libkmod: tools: Introduce 'module fallback' directory

Makefile.am

@@ -32,6 +32,7 @@ AM_CPPFLAGS = \
 	-DSYSCONFDIR=\""$(sysconfdir)"\" \
 	-DDISTCONFDIR=\""$(distconfdir)"\" \
 	-DMODULE_DIRECTORY=\""$(module_directory)"\" \
+	-DMODULE_FALLBACK_DIRECTORY=\""$(module_fallback_directory)"\" \
 	${zlib_CFLAGS}
 
 AM_CFLAGS = $(OUR_CFLAGS)
@@ -196,7 +197,7 @@ MODULE_PLAYGROUND = testsuite/module-playground
 BUILD_MODULES = $(AM_V_GEN) $(top_srcdir)/scripts/setup-modules.sh $(top_srcdir) $(top_builddir) $(MODULE_PLAYGROUND)
 ROOTFS = testsuite/rootfs
 ROOTFS_PRISTINE = $(top_srcdir)/testsuite/rootfs-pristine
-CREATE_ROOTFS = $(AM_V_GEN) $(top_srcdir)/scripts/setup-rootfs.sh $(ROOTFS_PRISTINE) $(ROOTFS) $(MODULE_PLAYGROUND) $(top_builddir)/config.h $(sysconfdir) $(module_directory)
+CREATE_ROOTFS = $(AM_V_GEN) $(top_srcdir)/scripts/setup-rootfs.sh $(ROOTFS_PRISTINE) $(ROOTFS) $(MODULE_PLAYGROUND) $(top_builddir)/config.h $(sysconfdir) $(module_directory) $(module_fallback_directory)
 
 build-module-playground:
 	$(BUILD_MODULES)

configure.ac

@@ -85,8 +85,13 @@ AC_ARG_WITH([module_directory],
         [], [with_module_directory=/lib/modules])
 AC_SUBST([module_directory], [$with_module_directory])
 
+AC_ARG_WITH([module_fallback_directory],
+        AS_HELP_STRING([--with-module-fallback_directory=DIR], [alternative directory in which to look for kernel modules @<:@default=/run/modules@:>@]),
+        [], [with_module_fallback_directory=/run/modules])
+AC_SUBST([module_fallback_directory], [$with_module_fallback_directory])
+
 # Check all directory arguments for consistency.
-for ac_var in	distconfdir module_directory
+for ac_var in	distconfdir module_directory module_fallback_directory
 do
   eval ac_val=\$$ac_var
   # Remove trailing slashes.

libkmod/libkmod.c

@@ -164,6 +164,7 @@ static int log_priority(const char *priority)
 }
 
 static const char *dirname_default_prefix = MODULE_DIRECTORY;
+static const char *dirname_fallback_prefix = MODULE_FALLBACK_DIRECTORY;
 
 static char *get_kernel_release(const char *dirname)
 {
@@ -179,6 +180,13 @@ static char *get_kernel_release(const char *dirname)
 	if (asprintf(&p, "%s/%s", dirname_default_prefix, u.release) < 0)
 		return NULL;
 
+	/* If main path doesn't exist, try fallback */
+	if (is_dir(p) <= 0) {
+		free(p);
+		if (asprintf(&p, "%s/%s", dirname_fallback_prefix, u.release) < 0)
+			return NULL;
+	}
+
 	return p;
 }
 

man/Makefile.am

@@ -18,6 +18,7 @@ define generate_manpage
 	sed -e 's|@SYSCONFDIR@|$(sysconfdir)|g' | \
 	sed -e 's|@DISTCONFDIR@|$(distconfdir)|g' | \
 	sed -e 's|@MODULE_DIRECTORY@|$(module_directory)|g' | \
+	sed -e 's|@MODULE_FALLBACK_DIRECTORY@|$(module_fallback_directory)|g' | \
 	$(SCDOC) > $@
 endef
 

meson.build

@@ -191,6 +191,12 @@ if moduledir == ''
 endif
 cdata.set_quoted('MODULE_DIRECTORY', moduledir)
 
+moduledir = get_option('modulefallbackdir')
+if moduledir == ''
+  moduledir = '/run/modules'
+endif
+cdata.set_quoted('MODULE_FALLBACK_DIRECTORY', moduledir)
+
 _completiondirs = [
   ['bashcompletiondir', 'bash-completion', 'bash-completion/completions', 'shell-completion/bash/@0@'],
   ['fishcompletiondir', 'fish',            'fish/vendor_functions.d',     'shell-completion/fish/@0@.fish'],

meson_options.txt

@@ -12,6 +12,12 @@ option(
   description : 'Directory to look for kernel modules. Default: /lib/modules',
 )
 
+option(
+  'modulefallbackdir',
+  type : 'string',
+  description : 'Alternative directory to look for kernel modules. Default: /run/modules',
+)
+
 option(
   'bashcompletiondir',
   type : 'string',

scripts/setup-rootfs.sh

@@ -8,6 +8,7 @@ MODULE_PLAYGROUND=$3
 CONFIG_H=$4
 SYSCONFDIR=$5
 MODULE_DIRECTORY=$6
+MODULE_FALLBACK_DIRECTORY=$7
 ANOTHER_MODULE_DIRECTORY=/foobar
 
 # create rootfs from rootfs-pristine
@@ -98,6 +99,8 @@ map=(
     ["test-modprobe/external/lib/modules/external/"]="mod-simple.ko"
     ["test-modprobe/module-from-abspath/home/foo/"]="mod-simple.ko"
     ["test-modprobe/module-from-relpath/home/foo/"]="mod-simple.ko"
+    ["test-modprobe/fallback$MODULE_FALLBACK_DIRECTORY/4.4.4/kernel/"]="mod-simple.ko"
+    ["test-modprobe/fallback-custom$MODULE_FALLBACK_DIRECTORY/3.3.3/kernel/"]="mod-simple.ko"
     ["test-depmod/modules-order-compressed$MODULE_DIRECTORY/4.4.4/kernel/drivers/block/cciss.ko"]="mod-fake-cciss.ko"
     ["test-depmod/modules-order-compressed$MODULE_DIRECTORY/4.4.4/kernel/drivers/scsi/hpsa.ko"]="mod-fake-hpsa.ko"
     ["test-depmod/modules-order-compressed$MODULE_DIRECTORY/4.4.4/kernel/drivers/scsi/scsi_mod.ko"]="mod-fake-scsi-mod.ko"
@@ -111,6 +114,8 @@ map=(
     ["test-modinfo/mod-simple-sha256.ko"]="mod-simple.ko"
     ["test-modinfo/mod-simple-pkcs7.ko"]="mod-simple.ko"
     ["test-modinfo/external/lib/modules/external/mod-simple.ko"]="mod-simple.ko"
+    ["test-modinfo/fallback$MODULE_FALLBACK_DIRECTORY/4.4.4/kernel/"]="mod-simple.ko"
+    ["test-modinfo/fallback-custom$MODULE_FALLBACK_DIRECTORY/3.3.3/kernel/"]="mod-simple.ko"
     ["test-weakdep$MODULE_DIRECTORY/4.4.4/kernel/mod-loop-a.ko"]="mod-loop-a.ko"
     ["test-weakdep$MODULE_DIRECTORY/4.4.4/kernel/mod-loop-b.ko"]="mod-loop-b.ko"
     ["test-weakdep$MODULE_DIRECTORY/4.4.4/kernel/mod-simple.ko"]="mod-simple.ko"

shared/util.c

@@ -377,7 +377,7 @@ char *path_make_absolute_cwd(const char *p)
 	return r;
 }
 
-static inline int is_dir(const char *path)
+int is_dir(const char *path)
 {
 	struct stat st;
 

shared/util.h

@@ -44,6 +44,7 @@ _nonnull_(1) char *freadline_wrapped(FILE *fp, unsigned int *linenum);
 /* path handling functions                                                  */
 /* ************************************************************************ */
 _must_check_ _nonnull_all_ char *path_make_absolute_cwd(const char *p);
+int is_dir(const char *path);
 int mkdir_p(const char *path, int len, mode_t mode);
 int mkdir_parents(const char *path, mode_t mode);
 unsigned long long stat_mstamp(const struct stat *st);

testsuite/rootfs-pristine/test-modinfo/correct-fallback-custom.txt

@@ -0,0 +1 @@
+/run/modules/3.3.3/kernel/mod-simple.ko

testsuite/rootfs-pristine/test-modinfo/correct-fallback.txt

@@ -0,0 +1 @@
+/run/modules/4.4.4/kernel/mod-simple.ko

testsuite/rootfs-pristine/test-modinfo/fallback-custom/run/modules/3.3.3/modules.alias

@@ -0,0 +1 @@
+# Aliases extracted from modules themselves.

testsuite/rootfs-pristine/test-modinfo/fallback-custom/run/modules/3.3.3/modules.dep

@@ -0,0 +1 @@
+kernel/mod-simple.ko:

testsuite/rootfs-pristine/test-modinfo/fallback-custom/run/modules/3.3.3/modules.devname

@@ -0,0 +1 @@
+# Device nodes to trigger on-demand module loading.

testsuite/rootfs-pristine/test-modinfo/fallback-custom/run/modules/3.3.3/modules.softdep

@@ -0,0 +1 @@
+# Soft dependencies extracted from modules themselves.

testsuite/rootfs-pristine/test-modinfo/fallback-custom/run/modules/3.3.3/modules.symbols

@@ -0,0 +1 @@
+# Aliases for symbols, used by symbol_request().

testsuite/rootfs-pristine/test-modinfo/fallback/run/modules/4.4.4/modules.alias

@@ -0,0 +1 @@
+# Aliases extracted from modules themselves.

testsuite/rootfs-pristine/test-modinfo/fallback/run/modules/4.4.4/modules.dep

@@ -0,0 +1 @@
+kernel/mod-simple.ko:

testsuite/rootfs-pristine/test-modinfo/fallback/run/modules/4.4.4/modules.devname

@@ -0,0 +1 @@
+# Device nodes to trigger on-demand module loading.

testsuite/rootfs-pristine/test-modinfo/fallback/run/modules/4.4.4/modules.softdep

@@ -0,0 +1 @@
+# Soft dependencies extracted from modules themselves.

testsuite/rootfs-pristine/test-modinfo/fallback/run/modules/4.4.4/modules.symbols

@@ -0,0 +1 @@
+# Aliases for symbols, used by symbol_request().

testsuite/rootfs-pristine/test-modprobe/fallback-custom/run/modules/3.3.3/modules.alias

@@ -0,0 +1 @@
+# Aliases extracted from modules themselves.

testsuite/rootfs-pristine/test-modprobe/fallback-custom/run/modules/3.3.3/modules.dep

@@ -0,0 +1 @@
+kernel/mod-simple.ko:

testsuite/rootfs-pristine/test-modprobe/fallback-custom/run/modules/3.3.3/modules.devname

@@ -0,0 +1 @@
+# Device nodes to trigger on-demand module loading.

testsuite/rootfs-pristine/test-modprobe/fallback-custom/run/modules/3.3.3/modules.softdep

@@ -0,0 +1 @@
+# Soft dependencies extracted from modules themselves.

testsuite/rootfs-pristine/test-modprobe/fallback-custom/run/modules/3.3.3/modules.symbols

@@ -0,0 +1 @@
+# Aliases for symbols, used by symbol_request().

testsuite/rootfs-pristine/test-modprobe/fallback/run/modules/4.4.4/modules.alias

@@ -0,0 +1 @@
+# Aliases extracted from modules themselves.

testsuite/rootfs-pristine/test-modprobe/fallback/run/modules/4.4.4/modules.dep

@@ -0,0 +1 @@
+kernel/mod-simple.ko:

testsuite/rootfs-pristine/test-modprobe/fallback/run/modules/4.4.4/modules.devname

@@ -0,0 +1 @@
+# Device nodes to trigger on-demand module loading.

testsuite/rootfs-pristine/test-modprobe/fallback/run/modules/4.4.4/modules.softdep

@@ -0,0 +1 @@
+# Soft dependencies extracted from modules themselves.

testsuite/rootfs-pristine/test-modprobe/fallback/run/modules/4.4.4/modules.symbols

@@ -0,0 +1 @@
+# Aliases for symbols, used by symbol_request().

testsuite/test-modinfo.c

@@ -124,4 +124,53 @@ DEFINE_TEST(test_modinfo_builtin,
 		.out = TESTSUITE_ROOTFS "test-modinfo/correct-builtin.txt",
 	})
 
+static noreturn int test_modinfo_fallback(const struct test *t)
+{
+	const char *const args[] = {
+		// clang-format off
+		progname,
+		"-F", "filename",
+		"mod-simple",
+		NULL,
+		// clang-format on
+	};
+	test_spawn_prog(progname, args);
+	exit(EXIT_FAILURE);
+}
+DEFINE_TEST(test_modinfo_fallback,
+	.description = "check if modinfo finds external module",
+	.config = {
+		[TC_ROOTFS] = TESTSUITE_ROOTFS "test-modinfo/fallback",
+		[TC_UNAME_R] = "4.4.4",
+	},
+	.output = {
+		.out = TESTSUITE_ROOTFS "test-modinfo/correct-fallback.txt",
+	})
+
+static noreturn int test_modinfo_fallback_custom(const struct test *t)
+{
+	const char *const args[] = {
+		// clang-format off
+		progname,
+		"-F", "filename",
+		"--set-version",
+		"3.3.3",
+		"mod-simple",
+		NULL,
+		// clang-format on
+	};
+	test_spawn_prog(progname, args);
+	exit(EXIT_FAILURE);
+}
+DEFINE_TEST(test_modinfo_fallback_custom,
+	.description = "check if modinfo finds external module",
+	.config = {
+		[TC_ROOTFS] = TESTSUITE_ROOTFS "test-modinfo/fallback-custom",
+		[TC_UNAME_R] = "4.4.4",
+	},
+	.output = {
+		.out = TESTSUITE_ROOTFS "test-modinfo/correct-fallback-custom.txt",
+	})
+
+
 TESTSUITE_MAIN();

testsuite/test-modprobe.c

@@ -484,4 +484,51 @@ DEFINE_TEST(modprobe_module_from_relpath,
 	.modules_loaded = "mod-simple",
 	);
 
+static noreturn int modprobe_fallback(const struct test *t)
+{
+	const char *progname = TOOLS_DIR "/modprobe";
+	const char *const args[] = {
+		progname,
+		"mod-simple",
+		NULL,
+	};
+
+	test_spawn_prog(progname, args);
+	exit(EXIT_FAILURE);
+}
+DEFINE_TEST(modprobe_fallback,
+	.description = "check modprobe able to load module from fallback path",
+	.config = {
+		[TC_UNAME_R] = "4.4.4",
+		[TC_ROOTFS] = TESTSUITE_ROOTFS "test-modprobe/fallback",
+		[TC_INIT_MODULE_RETCODES] = "",
+	},
+	.need_spawn = true,
+	.modules_loaded = "mod-simple",
+	);
+
+static noreturn int modprobe_fallback_custom(const struct test *t)
+{
+	const char *progname = TOOLS_DIR "/modprobe";
+	const char *const args[] = {
+		progname,
+		"--set-version",
+		"3.3.3",
+		"mod-simple",
+		NULL,
+	};
+
+	test_spawn_prog(progname, args);
+	exit(EXIT_FAILURE);
+}
+DEFINE_TEST(modprobe_fallback_custom,
+	.description = "check modprobe able to load module from fallback path with --set-version",
+	.config = {
+		[TC_ROOTFS] = TESTSUITE_ROOTFS "test-modprobe/fallback-custom",
+		[TC_INIT_MODULE_RETCODES] = "",
+	},
+	.need_spawn = true,
+	.modules_loaded = "mod-simple",
+	);
+
 TESTSUITE_MAIN();

tools/modinfo.c

@@ -443,6 +443,17 @@ static int do_modinfo(int argc, char *argv[])
 			    root, kversion);
 			return EXIT_FAILURE;
 		}
+
+		if (is_dir(dirname_buf) <= 0) {
+			n = snprintf(dirname_buf, sizeof(dirname_buf),
+				     "%s" MODULE_FALLBACK_DIRECTORY "/%s", root, kversion);
+			if (n >= (int)sizeof(dirname_buf)) {
+				ERR("bad directory %s" MODULE_FALLBACK_DIRECTORY "/%s: path too long\n",
+				    root, kversion);
+				return EXIT_FAILURE;
+			}
+		}
+
 		dirname = dirname_buf;
 	}
 

tools/modprobe.c

@@ -983,6 +983,18 @@ static int do_modprobe(int argc, char **orig_argv)
 			err = -1;
 			goto done;
 		}
+
+		if (is_dir(dirname_buf) <= 0) {
+			n = snprintf(dirname_buf, sizeof(dirname_buf),
+				     "%s" MODULE_FALLBACK_DIRECTORY "/%s", root, kversion);
+			if (n >= (int)sizeof(dirname_buf)) {
+				ERR("bad directory %s" MODULE_FALLBACK_DIRECTORY "/%s: path too long\n",
+				    root, kversion);
+				err = -1;
+				goto done;
+			}
+		}
+
 		dirname = dirname_buf;
 	}