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/* UndefinedBehaviorSanitizer, undefined behavior detector.
Copyright (C) 2013 Free Software Foundation, Inc.
Contributed by Marek Polacek <polacek@redhat.com>
This file is part of GCC.
GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.
GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
for more details.
You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3. If not see
<http://www.gnu.org/licenses/>. */
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tree.h"
#include "alloc-pool.h"
#include "cgraph.h"
#include "output.h"
#include "toplev.h"
#include "ubsan.h"
#include "c-family/c-common.h"
#include "c-family/c-ubsan.h"
/* Instrument division by zero and INT_MIN / -1. If not instrumenting,
return NULL_TREE. */
tree
ubsan_instrument_division (location_t loc, tree op0, tree op1)
{
tree t, tt;
tree type = TREE_TYPE (op0);
/* At this point both operands should have the same type,
because they are already converted to RESULT_TYPE.
Use TYPE_MAIN_VARIANT since typedefs can confuse us. */
gcc_assert (TYPE_MAIN_VARIANT (TREE_TYPE (op0))
== TYPE_MAIN_VARIANT (TREE_TYPE (op1)));
/* TODO: REAL_TYPE is not supported yet. */
if (TREE_CODE (type) != INTEGER_TYPE)
return NULL_TREE;
t = fold_build2 (EQ_EXPR, boolean_type_node,
op1, build_int_cst (type, 0));
/* We check INT_MIN / -1 only for signed types. */
if (!TYPE_UNSIGNED (type))
{
tree x;
tt = fold_build2 (EQ_EXPR, boolean_type_node, op1,
build_int_cst (type, -1));
x = fold_build2 (EQ_EXPR, boolean_type_node, op0,
TYPE_MIN_VALUE (type));
x = fold_build2 (TRUTH_AND_EXPR, boolean_type_node, x, tt);
t = fold_build2 (TRUTH_OR_EXPR, boolean_type_node, t, x);
}
/* If the condition was folded to 0, no need to instrument
this expression. */
if (integer_zerop (t))
return NULL_TREE;
/* In case we have a SAVE_EXPR in a conditional context, we need to
make sure it gets evaluated before the condition. */
t = fold_build2 (COMPOUND_EXPR, TREE_TYPE (t), op0, t);
tree data = ubsan_create_data ("__ubsan_overflow_data",
loc, NULL,
ubsan_type_descriptor (type, false),
NULL_TREE);
data = build_fold_addr_expr_loc (loc, data);
tt = builtin_decl_explicit (BUILT_IN_UBSAN_HANDLE_DIVREM_OVERFLOW);
tt = build_call_expr_loc (loc, tt, 3, data, ubsan_encode_value (op0),
ubsan_encode_value (op1));
t = fold_build3 (COND_EXPR, void_type_node, t, tt, void_zero_node);
return t;
}
/* Instrument left and right shifts. */
tree
ubsan_instrument_shift (location_t loc, enum tree_code code,
tree op0, tree op1)
{
tree t, tt = NULL_TREE;
tree type0 = TREE_TYPE (op0);
tree type1 = TREE_TYPE (op1);
tree op1_utype = unsigned_type_for (type1);
HOST_WIDE_INT op0_prec = TYPE_PRECISION (type0);
tree uprecm1 = build_int_cst (op1_utype, op0_prec - 1);
tree precm1 = build_int_cst (type1, op0_prec - 1);
t = fold_convert_loc (loc, op1_utype, op1);
t = fold_build2 (GT_EXPR, boolean_type_node, t, uprecm1);
/* For signed x << y, in C99/C11, the following:
(unsigned) x >> (precm1 - y)
if non-zero, is undefined. */
if (code == LSHIFT_EXPR
&& !TYPE_UNSIGNED (type0)
&& flag_isoc99)
{
tree x = fold_build2 (MINUS_EXPR, integer_type_node, precm1, op1);
tt = fold_convert_loc (loc, unsigned_type_for (type0), op0);
tt = fold_build2 (RSHIFT_EXPR, TREE_TYPE (tt), tt, x);
tt = fold_build2 (NE_EXPR, boolean_type_node, tt,
build_int_cst (TREE_TYPE (tt), 0));
}
/* For signed x << y, in C++11/C++14, the following:
x < 0 || ((unsigned) x >> (precm1 - y))
if > 1, is undefined. */
if (code == LSHIFT_EXPR
&& !TYPE_UNSIGNED (TREE_TYPE (op0))
&& (cxx_dialect == cxx11 || cxx_dialect == cxx1y))
{
tree x = fold_build2 (MINUS_EXPR, integer_type_node, precm1, op1);
tt = fold_convert_loc (loc, unsigned_type_for (type0), op0);
tt = fold_build2 (RSHIFT_EXPR, TREE_TYPE (tt), tt, x);
tt = fold_build2 (GT_EXPR, boolean_type_node, tt,
build_int_cst (TREE_TYPE (tt), 1));
x = fold_build2 (LT_EXPR, boolean_type_node, op0,
build_int_cst (type0, 0));
tt = fold_build2 (TRUTH_OR_EXPR, boolean_type_node, x, tt);
}
/* If the condition was folded to 0, no need to instrument
this expression. */
if (integer_zerop (t) && (tt == NULL_TREE || integer_zerop (tt)))
return NULL_TREE;
/* In case we have a SAVE_EXPR in a conditional context, we need to
make sure it gets evaluated before the condition. */
t = fold_build2 (COMPOUND_EXPR, TREE_TYPE (t), op0, t);
tree data = ubsan_create_data ("__ubsan_shift_data",
loc, NULL,
ubsan_type_descriptor (type0, false),
ubsan_type_descriptor (type1, false),
NULL_TREE);
data = build_fold_addr_expr_loc (loc, data);
t = fold_build2 (TRUTH_OR_EXPR, boolean_type_node, t,
tt ? tt : integer_zero_node);
tt = builtin_decl_explicit (BUILT_IN_UBSAN_HANDLE_SHIFT_OUT_OF_BOUNDS);
tt = build_call_expr_loc (loc, tt, 3, data, ubsan_encode_value (op0),
ubsan_encode_value (op1));
t = fold_build3 (COND_EXPR, void_type_node, t, tt, void_zero_node);
return t;
}
/* Instrument variable length array bound. */
tree
ubsan_instrument_vla (location_t loc, tree size)
{
tree type = TREE_TYPE (size);
tree t, tt;
t = fold_build2 (LE_EXPR, boolean_type_node, size, build_int_cst (type, 0));
tree data = ubsan_create_data ("__ubsan_vla_data",
loc, NULL,
ubsan_type_descriptor (type, false),
NULL_TREE);
data = build_fold_addr_expr_loc (loc, data);
tt = builtin_decl_explicit (BUILT_IN_UBSAN_HANDLE_VLA_BOUND_NOT_POSITIVE);
tt = build_call_expr_loc (loc, tt, 2, data, ubsan_encode_value (size));
t = fold_build3 (COND_EXPR, void_type_node, t, tt, void_zero_node);
return t;
}
/* Instrument missing return in C++ functions returning non-void. */
tree
ubsan_instrument_return (location_t loc)
{
tree data = ubsan_create_data ("__ubsan_missing_return_data", loc,
NULL, NULL_TREE);
tree t = builtin_decl_explicit (BUILT_IN_UBSAN_HANDLE_MISSING_RETURN);
return build_call_expr_loc (loc, t, 1, build_fold_addr_expr_loc (loc, data));
}
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