Add -f to insmod

When the flag is on, insmod will bypass vermagic and symbol version
checking in the kernel. This is to make it possible to update kernel
without recompiling kernel modules.

BUG=28803994

Change-Id: Ib4be6999ef52baefd4210ee0d242360e43318907

init/builtins.cpp

@@ -36,6 +36,7 @@
 #include <sys/wait.h>
 #include <unistd.h>
 #include <linux/loop.h>
+#include <linux/module.h>
 #include <ext4_crypt_init_extensions.h>
 
 #include <selinux/selinux.h>
@@ -44,6 +45,7 @@
 #include <fs_mgr.h>
 #include <android-base/file.h>
 #include <android-base/parseint.h>
+#include <android-base/strings.h>
 #include <android-base/stringprintf.h>
 #include <cutils/partition_utils.h>
 #include <cutils/android_reboot.h>
@@ -66,13 +68,13 @@
 
 static const int kTerminateServiceDelayMicroSeconds = 50000;
 
-static int insmod(const char *filename, const char *options) {
+static int insmod(const char *filename, const char *options, int flags) {
     int fd = open(filename, O_RDONLY | O_NOFOLLOW | O_CLOEXEC);
     if (fd == -1) {
         ERROR("insmod: open(\"%s\") failed: %s", filename, strerror(errno));
         return -1;
     }
-    int rc = syscall(__NR_finit_module, fd, options, 0);
+    int rc = syscall(__NR_finit_module, fd, options, flags);
     if (rc == -1) {
         ERROR("finit_module for \"%s\" failed: %s", filename, strerror(errno));
     }
@@ -269,17 +271,17 @@ static int do_ifup(const std::vector<std::string>& args) {
 }
 
 static int do_insmod(const std::vector<std::string>& args) {
-    std::string options;
+    int flags = 0;
+    auto it = args.begin() + 1;
 
-    if (args.size() > 2) {
-        options += args[2];
-        for (std::size_t i = 3; i < args.size(); ++i) {
-            options += ' ';
-            options += args[i];
-        }
+    if (!(*it).compare("-f")) {
+        flags = MODULE_INIT_IGNORE_VERMAGIC | MODULE_INIT_IGNORE_MODVERSIONS;
+        it++;
     }
 
-    return insmod(args[1].c_str(), options.c_str());
+    std::string filename = *it++;
+    std::string options = android::base::Join(std::vector<std::string>(it, args.end()), ' ');
+    return insmod(filename.c_str(), options.c_str(), flags);
 }
 
 static int do_mkdir(const std::vector<std::string>& args) {

init/readme.txt

@@ -278,8 +278,11 @@ hostname <name>
 ifup <interface>
    Bring the network interface <interface> online.
 
-insmod <path>
-   Install the module at <path>
+insmod [-f] <path> [<options>]
+   Install the module at <path> with the specified options.
+   -f
+   Force installation of the module even if the version of the running kernel
+   and the version of the kernel for which the module was compiled do not match.
 
 load_all_props
    Loads properties from /system, /vendor, et cetera.