debug marker

core/src/runtime/syscall.rs

@@ -118,6 +118,10 @@ pub enum SyscallCode {
 
     /// Execute the `MEMCPY_64` precompile.
     MEMCPY_64 = 0x00_00_01_31,
+
+    /// Just a debug marker
+    #[cfg(feature = "debug-syscall")]
+    DEBUG = 0x00_00_00_FF,
 }
 
 impl SyscallCode {
@@ -152,6 +156,8 @@ impl SyscallCode {
             0x00_01_01_21 => SyscallCode::BN254_SCALAR_MAC,
             0x00_00_01_30 => SyscallCode::MEMCPY_32,
             0x00_00_01_31 => SyscallCode::MEMCPY_64,
+            #[cfg(feature = "debug-syscall")]
+            0x00_00_00_FF => SyscallCode::DEBUG,
             _ => panic!("invalid syscall number: {}", value),
         }
     }
@@ -383,6 +389,12 @@ pub fn default_syscall_map() -> HashMap<SyscallCode, Arc<dyn Syscall>> {
         Arc::new(MemCopyChip::<U16, U64>::new()),
     );
 
+    #[cfg(feature = "debug-syscall")]
+    syscall_map.insert(
+        SyscallCode::DEBUG,
+        Arc::new(crate::syscall::SyscallDebug::new()),
+    );
+
     syscall_map
 }
 
@@ -485,6 +497,8 @@ mod tests {
                 SyscallCode::BN254_SCALAR_MAC => {
                     assert_eq!(code as u32, sp1_zkvm::syscalls::BN254_SCALAR_MAC)
                 }
+                #[cfg(feature = "debug-syscall")]
+                SyscallCode::DEBUG => assert_eq!(code as u32, sp1_zkvm::syscalls::DEBUG),
             }
         }
     }

core/src/syscall/debug.rs

@@ -0,0 +1,15 @@
+use crate::runtime::{Syscall, SyscallContext};
+
+pub struct SyscallDebug;
+
+impl SyscallDebug {
+    pub const fn new() -> Self {
+        Self
+    }
+}
+
+impl Syscall for SyscallDebug {
+    fn execute(&self, _: &mut SyscallContext, _: u32, _: u32) -> Option<u32> {
+        None
+    }
+}

core/src/syscall/mod.rs

@@ -1,4 +1,6 @@
 mod commit;
+#[cfg(feature = "debug-syscall")]
+mod debug;
 mod halt;
 mod hint;
 mod memcpy;
@@ -8,6 +10,8 @@ mod verify;
 mod write;
 
 pub use commit::*;
+#[cfg(feature = "debug-syscall")]
+pub use debug::*;
 pub use halt::*;
 pub use hint::*;
 pub use memcpy::*;