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/* UndefinedBehaviorSanitizer, undefined behavior detector.
Copyright (C) 2013-2022 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 "tm.h"
#include "c-family/c-common.h"
#include "ubsan.h"
#include "c-family/c-ubsan.h"
#include "stor-layout.h"
#include "builtins.h"
#include "gimplify.h"
#include "stringpool.h"
#include "attribs.h"
#include "asan.h"
#include "langhooks.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, x = NULL_TREE;
tree type = TREE_TYPE (op0);
enum sanitize_code flag = SANITIZE_DIVIDE;
/* 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. */
tree top0 = TYPE_MAIN_VARIANT (type);
tree top1 = TYPE_MAIN_VARIANT (TREE_TYPE (op1));
gcc_checking_assert (lang_hooks.types_compatible_p (top0, top1));
op0 = unshare_expr (op0);
op1 = unshare_expr (op1);
if (TREE_CODE (type) == INTEGER_TYPE
&& sanitize_flags_p (SANITIZE_DIVIDE))
t = fold_build2 (EQ_EXPR, boolean_type_node,
op1, build_int_cst (type, 0));
else if (TREE_CODE (type) == REAL_TYPE
&& sanitize_flags_p (SANITIZE_FLOAT_DIVIDE))
{
t = fold_build2 (EQ_EXPR, boolean_type_node,
op1, build_real (type, dconst0));
flag = SANITIZE_FLOAT_DIVIDE;
}
else
t = NULL_TREE;
/* We check INT_MIN / -1 only for signed types. */
if (TREE_CODE (type) == INTEGER_TYPE
&& sanitize_flags_p (SANITIZE_SI_OVERFLOW)
&& !TYPE_UNSIGNED (type))
{
tt = fold_build2 (EQ_EXPR, boolean_type_node, unshare_expr (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);
if (t == NULL_TREE || integer_zerop (t))
{
t = x;
x = NULL_TREE;
flag = SANITIZE_SI_OVERFLOW;
}
else if (flag_sanitize_undefined_trap_on_error
|| (((flag_sanitize_recover & SANITIZE_DIVIDE) == 0)
== ((flag_sanitize_recover & SANITIZE_SI_OVERFLOW) == 0)))
{
t = fold_build2 (TRUTH_OR_EXPR, boolean_type_node, t, x);
x = NULL_TREE;
}
else if (integer_zerop (x))
x = NULL_TREE;
}
else if (t == NULL_TREE)
return NULL_TREE;
/* 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), unshare_expr (op0), t);
t = fold_build2 (COMPOUND_EXPR, TREE_TYPE (t), unshare_expr (op1), t);
if (flag_sanitize_undefined_trap_on_error)
tt = build_call_expr_loc (loc, builtin_decl_explicit (BUILT_IN_TRAP), 0);
else
{
tree data = ubsan_create_data ("__ubsan_overflow_data", 1, &loc,
ubsan_type_descriptor (type), NULL_TREE,
NULL_TREE);
data = build_fold_addr_expr_loc (loc, data);
enum built_in_function bcode
= (flag_sanitize_recover & flag)
? BUILT_IN_UBSAN_HANDLE_DIVREM_OVERFLOW
: BUILT_IN_UBSAN_HANDLE_DIVREM_OVERFLOW_ABORT;
tt = builtin_decl_explicit (bcode);
op0 = unshare_expr (op0);
op1 = unshare_expr (op1);
tt = build_call_expr_loc (loc, tt, 3, data, ubsan_encode_value (op0),
ubsan_encode_value (op1));
if (x)
{
bcode = (flag_sanitize_recover & SANITIZE_SI_OVERFLOW)
? BUILT_IN_UBSAN_HANDLE_DIVREM_OVERFLOW
: BUILT_IN_UBSAN_HANDLE_DIVREM_OVERFLOW_ABORT;
tree xt = builtin_decl_explicit (bcode);
op0 = unshare_expr (op0);
op1 = unshare_expr (op1);
xt = build_call_expr_loc (loc, xt, 3, data, ubsan_encode_value (op0),
ubsan_encode_value (op1));
x = fold_build3 (COND_EXPR, void_type_node, x, xt, void_node);
}
}
t = fold_build3 (COND_EXPR, void_type_node, t, tt, x ? x : void_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);
if (!INTEGRAL_TYPE_P (type0))
return NULL_TREE;
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);
op0 = unshare_expr (op0);
op1 = unshare_expr (op1);
t = fold_convert_loc (loc, op1_utype, op1);
t = fold_build2 (GT_EXPR, boolean_type_node, t, uprecm1);
/* If this is not a signed operation, don't perform overflow checks.
Also punt on bit-fields. */
if (TYPE_OVERFLOW_WRAPS (type0)
|| maybe_ne (GET_MODE_BITSIZE (TYPE_MODE (type0)),
TYPE_PRECISION (type0))
|| !sanitize_flags_p (SANITIZE_SHIFT_BASE)
/* In C++20 and later, shifts are well defined except when
the second operand is not within bounds. */
|| cxx_dialect >= cxx20)
;
/* For signed x << y, in C99 and later, the following:
(unsigned) x >> (uprecm1 - y)
if non-zero, is undefined. */
else if (code == LSHIFT_EXPR && flag_isoc99 && cxx_dialect < cxx11)
{
tree x = fold_build2 (MINUS_EXPR, op1_utype, uprecm1,
fold_convert (op1_utype, unshare_expr (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 to C++17, the following:
x < 0 || ((unsigned) x >> (uprecm1 - y))
if > 1, is undefined. */
else if (code == LSHIFT_EXPR && cxx_dialect >= cxx11)
{
tree x = fold_build2 (MINUS_EXPR, op1_utype, uprecm1,
fold_convert (op1_utype, unshare_expr (op1)));
tt = fold_convert_loc (loc, unsigned_type_for (type0),
unshare_expr (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, unshare_expr (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), unshare_expr (op0), t);
t = fold_build2 (COMPOUND_EXPR, TREE_TYPE (t), unshare_expr (op1), t);
enum sanitize_code recover_kind = SANITIZE_SHIFT_EXPONENT;
tree else_t = void_node;
if (tt)
{
if (!sanitize_flags_p (SANITIZE_SHIFT_EXPONENT))
{
t = fold_build1 (TRUTH_NOT_EXPR, boolean_type_node, t);
t = fold_build2 (TRUTH_AND_EXPR, boolean_type_node, t, tt);
recover_kind = SANITIZE_SHIFT_BASE;
}
else
{
if (flag_sanitize_undefined_trap_on_error
|| ((!(flag_sanitize_recover & SANITIZE_SHIFT_EXPONENT))
== (!(flag_sanitize_recover & SANITIZE_SHIFT_BASE))))
t = fold_build2 (TRUTH_OR_EXPR, boolean_type_node, t, tt);
else
else_t = tt;
}
}
if (flag_sanitize_undefined_trap_on_error)
tt = build_call_expr_loc (loc, builtin_decl_explicit (BUILT_IN_TRAP), 0);
else
{
tree data = ubsan_create_data ("__ubsan_shift_data", 1, &loc,
ubsan_type_descriptor (type0),
ubsan_type_descriptor (type1), NULL_TREE,
NULL_TREE);
data = build_fold_addr_expr_loc (loc, data);
enum built_in_function bcode
= (flag_sanitize_recover & recover_kind)
? BUILT_IN_UBSAN_HANDLE_SHIFT_OUT_OF_BOUNDS
: BUILT_IN_UBSAN_HANDLE_SHIFT_OUT_OF_BOUNDS_ABORT;
tt = builtin_decl_explicit (bcode);
op0 = unshare_expr (op0);
op1 = unshare_expr (op1);
tt = build_call_expr_loc (loc, tt, 3, data, ubsan_encode_value (op0),
ubsan_encode_value (op1));
if (else_t != void_node)
{
bcode = (flag_sanitize_recover & SANITIZE_SHIFT_BASE)
? BUILT_IN_UBSAN_HANDLE_SHIFT_OUT_OF_BOUNDS
: BUILT_IN_UBSAN_HANDLE_SHIFT_OUT_OF_BOUNDS_ABORT;
tree else_tt = builtin_decl_explicit (bcode);
op0 = unshare_expr (op0);
op1 = unshare_expr (op1);
else_tt = build_call_expr_loc (loc, else_tt, 3, data,
ubsan_encode_value (op0),
ubsan_encode_value (op1));
else_t = fold_build3 (COND_EXPR, void_type_node, else_t,
else_tt, void_node);
}
}
t = fold_build3 (COND_EXPR, void_type_node, t, tt, else_t);
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));
if (flag_sanitize_undefined_trap_on_error)
tt = build_call_expr_loc (loc, builtin_decl_explicit (BUILT_IN_TRAP), 0);
else
{
tree data = ubsan_create_data ("__ubsan_vla_data", 1, &loc,
ubsan_type_descriptor (type), NULL_TREE,
NULL_TREE);
data = build_fold_addr_expr_loc (loc, data);
enum built_in_function bcode
= (flag_sanitize_recover & SANITIZE_VLA)
? BUILT_IN_UBSAN_HANDLE_VLA_BOUND_NOT_POSITIVE
: BUILT_IN_UBSAN_HANDLE_VLA_BOUND_NOT_POSITIVE_ABORT;
tt = builtin_decl_explicit (bcode);
tt = build_call_expr_loc (loc, tt, 2, data, ubsan_encode_value (size));
}
t = fold_build3 (COND_EXPR, void_type_node, t, tt, void_node);
return t;
}
/* Instrument missing return in C++ functions returning non-void. */
tree
ubsan_instrument_return (location_t loc)
{
if (flag_sanitize_undefined_trap_on_error)
return build_call_expr_loc (loc, builtin_decl_explicit (BUILT_IN_TRAP), 0);
tree data = ubsan_create_data ("__ubsan_missing_return_data", 1, &loc,
NULL_TREE, 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));
}
/* Instrument array bounds for ARRAY_REFs. We create special builtin,
that gets expanded in the sanopt pass, and make an array dimension
of it. ARRAY is the array, *INDEX is an index to the array.
Return NULL_TREE if no instrumentation is emitted.
IGNORE_OFF_BY_ONE is true if the ARRAY_REF is inside a ADDR_EXPR. */
tree
ubsan_instrument_bounds (location_t loc, tree array, tree *index,
bool ignore_off_by_one)
{
tree type = TREE_TYPE (array);
tree domain = TYPE_DOMAIN (type);
if (domain == NULL_TREE || TYPE_MAX_VALUE (domain) == NULL_TREE)
return NULL_TREE;
tree bound = TYPE_MAX_VALUE (domain);
if (ignore_off_by_one)
bound = fold_build2 (PLUS_EXPR, TREE_TYPE (bound), bound,
build_int_cst (TREE_TYPE (bound), 1));
/* Detect flexible array members and suchlike, unless
-fsanitize=bounds-strict. */
tree base = get_base_address (array);
if (!sanitize_flags_p (SANITIZE_BOUNDS_STRICT)
&& TREE_CODE (array) == COMPONENT_REF
&& base && (INDIRECT_REF_P (base) || TREE_CODE (base) == MEM_REF))
{
tree next = NULL_TREE;
tree cref = array;
/* Walk all structs/unions. */
while (TREE_CODE (cref) == COMPONENT_REF)
{
if (TREE_CODE (TREE_TYPE (TREE_OPERAND (cref, 0))) == RECORD_TYPE)
for (next = DECL_CHAIN (TREE_OPERAND (cref, 1));
next && TREE_CODE (next) != FIELD_DECL;
next = DECL_CHAIN (next))
;
if (next)
/* Not a last element. Instrument it. */
break;
/* Ok, this is the last field of the structure/union. But the
aggregate containing the field must be the last field too,
recursively. */
cref = TREE_OPERAND (cref, 0);
}
if (!next)
/* Don't instrument this flexible array member-like array in non-strict
-fsanitize=bounds mode. */
return NULL_TREE;
}
/* Don't emit instrumentation in the most common cases. */
tree idx = NULL_TREE;
if (TREE_CODE (*index) == INTEGER_CST)
idx = *index;
else if (TREE_CODE (*index) == BIT_AND_EXPR
&& TREE_CODE (TREE_OPERAND (*index, 1)) == INTEGER_CST)
idx = TREE_OPERAND (*index, 1);
if (idx
&& TREE_CODE (bound) == INTEGER_CST
&& tree_int_cst_sgn (idx) >= 0
&& tree_int_cst_le (idx, bound))
return NULL_TREE;
*index = save_expr (*index);
/* Create a "(T *) 0" tree node to describe the array type. */
tree zero_with_type = build_int_cst (build_pointer_type (type), 0);
return build_call_expr_internal_loc (loc, IFN_UBSAN_BOUNDS,
void_type_node, 3, zero_with_type,
*index, bound);
}
/* Return true iff T is an array that was instrumented by SANITIZE_BOUNDS. */
bool
ubsan_array_ref_instrumented_p (const_tree t)
{
if (TREE_CODE (t) != ARRAY_REF)
return false;
tree op1 = TREE_OPERAND (t, 1);
return TREE_CODE (op1) == COMPOUND_EXPR
&& TREE_CODE (TREE_OPERAND (op1, 0)) == CALL_EXPR
&& CALL_EXPR_FN (TREE_OPERAND (op1, 0)) == NULL_TREE
&& CALL_EXPR_IFN (TREE_OPERAND (op1, 0)) == IFN_UBSAN_BOUNDS;
}
/* Instrument an ARRAY_REF, if it hasn't already been instrumented.
IGNORE_OFF_BY_ONE is true if the ARRAY_REF is inside a ADDR_EXPR. */
void
ubsan_maybe_instrument_array_ref (tree *expr_p, bool ignore_off_by_one)
{
if (!ubsan_array_ref_instrumented_p (*expr_p)
&& sanitize_flags_p (SANITIZE_BOUNDS | SANITIZE_BOUNDS_STRICT)
&& current_function_decl != NULL_TREE)
{
tree op0 = TREE_OPERAND (*expr_p, 0);
tree op1 = TREE_OPERAND (*expr_p, 1);
tree e = ubsan_instrument_bounds (EXPR_LOCATION (*expr_p), op0, &op1,
ignore_off_by_one);
if (e != NULL_TREE)
{
tree t = copy_node (*expr_p);
TREE_OPERAND (t, 1) = build2 (COMPOUND_EXPR, TREE_TYPE (op1),
e, op1);
*expr_p = t;
}
}
}
static tree
ubsan_maybe_instrument_reference_or_call (location_t loc, tree op, tree ptype,
enum ubsan_null_ckind ckind)
{
if (!sanitize_flags_p (SANITIZE_ALIGNMENT | SANITIZE_NULL)
|| current_function_decl == NULL_TREE)
return NULL_TREE;
tree type = TREE_TYPE (ptype);
tree orig_op = op;
bool instrument = false;
unsigned int mina = 0;
if (sanitize_flags_p (SANITIZE_ALIGNMENT))
{
mina = min_align_of_type (type);
if (mina <= 1)
mina = 0;
}
while ((TREE_CODE (op) == NOP_EXPR
|| TREE_CODE (op) == NON_LVALUE_EXPR)
&& TREE_CODE (TREE_TYPE (op)) == POINTER_TYPE)
op = TREE_OPERAND (op, 0);
if (TREE_CODE (op) == NOP_EXPR
&& TREE_CODE (TREE_TYPE (op)) == REFERENCE_TYPE)
{
if (mina && mina > min_align_of_type (TREE_TYPE (TREE_TYPE (op))))
instrument = true;
}
else
{
if (sanitize_flags_p (SANITIZE_NULL) && TREE_CODE (op) == ADDR_EXPR)
{
bool strict_overflow_p = false;
/* tree_single_nonzero_warnv_p will not return true for non-weak
non-automatic decls with -fno-delete-null-pointer-checks,
which is disabled during -fsanitize=null. We don't want to
instrument those, just weak vars though. */
int save_flag_delete_null_pointer_checks
= flag_delete_null_pointer_checks;
flag_delete_null_pointer_checks = 1;
if (!tree_single_nonzero_warnv_p (op, &strict_overflow_p)
|| strict_overflow_p)
instrument = true;
flag_delete_null_pointer_checks
= save_flag_delete_null_pointer_checks;
}
else if (sanitize_flags_p (SANITIZE_NULL))
instrument = true;
if (mina && mina > 1)
{
if (!POINTER_TYPE_P (TREE_TYPE (op))
|| mina > get_pointer_alignment (op) / BITS_PER_UNIT)
instrument = true;
}
}
if (!instrument)
return NULL_TREE;
op = save_expr (orig_op);
gcc_assert (POINTER_TYPE_P (ptype));
if (TREE_CODE (ptype) == REFERENCE_TYPE)
ptype = build_pointer_type (TREE_TYPE (ptype));
tree kind = build_int_cst (ptype, ckind);
tree align = build_int_cst (pointer_sized_int_node, mina);
tree call
= build_call_expr_internal_loc (loc, IFN_UBSAN_NULL, void_type_node,
3, op, kind, align);
TREE_SIDE_EFFECTS (call) = 1;
return fold_build2 (COMPOUND_EXPR, TREE_TYPE (op), call, op);
}
/* Instrument a NOP_EXPR to REFERENCE_TYPE or INTEGER_CST with REFERENCE_TYPE
type if needed. */
void
ubsan_maybe_instrument_reference (tree *stmt_p)
{
tree stmt = *stmt_p;
tree op = stmt;
if (TREE_CODE (stmt) == NOP_EXPR)
op = TREE_OPERAND (stmt, 0);
op = ubsan_maybe_instrument_reference_or_call (EXPR_LOCATION (stmt), op,
TREE_TYPE (stmt),
UBSAN_REF_BINDING);
if (op)
{
if (TREE_CODE (stmt) == NOP_EXPR)
TREE_OPERAND (stmt, 0) = op;
else
*stmt_p = op;
}
}
/* Instrument a CALL_EXPR to a method if needed. */
void
ubsan_maybe_instrument_member_call (tree stmt, bool is_ctor)
{
if (call_expr_nargs (stmt) == 0)
return;
tree op = CALL_EXPR_ARG (stmt, 0);
if (op == error_mark_node
|| !POINTER_TYPE_P (TREE_TYPE (op)))
return;
op = ubsan_maybe_instrument_reference_or_call (EXPR_LOCATION (stmt), op,
TREE_TYPE (op),
is_ctor ? UBSAN_CTOR_CALL
: UBSAN_MEMBER_CALL);
if (op)
CALL_EXPR_ARG (stmt, 0) = op;
}