Merge pull request #1312 from topos-protocol/mcopy

Implement EIP-5656 (MCOPY)

evm/src/cpu/kernel/asm/core/exception.asm

@@ -227,9 +227,9 @@ min_stack_len_for_opcode:
     BYTES 0  // 0x59, MSIZE
     BYTES 0  // 0x5a, GAS
     BYTES 0  // 0x5b, JUMPDEST
-    %rep 3  // 0x5c-0x5e, invalid
-        BYTES 0
-    %endrep
+    BYTES 0  // 0x5c, invalid
+    BYTES 0  // 0x5d, invalid
+    BYTES 3  // 0x5e, MCOPY
 
     %rep 33 // 0x5f-0x7f, PUSH0-PUSH32
         BYTES 0

evm/src/cpu/kernel/asm/core/syscall.asm

@@ -88,7 +88,7 @@ global syscall_jumptable:
     JUMPTABLE panic // jumpdest is implemented natively
     JUMPTABLE panic // 0x5c is an invalid opcode
     JUMPTABLE panic // 0x5d is an invalid opcode
-    JUMPTABLE panic // 0x5e is an invalid opcode
+    JUMPTABLE sys_mcopy
     JUMPTABLE panic // 0x5f is an invalid opcode
 
     // 0x60-0x6f

evm/src/cpu/kernel/asm/memory/syscalls.asm

@@ -213,3 +213,67 @@ global sys_returndatacopy:
 returndatacopy_empty:
     %stack (kexit_info, dest_offset, offset, size) -> (kexit_info)
     EXIT_KERNEL
+
+// Same as %wcopy but with special handling in case of overlapping ranges.
+global sys_mcopy:
+    // stack: kexit_info, dest_offset, offset, size
+    PUSH @GAS_VERYLOW
+    // stack: Gverylow, kexit_info, dest_offset, offset, size
+    DUP5 %num_bytes_to_num_words %mul_const(@GAS_COPY) ADD %charge_gas
+
+    // stack: kexit_info, dest_offset, offset, size
+    DUP4
+    // stack: size, kexit_info, dest_offset, offset, size
+    ISZERO %jumpi(returndatacopy_empty) // If size is empty, just pop the stack and exit the kernel
+
+    %stack (kexit_info, dest_offset, offset, size) -> (dest_offset, size, kexit_info, dest_offset, offset, size)
+    %add_or_fault
+    // stack: expanded_num_bytes, kexit_info, dest_offset, offset, size, kexit_info
+    DUP1 %ensure_reasonable_offset
+    %update_mem_bytes
+
+    // stack: kexit_info, dest_offset, offset, size
+    DUP3 DUP3 EQ
+    // stack: dest_offset = offset, kexit_info, dest_offset, offset, size
+    %jumpi(returndatacopy_empty) // If SRC == DST, just pop the stack and exit the kernel
+
+    // stack: kexit_info, dest_offset, offset, size
+    PUSH @SEGMENT_MAIN_MEMORY
+    DUP5 DUP5 ADD
+    // stack: offset + size, segment, kexit_info, dest_offset, offset, size
+    DUP4 LT
+    // stack: dest_offset < offset + size, segment, kexit_info, dest_offset, offset, size
+    DUP5 DUP5 GT
+    // stack: dest_offset > offset, dest_offset < offset + size, segment, kexit_info, dest_offset, offset, size
+    AND
+    // stack: (dest_offset > offset) && (dest_offset < offset + size), segment, kexit_info, dest_offset, offset, size
+
+    // If both conditions are satisfied, that means we will get an overlap, in which case we need to process the copy
+    // in two chunks to prevent overwriting memory data before reading it.
+    %jumpi(mcopy_with_overlap)
+
+    // stack: segment, kexit_info, dest_offset, offset, size
+    PUSH wcopy_within_bounds
+    JUMP
+
+mcopy_with_overlap:
+    // We do have an overlap between the SRC and DST ranges. We will first copy the overlapping segment
+    // (i.e. end of the copy portion), then copy the remaining (i.e. beginning) portion. 
+
+    // stack: segment, kexit_info, dest_offset, offset, size
+    DUP4 DUP4 SUB
+    // stack: remaining_size = dest_offset - offset, segment, kexit_info, dest_offset, offset, size
+    DUP1 DUP7
+    SUB // overlapping_size = size - remaining_size
+    // stack: overlapping_size, remaining_size, segment, kexit_info, dest_offset, offset, size
+
+    // Shift the initial offsets to copy the overlapping segment first.
+    DUP2 DUP7 ADD
+    // stack: offset_first_copy, overlapping_size, remaining_size, segment, kexit_info, dest_offset, offset, size
+    DUP3 DUP7 ADD
+    // stack: dest_offset_first_copy, offset_first_copy, overlapping_size, remaining_size, segment, kexit_info, dest_offset, offset, size
+
+    GET_CONTEXT
+    %stack (context, dest_offset_first_copy, offset_first_copy, overlapping_size, remaining_size, segment, kexit_info, dest_offset, offset, size) ->
+        (context, segment, dest_offset_first_copy, context, segment, offset_first_copy, overlapping_size, wcopy_within_bounds, segment, kexit_info, dest_offset, offset, remaining_size)
+    %jump(memcpy_bytes)

evm/src/cpu/kernel/interpreter.rs

@@ -403,6 +403,7 @@ impl<'a> Interpreter<'a> {
             0x59 => self.run_msize(),                                   // "MSIZE",
             0x5a => todo!(),                                            // "GAS",
             0x5b => self.run_jumpdest(),                                // "JUMPDEST",
+            0x5e => self.run_mcopy(),                                   // "MCOPY",
             x if (0x5f..0x80).contains(&x) => self.run_push(x - 0x5f),  // "PUSH"
             x if (0x80..0x90).contains(&x) => self.run_dup(x - 0x7f),   // "DUP"
             x if (0x90..0xa0).contains(&x) => self.run_swap(x - 0x8f)?, // "SWAP"
@@ -1023,6 +1024,31 @@ impl<'a> Interpreter<'a> {
         assert!(!self.kernel_mode, "JUMPDEST is not needed in kernel code");
     }
 
+    fn run_mcopy(&mut self) {
+        let dest_offset = self.pop().as_usize();
+        let offset = self.pop().as_usize();
+        let size = self.pop().as_usize();
+
+        let intermediary_memory: Vec<U256> = (0..size)
+            .map(|i| {
+                self.generation_state.memory.mload_general(
+                    self.context,
+                    Segment::MainMemory,
+                    offset + i,
+                )
+            })
+            .collect();
+
+        for i in 0..size {
+            self.generation_state.memory.mstore_general(
+                self.context,
+                Segment::MainMemory,
+                dest_offset + i,
+                intermediary_memory[i],
+            );
+        }
+    }
+
     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() {

evm/src/witness/transition.rs

@@ -119,6 +119,7 @@ fn decode(registers: RegistersState, opcode: u8) -> Result<Operation, ProgramErr
         (0x59, _) => Ok(Operation::Syscall(opcode, 0, true)), // MSIZE
         (0x5a, _) => Ok(Operation::Syscall(opcode, 0, true)), // GAS
         (0x5b, _) => Ok(Operation::Jumpdest),
+        (0x5e, _) => Ok(Operation::Syscall(opcode, 3, false)), // MCOPY
         (0x5f..=0x7f, _) => Ok(Operation::Push(opcode - 0x5f)),
         (0x80..=0x8f, _) => Ok(Operation::Dup(opcode & 0xf)),
         (0x90..=0x9f, _) => Ok(Operation::Swap(opcode & 0xf)),