Implement magiskinit logging in Rust

native/src/init/getinfo.cpp

@@ -117,55 +117,6 @@ static bool check_key_combo() {
     return false;
 }
 
-static FILE *kmsg;
-extern "C" void klog_write(const char *msg, int len) {
-    fprintf(kmsg, "%.*s", len, msg);
-}
-
-static int klog_with_rs(LogLevel level, const char *fmt, va_list ap) {
-    char buf[4096];
-    strscpy(buf, "magiskinit: ", sizeof(buf));
-    int len = vssprintf(buf + 12, sizeof(buf) - 12, fmt, ap) + 12;
-    log_with_rs(level, rust::Str(buf, len));
-    return len;
-}
-
-void setup_klog() {
-    // Shut down first 3 fds
-    int fd;
-    if (access("/dev/null", W_OK) == 0) {
-        fd = xopen("/dev/null", O_RDWR | O_CLOEXEC);
-    } else {
-        mknod("/null", S_IFCHR | 0666, makedev(1, 3));
-        fd = xopen("/null", O_RDWR | O_CLOEXEC);
-        unlink("/null");
-    }
-    xdup3(fd, STDIN_FILENO, O_CLOEXEC);
-    xdup3(fd, STDOUT_FILENO, O_CLOEXEC);
-    xdup3(fd, STDERR_FILENO, O_CLOEXEC);
-    if (fd > STDERR_FILENO)
-        close(fd);
-
-    if (access("/dev/kmsg", W_OK) == 0) {
-        fd = xopen("/dev/kmsg", O_WRONLY | O_CLOEXEC);
-    } else {
-        mknod("/kmsg", S_IFCHR | 0666, makedev(1, 11));
-        fd = xopen("/kmsg", O_WRONLY | O_CLOEXEC);
-        unlink("/kmsg");
-    }
-
-    kmsg = fdopen(fd, "w");
-    setbuf(kmsg, nullptr);
-    rust::setup_klog();
-    cpp_logger = klog_with_rs;
-
-    // Disable kmsg rate limiting
-    if (FILE *rate = fopen("/proc/sys/kernel/printk_devkmsg", "w")) {
-        fprintf(rate, "on\n");
-        fclose(rate);
-    }
-}
-
 void BootConfig::set(const kv_pairs &kv) {
     for (const auto &[key, value] : kv) {
         if (key == "androidboot.slot_suffix") {
@@ -231,7 +182,7 @@ void load_kernel_info(BootConfig *config) {
     mount_list.emplace_back("/sys");
 
     // Log to kernel
-    setup_klog();
+    rust::setup_klog();
 
     config->set(parse_cmdline(full_read("/proc/cmdline")));
     config->set(parse_bootconfig(full_read("/proc/bootconfig")));

native/src/init/init.cpp

@@ -90,6 +90,7 @@ int main(int argc, char *argv[]) {
     BootConfig config{};
 
     if (argc > 1 && argv[1] == "selinux_setup"sv) {
+        rust::setup_klog();
         init = new SecondStageInit(argv);
     } else {
         // This will also mount /sys and /proc

native/src/init/init.hpp

@@ -28,7 +28,6 @@ int magisk_proxy_main(int argc, char *argv[]);
 bool unxz(int fd, const uint8_t *buf, size_t size);
 void load_kernel_info(BootConfig *config);
 bool check_two_stage();
-void setup_klog();
 const char *backup_init();
 void restore_ramdisk_init();
 int dump_preload(const char *path, mode_t mode);
@@ -87,7 +86,6 @@ private:
     bool prepare();
 public:
     SecondStageInit(char *argv[]) : MagiskInit(argv) {
-        setup_klog();
         LOGD("%s\n", __FUNCTION__);
     };
 

native/src/init/logging.rs

@@ -1,27 +1,69 @@
-use base::ffi::LogLevel;
-use base::*;
 use std::fmt::Arguments;
+use std::fs;
+use std::fs::File;
+use std::io::Write;
+use std::sync::OnceLock;
 
-extern "C" {
-    fn klog_write(msg: *const u8, len: i32);
-}
+use base::ffi::LogLevel;
+use base::libc::{
+    close, makedev, mknod, open, syscall, unlink, SYS_dup3, O_CLOEXEC, O_RDWR, STDERR_FILENO,
+    STDIN_FILENO, STDOUT_FILENO, S_IFCHR,
+};
+use base::*;
+
+static KMSG: OnceLock<File> = OnceLock::new();
 
 pub fn setup_klog() {
-    const PREFIX: &[u8; 12] = b"magiskinit: ";
-    const PFX_LEN: usize = PREFIX.len();
+    // Shut down first 3 fds
+    unsafe {
+        let mut fd = open(str_ptr!("/dev/null"), O_RDWR | O_CLOEXEC);
+        if fd < 0 {
+            mknod(str_ptr!("/null"), S_IFCHR | 0666, makedev(1, 3));
+            fd = open(str_ptr!("/null"), O_RDWR | O_CLOEXEC);
+            fs::remove_file("/null").ok();
+        }
+
+        syscall(SYS_dup3, fd, STDIN_FILENO, O_CLOEXEC);
+        syscall(SYS_dup3, fd, STDOUT_FILENO, O_CLOEXEC);
+        syscall(SYS_dup3, fd, STDERR_FILENO, O_CLOEXEC);
+        if fd > STDERR_FILENO {
+            close(fd);
+        }
+    }
+
+    if let Ok(kmsg) = File::options().write(true).open("/dev/kmsg") {
+        KMSG.set(kmsg).ok();
+    } else {
+        unsafe {
+            mknod(str_ptr!("/kmsg"), S_IFCHR | 0666, makedev(1, 11));
+            KMSG.set(File::options().write(true).open("/kmsg").unwrap())
+                .ok();
+            unlink(str_ptr!("/kmsg"));
+        }
+    }
+
+    // Disable kmsg rate limiting
+    if let Ok(mut rate) = File::options()
+        .write(true)
+        .open("/proc/sys/kernel/printk_devkmsg")
+    {
+        writeln!(rate, "on").ok();
+    }
 
     fn klog_fmt(_: LogLevel, args: Arguments) {
-        let mut buf: [u8; 4096] = [0; 4096];
-        buf[..PFX_LEN].copy_from_slice(PREFIX);
-        let len = fmt_to_buf(&mut buf[PFX_LEN..], args) + PFX_LEN;
-        unsafe {
-            klog_write(buf.as_ptr(), len as i32);
+        if let Some(kmsg) = KMSG.get().as_mut() {
+            let mut buf: [u8; 4096] = [0; 4096];
+            let len = fmt_to_buf(&mut buf, format_args!("magiskinit: {}", args));
+            kmsg.write_all(&buf[..len]).ok();
         }
     }
 
     fn klog_write_impl(_: LogLevel, msg: &[u8]) {
-        unsafe {
-            klog_write(msg.as_ptr(), msg.len() as i32);
+        if let Some(kmsg) = KMSG.get().as_mut() {
+            let mut buf: [u8; 4096] = [0; 4096];
+            let mut len = copy_str(&mut buf, b"magiskinit: ");
+            len += copy_str(&mut buf[len..], msg);
+            kmsg.write_all(&buf[..len]).ok();
         }
     }
 

native/src/init/rootdir.cpp

@@ -349,7 +349,7 @@ void MagiskInit::patch_rw_root() {
 }
 
 int magisk_proxy_main(int argc, char *argv[]) {
-    setup_klog();
+    rust::setup_klog();
     LOGD("%s\n", __FUNCTION__);
 
     // Mount rootfs as rw to do post-init rootfs patches