Implement magiskinit logging in Rust

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();
         }
     }