criu/config.c: added cli option for build-id

file_validation_method field added to cr_options structure in
"criu/include/cr_options.h" along with the constants:
FILE_VALIDATION_FILE_SIZE
FILE_VALIDATION_BUILD_ID
FILE_VALIDATION_DEFAULT (Equal to FILE_VALIDATION_BUILD_ID)

Usage and description information is yet to be added

Usage:
--file-validation="filesize" (To use only the file size check)
--file-validation="buildid" (To try and use only the build-id check)

Signed-off-by: Ajay Bharadwaj <ajayrbharadwaj@gmail.com>

Documentation/criu.txt

@@ -400,6 +400,22 @@ By default the option is set to *fpu* and *ins*.
     option is intended for post-copy (lazy) migration and should be
     used in conjunction with *restore* with appropriate options.
 
+*--file-validation* ['mode']::
+    Set the method to be used to validate open files. Validation is done
+    to ensure that the version of the file being restored is the same
+    version when it was dumped.
+
+The 'mode' may be one of the following:
+
+    *filesize*:::
+                To explicitly use only the file size check all the time.
+                This is the fastest and least intensive check.
+
+    *buildid*:::
+                To validate ELF files with their build-ID. If the
+                build-ID cannot be obtained, 'chksm-first' method will be
+                used. This is the default if mode is unspecified.
+
 *restore*
 ~~~~~~~~~
 Restores previously checkpointed processes.
@@ -576,6 +592,22 @@ are not adequate, but this can be suppressed by using *--cpu-cap=none*.
    restored process.
    This option requires running *lazy-pages* daemon.
 
+*--file-validation* ['mode']::
+    Set the method to be used to validate open files. Validation is done
+    to ensure that the version of the file being restored is the same
+    version when it was dumped.
+
+The 'mode' may be one of the following:
+
+    *filesize*:::
+                To explicitly use only the file size check all the time.
+                This is the fastest and least intensive check.
+
+    *buildid*:::
+                To validate ELF files with their build-ID. If the
+                build-ID cannot be obtained, 'chksm-first' method will be
+                used. This is the default if mode is unspecified.
+
 *check*
 ~~~~~~~
 Checks whether the kernel supports the features needed by *criu* to

criu/config.c

@@ -280,6 +280,7 @@ void init_opts(void)
 	opts.status_fd = -1;
 	opts.log_level = DEFAULT_LOGLEVEL;
 	opts.pre_dump_mode = PRE_DUMP_SPLICE;
+	opts.file_validation_method = FILE_VALIDATION_DEFAULT;
 }
 
 bool deprecated_ok(char *what)
@@ -420,6 +421,22 @@ static int parse_join_ns(const char *ptr)
 	return 0;
 }
 
+static int parse_file_validation_method(struct cr_options *opts, const char *optarg)
+{
+	if (!strcmp(optarg, "filesize"))
+		opts->file_validation_method = FILE_VALIDATION_FILE_SIZE;
+	else if (!strcmp(optarg, "buildid"))
+		opts->file_validation_method = FILE_VALIDATION_BUILD_ID;
+	else
+		goto Esyntax;
+
+	return 0;
+
+Esyntax:
+	pr_err("Unknown file validation method `%s' selected\n", optarg);
+	return -1;
+}
+
 /*
  * parse_options() is the point where the getopt parsing happens. The CLI
  * parsing as well as the configuration file parsing happens here.
@@ -523,6 +540,7 @@ int parse_options(int argc, char **argv, bool *usage_error,
 		{"tls-no-cn-verify",		no_argument,		&opts.tls_no_cn_verify, true},
 		{ "cgroup-yard",		required_argument,	0, 1096 },
 		{ "pre-dump-mode",		required_argument,	0, 1097},
+		{ "file-validation",		required_argument,	0, 1098	},
 		{ },
 	};
 
@@ -848,6 +866,10 @@ int parse_options(int argc, char **argv, bool *usage_error,
 				return 1;
 			}
 			break;
+		case 1098:
+			if (parse_file_validation_method(&opts, optarg))
+				return 2;
+			break;
 		case 'V':
 			pr_msg("Version: %s\n", CRIU_VERSION);
 			if (strcmp(CRIU_GITID, "0"))

criu/crtools.c

@@ -437,6 +437,9 @@ usage:
 "			Namespace can be specified as either pid or file path.\n"
 "			OPTIONS can be used to specify parameters for userns:\n"
 "			    user:PID,UID,GID\n"
+"  --file-validation METHOD\n"
+			"pass the validation method to be used; argument\n"
+			"can be 'filesize' or 'buildid' (default).\n"
 "\n"
 "Check options:\n"
 "  Without options, \"criu check\" checks availability of absolutely required\n"

criu/files-reg.c

@@ -1632,7 +1632,8 @@ static bool store_validation_data(RegFileEntry *rfe,
 	rfe->has_size = true;
 	rfe->size = p->stat.st_size;
 
-	result = store_validation_data_build_id(rfe, lfd, p);
+	if (opts.file_validation_method == FILE_VALIDATION_BUILD_ID)
+		result = store_validation_data_build_id(rfe, lfd, p);
 
 	if (result == -1)
 		return false;
@@ -2053,7 +2054,8 @@ static bool validate_file(const int fd, const struct stat *fd_status,
 		return false;
 	}
 
-	result = validate_with_build_id(fd, fd_status, rfi);
+	if (opts.file_validation_method == FILE_VALIDATION_BUILD_ID)
+		result = validate_with_build_id(fd, fd_status, rfi);
 
 	if (result == -1)
 		return false;

criu/include/cr_options.h

@@ -63,6 +63,24 @@ struct cg_root_opt {
 
 #define DEFAULT_TIMEOUT		10
 
+enum FILE_VALIDATION_OPTIONS
+{
+	/*
+	 * This constant indicates that the file validation should be tried with the
+	 * file size method by default.
+	 */
+	FILE_VALIDATION_FILE_SIZE,
+
+	/*
+	 * This constant indicates that the file validation should be tried with the
+	 * build-ID method by default.
+	 */
+	FILE_VALIDATION_BUILD_ID
+};
+
+/* This constant dictates which file validation method should be tried by default. */
+#define FILE_VALIDATION_DEFAULT			FILE_VALIDATION_BUILD_ID
+
 struct irmap;
 
 struct irmap_path_opt {
@@ -153,6 +171,9 @@ struct cr_options {
 	char			*tls_key;
 	int			tls;
 	int			tls_no_cn_verify;
+
+	/* This stores which method to use for file validation. */
+	int 			file_validation_method;
 };
 
 extern struct cr_options opts;