[PATCH v5 0/2] Remove redundant trace-cmd plugin handling logic

[PATCH v5 0/2] Remove redundant trace-cmd plugin handling logic

[Tzvetomir Stoyanov (VMware)]

Currently there are no trace-cmd related plugins, all of them
are designed to be used with libtraceeevnt. As both libtraceevent
and trace-cmd have logic for managing plugins, the one in trace-cmd
is redundant. Those redundant code is removed and replaced with calls
to libtraceeevnt plugin APIs. When trace-cmd has to load any plugins,
it uses libtraceeevnt to do the job.

All existing plugins are moved from plugins/ to lib/traceevent/plugins
directory, as all of them are designed to be used with the traceevent
library.

An initial infrastructure for trace-cmd specific plugins is added - 
new lib/trace-cmd/plugins directory and an initial set of APIs
for working with trace-cmd plugins.

[
  changes:
   - Removed accepted patches from the patch set.
   - Moved logic which loads traceevent development
     plugins from libtraceevent to trace-cmd application.
]

Tzvetomir Stoyanov (VMware) (2):
  trace-cmd: Load libtraceevent plugins from build folder, if exists.
  trace-cmd: Add initial infrastructure for trace-cmd specific plugins.

 .gitignore                       |   1 +
 Makefile                         |  40 +++-
 include/trace-cmd/trace-cmd.h    |  42 +++++
 include/traceevent/event-parse.h |   3 +
 lib/trace-cmd/Makefile           |   1 +
 lib/trace-cmd/plugins/Makefile   |  58 ++++++
 lib/trace-cmd/trace-input.c      |   7 +-
 lib/trace-cmd/trace-plugin.c     | 313 +++++++++++++++++++++++++++++++
 lib/trace-cmd/trace-util.c       |  46 +++++
 lib/traceevent/event-plugin.c    |  38 ++++
 tracecmd/trace-check-events.c    |   7 +-
 tracecmd/trace-list.c            |  14 +-
 12 files changed, 538 insertions(+), 32 deletions(-)
 create mode 100644 lib/trace-cmd/plugins/Makefile
 create mode 100644 lib/trace-cmd/trace-plugin.c

-- 
2.21.0

[PATCH v5 1/2] trace-cmd: Load libtraceevent plugins from build folder, if exists.

[Tzvetomir Stoyanov (VMware)]

When a development version of trace-cmd is built and run on the machine,
by default it loads only installed plugins, from system directories.
Thus, the development plugins will not be loaded. To simplify the development
process, a new logic is added:
  At plugins load time, check the location of trace-cmd application and look
  for "plugins" directory around it. If found, load plugins from it. Those
  plugins will be loaded last, so in case of duplication the "development"
  plugins win.
A two new APIs are introduced to libtraceevent, in order to accomplish this
logic:
 tep_load_plugins_dir() - loads tep plugins from a specific directory.
 tep_plugins_append() - Append two plugin lists.

Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
---
 include/trace-cmd/trace-cmd.h    |  2 ++
 include/traceevent/event-parse.h |  3 +++
 lib/trace-cmd/trace-input.c      |  7 +----
 lib/trace-cmd/trace-util.c       | 46 ++++++++++++++++++++++++++++++++
 lib/traceevent/event-plugin.c    | 38 ++++++++++++++++++++++++++
 tracecmd/trace-check-events.c    |  7 +----
 tracecmd/trace-list.c            | 14 ++--------
 7 files changed, 93 insertions(+), 24 deletions(-)

diff --git a/include/trace-cmd/trace-cmd.h b/include/trace-cmd/trace-cmd.h
index 4090eba..f692783 100644
--- a/include/trace-cmd/trace-cmd.h
+++ b/include/trace-cmd/trace-cmd.h
@@ -24,6 +24,8 @@ void tracecmd_parse_ftrace_printk(struct tep_handle *pevent, char *file, unsigne
 extern int tracecmd_disable_sys_plugins;
 extern int tracecmd_disable_plugins;
 
+struct tep_plugin_list *trace_load_tep_plugins(struct tep_handle *tep);
+
 char **tracecmd_event_systems(const char *tracing_dir);
 char **tracecmd_system_events(const char *tracing_dir, const char *system);
 struct tep_handle *tracecmd_local_events(const char *tracing_dir);
diff --git a/include/traceevent/event-parse.h b/include/traceevent/event-parse.h
index 5dff952..10320d5 100644
--- a/include/traceevent/event-parse.h
+++ b/include/traceevent/event-parse.h
@@ -380,6 +380,9 @@ struct tep_plugin_list;
 #define INVALID_PLUGIN_LIST_OPTION	((char **)((unsigned long)-1))
 
 struct tep_plugin_list *tep_load_plugins(struct tep_handle *tep);
+struct tep_plugin_list *tep_load_plugins_dir(struct tep_handle *tep, char *path);
+void tep_plugins_append(struct tep_plugin_list *list1,
+			struct tep_plugin_list *list2);
 void tep_unload_plugins(struct tep_plugin_list *plugin_list,
 			struct tep_handle *tep);
 void tep_load_plugins_hook(struct tep_handle *tep, const char *suffix,
diff --git a/lib/trace-cmd/trace-input.c b/lib/trace-cmd/trace-input.c
index 6102eb3..bdeb2bc 100644
--- a/lib/trace-cmd/trace-input.c
+++ b/lib/trace-cmd/trace-input.c
@@ -2886,15 +2886,10 @@ struct tracecmd_input *tracecmd_alloc_fd(int fd)
 	if (!handle->pevent)
 		goto failed_read;
 
-	if (tracecmd_disable_plugins)
-		tep_set_flag(handle->pevent, TEP_DISABLE_PLUGINS);
-	if (tracecmd_disable_sys_plugins)
-		tep_set_flag(handle->pevent, TEP_DISABLE_SYS_PLUGINS);
-
 	/* register default ftrace functions first */
 	tracecmd_ftrace_overrides(handle, &handle->finfo);
 
-	handle->plugin_list = tep_load_plugins(handle->pevent);
+	handle->plugin_list = trace_load_tep_plugins(handle->pevent);
 
 	tep_set_file_bigendian(handle->pevent, buf[0]);
 	tep_set_local_bigendian(handle->pevent, tracecmd_host_bigendian());
diff --git a/lib/trace-cmd/trace-util.c b/lib/trace-cmd/trace-util.c
index 8aa3b6c..303337d 100644
--- a/lib/trace-cmd/trace-util.c
+++ b/lib/trace-cmd/trace-util.c
@@ -860,6 +860,52 @@ void trace_util_free_plugin_files(char **files)
 	free(files);
 }
 
+static char *get_source_plugins_dir(void)
+{
+	char *p, path[PATH_MAX+1];
+	int ret;
+
+	ret = readlink("/proc/self/exe", path, PATH_MAX);
+	if (ret > PATH_MAX || ret < 0)
+		return NULL;
+
+	dirname(path);
+	p = strrchr(path, '/');
+	if (!p)
+		return NULL;
+	/* Check if we are in the the source tree */
+	if (strcmp(p, "/tracecmd") != 0)
+		return NULL;
+
+	strcpy(p, "/lib/traceevent/plugins");
+	return strdup(path);
+}
+
+struct tep_plugin_list*
+trace_load_tep_plugins(struct tep_handle *tep)
+{
+	struct tep_plugin_list *list_dev;
+	struct tep_plugin_list *list;
+	char *path;
+
+	if (tracecmd_disable_plugins)
+		tep_set_flag(tep, TEP_DISABLE_PLUGINS);
+	if (tracecmd_disable_sys_plugins)
+		tep_set_flag(tep, TEP_DISABLE_SYS_PLUGINS);
+
+	list = tep_load_plugins(tep);
+
+	path = get_source_plugins_dir();
+	if (path) {
+		list_dev = tep_load_plugins_dir(tep, path);
+		tep_plugins_append(list_dev, list);
+		list = list_dev;
+		free(path);
+	}
+
+	return list;
+}
+
 char *tracecmd_get_tracing_file(const char *name)
 {
 	static const char *tracing;
diff --git a/lib/traceevent/event-plugin.c b/lib/traceevent/event-plugin.c
index 6ea4ac0..ce9d53c 100644
--- a/lib/traceevent/event-plugin.c
+++ b/lib/traceevent/event-plugin.c
@@ -599,6 +599,44 @@ tep_load_plugins(struct tep_handle *tep)
 	return list;
 }
 
+/**
+ * tep_load_plugins_dir - load traceevent plugins from a directory
+ * @tep: Trace event handler.
+ * @path: Path to a directory. All files with extension .so in that
+ *	  directory will be loaded as plugins.
+ *
+ * Returns a list of loaded plugins
+ */
+struct tep_plugin_list*
+tep_load_plugins_dir(struct tep_handle *tep, char *path)
+{
+	struct tep_plugin_list *list = NULL;
+
+	if (tep && tep->flags & TEP_DISABLE_PLUGINS)
+		return NULL;
+
+	load_plugins_dir(tep, ".so", path, load_plugin, &list);
+	return list;
+}
+
+/**
+ * tep_plugins_append - Concatenate two plugin lists.
+ * @list1: The first plugin list.
+ * @list2: The second plugin list.
+ *
+ * The second plugin list (list2) is appended to the first one (list1).
+ */
+void tep_plugins_append(struct tep_plugin_list *list1,
+			struct tep_plugin_list *list2)
+{
+	struct tep_plugin_list *list = list1;
+
+	while (list && list->next)
+		list = list->next;
+	if (list)
+		list->next = list2;
+}
+
 void
 tep_unload_plugins(struct tep_plugin_list *plugin_list, struct tep_handle *tep)
 {
diff --git a/tracecmd/trace-check-events.c b/tracecmd/trace-check-events.c
index b09fcd0..eb840c6 100644
--- a/tracecmd/trace-check-events.c
+++ b/tracecmd/trace-check-events.c
@@ -43,12 +43,7 @@ void trace_check_events(int argc, char **argv)
 	if (!pevent)
 		exit(EINVAL);
 
-	if (tracecmd_disable_plugins)
-		tep_set_flag(pevent, TEP_DISABLE_PLUGINS);
-	if (tracecmd_disable_sys_plugins)
-		tep_set_flag(pevent, TEP_DISABLE_SYS_PLUGINS);
-
-	list = tep_load_plugins(pevent);
+	list = trace_load_tep_plugins(pevent);
 	ret = tracecmd_fill_local_events(tracing, pevent, &parsing_failures);
 	if (ret || parsing_failures)
 		ret = EINVAL;
diff --git a/tracecmd/trace-list.c b/tracecmd/trace-list.c
index 65099a5..840eeac 100644
--- a/tracecmd/trace-list.c
+++ b/tracecmd/trace-list.c
@@ -317,14 +317,9 @@ static void show_plugin_options(void)
 	if (!pevent)
 		die("Can not allocate pevent\n");
 
-	if (tracecmd_disable_plugins)
-		tep_set_flag(pevent, TEP_DISABLE_PLUGINS);
-	if (tracecmd_disable_sys_plugins)
-		tep_set_flag(pevent, TEP_DISABLE_SYS_PLUGINS);
-
 	trace_seq_init(&s);
 
-	list = tep_load_plugins(pevent);
+	list = trace_load_tep_plugins(pevent);
 	tep_plugin_print_options(&s);
 	trace_seq_do_printf(&s);
 	tep_unload_plugins(list, pevent);
@@ -348,14 +343,9 @@ static void show_plugins(void)
 	if (!pevent)
 		die("Can not allocate pevent\n");
 
-	if (tracecmd_disable_plugins)
-		tep_set_flag(pevent, TEP_DISABLE_PLUGINS);
-	if (tracecmd_disable_sys_plugins)
-		tep_set_flag(pevent, TEP_DISABLE_SYS_PLUGINS);
-
 	trace_seq_init(&s);
 
-	list = tep_load_plugins(pevent);
+	list = trace_load_tep_plugins(pevent);
 	tep_print_plugins(&s, "  ", "\n", list);
 
 	trace_seq_do_printf(&s);
-- 
2.21.0

[PATCH v5 2/2] trace-cmd: Add initial infrastructure for trace-cmd specific plugins.

[Tzvetomir Stoyanov (VMware)]

Create a new directory lib/trace-cmd/plugins, where the libtracecmd
plugins will be placed. Plugins compilation is integrated in
the trace-cmd build process. New plugins are installed in
$(HOME)/.local/lib/trace-cmd/plugins or $(libdir)/trace-cmd/plugins directories.
Current python_plugin.so is part of libtraceevent plugins, so the python
plugins path is changed from
$(HOME)/.trace-cmd/python to $(HOME)/.local/lib/traceevent/python
and
$(libdir)/trace-cmd/python to $(libdir)/traceevent/python

Added an initial set of APIs for working with trace-cmd plugins.

Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
---
 .gitignore                     |   1 +
 Makefile                       |  40 ++++-
 include/trace-cmd/trace-cmd.h  |  40 +++++
 lib/trace-cmd/Makefile         |   1 +
 lib/trace-cmd/plugins/Makefile |  58 ++++++
 lib/trace-cmd/trace-plugin.c   | 313 +++++++++++++++++++++++++++++++++
 6 files changed, 445 insertions(+), 8 deletions(-)
 create mode 100644 lib/trace-cmd/plugins/Makefile
 create mode 100644 lib/trace-cmd/trace-plugin.c

diff --git a/.gitignore b/.gitignore
index 20bb5a3..6759e51 100644
--- a/.gitignore
+++ b/.gitignore
@@ -20,3 +20,4 @@ TAGS
 cscope*
 traceevent_plugin_dir
 trace_python_dir
+tracecmd_plugin_dir
diff --git a/Makefile b/Makefile
index bbdf15e..ab76f1f 100644
--- a/Makefile
+++ b/Makefile
@@ -57,14 +57,17 @@ export DESTDIR DESTDIR_SQ
 
 ifeq ($(prefix),$(HOME))
 plugin_traceevent_dir = $(HOME)/.local/lib/traceevent/plugins
-python_dir = $(HOME)/.trace-cmd/python
+plugin_tracecmd_dir = $(libdir)/trace-cmd/plugins
+python_dir ?= $(libdir)/traceevent/python
 var_dir = $(HOME)/.trace-cmd/
 else
 plugin_traceevent_dir = $(libdir)/traceevent/plugins
 python_dir ?= $(libdir)/trace-cmd/python
 PLUGIN_DIR_TRACEEVENT = -DPLUGIN_TRACEEVENT_DIR="$(plugin_traceevent_dir)"
+PLUGIN_DIR_TRACECMD = -DPLUGIN_TRACECMD_DIR="$(plugin_tracecmd_dir)"
 PYTHON_DIR = -DPYTHON_DIR="$(python_dir)"
 PLUGIN_DIR_TRACEEVENT_SQ = '$(subst ','\'',$(PLUGIN_DIR_TRACEEVENT))'
+PLUGIN_DIR_TRACECMD_SQ = '$(subst ','\'',$(PLUGIN_DIR_TRACECMD))'
 PYTHON_DIR_SQ = '$(subst ','\'',$(PYTHON_DIR))'
 var_dir = /var
 endif
@@ -73,6 +76,7 @@ endif
 bindir_SQ = $(subst ','\'',$(bindir))
 bindir_relative_SQ = $(subst ','\'',$(bindir_relative))
 plugin_traceevent_dir_SQ = $(subst ','\'',$(plugin_traceevent_dir))
+plugin_tracecmd_dir_SQ = $(subst ','\'',$(plugin_tracecmd_dir))
 python_dir_SQ = $(subst ','\'',$(python_dir))
 
 VAR_DIR = -DVAR_DIR="$(var_dir)"
@@ -86,9 +90,11 @@ HELP_DIR_SQ = '$(subst ','\'',$(HELP_DIR))'
 BASH_COMPLETE_DIR ?= /etc/bash_completion.d
 
 export PLUGIN_DIR_TRACEEVENT
+export PLUGIN_DIR_TRACECMD
 export PYTHON_DIR
 export PYTHON_DIR_SQ
 export plugin_traceevent_dir_SQ
+export plugin_tracecmd_dir_SQ
 export python_dir_SQ
 export var_dir
 
@@ -239,7 +245,8 @@ LIBS += -laudit
 endif
 
 # Append required CFLAGS
-override CFLAGS += $(INCLUDES) $(PLUGIN_DIR_TRACEEVENT_SQ) $(VAR_DIR)
+override CFLAGS += $(INCLUDES) $(VAR_DIR)
+override CFLAGS += $(PLUGIN_DIR_TRACEEVENT_SQ) $(PLUGIN_DIR_TRACECMD_SQ)
 override CFLAGS += $(udis86-flags) $(blk-flags)
 override LDFLAGS += $(udis86-ldflags)
 
@@ -268,13 +275,16 @@ gui: force $(CMD_TARGETS) $(kshark-dir)/build/Makefile
 	@echo "gui build complete"
 	@echo "  kernelshark located at $(kshark-dir)/bin"
 
-trace-cmd: force $(LIBTRACEEVENT_STATIC) $(LIBTRACECMD_STATIC)
+trace-cmd: force $(LIBTRACEEVENT_STATIC) $(LIBTRACECMD_STATIC) \
+	force $(obj)/lib/trace-cmd/plugins/tracecmd_plugin_dir
 	$(Q)$(MAKE) -C $(src)/tracecmd $(obj)/tracecmd/$@
 
-$(LIBTRACEEVENT_SHARED): force $(obj)/lib/traceevent/plugins/traceevent_plugin_dir
+$(LIBTRACEEVENT_SHARED): force $(obj)/lib/traceevent/plugins/trace_python_dir \
+			 $(obj)/lib/traceevent/plugins/traceevent_plugin_dir
 	$(Q)$(MAKE) -C $(src)/lib/traceevent $@
 
-$(LIBTRACEEVENT_STATIC): force $(obj)/lib/traceevent/plugins/traceevent_plugin_dir
+$(LIBTRACEEVENT_STATIC): force $(obj)/lib/traceevent/plugins/trace_python_dir \
+			 $(obj)/lib/traceevent/plugins/traceevent_plugin_dir
 	$(Q)$(MAKE) -C $(src)/lib/traceevent $@
 
 $(LIBTRACECMD_STATIC): force
@@ -290,12 +300,21 @@ libtracecmd.so: $(LIBTRACECMD_SHARED)
 
 libs: $(LIBTRACECMD_SHARED) $(LIBTRACEEVENT_SHARED)
 
-plugins: force $(obj)/lib/traceevent/plugins/traceevent_plugin_dir $(obj)/lib/traceevent/plugins/trace_python_dir
+plugins_traceevent: force $(obj)/lib/traceevent/plugins/traceevent_plugin_dir \
+		   $(obj)/lib/traceevent/plugins/trace_python_dir
 	$(Q)$(MAKE) -C $(src)/lib/traceevent/plugins
 
+plugins_tracecmd: force $(obj)/lib/trace-cmd/plugins/tracecmd_plugin_dir
+	$(Q)$(MAKE) -C $(src)/lib/trace-cmd/plugins
+
+plugins: plugins_traceevent plugins_tracecmd
+
 $(obj)/lib/traceevent/plugins/traceevent_plugin_dir: force
 	$(Q)$(MAKE) -C $(src)/lib/traceevent/plugins $@
 
+$(obj)/lib/trace-cmd/plugins/tracecmd_plugin_dir: force
+	$(Q)$(MAKE) -C $(src)/lib/trace-cmd/plugins $@
+
 $(obj)/lib/traceevent/plugins/trace_python_dir: force
 	$(Q)$(MAKE) -C $(src)/lib/traceevent/plugins $@
 
@@ -322,8 +341,12 @@ cscope: force
 	$(RM) cscope*
 	$(call find_tag_files) | cscope -b -q
 
-install_plugins: force
-	$(Q)$(MAKE) -C $(src)/lib/traceevent/plugins $@
+install_plugins_traceevent: force
+	$(Q)$(MAKE) -C $(src)/lib/traceevent/plugins install_plugins
+install_plugins_tracecmd: force
+	$(Q)$(MAKE) -C $(src)/lib/trace-cmd/plugins install_plugins
+
+install_plugins: install_plugins_traceevent install_plugins_tracecmd
 
 install_python: force
 	$(Q)$(MAKE) -C $(src)/python $@
@@ -371,6 +394,7 @@ clean:
 	$(MAKE) -C $(src)/lib/traceevent clean
 	$(MAKE) -C $(src)/lib/trace-cmd clean
 	$(MAKE) -C $(src)/lib/traceevent/plugins clean
+	$(MAKE) -C $(src)/lib/trace-cmd/plugins clean
 	$(MAKE) -C $(src)/python clean
 	$(MAKE) -C $(src)/tracecmd clean
 	if [ -f $(kshark-dir)/build/Makefile ]; then $(MAKE) -C $(kshark-dir)/build clean; fi
diff --git a/include/trace-cmd/trace-cmd.h b/include/trace-cmd/trace-cmd.h
index f692783..c914067 100644
--- a/include/trace-cmd/trace-cmd.h
+++ b/include/trace-cmd/trace-cmd.h
@@ -54,6 +54,46 @@ struct tracecmd_output;
 struct tracecmd_recorder;
 struct hook_list;
 
+/* --- tracecmd plugins --- */
+
+extern int tracecmd_disable_sys_plugins;
+extern int tracecmd_disable_plugins;
+
+enum tracecmd_context {
+	TRACECMD_INPUT,
+	TRACECMD_OUTPUT,
+};
+
+enum tracecmd_plugin_flag {
+	TRACECMD_DISABLE_SYS_PLUGINS	= 1,
+	TRACECMD_DISABLE_PLUGINS	= 1 << 1,
+};
+
+struct trace_plugin_context;
+
+struct trace_plugin_context *
+tracecmd_plugin_context_create(enum tracecmd_context context, void *data);
+
+void tracecmd_plugin_set_flag(struct trace_plugin_context *context,
+			      enum tracecmd_plugin_flag flag);
+
+#define TRACECMD_PLUGIN_LOADER tracecmd_plugin_loader
+#define TRACECMD_PLUGIN_UNLOADER tracecmd_plugin_unloader
+#define TRACECMD_PLUGIN_ALIAS tracecmd_plugin_alias
+#define _MAKE_STR(x)	#x
+#define MAKE_STR(x)	_MAKE_STR(x)
+#define TRACECMD_PLUGIN_LOADER_NAME MAKE_STR(TRACECMD_PLUGIN_LOADER)
+#define TRACECMD_PLUGIN_UNLOADER_NAME MAKE_STR(TRACECMD_PLUGIN_UNLOADER)
+#define TRACECMD_PLUGIN_ALIAS_NAME MAKE_STR(TRACECMD_PLUGIN_ALIAS)
+
+typedef int (*tracecmd_plugin_load_func)(struct trace_plugin_context *trace);
+typedef int (*tracecmd_plugin_unload_func)(struct trace_plugin_context *trace);
+
+struct tracecmd_input *
+tracecmd_plugin_context_input(struct trace_plugin_context *trace_context);
+struct tracecmd_output *
+tracecmd_plugin_context_output(struct trace_plugin_context *trace_context);
+
 void tracecmd_set_quiet(struct tracecmd_output *handle, bool set_quiet);
 bool tracecmd_get_quiet(struct tracecmd_output *handle);
 
diff --git a/lib/trace-cmd/Makefile b/lib/trace-cmd/Makefile
index 3b4b5aa..6f3e6b1 100644
--- a/lib/trace-cmd/Makefile
+++ b/lib/trace-cmd/Makefile
@@ -15,6 +15,7 @@ OBJS += trace-recorder.o
 OBJS += trace-util.o
 OBJS += trace-filter-hash.o
 OBJS += trace-msg.o
+OBJS += trace-plugin.o
 
 # Additional util objects
 OBJS += trace-blk-hack.o
diff --git a/lib/trace-cmd/plugins/Makefile b/lib/trace-cmd/plugins/Makefile
new file mode 100644
index 0000000..240e6be
--- /dev/null
+++ b/lib/trace-cmd/plugins/Makefile
@@ -0,0 +1,58 @@
+include $(src)/scripts/utils.mk
+
+bdir:=$(obj)/lib/trace-cmd/plugins
+
+PLUGIN_OBJS =
+
+PLUGIN_OBJS := $(PLUGIN_OBJS:%.o=$(bdir)/%.o)
+PLUGIN_BUILD := $(PLUGIN_OBJS:$(bdir)/%.o=$(bdir)/%.so)
+
+PLUGINS := $(PLUGIN_BUILD)
+
+DEPS := $(PLUGIN_OBJS:$(bdir)/%.o=$(bdir)/.%.d)
+
+all: $(PLUGINS)
+
+$(bdir):
+	@mkdir -p $(bdir)
+
+$(PLUGIN_OBJS): | $(bdir)
+$(DEPS): | $(bdir)
+
+$(PLUGIN_OBJS): $(bdir)/%.o : %.c
+	$(Q)$(do_compile_plugin_obj)
+
+$(PLUGIN_BUILD): $(bdir)/%.so: $(bdir)/%.o
+	$(Q)$(do_plugin_build)
+
+$(DEPS): $(bdir)/.%.d: %.c
+	$(Q)$(CC) -M $(CPPFLAGS) $(CFLAGS) $< > $@
+
+$(PLUGIN_OBJS): $(bdir)/%.o : $(bdir)/.%.d
+
+PLUGINS_INSTALL = $(subst .so,.install,$(PLUGINS))
+
+$(PLUGINS_INSTALL): $(bdir)/%.install : $(bdir)/%.so force
+	$(Q)$(call do_install_data,$<,$(plugin_tracecmd_dir_SQ))
+
+install_plugins: $(PLUGINS_INSTALL)
+
+# The following targets are necessary to trigger a rebuild when
+# $(PLUGIN_DIR_TRACECMD) change. Without them, a full clean build would
+# necessary in order to get the binaries updated.
+
+$(bdir)/tracecmd_plugin_dir: $(bdir) force
+	$(Q)$(N)$(call update_dir, 'PLUGIN_DIR_TRACECMD=$(PLUGIN_DIR_TRACECMD)')
+
+dep_includes := $(wildcard $(DEPS))
+
+ifneq ($(dep_includes),)
+  include $(dep_includes)
+endif
+
+clean:
+	$(RM) -f $(bdir)/*.a $(bdir)/*.so $(bdir)/*.o $(bdir)/.*.d\
+		$(bdir)/tracecmd_plugin_dir
+
+force:
+.PHONY: clean force
diff --git a/lib/trace-cmd/trace-plugin.c b/lib/trace-cmd/trace-plugin.c
new file mode 100644
index 0000000..6bec18b
--- /dev/null
+++ b/lib/trace-cmd/trace-plugin.c
@@ -0,0 +1,313 @@
+// SPDX-License-Identifier: LGPL-2.1
+/*
+ * Copyright (C) 2009, 2010 Red Hat Inc, Steven Rostedt <srostedt@redhat.com>
+ *
+ */
+#include <stdlib.h>
+#include <unistd.h>
+#include <dlfcn.h>
+#include <sys/stat.h>
+#include <libgen.h>
+#include "trace-cmd.h"
+#include "trace-local.h"
+
+#define LOCAL_PLUGIN_DIR ".local/lib/trace-cmd/plugins/"
+
+struct trace_plugin_list {
+	struct trace_plugin_list	*next;
+	char				*name;
+	void				*handle;
+};
+
+struct trace_plugin_context {
+	enum tracecmd_context context;
+	enum tracecmd_plugin_flag flags;
+	union {
+		void				*data;
+		struct tracecmd_input		*trace_input;
+		struct tracecmd_output		*trace_output;
+	};
+};
+
+/**
+ * tracecmd_plugin_context_create - Create and initialize tracecmd plugins context.
+ * @context: Context of the trace-cmd command.
+ * @data: Pointer to the context specific data, which will be passed to plugins.
+ *
+ * Returns a pointer to created tracecmd plugins context, or NULL in case memory
+ * allocation fails. The returned pointer should be freed by free ().
+ */
+struct trace_plugin_context *
+tracecmd_plugin_context_create(enum tracecmd_context context, void *data)
+{
+	struct trace_plugin_context *trace;
+
+	trace = calloc(1, sizeof(struct trace_plugin_context));
+	if (!trace)
+		return NULL;
+	trace->context = context;
+	trace->data = data;
+	return trace;
+}
+
+/**
+ * tracecmd_plugin_set_flag - Set a flag to tracecmd plugins context.
+ * @context: Context of the trace-cmd command.
+ * @flag: Flag, whil will be set.
+ *
+ */
+void tracecmd_plugin_set_flag(struct trace_plugin_context *context,
+			      enum tracecmd_plugin_flag flag)
+{
+	if (context)
+		context->flags |= flag;
+}
+
+/**
+ * tracecmd_plugin_context_input - Get a tracecmd_input plugin context.
+ * @context: Context of the trace-cmd command.
+ *
+ * Returns pointer to tracecmd_input, if such context is available or
+ * NULL otherwise.
+ */
+struct tracecmd_input *
+tracecmd_plugin_context_input(struct trace_plugin_context *context)
+{
+	if (!context || context->context != TRACECMD_INPUT)
+		return NULL;
+	return context->trace_input;
+}
+
+/**
+ * tracecmd_plugin_context_output - Get a tracecmd_output plugin context
+ * @context: Context of the trace-cmd command.
+ *
+ * Returns pointer to tracecmd_output, if such context is available or
+ * NULL otherwise.
+ */
+struct tracecmd_output *
+tracecmd_plugin_context_output(struct trace_plugin_context *context)
+{
+	if (!context || context->context != TRACECMD_OUTPUT)
+		return NULL;
+	return context->trace_output;
+}
+
+static void
+load_plugin(struct trace_plugin_context *trace, const char *path,
+	    const char *file, void *data)
+{
+	struct trace_plugin_list **plugin_list = data;
+	tracecmd_plugin_load_func func;
+	struct trace_plugin_list *list;
+	const char *alias;
+	char *plugin;
+	void *handle;
+	int ret;
+
+	ret = asprintf(&plugin, "%s/%s", path, file);
+	if (ret < 0) {
+		warning("could not allocate plugin memory\n");
+		return;
+	}
+
+	handle = dlopen(plugin, RTLD_NOW | RTLD_GLOBAL);
+	if (!handle) {
+		warning("could not load plugin '%s'\n%s\n",
+			plugin, dlerror());
+		goto out_free;
+	}
+
+	alias = dlsym(handle, TRACECMD_PLUGIN_ALIAS_NAME);
+	if (!alias)
+		alias = file;
+
+	func = dlsym(handle, TRACECMD_PLUGIN_LOADER_NAME);
+	if (!func) {
+		warning("could not find func '%s' in plugin '%s'\n%s\n",
+			TRACECMD_PLUGIN_LOADER_NAME, plugin, dlerror());
+		goto out_free;
+	}
+
+	list = malloc(sizeof(*list));
+	if (!list) {
+		warning("could not allocate plugin memory\n");
+		goto out_free;
+	}
+
+	list->next = *plugin_list;
+	list->handle = handle;
+	list->name = plugin;
+	*plugin_list = list;
+
+	pr_stat("registering plugin: %s", plugin);
+	func(trace);
+	return;
+
+ out_free:
+	free(plugin);
+}
+
+static void
+load_plugins_dir(struct trace_plugin_context *trace, const char *suffix,
+		 const char *path,
+		 void (*load_plugin)(struct trace_plugin_context *trace,
+				     const char *path,
+				     const char *name,
+				     void *data),
+		 void *data)
+{
+	struct dirent *dent;
+	struct stat st;
+	DIR *dir;
+	int ret;
+
+	ret = stat(path, &st);
+	if (ret < 0)
+		return;
+
+	if (!S_ISDIR(st.st_mode))
+		return;
+
+	dir = opendir(path);
+	if (!dir)
+		return;
+
+	while ((dent = readdir(dir))) {
+		const char *name = dent->d_name;
+
+		if (strcmp(name, ".") == 0 ||
+		    strcmp(name, "..") == 0)
+			continue;
+
+		/* Only load plugins that end in suffix */
+		if (strcmp(name + (strlen(name) - strlen(suffix)), suffix) != 0)
+			continue;
+
+		load_plugin(trace, path, name, data);
+	}
+
+	closedir(dir);
+}
+
+static char *get_source_plugins_dir(void)
+{
+	char *p, path[PATH_MAX+1];
+	int ret;
+
+	ret = readlink("/proc/self/exe", path, PATH_MAX);
+	if (ret > PATH_MAX || ret < 0)
+		return NULL;
+
+	dirname(path);
+	p = strrchr(path, '/');
+	if (!p)
+		return NULL;
+	/* Check if we are in the the source tree */
+	if (strcmp(p, "/tracecmd") != 0)
+		return NULL;
+
+	strcpy(p, "/lib/trace-cmd/plugins");
+	return strdup(path);
+}
+
+static void
+load_plugins_hook(struct trace_plugin_context *trace, const char *suffix,
+		  void (*load_plugin)(struct trace_plugin_context *trace,
+				      const char *path,
+				      const char *name,
+				      void *data),
+		  void *data)
+{
+	char *home;
+	char *path;
+	char *envdir;
+	int ret;
+
+	if (trace && trace->flags & TRACECMD_DISABLE_PLUGINS)
+		return;
+
+	/*
+	 * If a system plugin directory was defined,
+	 * check that first.
+	 */
+#ifdef PLUGIN_TRACECMD_DIR
+	if (!trace || !(trace->flags & TRACECMD_DISABLE_SYS_PLUGINS))
+		load_plugins_dir(trace, suffix, PLUGIN_TRACECMD_DIR,
+				 load_plugin, data);
+#endif
+
+	/*
+	 * Next let the environment-set plugin directory
+	 * override the system defaults.
+	 */
+	envdir = getenv("TRACECMD_PLUGIN_DIR");
+	if (envdir)
+		load_plugins_dir(trace, suffix, envdir, load_plugin, data);
+
+	/*
+	 * Now let the home directory override the environment
+	 * or system defaults.
+	 */
+	home = getenv("HOME");
+	if (!home)
+		return;
+
+	ret = asprintf(&path, "%s/%s", home, LOCAL_PLUGIN_DIR);
+	if (ret < 0) {
+		warning("could not allocate plugin memory\n");
+		return;
+	}
+
+	load_plugins_dir(trace, suffix, path, load_plugin, data);
+
+	free(path);
+
+	path = get_source_plugins_dir();
+	if (path) {
+		load_plugins_dir(trace, suffix, path, load_plugin, data);
+		free(path);
+	}
+}
+
+/**
+ * tracecmd_load_plugins - Load trace-cmd specific plugins.
+ * @context: Context of the trace-cmd command, will be passed to the plugins
+ *	     at load time.
+ *
+ * Returns a list of loaded plugins
+ */
+struct trace_plugin_list*
+tracecmd_load_plugins(struct trace_plugin_context *trace)
+{
+	struct trace_plugin_list *list = NULL;
+
+	load_plugins_hook(trace, ".so", load_plugin, &list);
+	return list;
+}
+
+/**
+ * tracecmd_unload_plugins - Unload trace-cmd specific plugins.
+ * @plugin_list - List of plugins, previously loaded with tracecmd_load_plugins.
+ * @context: Context of the trace-cmd command, will be passed to the plugins
+ *	     at unload time.
+ *
+ */
+void
+tracecmd_unload_plugins(struct trace_plugin_list *plugin_list,
+			struct trace_plugin_context *trace)
+{
+	tracecmd_plugin_unload_func func;
+	struct trace_plugin_list *list;
+
+	while (plugin_list) {
+		list = plugin_list;
+		plugin_list = list->next;
+		func = dlsym(list->handle, TRACECMD_PLUGIN_UNLOADER_NAME);
+		if (func)
+			func(trace);
+		dlclose(list->handle);
+		free(list->name);
+		free(list);
+	}
+}
-- 
2.21.0