[PATCH 26/34] perf clang jit: Actually JIT and hook in bpf loader

[Wang Nan]

Makes perf_clang__compile_bpf() actually uses clang jit to compile perf
hooks. Returns a map through perf_clang__compile_bpf(), and set hooks
after bpf_object is created.

After this path jitting takes actions for bpf loader. For example:
  $ cat ./test.c
  /******************************************************/
  #define SEC(name) __attribute__((section(name), used))
  SEC("dofork=_do_fork")
  int dofork(void *ctx)
  {
      return 0;
  }
  extern int printf(const char *fmt, ...);
  SEC("perfhook:record_start")
  void record_start(void)
  {
      printf("Welcom to perf record\n");
  }
  SEC("perfhook:record_end")
  void record_end(void)
  {
      printf("Goodbye, perf record\n");
  }
  char _license[] SEC("license") = "GPL";
  int _version SEC("version") = LINUX_VERSION_CODE;
  /******************************************************/
  $ perf record -e ./test.c sleep 1
  Welcom to perf record
  [ perf record: Woken up 1 times to write data ]
  Goodbye, perf record
  [ perf record: Captured and wrote 0.014 MB perf.data ]

Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxx>
Cc: He Kuang <hekuang@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Zefan Li <lizefan@xxxxxxxxxx>
Cc: pi3orama@xxxxxxx
---
 tools/perf/util/bpf-loader.c  | 11 ++++++++++-
 tools/perf/util/c++/clang-c.h | 18 ++++++++++++++++--
 tools/perf/util/c++/clang.cpp | 28 +++++++++++++++++++++++++++-
 3 files changed, 53 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index a0ea334f..e50045f 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -85,9 +85,11 @@ struct bpf_object *bpf__prepare_load(const char *filename, bool source)
 		int err;
 		void *obj_buf;
 		size_t obj_buf_sz;
+		jitted_funcs_map_t jitted_funcs_map;
 
 		perf_clang__init();
-		err = perf_clang__compile_bpf(filename, &obj_buf, &obj_buf_sz);
+		err = perf_clang__compile_bpf(filename, &obj_buf,
+					      &obj_buf_sz, &jitted_funcs_map);
 		perf_clang__cleanup();
 		if (err) {
 			pr_warning("bpf: builtin compiling failed: %d, try external compiler\n", err);
@@ -101,6 +103,13 @@ struct bpf_object *bpf__prepare_load(const char *filename, bool source)
 		if (!IS_ERR(obj) && llvm_param.dump_obj)
 			llvm__dump_obj(filename, obj_buf, obj_buf_sz);
 
+		/*
+		 * Call perf_clang__hook_jitted_func even IS_ERR(obj) to make sure
+		 * the C++ map pointer is deleted.
+		 */
+		if (jitted_funcs_map)
+			perf_clang__hook_jitted_func(jitted_funcs_map, obj, IS_ERR(obj));
+
 		free(obj_buf);
 	} else
 		obj = bpf_object__open(filename);
diff --git a/tools/perf/util/c++/clang-c.h b/tools/perf/util/c++/clang-c.h
index 9f75e41..021b1ad 100644
--- a/tools/perf/util/c++/clang-c.h
+++ b/tools/perf/util/c++/clang-c.h
@@ -8,6 +8,7 @@
 extern "C" {
 #endif
 
+typedef void *jitted_funcs_map_t;
 #ifdef HAVE_LIBCLANGLLVM_SUPPORT
 extern void perf_clang__init(void);
 extern void perf_clang__cleanup(void);
@@ -20,7 +21,11 @@ extern void test__clang_callback(int x);
 
 extern int perf_clang__compile_bpf(const char *filename,
 				   void **p_obj_buf,
-				   size_t *p_obj_buf_sz);
+				   size_t *p_obj_buf_sz,
+				   jitted_funcs_map_t *p_funcs_map);
+
+extern int
+perf_clang__hook_jitted_func(jitted_funcs_map_t map, void *ctx, bool is_err);
 #else
 
 
@@ -34,7 +39,16 @@ static inline int test__clang_jit(void) { return -1;}
 static inline int
 perf_clang__compile_bpf(const char *filename __maybe_unused,
 			void **p_obj_buf __maybe_unused,
-			size_t *p_obj_buf_sz __maybe_unused)
+			size_t *p_obj_buf_sz __maybe_unused,
+			jitted_funcs_map_t *p_funcs_map __maybe_unused)
+{
+	return -ENOTSUP;
+}
+
+static inline int
+perf_clang__hook_jitted_func(jitted_funcs_map_t map __maybe_unused,
+			     void *ctx __maybe_unused,
+			     bool is_err __maybe_unused)
 {
 	return -ENOTSUP;
 }
diff --git a/tools/perf/util/c++/clang.cpp b/tools/perf/util/c++/clang.cpp
index 325fbe4..f2608f5 100644
--- a/tools/perf/util/c++/clang.cpp
+++ b/tools/perf/util/c++/clang.cpp
@@ -388,7 +388,8 @@ void perf_clang__cleanup(void)
 
 int perf_clang__compile_bpf(const char *_filename,
 			    void **p_obj_buf,
-			    size_t *p_obj_buf_sz)
+			    size_t *p_obj_buf_sz,
+			    jitted_funcs_map_t *p_funcs_map)
 {
 	using namespace perf;
 
@@ -415,6 +416,31 @@ int perf_clang__compile_bpf(const char *_filename,
 	memcpy(buffer, O->data(), size);
 	*p_obj_buf = buffer;
 	*p_obj_buf_sz = size;
+
+	if (M->doJIT())
+		return -1;
+
+	if (p_funcs_map)
+		*p_funcs_map = (jitted_funcs_map_t)(M->copyJITResult());
+	return 0;
+}
+
+int perf_clang__hook_jitted_func(jitted_funcs_map_t map, void *ctx, bool is_err)
+{
+	std::unique_ptr<perf::PerfModule::HookMap>
+		hook_map((perf::PerfModule::HookMap *)map);
+
+	/* Do nothing but ensure map is deleted */
+	if (is_err)
+		return -1;
+
+	for (auto i : *hook_map) {
+		const char *hook_name = i.first.c_str();
+		perf_hook_func_t hook_func = i.second;
+
+		if (perf_hooks__set_hook(hook_name, hook_func, ctx))
+			return -1;
+	}
 	return 0;
 }
 }
-- 
2.10.1