parasite: Refactor code to follow calling convention

It happened some routines in parasite service code
were not following calling convention so I fixed the
callers and added a comment about adding new code here.

At the same time the 3 error code madness is dropped
as being requested by Pavel -- now we return one error
code only.

The PARASITE_ERR_ codes were dropped as well due to
become redundant.

The status of parasite service routine is set via
SET_PARASITE_RET helper. In case if there is no error --
just return 0. The calling code should not expect to
find anything sane in parasite_status_t because parasite
code might not touch it at all.

Same time, due to this convention the parasite's
dump_socket_queue is getting rid of third @err
member, because it's now returned as a regular
error code.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

include/parasite.h

@@ -16,19 +16,6 @@
 
 #define PARASITE_MAX_SIZE	(64 << 10)
 
-/* we need own error code for diagnostics */
-#define PARASITE_ERR_FAIL	-1024
-#define PARASITE_ERR_OPEN	-1025
-#define PARASITE_ERR_MMAP	-1026
-#define PARASITE_ERR_MINCORE	-1027
-#define PARASITE_ERR_MUNMAP	-1028
-#define PARASITE_ERR_CLOSE	-1029
-#define PARASITE_ERR_WRITE	-1030
-#define PARASITE_ERR_MPROTECT	-1031
-#define PARASITE_ERR_SIGACTION  -1032
-#define PARASITE_ERR_GETITIMER  -1033
-#define PARASITE_ERR_IOCTL	-1034
-
 enum {
 	PARASITE_CMD_INIT,
 	PARASITE_CMD_SET_LOGFD,
@@ -48,16 +35,14 @@ enum {
 };
 
 typedef struct  {
-	long			ret;		/* custom ret code */
-	long			sys_ret;	/* syscall ret code */
+	long			ret;		/* ret code */
 	long			line;		/* where we're failed */
 } parasite_status_t;
 
-#define SET_PARASITE_STATUS(st, ret_code, sys_ret_code)	\
-	do {						\
-		(st)->ret	= ret_code,		\
-		(st)->sys_ret	= sys_ret_code,		\
-		(st)->line	= __LINE__;		\
+#define SET_PARASITE_RET(st, err)		\
+	do {					\
+		(st)->ret	= err,		\
+		(st)->line	= __LINE__;	\
 	} while (0)
 
 struct parasite_init_args {

parasite-syscall.c

@@ -248,19 +248,21 @@ static int parasite_execute_by_pid(unsigned long cmd, struct parasite_ctl *ctl,
 	}
 
 	memcpy(ctl->addr_cmd, &cmd, sizeof(cmd));
-	memcpy(ctl->addr_args, args, args_size);
+	if (args)
+		memcpy(ctl->addr_args, args, args_size);
 
 	parasite_setup_regs(ctl->parasite_ip, &regs);
 
 	ret = __parasite_execute(ctl, pid, &regs);
 
-	memcpy(args, ctl->addr_args, args_size);
-	if (!ret)
-		ret = args->ret;
+	if (args)
+		memcpy(args, ctl->addr_args, args_size);
+
+	BUG_ON(ret && !args);
 
 	if (ret)
 		pr_err("Parasite exited with %d ret (%li at %li)\n",
-		       ret, args->sys_ret, args->line);
+		       ret, args->ret, args->line);
 
 	if (ctl->pid != pid)
 		if (ptrace(PTRACE_SETREGS, pid, NULL, &regs_orig)) {
@@ -542,9 +544,8 @@ int parasite_dump_pages_seized(struct parasite_ctl *ctl, struct list_head *vma_a
 
 	ret = parasite_execute(PARASITE_CMD_DUMPPAGES_INIT, ctl, st, sizeof(*st));
 	if (ret < 0) {
-		pr_err("Dumping pages failed with %li (%li) at %li\n",
+		pr_err("Dumping pages failed with %li at %li\n",
 				parasite_dumppages.status.ret,
-				parasite_dumppages.status.sys_ret,
 				parasite_dumppages.status.line);
 		goto out;
 	}
@@ -582,9 +583,8 @@ int parasite_dump_pages_seized(struct parasite_ctl *ctl, struct list_head *vma_a
 				       (parasite_status_t *) &parasite_dumppages,
 				       sizeof(parasite_dumppages));
 		if (ret) {
-			pr_err("Dumping pages failed with %li (%li) at %li\n",
+			pr_err("Dumping pages failed with %li at %li\n",
 				 parasite_dumppages.status.ret,
-				 parasite_dumppages.status.sys_ret,
 				 parasite_dumppages.status.line);
 
 			goto out;
@@ -594,7 +594,7 @@ int parasite_dump_pages_seized(struct parasite_ctl *ctl, struct list_head *vma_a
 		nrpages_dumped += parasite_dumppages.nrpages_dumped;
 	}
 
-	parasite_execute(PARASITE_CMD_DUMPPAGES_FINI, ctl, st, sizeof(*st));
+	parasite_execute(PARASITE_CMD_DUMPPAGES_FINI, ctl, NULL, 0);
 
 	if (write_img(cr_fdset->fds[CR_FD_PAGES], &zero_page_entry))
 		goto out;
@@ -620,11 +620,7 @@ int parasite_cure_seized(struct parasite_ctl *ctl)
 
 	if (ctl->parasite_ip) {
 		ctl->signals_blocked = 0;
-
-		if (parasite_execute(PARASITE_CMD_FINI, ctl, &args, sizeof(args))) {
-			pr_err("Can't finalize parasite (pid: %d) task\n", ctl->pid);
-			ret = -1;
-		}
+		parasite_execute(PARASITE_CMD_FINI, ctl, NULL, 0);
 	}
 
 	if (ctl->remote_map) {