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

   1 Make sure that statements such as:
   2
   3   strcpy (dst, "/gnu/store/…");
   4
   5 or
   6
   7   static const char str[] = "/gnu/store/…";
   8   …
   9   strcpy (dst, str);
  10
  11 do not result in chunked /gnu/store strings that are undetectable by
  12 Guix's GC and its grafting code.  See <https://bugs.gnu.org/24703>
  13 and <https://bugs.gnu.org/30395>.
  14
  15
  16 --- gcc-5.3.0/gcc/builtins.c    2016-10-18 10:50:46.080616285 +0200
  17 +++ gcc-5.3.0/gcc/builtins.c    2016-11-09 15:26:43.693042737 +0100
  18 @@ -3192,6 +3192,58 @@ determine_block_size (tree len, rtx len_
  19                           GET_MODE_MASK (GET_MODE (len_rtx)));
  20  }
  21
  22 +extern void debug_tree (tree);
  23 +
  24 +/* Return true if STR contains the string "/gnu/store".  */
  25 +
  26 +bool
  27 +store_reference_p (tree str)
  28 +{
  29 +  if (getenv ("GUIX_GCC_DEBUG") != NULL)
  30 +    debug_tree (str);
  31 +
  32 +  if (TREE_CODE (str) == ADDR_EXPR)
  33 +    str = TREE_OPERAND (str, 0);
  34 +
  35 +  if (TREE_CODE (str) == VAR_DECL
  36 +      && TREE_STATIC (str)
  37 +      && TREE_READONLY (str))
  38 +    {
  39 +      /* STR may be a 'static const' variable whose initial value
  40 +         is a string constant.  See <https://bugs.gnu.org/30395>.  */
  41 +      str = DECL_INITIAL (str);
  42 +      if (str == NULL_TREE)
  43 +        return false;
  44 +    }
  45 +
  46 +  if (TREE_CODE (str) != STRING_CST)
  47 +    return false;
  48 +
  49 +  int len;
  50 +  const char *store;
  51 +
  52 +  store = getenv ("NIX_STORE") ? getenv ("NIX_STORE") : "/gnu/store";
  53 +  len = strlen (store);
  54 +
  55 +  /* Size of the hash part of store file names, including leading slash and
  56 +     trailing hyphen.  */
  57 +  const int hash_len = 34;
  58 +
  59 +  if (TREE_STRING_LENGTH (str) < len + hash_len)
  60 +    return false;
  61 +
  62 +  /* We cannot use 'strstr' because 'TREE_STRING_POINTER' returns a string
  63 +     that is not necessarily NUL-terminated.  */
  64 +
  65 +  for (int i = 0; i < TREE_STRING_LENGTH (str) - (len + hash_len); i++)
  66 +    {
  67 +      if (strncmp (TREE_STRING_POINTER (str) + i, store, len) == 0)
  68 +       return true;
  69 +    }
  70 +
  71 +  return false;
  72 +}
  73 +
  74  /* Helper function to do the actual work for expand_builtin_memcpy.  */
  75
  76  static rtx
  77 @@ -3207,6 +3243,13 @@ expand_builtin_memcpy_args (tree dest, t
  78    unsigned HOST_WIDE_INT max_size;
  79    unsigned HOST_WIDE_INT probable_max_size;
  80
  81 +  /* Do not emit block moves, which translate to the 'movabs' instruction on
  82 +     x86_64, when SRC refers to store items.  That way, store references
  83 +     remain visible to the Guix GC and grafting code.  See
  84 +     <https://bugs.gnu.org/24703>.  */
  85 +  if (store_reference_p (src))
  86 +    return NULL_RTX;
  87 +
  88    /* If DEST is not a pointer type, call the normal function.  */
  89    if (dest_align == 0)
  90      return NULL_RTX;
  91
  92 --- gcc-5.5.0/gcc/gimple-fold.c 2018-03-20 11:36:16.709442004 +0100
  93 +++ gcc-5.5.0/gcc/gimple-fold.c 2018-03-20 11:46:43.838487065 +0100
  94 @@ -769,6 +769,8 @@ var_decl_component_p (tree var)
  95    return SSA_VAR_P (inner);
  96  }
  97
  98 +extern bool store_reference_p (tree);
  99 +
 100  /* Fold function call to builtin mem{{,p}cpy,move}.  Return
 101     false if no simplification can be made.
 102     If ENDP is 0, return DEST (like memcpy).
 103 @@ -1099,6 +1101,9 @@ gimple_fold_builtin_memory_op (gimple_st
 104        if (!srctype)
 105         return false;
 106
 107 +      if (store_reference_p (src))
 108 +        return false;
 109 +
 110        src_align = get_pointer_alignment (src);
 111        dest_align = get_pointer_alignment (dest);
 112        if (dest_align < TYPE_ALIGN (desttype)