interpret/allocation: expose init + write_wildcards on a range

Author: nia-e

compiler/rustc_middle/src/mir/interpret/allocation.rs

@@ -809,11 +809,17 @@ impl<Prov: Provenance, Extra, Bytes: AllocBytes> Allocation<Prov, Extra, Bytes>
                 uninit_bytes.fill(0);
             }
         }
-        // Mark everything as initialized now.
-        self.mark_init(full_range, true);
+        self.mark_foreign_write(full_range);
+    }
 
-        // Set provenance of all bytes to wildcard.
-        self.provenance.write_wildcards(self.len());
+    /// Mark all bytes in the given range as initialised, setting provenances
+    /// to wildcards. This entirely breaks the normal mechanisms for tracking
+    /// initialisation and is only provided for Miri operating in native-lib
+    /// mode. Only call this if you're certain the underlying bytes were in
+    /// fact actually initialised!
+    pub fn mark_foreign_write(&mut self, range: AllocRange) {
+        self.mark_init(range, true);
+        self.provenance.write_wildcards(range);
     }
 
     /// Remove all provenance in the given memory range.

compiler/rustc_middle/src/mir/interpret/allocation/provenance_map.rs

@@ -212,10 +212,10 @@ impl<Prov: Provenance> ProvenanceMap<Prov> {
         Ok(())
     }
 
-    /// Overwrites all provenance in the allocation with wildcard provenance.
+    /// Overwrites all provenance in the given range with wildcard provenance.
     ///
     /// Provided for usage in Miri and panics otherwise.
-    pub fn write_wildcards(&mut self, alloc_size: usize) {
+    pub fn write_wildcards(&mut self, range: AllocRange) {
         assert!(
             Prov::OFFSET_IS_ADDR,
             "writing wildcard provenance is not supported when `OFFSET_IS_ADDR` is false"
@@ -224,9 +224,8 @@ impl<Prov: Provenance> ProvenanceMap<Prov> {
 
         // Remove all pointer provenances, then write wildcards into the whole byte range.
         self.ptrs.clear();
-        let last = Size::from_bytes(alloc_size);
         let bytes = self.bytes.get_or_insert_with(Box::default);
-        for offset in Size::ZERO..last {
+        for offset in range.start..range.start + range.size {
             bytes.insert(offset, wildcard);
         }
     }