libmodprobe: parse kernel command line for module options

Bug: 145808811
Test: atest libmodprobe_tests, verify on flame
Change-Id: I0b41b1610fe13ae526d38f029da888f6f0d8a02d
diff --git a/libmodprobe/libmodprobe_ext.cpp b/libmodprobe/libmodprobe_ext.cpp
index 8bebe4c..99472c1 100644
--- a/libmodprobe/libmodprobe_ext.cpp
+++ b/libmodprobe/libmodprobe_ext.cpp
@@ -17,11 +17,20 @@
 #include <sys/stat.h>
 #include <sys/syscall.h>
 
+#include <android-base/file.h>
 #include <android-base/logging.h>
 #include <android-base/unique_fd.h>
 
 #include <modprobe/modprobe.h>
 
+std::string Modprobe::GetKernelCmdline(void) {
+    std::string cmdline;
+    if (!android::base::ReadFileToString("/proc/cmdline", &cmdline)) {
+        return "";
+    }
+    return cmdline;
+}
+
 bool Modprobe::Insmod(const std::string& path_name, const std::string& parameters) {
     android::base::unique_fd fd(
             TEMP_FAILURE_RETRY(open(path_name.c_str(), O_RDONLY | O_NOFOLLOW | O_CLOEXEC)));