Provide richer error messages

Make sure most syscall/libc calls results are mapped to OsResult
that can produce more detailed error messages.

native/src/init/init.rs

@@ -130,7 +130,7 @@ impl MagiskInit {
                     null(),
                 )
             }
-            .as_os_err()?;
+            .check_io_err()?;
             self.mount_list.push("/proc".to_string());
         }
         if !path!("/sys/block").exists() {
@@ -144,7 +144,7 @@ impl MagiskInit {
                     null(),
                 )
             }
-            .as_os_err()?;
+            .check_io_err()?;
             self.mount_list.push("/sys".to_string());
         }
 

native/src/init/mount.rs

@@ -45,7 +45,7 @@ pub(crate) fn switch_root(path: &Utf8CStr) {
             mounts.insert(info.target);
         }
         unsafe {
-            chdir(path.as_ptr()).as_os_err()?;
+            chdir(path.as_ptr()).check_io_err()?;
             FsPath::from(path).move_mount_to(path!("/"))?;
             chroot(raw_cstr!("."));
         }
@@ -89,7 +89,7 @@ impl MagiskInit {
                 raw_cstr!("mode=755").cast(),
             )
         }
-        .as_os_err()
+        .check_io_err()
         .log_ok();
 
         path!("/init").copy_to(path!("/data/magiskinit")).log_ok();
@@ -108,7 +108,7 @@ impl MagiskInit {
         }
         unsafe {
             execve(raw_cstr!("/init"), self.argv.cast(), environ.cast())
-                .as_os_err()
+                .check_io_err()
                 .log_ok();
             exit(1);
         }

native/src/init/selinux.rs

@@ -151,7 +151,7 @@ impl MagiskInit {
                             0,
                             ptr::null(),
                         )
-                        .as_os_err()?;
+                        .check_io_err()?;
                     }
                 }
 
@@ -174,7 +174,7 @@ impl MagiskInit {
         }
 
         // Create a new process waiting for init operations
-        let pid = unsafe { libc::fork().check_os_err()? };
+        let pid = unsafe { libc::fork() };
         if pid != 0 {
             return Ok(());
         }