fs: Support umask dump/restore

This one is bound to task's fs info (with cwd and root)
thus put it in the fs.img file.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

arch/x86/syscall-x86-64.def

@@ -47,6 +47,7 @@ __NR_mkdir		83		sys_mkdir		(const char *name, int mode)
 __NR_rmdir		84		sys_rmdir		(const char *name)
 __NR_unlink		87		sys_unlink		(char *pathname)
 __NR_readlink		89		sys_readlink		(const char *path, char *buf, int bufsize)
+__NR_umask		95		sys_umask		(int mask)
 __NR_getgroups		115		sys_getgroups		(int gsize, unsigned int *groups)
 __NR_setresuid		117		sys_setresuid		(int uid, int euid, int suid)
 __NR_setresgid		119		sys_setresgid		(int gid, int egid, int sgid)

cr-dump.c

@@ -393,12 +393,15 @@ err:
 	return ret;
 }
 
-static int dump_task_fs(pid_t pid, struct cr_fdset *fdset)
+static int dump_task_fs(pid_t pid, struct parasite_dump_misc *misc, struct cr_fdset *fdset)
 {
 	struct fd_parms p = FD_PARMS_INIT;
 	FsEntry fe = FS_ENTRY__INIT;
 	int fd, ret;
 
+	fe.has_umask = true;
+	fe.umask = misc->umask;
+
 	fd = open_proc(pid, "cwd");
 	if (fd < 0)
 		return -1;
@@ -1460,7 +1463,7 @@ static int dump_one_task(struct pstree_item *item)
 		goto err;
 	}
 
-	ret = dump_task_fs(pid, cr_fdset);
+	ret = dump_task_fs(pid, &misc, cr_fdset);
 	if (ret) {
 		pr_err("Dump fs (pid: %d) failed with %d\n", pid, ret);
 		goto err;

files.c

@@ -599,6 +599,11 @@ int prepare_fs(int pid)
 	 * by path thus exposing this (yet unclean) logic here.
 	 */
 
+	if (fe->has_umask) {
+		pr_info("Restoring umask to %o\n", fe->umask);
+		umask(fe->umask);
+	}
+
 	ret = 0;
 close:
 	close_safe(&cwd);

include/parasite.h

@@ -84,6 +84,7 @@ struct parasite_dump_misc {
 	u32 sid;
 	u32 pgid;
 	u32 tls;
+	u32 umask;
 };
 
 #define PARASITE_MAX_GROUPS	(PAGE_SIZE / sizeof(unsigned int))

pie/parasite.c

@@ -290,6 +290,8 @@ static int dump_misc(struct parasite_dump_misc *args)
 	args->sid = sys_getsid();
 	args->pgid = sys_getpgid(0);
 	args->tls = arch_get_tls();
+	args->umask = sys_umask(0);
+	sys_umask(args->umask); /* never fails */
 
 	return 0;
 }

protobuf/fs.proto

 message fs_entry {
 	required uint32		cwd_id		= 1;
 	required uint32		root_id		= 2;
+	optional uint32		umask		= 3;
 }

test/zdtm.sh

@@ -30,6 +30,7 @@ static/xids00
 static/groups
 static/pthread00
 static/pthread01
+static/umask00
 streaming/pipe_loop00
 streaming/pipe_shared00
 transition/file_read