Return result type from syscall and format info on panic.

rust/lib/mammoth/src/syscall.rs

@@ -8,22 +8,84 @@ use core::panic::PanicInfo;
 
 include!("bindings.rs");
 
-pub fn syscall<T>(id: u64, req: &T) -> u64 {
-    unsafe { SysCall1(id, req as *const T as *const c_void) }
+pub enum ZError {
+    UNKNOWN = 0x0,
+    // First set of error codes generally indicate user errors.
+    INVALID_ARGUMENT = 0x1,
+    NOT_FOUND = 0x2,
+    PERMISSION_DENIED = 0x3,
+    NULL_PTR = 0x4,
+    EMPTY = 0x5,
+    ALREADY_EXISTS = 0x6,
+    BUFFER_SIZE = 0x7,
+    FAILED_PRECONDITION = 0x8,
+
+    // Second set of error codes generally indicate service errors.
+    INTERNAL = 0x100,
+    UNIMPLEMENTED = 0x101,
+    EXHAUSTED = 0x102,
+    INVALID_RESPONSE = 0x103,
+
+    // Kernel specific error codes (relating to capabilities).
+    CAP_NOT_FOUND = 0x1000,
+    CAP_WRONG_TYPE = 0x1001,
+    CAP_PERMISSION_DENIED = 0x1002,
 }
 
-pub fn checked_syscall<T>(id: u64, req: &T) {
-    if syscall(id, req) != 0 {
-        debug("Bad syscall response.");
-        panic!();
+impl From<u64> for ZError {
+    fn from(value: u64) -> Self {
+        match value {
+            0x1 => ZError::INVALID_ARGUMENT,
+            0x2 => ZError::NOT_FOUND,
+            0x3 => ZError::PERMISSION_DENIED,
+            0x4 => ZError::NULL_PTR,
+            0x5 => ZError::EMPTY,
+            0x6 => ZError::ALREADY_EXISTS,
+            0x7 => ZError::BUFFER_SIZE,
+            0x8 => ZError::FAILED_PRECONDITION,
+
+            0x100 => ZError::INTERNAL,
+            0x101 => ZError::UNIMPLEMENTED,
+            0x102 => ZError::EXHAUSTED,
+            0x103 => ZError::INVALID_RESPONSE,
+
+            0x1000 => ZError::CAP_NOT_FOUND,
+            0x1001 => ZError::CAP_WRONG_TYPE,
+            0x1002 => ZError::CAP_PERMISSION_DENIED,
+            _ => ZError::UNKNOWN,
+        }
     }
 }
 
+impl fmt::Debug for ZError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str("ZError")
+    }
+}
+
+#[must_use]
+pub fn syscall<T>(id: u64, req: &T) -> Result<(), ZError> {
+    unsafe {
+        let resp = SysCall1(id, req as *const T as *const c_void);
+        if resp != 0 {
+            return Err(ZError::from(resp));
+        }
+    }
+    Ok(())
+}
+
 #[panic_handler]
-fn panic(_info: &PanicInfo) -> ! {
+fn panic(info: &PanicInfo) -> ! {
+    unsafe {
+        if crate::mem::CAN_ALLOC {
+            crate::debug!("Panic occured: {}", info);
+        } else {
+            debug("Panic occured before heap initialized.")
+        }
+    }
     // Internal error.
     let req = ZProcessExitReq { code: 0x100 };
-    syscall(kZionProcessExit, &req);
+    let _ = syscall(kZionProcessExit, &req);
     unreachable!()
 }
 
@@ -32,7 +94,7 @@ pub fn debug(msg: &str) {
         message: msg.as_ptr() as *const i8,
         size: msg.len() as u64,
     };
-    syscall(kZionDebug, &req);
+    syscall(kZionDebug, &req).expect("Failed to write");
 }
 
 pub struct Writer {
@@ -73,7 +135,9 @@ macro_rules! debug {
     ($fmt:literal, $($val:expr),+) => {{
         use core::fmt::Write as _;
         use alloc::string::String;
-        let mut w = mammoth::syscall::Writer::new();
+        // TODO: Find a way to do this so we don't have to import writer.
+        // We can't fully qualify this if we want to use it in this crate.
+        let mut w = Writer::new();
         write!(&mut w, $fmt, $($val),*).expect("Failed to format");
         let s: String = w.into();
         debug(&s);