644
--- a/cmake/FindLibBcc.cmake
+++ b/cmake/FindLibBcc.cmake
@@ -7,6 +7,8 @@
 #  LIBBCC_DEFINITIONS - Compiler switches required for using libbcc
 #  LIBBCC_BPF_LIBRARY_STATIC - libbpf static library (for static compilation)
 #  LIBBCC_LOADER_LIBRARY_STATIC - libbcc helper static library (for static compilation)
+#  LIBBCC_ATTACH_KPROBE_SIX_ARGS_SIGNATURE
+#  LIBBCC_ATTACH_UPROBE_SEVEN_ARGS_SIGNATURE
 #
 # Note that the shared libbcc binary has libbpf and bcc_loader already compiled in but
 # the static doesn't. So when creating a static build those have to be included too.
@@ -92,5 +94,14 @@ int main(void) {
   return 0;
 }
 " LIBBCC_ATTACH_KPROBE_SIX_ARGS_SIGNATURE)
+
+CHECK_CXX_SOURCE_COMPILES("
+#include <bcc/libbpf.h>
+
+int main(void) {
+  bpf_attach_uprobe(0, BPF_PROBE_ENTRY, \"\", \"\", 0, 0, 0);
+  return 0;
+}
+" LIBBCC_ATTACH_UPROBE_SEVEN_ARGS_SIGNATURE)
 SET(CMAKE_REQUIRED_LIBRARIES)
 endif()
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 35d2400..b4eee17 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -82,6 +82,9 @@ endif(HAVE_BFD_DISASM)
 if(LIBBCC_ATTACH_KPROBE_SIX_ARGS_SIGNATURE)
   target_compile_definitions(bpftrace PRIVATE LIBBCC_ATTACH_KPROBE_SIX_ARGS_SIGNATURE)
 endif(LIBBCC_ATTACH_KPROBE_SIX_ARGS_SIGNATURE)
+if(LIBBCC_ATTACH_UPROBE_SEVEN_ARGS_SIGNATURE)
+  target_compile_definitions(bpftrace PRIVATE LIBBCC_ATTACH_UPROBE_SEVEN_ARGS_SIGNATURE)
+endif(LIBBCC_ATTACH_UPROBE_SEVEN_ARGS_SIGNATURE)
 
 if (ALLOW_UNSAFE_PROBE)
   target_compile_definitions(bpftrace PRIVATE HAVE_UNSAFE_PROBE)
diff --git a/src/attached_probe.cpp b/src/attached_probe.cpp
index afad9ed..811226a 100644
--- a/src/attached_probe.cpp
+++ b/src/attached_probe.cpp
@@ -790,12 +790,23 @@ void AttachedProbe::attach_uprobe(bool safe_mode)
 {
   resolve_offset_uprobe(safe_mode);
 
-  int perf_event_fd = bpf_attach_uprobe(progfd_,
-                                        attachtype(probe_.type),
-                                        eventname().c_str(),
-                                        probe_.path.c_str(),
-                                        offset_,
-                                        probe_.pid);
+  int perf_event_fd =
+#ifdef LIBBCC_ATTACH_UPROBE_SEVEN_ARGS_SIGNATURE
+      bpf_attach_uprobe(progfd_,
+                        attachtype(probe_.type),
+                        eventname().c_str(),
+                        probe_.path.c_str(),
+                        offset_,
+                        probe_.pid,
+                        0);
+#else
+      bpf_attach_uprobe(progfd_,
+                        attachtype(probe_.type),
+                        eventname().c_str(),
+                        probe_.path.c_str(),
+                        offset_,
+                        probe_.pid);
+#endif // LIBBCC_ATTACH_UPROBE_SEVEN_ARGS_SIGNATURE
 
   if (perf_event_fd < 0)
     throw std::runtime_error("Error attaching probe: " + probe_.name);
@@ -904,8 +915,23 @@ void AttachedProbe::attach_usdt(int pid)
 
   offset_ = resolve_offset(probe_.path, probe_.attach_point, probe_.loc);
 
-  int perf_event_fd = bpf_attach_uprobe(progfd_, attachtype(probe_.type),
-      eventname().c_str(), probe_.path.c_str(), offset_, pid == 0 ? -1 : pid);
+  int perf_event_fd =
+#ifdef LIBBCC_ATTACH_UPROBE_SEVEN_ARGS_SIGNATURE
+      bpf_attach_uprobe(progfd_,
+                        attachtype(probe_.type),
+                        eventname().c_str(),
+                        probe_.path.c_str(),
+                        offset_,
+                        pid == 0 ? -1 : pid,
+                        0);
+#else
+      bpf_attach_uprobe(progfd_,
+                        attachtype(probe_.type),
+                        eventname().c_str(),
+                        probe_.path.c_str(),
+                        offset_,
+                        pid == 0 ? -1 : pid);
+#endif // LIBBCC_ATTACH_UPROBE_SEVEN_ARGS_SIGNATURE
 
   if (perf_event_fd < 0)
   {
diff --git a/src/main.cpp b/src/main.cpp
index 71a06c1..bf76da8 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -155,6 +155,12 @@ static int info()
             << "yes" << std::endl;
 #else
             << "no" << std::endl;
+#endif
+  std::cerr << "  bcc bpf_attach_uprobe refcount: "
+#ifdef LIBBCC_ATTACH_UPROBE_SEVEN_ARGS_SIGNATURE
+            << "yes" << std::endl;
+#else
+            << "no" << std::endl;
 #endif
   std::cerr << "  libbpf: "
 #ifdef HAVE_LIBBPF
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index ed0ccf8..d94868a 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -103,6 +103,9 @@ endif(HAVE_BFD_DISASM)
 if(LIBBCC_ATTACH_KPROBE_SIX_ARGS_SIGNATURE)
   target_compile_definitions(bpftrace_test PRIVATE LIBBCC_ATTACH_KPROBE_SIX_ARGS_SIGNATURE)
 endif(LIBBCC_ATTACH_KPROBE_SIX_ARGS_SIGNATURE)
+if(LIBBCC_ATTACH_UPROBE_SEVEN_ARGS_SIGNATURE)
+  target_compile_definitions(bpftrace_test PRIVATE LIBBCC_ATTACH_UPROBE_SEVEN_ARGS_SIGNATURE)
+endif(LIBBCC_ATTACH_UPROBE_SEVEN_ARGS_SIGNATURE)
 
 target_link_libraries(bpftrace_test arch ast parser resources)
 
-- 
2.25.4