[PATCH] depmod: Introduce a outdir option

* [PATCH] depmod: Introduce a outdir option
@ 2023-01-30 18:33 Emil Velikov
  2023-02-02  7:14 ` Lucas De Marchi
  0 siblings, 1 reply; 2+ messages in thread
From: Emil Velikov @ 2023-01-30 18:33 UTC (permalink / raw)
  To: linux-modules; +Cc: emil.l.velikov

From: Emil Velikov <emil.velikov@collabora.com>

This option is equivalent to basedir, with the small difference being
that's where the meta-data files are generated. In other words, this
allows us to have read-only input modules and modules.dep, while still
being able to generate the meta-data files.

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
---

Hello team,

Here's a handy feature behind the request at
https://github.com/kmod-project/kmod/issues/13

This is my first time hacking on kmod, so hope I didn't make too many
mistakes :-) There are a few TODO notes below where your input is
greatly appreciated.

TODO:
 - Add tests - team, any pointers or requests?
 - Split the dirnamelen shorthand tenary operator change - is it worth
   it?
---
 man/depmod.xml | 19 +++++++++++++++++++
 tools/depmod.c | 25 ++++++++++++++++++++++---
 2 files changed, 41 insertions(+), 3 deletions(-)

diff --git a/man/depmod.xml b/man/depmod.xml
index ea0be27..c53624d 100644
--- a/man/depmod.xml
+++ b/man/depmod.xml
@@ -45,6 +45,7 @@
     <cmdsynopsis>
       <command>depmod</command>
       <arg><option>-b <replaceable>basedir</replaceable></option></arg>
+      <arg><option>-o <replaceable>outdir</replaceable></option></arg>
       <arg><option>-e</option></arg>
       <arg><option>-E <replaceable>Module.symvers</replaceable></option></arg>
       <arg><option>-F <replaceable>System.map</replaceable></option></arg>
@@ -151,6 +152,24 @@
           </para>
         </listitem>
       </varlistentry>
+      <varlistentry>
+        <term>
+          <option>-o <replaceable>outdir</replaceable></option>
+        </term>
+        <term>
+          <option>--outdir <replaceable>outdir</replaceable></option>
+        </term>
+        <listitem>
+          <para>
+            If your modules are stored in a read-only location, you may want to
+            create the output meta-data files in another location. Setting
+            <replaceable>outdir</replaceable> serves as a root to that location
+            similar to how we use <replaceable>basedir</replaceable>. Use this
+            option if you are a distribution vendor who needs to pre-generate
+            the meta-data files rather than running depmod again later.
+          </para>
+        </listitem>
+      </varlistentry>
       <varlistentry>
         <term>
           <option>-C</option>
diff --git a/tools/depmod.c b/tools/depmod.c
index 364b7d4..aaf2327 100644
--- a/tools/depmod.c
+++ b/tools/depmod.c
@@ -58,11 +58,12 @@ static const char *default_cfg_paths[] = {
 	NULL
 };
 
-static const char cmdopts_s[] = "aAb:C:E:F:euqrvnP:wmVh";
+static const char cmdopts_s[] = "aAb:o:C:E:F:euqrvnP:wmVh";
 static const struct option cmdopts[] = {
 	{ "all", no_argument, 0, 'a' },
 	{ "quick", no_argument, 0, 'A' },
 	{ "basedir", required_argument, 0, 'b' },
+	{ "outdir", required_argument, 0, 'o' },
 	{ "config", required_argument, 0, 'C' },
 	{ "symvers", required_argument, 0, 'E' },
 	{ "filesyms", required_argument, 0, 'F' },
@@ -104,6 +105,7 @@ static void help(void)
 		"\n"
 		"The following options are useful for people managing distributions:\n"
 		"\t-b, --basedir=DIR    Use an image of a module tree.\n"
+		"\t-o, --outdir=DIR     The output equivalent of basedir.\n"
 		"\t-F, --filesyms=FILE  Use the file instead of the\n"
 		"\t                     current kernel symbols.\n"
 		"\t-E, --symvers=FILE   Use Module.symvers file to check\n"
@@ -467,6 +469,8 @@ struct cfg {
 	const char *kversion;
 	char dirname[PATH_MAX];
 	size_t dirnamelen;
+	char outdirname[PATH_MAX];
+	size_t outdirnamelen;
 	char sym_prefix;
 	uint8_t check_symvers;
 	uint8_t print_unknown;
@@ -2576,7 +2580,7 @@ static int depmod_output(struct depmod *depmod, FILE *out)
 		{ "modules.devname", output_devname },
 		{ }
 	};
-	const char *dname = depmod->cfg->dirname;
+	const char *dname = depmod->cfg->outdirname;
 	int dfd, err = 0;
 	struct timeval tv;
 
@@ -2585,6 +2589,11 @@ static int depmod_output(struct depmod *depmod, FILE *out)
 	if (out != NULL)
 		dfd = -1;
 	else {
+		err = mkdir_p(dname, strlen(dname), 0755);
+		if (err < 0) {
+			CRIT("could not create directory %s: %m\n", dname);
+			return err;
+		}
 		dfd = open(dname, O_RDONLY);
 		if (dfd < 0) {
 			err = -errno;
@@ -2898,6 +2907,7 @@ static int do_depmod(int argc, char *argv[])
 	FILE *out = NULL;
 	int err = 0, all = 0, maybe_all = 0, n_config_paths = 0;
 	_cleanup_free_ char *root = NULL;
+	_cleanup_free_ char *out_root = NULL;
 	_cleanup_free_ const char **config_paths = NULL;
 	const char *system_map = NULL;
 	const char *module_symvers = NULL;
@@ -2927,6 +2937,11 @@ static int do_depmod(int argc, char *argv[])
 				free(root);
 			root = path_make_absolute_cwd(optarg);
 			break;
+		case 'o':
+			if (out_root)
+				free(out_root);
+			out_root = path_make_absolute_cwd(optarg);
+			break;
 		case 'C': {
 			size_t bytes = sizeof(char *) * (n_config_paths + 2);
 			void *tmp = realloc(config_paths, bytes);
@@ -3009,7 +3024,11 @@ static int do_depmod(int argc, char *argv[])
 
 	cfg.dirnamelen = snprintf(cfg.dirname, PATH_MAX,
 				  "%s/lib/modules/%s",
-				  root == NULL ? "" : root, cfg.kversion);
+				  root ?: "", cfg.kversion);
+
+	cfg.outdirnamelen = snprintf(cfg.outdirname, PATH_MAX,
+				     "%s/lib/modules/%s",
+				     out_root ?: (root ?: ""), cfg.kversion);
 
 	if (optind == argc)
 		all = 1;
-- 
2.39.1


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