guix/gnu/packages/patches/gcc-12-strmov-store-file-names.patch

Make sure that statements such as:

  strcpy (dst, "/gnu/store/…");

or

  static const char str[] = "/gnu/store/…";
  …
  strcpy (dst, str);

do not result in chunked /gnu/store strings that are undetectable by
Guix's GC and its grafting code.  See <https://bugs.gnu.org/24703>
and <https://bugs.gnu.org/30395>.

diff --git a/gcc/builtins.cc b/gcc/builtins.cc
index 5b085e3a1..480bc0b54 100644
--- a/gcc/builtins.cc
+++ b/gcc/builtins.cc
@@ -3363,6 +3363,58 @@ expand_builtin_mempcpy (tree exp, rtx target)
 				      target, exp, /*retmode=*/ RETURN_END);
 }
 
+extern void debug_tree (tree);
+
+/* Return true if STR contains the string "/gnu/store".  */
+
+bool
+store_reference_p (tree str)
+{
+  if (getenv ("GUIX_GCC_DEBUG") != NULL)
+    debug_tree (str);
+
+  if (TREE_CODE (str) == ADDR_EXPR)
+    str = TREE_OPERAND (str, 0);
+
+  if (TREE_CODE (str) == VAR_DECL
+      && TREE_STATIC (str)
+      && TREE_READONLY (str))
+    {
+      /* STR may be a 'static const' variable whose initial value
+         is a string constant.  See <https://bugs.gnu.org/30395>.  */
+      str = DECL_INITIAL (str);
+      if (str == NULL_TREE)
+        return false;
+    }
+
+  if (TREE_CODE (str) != STRING_CST)
+    return false;
+
+  int len;
+  const char *store;
+
+  store = getenv ("NIX_STORE") ? getenv ("NIX_STORE") : "/gnu/store";
+  len = strlen (store);
+
+  /* Size of the hash part of store file names, including leading slash and
+     trailing hyphen.  */
+  const int hash_len = 34;
+
+  if (TREE_STRING_LENGTH (str) < len + hash_len)
+    return false;
+
+  /* We cannot use 'strstr' because 'TREE_STRING_POINTER' returns a string
+     that is not necessarily NUL-terminated.  */
+
+  for (int i = 0; i < TREE_STRING_LENGTH (str) - (len + hash_len); i++)
+    {
+      if (strncmp (TREE_STRING_POINTER (str) + i, store, len) == 0)
+	return true;
+    }
+
+  return false;
+}
+
 /* Helper function to do the actual work for expand of memory copy family
    functions (memcpy, mempcpy, stpcpy).  Expansing should assign LEN bytes
    of memory from SRC to DEST and assign to TARGET if convenient.  Return
@@ -3384,6 +3436,13 @@ expand_builtin_memory_copy_args (tree dest, tree src, tree len,
 
   bool is_move_done;
 
+  /* Do not emit block moves, which translate to the 'movabs' instruction on
+     x86_64, when SRC refers to store items.  That way, store references
+     remain visible to the Guix GC and grafting code.  See
+     <https://bugs.gnu.org/24703>.  */
+  if (store_reference_p (src))
+    return NULL_RTX;
+
   /* If DEST is not a pointer type, call the normal function.  */
   if (dest_align == 0)
     return NULL_RTX;
diff --git a/gcc/gimple-fold.cc b/gcc/gimple-fold.cc
index 863ee3d39..4cc46c265 100644
--- a/gcc/gimple-fold.cc
+++ b/gcc/gimple-fold.cc
@@ -856,6 +856,8 @@ var_decl_component_p (tree var)
 	      && TREE_CODE (TREE_OPERAND (inner, 0)) == ADDR_EXPR));
 }
 
+extern bool store_reference_p (tree);
+
 /* Return TRUE if the SIZE argument, representing the size of an
    object, is in a range of values of which exactly zero is valid.  */
 
@@ -960,6 +962,9 @@ gimple_fold_builtin_memory_op (gimple_stmt_iterator *gsi,
 	= build_int_cst (build_pointer_type_for_mode (char_type_node,
 						      ptr_mode, true), 0);
 
+      if (store_reference_p (src))
+        return false;
+
       /* If we can perform the copy efficiently with first doing all loads
          and then all stores inline it that way.  Currently efficiently
 	 means that we can load all the memory into a single integer