[WIP] init: quirks: implement shared OverrideFileWith logic

Use a callback function to handle replacement etc.

init/quirks.cpp

@@ -6,6 +6,8 @@
 #include <vector>
 
 #include <sys/mount.h>
+#include <sys/stat.h>
+#include <unistd.h>
 
 // Default destructor for DeviceQuirk
 DeviceQuirk::~DeviceQuirk() {
@@ -52,7 +54,7 @@ void EnsureTmpMount() {
     }
 }
 
-void Quirks::OverrideFileReplaceSubstr(filesystem::path p, string pattern, string replacement) {
+void Quirks::OverrideFileWith(filesystem::path p, function<void(istream&, ostream&)> proc) {
     if (!filesystem::is_regular_file(p)) return;
     
     EnsureTmpMount();
@@ -61,13 +63,39 @@ void Quirks::OverrideFileReplaceSubstr(filesystem::path p, string pattern, strin
     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);
+    ifstream ifs;
+    ifs.open(p, ifstream::in);
     
-    int err = mount(tmp_path.c_str(), p.c_str(), nullptr, MS_BIND, nullptr);
+    ofstream ofs(tmp_path);
+    proc(ifs, ofs);
+    
+    ifs.close();
+    ofs.close();
+    
+    // Synchronize ownership and permission
+    // C++ filesystem does not support uid / gid manipulation
+    struct stat st;
+    int err = stat(p.c_str(), &st);
+    if (err < 0) {
+        ALOGE("Failed to stat %s: %d\n", tmp_path.c_str(), errno);
+        return;
+    }
+    
+    err = chown(tmp_path.c_str(), st.st_uid, st.st_gid);
+    if (err < 0) {
+        ALOGE("Failed to chown %s: %d\n", tmp_path.c_str(), errno);
+    }
+    err = chmod(tmp_path.c_str(), st.st_mode);
+    if (err < 0) {
+        ALOGE("Failed to chmod %s: %d\n", tmp_path.c_str(), errno);
+    }
+    
+    // Bind mount and override the file
+    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);
+        return;
     }
     
     // Call restorecon via execl, because for some reason
@@ -75,3 +103,9 @@ void Quirks::OverrideFileReplaceSubstr(filesystem::path p, string pattern, strin
     // (probably related to other magic present in our process)
     fork_execl("/system/bin/restorecon", "restorecon", p.c_str());
 }
+
+void Quirks::OverrideFileReplaceSubstr(filesystem::path p, string pattern, string replacement) {
+    Quirks::OverrideFileWith(p, [](istream& is, ostream& os) {
+        os << is.rdbuf();
+    });
+}

init/quirks.h

@@ -1,5 +1,8 @@
 #pragma once
 #include <filesystem>
+#include <fstream>
+#include <functional>
+#include <iostream>
 #include <string>
 
 #include <sys/wait.h>
@@ -28,5 +31,6 @@ namespace Quirks {
     void Add(DeviceQuirk* quirk);
     void Run();
     
+    void OverrideFileWith(filesystem::path p, function<void(istream&, ostream&)> proc);
     void OverrideFileReplaceSubstr(filesystem::path p, string pattern, string replacement);
 }