From 9b259cb9172229ddd35d9a12f0c4d4dccf7303ed Mon Sep 17 00:00:00 2001
From: Daniel Lubarov <daniel@lubarov.com>
Date: Mon, 5 Sep 2022 10:12:23 -0700
Subject: [PATCH] Feedback

---
 evm/src/cpu/kernel/asm/exp.asm    | 3 ---
 evm/src/cpu/kernel/interpreter.rs | 6 +++++-
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/evm/src/cpu/kernel/asm/exp.asm b/evm/src/cpu/kernel/asm/exp.asm
index 3640b2f6..f025e312 100644
--- a/evm/src/cpu/kernel/asm/exp.asm
+++ b/evm/src/cpu/kernel/asm/exp.asm
@@ -10,7 +10,6 @@
 /// Note that this correctly handles exp(0, 0) == 1.
 
 global exp:
-    jumpdest
     // stack: x, e, retdest
     dup2
     // stack: e, x, e, retdest
@@ -27,7 +26,6 @@ global exp:
     jump
 
 step_case:
-    jumpdest
     // stack: x, e, retdest
     push recursion_return
     // stack: recursion_return, x, e, retdest
@@ -43,7 +41,6 @@ step_case:
     // stack: x * x, e / 2, recursion_return, x, e, retdest
     %jump(exp)
 recursion_return:
-    jumpdest
     // stack: exp(x * x, e / 2), x, e, retdest
     push 2
     // stack: 2, exp(x * x, e / 2), x, e, retdest
diff --git a/evm/src/cpu/kernel/interpreter.rs b/evm/src/cpu/kernel/interpreter.rs
index 17be0523..64d70529 100644
--- a/evm/src/cpu/kernel/interpreter.rs
+++ b/evm/src/cpu/kernel/interpreter.rs
@@ -250,7 +250,7 @@ impl<'a> Interpreter<'a> {
             0x58 => todo!(),                                           // "GETPC",
             0x59 => todo!(),                                           // "MSIZE",
             0x5a => todo!(),                                           // "GAS",
-            0x5b => (),                                                // "JUMPDEST",
+            0x5b => self.run_jumpdest(),                               // "JUMPDEST",
             0x5c => todo!(),                                           // "GET_STATE_ROOT",
             0x5d => todo!(),                                           // "SET_STATE_ROOT",
             0x5e => todo!(),                                           // "GET_RECEIPT_ROOT",
@@ -490,6 +490,10 @@ impl<'a> Interpreter<'a> {
         }
     }
 
+    fn run_jumpdest(&mut self) {
+        assert!(!self.kernel_mode, "JUMPDEST is not needed in kernel code");
+    }
+
     fn jump_to(&mut self, offset: usize) {
         // The JUMPDEST rule is not enforced in kernel mode.
         if !self.kernel_mode && self.jumpdests.binary_search(&offset).is_err() {