[WIP] init: initial implementation of "quirks" support

init/Android.bp

@@ -1,10 +1,19 @@
 cc_binary {
     name: "init_gsi",
     system_ext_specific: true,
-    srcs: ["init_gsi.cpp"],
-    shared_libs: ["libbase", "libdl", "libutils"],
-    static_libs: ["libresetprop"],
+    srcs: [
+        "init_gsi.cpp",
+        "quirks.cpp",
+        
+        // SoC-specific quirks
+        "quirks/soc/mtk_ril.cpp",
+    ],
+    shared_libs: ["libbase", "libdl", "liblog", "libutils"],
+    static_libs: ["libresetprop", "libc++fs"],
     init_rc: ["init_gsi.rc"],
+    cflags: [
+        "-std=gnu++17",
+    ],
     target: {
         android: {
             ldflags: ["-Wl,--rpath,/system/${LIB}/bootstrap"],

init/init_gsi.cpp

@@ -4,6 +4,8 @@
 #include <string>
 #include <iostream>
 
+#include "quirks.h"
+
 using namespace android;
 using namespace std;
 
@@ -31,7 +33,7 @@ std::string RO_PROP_SOURCES[] = {
     "", "product", "odm", "vendor", "system_ext", "system", "bootimage",
 };
 
-int main() {
+void handle_device_model_props() {
     string device = base::GetProperty("ro.product.vendor.device", "");
     string model = base::GetProperty("ro.product.vendor.model", "");
     string name = base::GetProperty("ro.product.vendor.name", "");
@@ -48,6 +50,10 @@ int main() {
     }
     
     override_ro_prop("ro", "", "build.stock_fingerprint", fingerprint);
-    
+}
+
+int main() {
+    handle_device_model_props();
+    Quirks::Run();
     return 0;
 }

init/init_gsi.rc

@@ -1,2 +1,2 @@
 on post-fs
-    exec -- /system_ext/bin/init_gsi
+    exec u:r:init_gsi:s0 root -- /system_ext/bin/init_gsi

init/quirks.cpp

@@ -0,0 +1,77 @@
+#define LOG_TAG "init_gsi_quirks"
+#include <utils/Log.h>
+
+#include "quirks.h"
+
+#include <vector>
+
+#include <sys/mount.h>
+
+// Default destructor for DeviceQuirk
+DeviceQuirk::~DeviceQuirk() {
+    
+}
+
+static std::vector<DeviceQuirk*>* quirks = nullptr;
+
+void Quirks::Add(DeviceQuirk* quirk) {
+    if (quirks == nullptr) {
+        quirks = new std::vector<DeviceQuirk*>();
+    }
+    quirks->push_back(quirk);
+}
+
+void Quirks::Run() {
+    if (quirks == nullptr) return;
+    
+    for (DeviceQuirk* quirk : *quirks) {
+        if (quirk->ShouldRun()) {
+            quirk->Run();
+        }
+    }
+}
+
+// Utility functions for use with quirks
+#define QUIRKS_TMP_BASE_PATH "/mnt/quirks"
+#define QUIRKS_TMP_FILES_PATH QUIRKS_TMP_BASE_PATH "/files"
+
+void EnsureDirectory(filesystem::path p) {
+    if (!filesystem::is_directory(p)) {
+        filesystem::create_directories(p);
+    }
+}
+
+void EnsureTmpMount() {
+    if (filesystem::is_directory(QUIRKS_TMP_BASE_PATH)) return;
+    
+    EnsureDirectory(QUIRKS_TMP_BASE_PATH);
+    int err = mount("tmpfs", QUIRKS_TMP_BASE_PATH, "tmpfs", 0, "mode=755,gid=0");
+    
+    if (err < 0) {
+        ALOGE("mount tmpfs on %s err = %d\n", QUIRKS_TMP_BASE_PATH, errno);
+    }
+}
+
+void Quirks::OverrideFileReplaceSubstr(filesystem::path p, string pattern, string replacement) {
+    if (!filesystem::is_regular_file(p)) return;
+    
+    EnsureTmpMount();
+    EnsureDirectory(QUIRKS_TMP_FILES_PATH);
+    
+    filesystem::path tmp_path = QUIRKS_TMP_FILES_PATH + p.string();
+    EnsureDirectory(tmp_path.parent_path());
+    
+    // TODO: Actually implement pattern replacement
+    filesystem::copy_file(p, tmp_path);
+    
+    int err = mount(tmp_path.c_str(), p.c_str(), nullptr, MS_BIND, nullptr);
+    
+    if (err < 0) {
+        ALOGE("bind mount %s on %s err = %d\n", tmp_path.c_str(), p.c_str(), errno);
+    }
+    
+    // Call restorecon via execl, because for some reason
+    // libselinux functions will segfault in our case
+    // (probably related to other magic present in our process)
+    fork_execl("/system/bin/restorecon", "restorecon", p.c_str());
+}

init/quirks.h

@@ -0,0 +1,32 @@
+#pragma once
+#include <filesystem>
+#include <string>
+
+#include <sys/wait.h>
+#include <unistd.h>
+
+using namespace std;
+
+template<typename... Args>
+void fork_execl(Args... args) {
+    int pid, status;
+    if ((pid = fork()) == 0) {
+        execl(args..., nullptr);
+    } else {
+        waitpid(pid, &status, 0);
+    }
+}
+
+class DeviceQuirk {
+public:
+    virtual bool ShouldRun();
+    virtual void Run();
+    virtual ~DeviceQuirk();
+};
+
+namespace Quirks {
+    void Add(DeviceQuirk* quirk);
+    void Run();
+    
+    void OverrideFileReplaceSubstr(filesystem::path p, string pattern, string replacement);
+}

init/quirks/soc/mtk_ril.cpp

@@ -0,0 +1,38 @@
+#include "../../quirks.h"
+
+#include <filesystem>
+
+using namespace std;
+
+const string PATHS[] = {
+    "/vendor/lib/libmtk-ril.so",
+    "/vendor/lib/mtk-ril.so",
+    "/vendor/lib64/libmtk-ril.so",
+    "/vendor/lib64/mtk-ril.so"
+};
+
+class MtkRilQuirk : DeviceQuirk {
+public:
+    MtkRilQuirk() {
+        Quirks::Add(this);
+    }
+    
+    bool ShouldRun() {
+        for (auto& p : PATHS) {
+            if (filesystem::exists(p)) {
+                return true;
+            }
+        }
+        return false;
+    }
+    
+    void Run() {
+        for (auto& p : PATHS) {
+            if (filesystem::exists(p)) {
+                Quirks::OverrideFileReplaceSubstr(p, "AT+EAIC=2", "AT+EAIC=3");
+            }
+        }
+    }
+};
+
+static MtkRilQuirk* _ignored = new MtkRilQuirk();