libmodprobe: add support to remove modules

Add a remove method which will unload a given module from the kernel,
along with any modules it depended on, assuming those modules are now
unused.

Change-Id: Ie66dc153ef1771f50e26421d38d3656e95954780

libmodprobe/include/modprobe/modprobe.h

@@ -26,11 +26,13 @@ class Modprobe {
 
     bool LoadListedModules();
     bool LoadWithAliases(const std::string& module_name, bool strict);
+    bool Remove(const std::string& module_name);
 
   private:
     std::string MakeCanonical(const std::string& module_path);
     bool InsmodWithDeps(const std::string& module_name);
     bool Insmod(const std::string& path_name);
+    bool Rmmod(const std::string& module_name);
     std::vector<std::string> GetDependencies(const std::string& module);
     bool ModuleExists(const std::string& module_name);
 

libmodprobe/libmodprobe.cpp

@@ -315,3 +315,18 @@ bool Modprobe::LoadListedModules() {
     }
     return true;
 }
+
+bool Modprobe::Remove(const std::string& module_name) {
+    auto dependencies = GetDependencies(MakeCanonical(module_name));
+    if (dependencies.empty()) {
+        LOG(ERROR) << "Empty dependencies for module " << module_name;
+        return false;
+    }
+    if (!Rmmod(dependencies[0])) {
+        return false;
+    }
+    for (auto dep = dependencies.begin() + 1; dep != dependencies.end(); ++dep) {
+        Rmmod(*dep);
+    }
+    return true;
+}

libmodprobe/libmodprobe_ext.cpp

@@ -51,6 +51,15 @@ bool Modprobe::Insmod(const std::string& path_name) {
     return true;
 }
 
+bool Modprobe::Rmmod(const std::string& module_name) {
+    int ret = syscall(__NR_delete_module, MakeCanonical(module_name).c_str(), O_NONBLOCK);
+    if (ret != 0) {
+        PLOG(ERROR) << "Failed to remove module '" << module_name << "'";
+        return false;
+    }
+    return true;
+}
+
 bool Modprobe::ModuleExists(const std::string& module_name) {
     struct stat fileStat;
     auto deps = GetDependencies(module_name);

libmodprobe/libmodprobe_ext_test.cpp

@@ -51,6 +51,16 @@ bool Modprobe::Insmod(const std::string& path_name) {
     return true;
 }
 
+bool Modprobe::Rmmod(const std::string& module_name) {
+    for (auto it = modules_loaded.begin(); it != modules_loaded.end(); it++) {
+        if (*it == module_name) {
+            modules_loaded.erase(it);
+            return true;
+        }
+    }
+    return false;
+}
+
 bool Modprobe::ModuleExists(const std::string& module_name) {
     auto deps = GetDependencies(module_name);
     if (deps.empty()) {

libmodprobe/libmodprobe_test.cpp

@@ -56,6 +56,14 @@ TEST(libmodprobe, Test) {
             "/test13.ko",
     };
 
+    std::vector<std::string> expected_after_remove = {
+            "/test14.ko", "/test15.ko",         "/test1.ko",
+            "/test6.ko",  "/test2.ko",          "/test5.ko",
+            "/test8.ko",  "/test7.ko param1=4", "/test9.ko param_x=1 param_y=2 param_z=3",
+            "/test10.ko", "/test12.ko",         "/test11.ko",
+            "/test13.ko",
+    };
+
     const std::string modules_dep =
             "test1.ko:\n"
             "test2.ko:\n"
@@ -131,4 +139,18 @@ TEST(libmodprobe, Test) {
     }
 
     EXPECT_TRUE(modules_loaded == expected_modules_loaded);
+
+    EXPECT_TRUE(m.Remove("test4"));
+
+    GTEST_LOG_(INFO) << "Expected modules loaded after removing test4 (in order):";
+    for (auto i = expected_after_remove.begin(); i != expected_after_remove.end(); ++i) {
+        *i = dir.path + *i;
+        GTEST_LOG_(INFO) << "\"" << *i << "\"";
+    }
+    GTEST_LOG_(INFO) << "Actual modules loaded after removing test4 (in order):";
+    for (auto i = modules_loaded.begin(); i != modules_loaded.end(); ++i) {
+        GTEST_LOG_(INFO) << "\"" << *i << "\"";
+    }
+
+    EXPECT_TRUE(modules_loaded == expected_after_remove);
 }