Add memory operation syscalls (#16447)

sdk/program/src/program_stubs.rs

@@ -12,12 +12,13 @@ lazy_static::lazy_static! {
     static ref SYSCALL_STUBS: Arc<RwLock<Box<dyn SyscallStubs>>> = Arc::new(RwLock::new(Box::new(DefaultSyscallStubs {})));
 }
 
-// The default syscall stubs don't do much, but `set_syscalls()` can be used to swap in
-// alternatives
+// The default syscall stubs may not do much, but `set_syscalls()` can be used
+// to swap in alternatives
 pub fn set_syscall_stubs(syscall_stubs: Box<dyn SyscallStubs>) -> Box<dyn SyscallStubs> {
     std::mem::replace(&mut SYSCALL_STUBS.write().unwrap(), syscall_stubs)
 }
 
+#[allow(clippy::integer_arithmetic)]
 pub trait SyscallStubs: Sync + Send {
     fn sol_log(&self, message: &str) {
         println!("{}", message);
@@ -34,7 +35,6 @@ pub trait SyscallStubs: Sync + Send {
         sol_log("SyscallStubs: sol_invoke_signed() not available");
         Ok(())
     }
-
     fn sol_get_clock_sysvar(&self, _var_addr: *mut u8) -> u64 {
         UNSUPPORTED_SYSVAR
     }
@@ -47,6 +47,39 @@ pub trait SyscallStubs: Sync + Send {
     fn sol_get_rent_sysvar(&self, _var_addr: *mut u8) -> u64 {
         UNSUPPORTED_SYSVAR
     }
+    /// # Safety
+    unsafe fn sol_memcpy(&self, dst: *mut u8, src: *const u8, n: usize) {
+        // cannot be overlapping
+        if dst as usize + n > src as usize && src as usize > dst as usize {
+            panic!("memcpy does not support oveerlapping regions");
+        }
+        std::ptr::copy_nonoverlapping(src, dst, n as usize);
+    }
+    /// # Safety
+    unsafe fn sol_memmove(&self, dst: *mut u8, src: *const u8, n: usize) {
+        std::ptr::copy(src, dst, n as usize);
+    }
+    /// # Safety
+    unsafe fn sol_memcmp(&self, s1: *const u8, s2: *const u8, n: usize, result: *mut i32) {
+        let mut i = 0;
+        while i < n {
+            let a = *s1.add(i);
+            let b = *s2.add(i);
+            if a != b {
+                *result = a as i32 - b as i32;
+                return;
+            }
+            i += 1;
+        }
+        *result = 0
+    }
+    /// # Safety
+    unsafe fn sol_memset(&self, s: *mut u8, c: u8, n: usize) {
+        let s = std::slice::from_raw_parts_mut(s, n);
+        for val in s.iter_mut().take(n) {
+            *val = c;
+        }
+    }
 }
 
 struct DefaultSyscallStubs {}
@@ -96,3 +129,27 @@ pub(crate) fn sol_get_fees_sysvar(var_addr: *mut u8) -> u64 {
 pub(crate) fn sol_get_rent_sysvar(var_addr: *mut u8) -> u64 {
     SYSCALL_STUBS.read().unwrap().sol_get_rent_sysvar(var_addr)
 }
+
+pub(crate) fn sol_memcpy(dst: *mut u8, src: *const u8, n: usize) {
+    unsafe {
+        SYSCALL_STUBS.read().unwrap().sol_memcpy(dst, src, n);
+    }
+}
+
+pub(crate) fn sol_memmove(dst: *mut u8, src: *const u8, n: usize) {
+    unsafe {
+        SYSCALL_STUBS.read().unwrap().sol_memmove(dst, src, n);
+    }
+}
+
+pub(crate) fn sol_memcmp(s1: *const u8, s2: *const u8, n: usize, result: *mut i32) {
+    unsafe {
+        SYSCALL_STUBS.read().unwrap().sol_memcmp(s1, s2, n, result);
+    }
+}
+
+pub(crate) fn sol_memset(s: *mut u8, c: u8, n: usize) {
+    unsafe {
+        SYSCALL_STUBS.read().unwrap().sol_memset(s, c, n);
+    }
+}