compel: Add fds plugin (v2)

This is just export by reasonable name of the existing
code, that sends and receives FDs via compel RPC socket.

v2:
 Rebase on recent criu-dev
 Fix parallel build
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

Makefile.compel

@@ -22,7 +22,7 @@ compel-deps		+= compel/include/asm
 compel-deps		+= $(COMPEL_VERSION_HEADER)
 compel-deps		+= $(CONFIG_HEADER)
 compel-deps		+= include/common/asm
-compel-plugins		+= compel/plugins/std.built-in.o
+compel-plugins		+= compel/plugins/std.built-in.o compel/plugins/fds.built-in.o
 
 LIBCOMPEL_SO		:= libcompel.so
 LIBCOMPEL_A		:= libcompel.a
@@ -50,7 +50,10 @@ compel/plugins/%: $(compel-deps) .FORCE
 compel/plugins/std.built-in.o: $(compel-deps) .FORCE
 	$(Q) $(MAKE) $(build)=compel/plugins $@
 
-compel/plugins/shmem.built-in.o: $(compel-deps) .FORCE
+compel/plugins/shmem.built-in.o: $(compel-deps) compel/plugins/std.built-in.o .FORCE
+	$(Q) $(MAKE) $(build)=compel/plugins $@
+
+compel/plugins/fds.built-in.o: $(compel-deps) compel/plugins/std.built-in.o .FORCE
 	$(Q) $(MAKE) $(build)=compel/plugins $@
 
 compel/compel: compel/built-in.o compel/$(LIBCOMPEL_A) | $(compel-deps)

compel/plugins/Makefile

@@ -48,6 +48,11 @@ std-obj-y		+= std/string.o
 std-obj-y		+= std/infect.o
 std-obj-y		+= ./$(PLUGIN_ARCH_DIR)/std/parasite-head.o
 
+#
+# FDS plugin
+target			+= fds
+fds-obj-y		+= fds/fds.o
+
 ifeq ($(SRCARCH),x86)
 	std-obj-y	+= ./$(PLUGIN_ARCH_DIR)/std/memcpy.o
 endif

compel/plugins/fds/fds.c

+#include <errno.h>
+
+#include "uapi/plugins.h"
+#include "uapi/plugins/std.h"
+#include <compel/plugins/std/infect.h>
+
+#define pr_err(fmt, ...)
+
+#include "common/compiler.h"
+#include "common/bug.h"
+
+#define __sys(foo)	sys_##foo
+#define __sys_err(ret)	ret
+
+#include "common/scm.h"
+
+int fds_send_fd(int fd)
+{
+	return send_fd(parasite_get_rpc_sock(), NULL, 0, fd);
+}
+
+int fds_recv_fd(void)
+{
+	return recv_fd(parasite_get_rpc_sock());
+}

compel/plugins/include/uapi/plugin-fds.h

+#ifndef COMPEL_PLUGIN_STD_STD_H__
+#define COMPEL_PLUGIN_STD_STD_H__
+
+extern int fds_send_fd(int fd);
+extern int fds_recv_fd(void);
+
+#endif /* COMPEL_PLUGIN_STD_STD_H__ */