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

   1 Make sure that statements such as:
   2
   3   strcpy (dst, "/gnu/store/…");
   4
   5 do not result in chunked /gnu/store strings that are undetectable by
   6 Guix's GC and its grafting code.  See <http://bugs.gnu.org/24703>.
   7
   8 --- gcc-5.3.0/gcc/builtins.c    2016-10-18 10:50:46.080616285 +0200
   9 +++ gcc-5.3.0/gcc/builtins.c    2016-11-09 15:26:43.693042737 +0100
  10 @@ -3192,6 +3192,42 @@ determine_block_size (tree len, rtx len_
  11                           GET_MODE_MASK (GET_MODE (len_rtx)));
  12  }
  13
  14 +/* Return true if STR contains the string "/gnu/store".  */
  15 +
  16 +static bool
  17 +store_reference_p (tree str)
  18 +{
  19 +  if (TREE_CODE (str) == ADDR_EXPR)
  20 +    str = TREE_OPERAND (str, 0);
  21 +
  22 +  if (TREE_CODE (str) != STRING_CST)
  23 +    return false;
  24 +
  25 +  int len;
  26 +  const char *store;
  27 +
  28 +  store = getenv ("NIX_STORE") ? getenv ("NIX_STORE") : "/gnu/store";
  29 +  len = strlen (store);
  30 +
  31 +  /* Size of the hash part of store file names, including leading slash and
  32 +     trailing hyphen.  */
  33 +  const int hash_len = 34;
  34 +
  35 +  if (TREE_STRING_LENGTH (str) < len + hash_len)
  36 +    return false;
  37 +
  38 +  /* We cannot use 'strstr' because 'TREE_STRING_POINTER' returns a string
  39 +     that is not necessarily NUL-terminated.  */
  40 +
  41 +  for (int i = 0; i < TREE_STRING_LENGTH (str) - (len + hash_len); i++)
  42 +    {
  43 +      if (strncmp (TREE_STRING_POINTER (str) + i, store, len) == 0)
  44 +       return true;
  45 +    }
  46 +
  47 +  return false;
  48 +}
  49 +
  50  /* Helper function to do the actual work for expand_builtin_memcpy.  */
  51
  52  static rtx
  53 @@ -3207,6 +3243,13 @@ expand_builtin_memcpy_args (tree dest, t
  54    unsigned HOST_WIDE_INT max_size;
  55    unsigned HOST_WIDE_INT probable_max_size;
  56
  57 +  /* Do not emit block moves, which translate to the 'movabs' instruction on
  58 +     x86_64, when SRC refers to store items.  That way, store references
  59 +     remain visible to the Guix GC and grafting code.  See
  60 +     <http://bugs.gnu.org/24703>.  */
  61 +  if (store_reference_p (src))
  62 +    return NULL_RTX;
  63 +
  64    /* If DEST is not a pointer type, call the normal function.  */
  65    if (dest_align == 0)
  66      return NULL_RTX;