This patch changes 'modprobe' & co. so they honor the 'LINUX_MODULE_DIRECTORY'
environment variable, rather than looking for modules exclusively in
/lib/modules.

Original patch by David Guibert, from Nixpkgs; adjusted to use
'LINUX_MODULE_DIRECTORY' rather than 'MODULE_DIR' as the variable name.

diff --git a/depmod.c b/depmod.c
index a1d2f8c..ff579c7 100644
--- a/depmod.c
+++ b/depmod.c
@@ -48,9 +48,6 @@
 
 #include "testing.h"
 
-#ifndef MODULE_DIR
-#define MODULE_DIR "/lib/modules/"
-#endif
 
 #ifndef MODULE_BUILTIN_KEY
 #define MODULE_BUILTIN_KEY "built-in"
@@ -1516,6 +1513,7 @@ static int parse_config_file(const char *filename,
 	char *line;
 	unsigned int linenum = 0;
 	FILE *cfile;
+ 	char *module_dir;
 
 	cfile = fopen(filename, "r");
 	if (!cfile) {
@@ -1525,6 +1523,10 @@ static int parse_config_file(const char *filename,
 		return 0;
 	}
 
+        if((module_dir = getenv("LINUX_MODULE_DIRECTORY")) == NULL) {
+                module_dir = "/lib/modules";
+        }
+
 	while ((line = getline_wrapped(cfile, &linenum)) != NULL) {
 		char *ptr = line;
 		char *cmd, *modname;
@@ -1549,8 +1551,8 @@ static int parse_config_file(const char *filename,
 							     0, *search);
 					continue;
 				}
-				nofail_asprintf(&dirname, "%s%s%s/%s", basedir,
-					MODULE_DIR, kernelversion, search_path);
+				nofail_asprintf(&dirname, "%s%s/%s/%s", basedir,
+					module_dir, kernelversion, search_path);
 				len = strlen(dirname);
 				*search = add_search(dirname, len, *search);
 				free(dirname);
@@ -1564,8 +1566,8 @@ static int parse_config_file(const char *filename,
 			if (!regex_match(kernelversion, (const char *)version))
 				continue;
 
-			nofail_asprintf(&pathname, "%s%s%s/%s/%s.ko", basedir,
-				MODULE_DIR, kernelversion, subdir, modname);
+			nofail_asprintf(&pathname, "%s%s/%s/%s/%s.ko", basedir,
+				module_dir, kernelversion, subdir, modname);
 
 			*overrides = add_override(pathname, *overrides);
 			free(pathname);
@@ -1737,6 +1739,7 @@ int main(int argc, char *argv[])
 	char *basedir = "", *dirname, *version;
 	char *system_map = NULL, *module_symvers = NULL;
 	int i;
+ 	char *module_dir;
 	const char *config = NULL;
 
 	if (native_endianness() == 0)
@@ -1832,7 +1835,11 @@ int main(int argc, char *argv[])
 	if (optind == argc)
 		all = 1;
 
-	nofail_asprintf(&dirname, "%s%s%s", basedir, MODULE_DIR, version);
+        if((module_dir = getenv("LINUX_MODULE_DIRECTORY")) == NULL) {
+                module_dir = "/lib/modules";
+        }
+
+	nofail_asprintf(&dirname, "%s%s/%s", basedir, module_dir, version);
 
 	if (maybe_all) {
 		if (!doing_stdout && !depfile_out_of_date(dirname))
@@ -1849,8 +1856,8 @@ int main(int argc, char *argv[])
 		char *dirname;
 		size_t len;
 
-		nofail_asprintf(&dirname, "%s%s%s/updates", basedir,
-				MODULE_DIR, version);
+		nofail_asprintf(&dirname, "%s%s/%s/updates", basedir,
+				module_dir, version);
 		len = strlen(dirname);
 		search = add_search(dirname, len, search);
 	}
diff --git a/modinfo.c b/modinfo.c
index 1dd8469..6a1865b 100644
--- a/modinfo.c
+++ b/modinfo.c
@@ -19,9 +19,6 @@
 #include "zlibsupport.h"
 #include "testing.h"
 
-#ifndef MODULE_DIR
-#define MODULE_DIR "/lib/modules"
-#endif
 
 struct param
 {
@@ -193,6 +190,11 @@ static struct elf_file *grab_module(const char *name,
 	struct utsname buf;
 	char *depname, *p, *moddir;
 	struct elf_file *module;
+ 	char *module_dir;
+
+        if((module_dir = getenv("LINUX_MODULE_DIRECTORY")) == NULL) {
+                module_dir = "/lib/modules";
+        }
 
 	if (strchr(name, '.') || strchr(name, '/')) {
 		module = grab_elf_file(name);
@@ -207,9 +209,9 @@ static struct elf_file *grab_module(const char *name,
 		kernel = buf.release;
 	}
 	if (strlen(basedir))
-		nofail_asprintf(&moddir, "%s/%s/%s", basedir, MODULE_DIR, kernel);
+		nofail_asprintf(&moddir, "%s/%s/%s", basedir, module_dir, kernel);
 	else
-		nofail_asprintf(&moddir, "%s/%s", MODULE_DIR, kernel);
+		nofail_asprintf(&moddir, "%s/%s", module_dir, kernel);
 
 	/* Search for it in modules.dep. */
 	nofail_asprintf(&depname, "%s/%s", moddir, "modules.dep");
diff --git a/modprobe.c b/modprobe.c
index 5464f45..cb57917 100644
--- a/modprobe.c
+++ b/modprobe.c
@@ -86,10 +86,6 @@ typedef enum
 
 } modprobe_flags_t;
 
-#ifndef MODULE_DIR
-#define MODULE_DIR "/lib/modules"
-#endif
-
 /**
  * print_usage - output the prefered program usage
  *
@@ -2136,6 +2132,7 @@ int main(int argc, char *argv[])
 	struct modprobe_conf conf = {};
 
 	recursion_depth = 0;
+ 	char *module_dir = NULL;
 
 	/* Prepend options from environment. */
 	argv = merge_args(getenv("MODPROBE_OPTIONS"), argv, &argc);
@@ -2233,7 +2230,11 @@ int main(int argc, char *argv[])
 	if (argc < optind + 1 && !dump_config && !list_only)
 		print_usage(argv[0]);
 
-	nofail_asprintf(&dirname, "%s%s/%s", basedir, MODULE_DIR, buf.release);
+	if((module_dir = getenv("LINUX_MODULE_DIRECTORY")) == NULL) {
+		module_dir = "/lib/modules";
+	}
+
+	nofail_asprintf(&dirname, "%s%s/%s", basedir, module_dir, buf.release);
 
 	/* Old-style -t xxx wildcard?  Only with -l. */
 	if (list_only) {
