modprobe documentation discrepancy (modules.dep support)

modprobe documentation discrepancy (modules.dep support)

[Andrej Krutak]

Hi,

the modprobe documentation states that:

%<--------
modprobe expects an up-to-date modules.dep.bin file (or fallback human 
readable modules.dep file)
%<--------

but in reality no fallback happens in the current code. module-init-tools did 
the fallback, so I suppose this is a leftover from the previous documentation.

I guess the simplest thing to do would be removing the documentation. On the 
other hand the depmod.pl script (from ltib.org) doesn't create the binary 
file, so not supporting "legacy" modules.dep breaks some stuff...

-- 
Best regards | S pozdravom | Mit freundlichen Gr��en | Cordialement

Andrej Krutak
SYSGO

[PATCH] Re: modprobe documentation discrepancy (modules.dep support)

[Andrej Krutak]

Hi again,

below is a patch to (re-)add support for modules.dep (in addition to
modules.dep.bin), in a very dirty way. Basically I just took parts of the 
original code from module-init-tools...

Also, it fixes the CHECK_ERR_AND_FINISH macro.


However, this doesn't fix the whole "problem" - 'modprobe nonexistingmodule'
is called, no error is printed, because of the faulty processing of subsequent
non-existent files (like modules.builtin.bin etc. - which depmod.pl doesn't 
generate).

To fully fix this, one would have to also add support for the other
legacy files. Well, at least a support to handle the missing files gracefully.

Fixing this is important for when you want to cross-compile the kernel in a 
non-linux environment. I didn't find find any other tool than depmod.pl that 
could generate all the files required by modprobe (but depmod.pl, as mentioned 
before, doesn't generate other .bin files) - and kmod/module-init-tools can't 
be cross-compiled for cygwin/mingw32...


Best regards,
Andrej Krutak
SYSGO

---
 libkmod/libkmod-module.c |    4 +-
 libkmod/libkmod.c        |  107 
+++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 107 insertions(+), 4 deletions(-)

diff --git a/libkmod/libkmod-module.c b/libkmod/libkmod-module.c
index 3d3325f..e737d30 100644
--- a/libkmod/libkmod-module.c
+++ b/libkmod/libkmod-module.c
@@ -473,7 +473,7 @@ KMOD_EXPORT struct kmod_module *kmod_module_ref(struct 
kmod_module *mod)
 		if ((_err) < 0)						\
 			goto _label_err;				\
 		if (*(_list) != NULL)					\
-			goto finish;					\
+			goto label_finish;					\
 	} while (0)
 
 /**
@@ -553,7 +553,7 @@ finish:
 	DBG(ctx, "lookup %s=%d, list=%p\n", alias, err, *list);
 	return err;
 fail:
-	DBG(ctx, "Failed to lookup %s\n", alias);
+	DBG(ctx, "Failed to lookup %s (%d)\n", alias, err);
 	kmod_module_unref_list(*list);
 	*list = NULL;
 	return err;
diff --git a/libkmod/libkmod.c b/libkmod/libkmod.c
index ef83e31..4a60416 100644
--- a/libkmod/libkmod.c
+++ b/libkmod/libkmod.c
@@ -533,11 +533,106 @@ finish:
 	return err;
 }
 
+/**
+ * modname_equal - compare module names (up to len), with '_' and '-' equal
+ *
+ * @a:		first module name
+ * @b:		second module name
+ * @len:	length to compare
+ *
+ */
+static int modname_equal(const char *a, const char *b, unsigned int len)
+{
+	unsigned int i;
+
+	if (strlen(b) != len)
+		return 0;
+
+	for (i = 0; i < len; i++) {
+		if ((a[i] == '_' || a[i] == '-')
+		    && (b[i] == '_' || b[i] == '-'))
+			continue;
+		if (a[i] != b[i])
+			return 0;
+	}
+	return 1;
+}
+
+static char *my_basename(const char *path)
+{
+	const char *base = strrchr(path, '/');
+	if (base)
+		return (char *) base + 1;
+	return (char *) path;
+}
+
+
+/**
+ * add_modules_dep_line - parse a dep line from the module.dep[.bin] file
+ *
+ * @line:	input file line
+ * @name:	module name
+ *
+ * Add dependency information if this line of the dep file matches mod name
+ */
+static int is_module_line(char *line,
+				const char *name)
+{
+	char *ptr;
+	int len;
+	char *modname;
+	int rv;
+
+	line = strdup(line);
+
+	/* Ignore lines without : or which start with a # */
+	ptr = strchr(line, ':');
+	if (ptr == NULL || line[strspn(line, "\t ")] == '#') {
+		free(line);
+		return 0;
+	}
+
+	/* Is this the module we are looking for? */
+	*ptr = '\0';
+	modname = my_basename(line);
+
+	len = strlen(modname);
+	if (strchr(modname, '.'))
+		len = strchr(modname, '.') - modname;
+
+	rv = modname_equal(modname, name, len);
+
+	free(line);
+	return rv;
+}
+
+static char *kmod_search_moddep_legacy(struct kmod_ctx *ctx, const char 
*name, const char *fn)
+{
+	char *line;
+	FILE *modules_dep;
+	
+	modules_dep = fopen(fn, "r");
+	if (!modules_dep)
+		return NULL;
+
+	/* Stop at first line, as we can have duplicates (eg. symlinks
+           from boot/ */
+	while ((line = getline_wrapped(modules_dep, NULL)) != NULL) {
+		if (is_module_line(line, name))
+			break;
+		free(line);
+	}
+	fclose(modules_dep);
+
+	return line;
+}
+
 char *kmod_search_moddep(struct kmod_ctx *ctx, const char *name)
 {
 	struct index_file *idx;
 	char fn[PATH_MAX];
 	char *line;
+	
 
 	if (ctx->indexes[KMOD_INDEX_MODULES_DEP]) {
 		DBG(ctx, "use mmaped index '%s' modname=%s\n",
@@ -553,8 +648,16 @@ char *kmod_search_moddep(struct kmod_ctx *ctx, const char 
*name)
 
 	idx = index_file_open(fn);
 	if (idx == NULL) {
-		DBG(ctx, "could not open moddep file '%s'\n", fn);
-		return NULL;
+		struct stat st;
+		
+		snprintf(fn, sizeof(fn), "%s/%s", ctx->dirname,
+					index_files[KMOD_INDEX_MODULES_DEP].fn);
+		if (stat(fn, &st) != 0) {
+			DBG(ctx, "could not open moddep file '%s[.bin]'\n", fn);
+			return NULL;
+		}
+		
+		return kmod_search_moddep_legacy(ctx, name, fn);
 	}
 
 	line = index_search(idx, name);
-- 
1.7.9.5

Re: [PATCH] Re: modprobe documentation discrepancy (modules.dep support)

[Lucas De Marchi]

On Wed, Feb 26, 2014 at 1:19 PM, Andrej Krutak <andrej.krutak@sysgo.com> wrote:
> Hi again,
>
> below is a patch to (re-)add support for modules.dep (in addition to
> modules.dep.bin), in a very dirty way. Basically I just took parts of the
> original code from module-init-tools...
>
> Also, it fixes the CHECK_ERR_AND_FINISH macro.
>
>
> However, this doesn't fix the whole "problem" - 'modprobe nonexistingmodule'
> is called, no error is printed, because of the faulty processing of subsequent
> non-existent files (like modules.builtin.bin etc. - which depmod.pl doesn't
> generate).
>
> To fully fix this, one would have to also add support for the other
> legacy files. Well, at least a support to handle the missing files gracefully.
>
> Fixing this is important for when you want to cross-compile the kernel in a
> non-linux environment. I didn't find find any other tool than depmod.pl that
> could generate all the files required by modprobe (but depmod.pl, as mentioned
> before, doesn't generate other .bin files) - and kmod/module-init-tools can't
> be cross-compiled for cygwin/mingw32...

I think it's better to just remove the reference in the man page. We
don't support other tools poking /lib/modules/* files. They are
private to kmod and we can break them in a future version.

I'd rather advise you to fix your setup so you don't need to
cross-compile depmod. If you want to cross-compile... well, you need
to provide the patches to at least adding the stubs for things that
doesn't exist there... But this patch would probably never be accepted
upstream since it's such a weird thing to do, sorry.

Lucas De Marchi