Better debug print for TrapFrame on RV32

kernel/src/arch/riscv32/context.rs

@@ -1,6 +1,6 @@
 use super::super::riscv::register::*;
 
-#[derive(Debug, Clone)]
+#[derive(Clone)]
 #[repr(C)]
 pub struct TrapFrame {
     pub x: [usize; 32],
@@ -34,8 +34,29 @@ impl TrapFrame {
         tf.sstatus.set_spp(sstatus::SPP::User);
         tf
     }
-    pub fn is_user(&self) -> bool {
-        unimplemented!()
+}
+
+use core::fmt::{Debug, Formatter, Error};
+impl Debug for TrapFrame {
+    fn fmt(&self, f: &mut Formatter) -> Result<(), Error> {
+        struct Regs<'a>(&'a [usize; 32]);
+        impl<'a> Debug for Regs<'a> {
+            fn fmt(&self, f: &mut Formatter) -> Result<(), Error> {
+                const REG_NAME: [&str; 32] = [
+                    "zero", "ra", "sp", "gp", "tp", "t0", "t1", "t2",
+                    "s0", "s1", "a0", "a1", "a2", "a3", "a4", "a5", "a6", "a7",
+                    "s2", "s3", "s4", "s5", "s6", "s7", "s8", "s9", "s10", "s11",
+                    "t3", "t4", "t5", "t6"];
+                f.debug_map().entries(REG_NAME.iter().zip(self.0)).finish()
+            }
+        }
+        f.debug_struct("TrapFrame")
+            .field("regs", &Regs(&self.x))
+            .field("sstatus", &self.sstatus)
+            .field("sepc", &self.sepc)
+            .field("sbadaddr", &self.sbadaddr)
+            .field("scause", &self.scause)
+            .finish()
     }
 }