compel: plugins -- Add shmem plugin

The shmem pluging allows creation of shared memory segment between
parasite code and the caller.
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

compel/include/shmem.h

+#ifndef __COMPEL_PLUGIN_SHMEM_PRIV_H__
+#define __COMPEL_PLUGIN_SHMEM_PRIV_H__
+
+struct shmem_plugin_msg {
+	unsigned long start;
+	unsigned long len;
+};
+
+#endif /* __COMPEL_PLUGIN_SHMEM_PRIV_H__ */
+

compel/plugins/Makefile

@@ -2,6 +2,9 @@
 
 ARCH_DIR		:= compel/arch/$(ARCH)/plugins
 
+#
+# CFLAGS, ASFLAGS, LDFLAGS
+
 # General compel includes
 ccflags-y		+= -iquote $(SRC_DIR)/compel/include
 
@@ -20,6 +23,10 @@ asflags-y		+= -iquote $(SRC_DIR)/$(ARCH_DIR)
 asflags-y		+= -Wstrict-prototypes -Wa,--noexecstack
 asflags-y		+= -D__ASSEMBLY__ -nostdlib -fomit-frame-pointer
 
+#
+# Shmem plugin
+target			+= shmem
+shmem-obj-y		+= shmem/shmem.o
 
 #
 # STD plugin

compel/plugins/include/std-priv.h

+#ifndef __COMPEL_PLUGIN_STD_PRIV_H__
+#define __COMPEL_PLUGIN_STD_PRIV_H__
+
+extern int std_ctl_sock(void);
+
+#endif /* __COMPEL_PLUGIN_STD_PRIV_H__ */

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

+#ifndef __COMPEL_PLUGIN_SHMEM_H__
+#define __COMPEL_PLUGIN_SHMEM_H__
+
+/*
+ * Creates local shmem mapping and announces it
+ * to the peer. Peer can later "receive" one. The
+ * local area should be munmap()-ed at the end.
+ */
+extern void *shmem_create(unsigned long size);
+/*
+ * "Receives" shmem from peer and maps it. The
+ * locally mapped area should be munmap()-ed at
+ * the end
+ */
+extern void *shmem_receive(unsigned long *size);
+
+#endif /* __COMPEL_PLUGIN_SHMEM_H__ */

compel/plugins/shmem/shmem.c

+#include <sys/mman.h>
+
+#include "uapi/plugins.h"
+#include "uapi/plugin-shmem.h"
+#include "uapi/std/syscall.h"
+#include "shmem.h"
+#include "std-priv.h"
+
+void *shmem_create(unsigned long size)
+{
+	int ret;
+	void *mem;
+	struct shmem_plugin_msg spi;
+
+	mem = (void *)sys_mmap(NULL, size, PROT_READ | PROT_WRITE,
+			MAP_SHARED | MAP_ANON, 0, 0);
+	if (mem == MAP_FAILED)
+		return NULL;
+
+	spi.start = (unsigned long)mem;
+	spi.len = size;
+
+	ret = sys_write(std_ctl_sock(), &spi, sizeof(spi));
+	if (ret != sizeof(spi)) {
+		sys_munmap(mem, size);
+		return NULL;
+	}
+
+	return mem;
+}
+
+void *shmem_receive(unsigned long *size)
+{
+	/* master -> parasite not implemented yet */
+	return NULL;
+}
+
+PLUGIN_REGISTER_DUMMY(shmem)