fix(executor): back all memory with a uniform page map, not just private input

store_byte used infallible allocation while every other private-input
write path was fallible, and store_private_inputs could write 4 bytes
past MAX_PRIVATE_INPUT_SIZE (the length prefix wasn't accounted for in
the accepted payload size), corrupting the tail of a maximal-size
input on readback.

Rather than patch the private-input-only paged HashMap, drop the
special case entirely: back the whole address space with one
HashMap<page_idx, Box<page>>, so private input is just memory written
at a fixed address like anything else. This removes the page/region
alignment invariant the split design depended on, and every write
(private or not) now goes through the same fallible page allocator.

Author: Oppen

executor/src/tests/memory_tests.rs

@@ -5,8 +5,8 @@ use crate::vm::memory::{Memory, MemoryError};
 #[test]
 fn test_commit_public_output_single() {
     let mut memory = Memory::default();
-    memory.store_byte(0x100, b'a');
-    memory.store_byte(0x101, b'b');
+    memory.store_byte(0x100, b'a').unwrap();
+    memory.store_byte(0x101, b'b').unwrap();
 
     memory
         .commit_public_output(0x100, 2)
@@ -23,10 +23,10 @@ fn test_commit_public_output_single() {
 #[test]
 fn test_commit_public_output_appends() {
     let mut memory = Memory::default();
-    memory.store_byte(0x100, b'a');
-    memory.store_byte(0x101, b'b');
-    memory.store_byte(0x104, b'c');
-    memory.store_byte(0x105, b'd');
+    memory.store_byte(0x100, b'a').unwrap();
+    memory.store_byte(0x101, b'b').unwrap();
+    memory.store_byte(0x104, b'c').unwrap();
+    memory.store_byte(0x105, b'd').unwrap();
 
     memory
         .commit_public_output(0x100, 2)

executor/src/vm/instruction/execution.rs

@@ -189,7 +189,7 @@ impl Instruction {
                 match width {
                     LoadStoreWidth::Byte => {
                         let value = read_value & 0xFF;
-                        memory.store_byte(addr, value as u8);
+                        memory.store_byte(addr, value as u8)?;
                     }
                     LoadStoreWidth::Half => {
                         let value = read_value & 0xFFFF;