Re: [PATCH 7/12] ubsan: _BitInt -fsanitize=undefined support [PR102989]
On Wed, 9 Aug 2023, Jakub Jelinek wrote:
> Hi!
>
> The following patch introduces some -fsanitize=undefined support for _BitInt,
> but some of the diagnostics is limited by lack of proper support in the
> library.
> I've filed https://github.com/llvm/llvm-project/issues/64100 to request
> proper support, for now some of the diagnostics might have less or more
> confusing or inaccurate wording but UB should still be diagnosed when it
> happens.
OK, you're the expert here.
Richard.
> 2023-08-09 Jakub Jelinek
>
> PR c/102989
> gcc/
> * internal-fn.cc (expand_ubsan_result_store): Add LHS, MODE and
> DO_ERROR arguments. For non-mode precision BITINT_TYPE results
> check if all padding bits up to mode precision are zeros or sign
> bit copies and if not, jump to DO_ERROR.
> (expand_addsub_overflow, expand_neg_overflow, expand_mul_overflow):
> Adjust expand_ubsan_result_store callers.
> * ubsan.cc: Include target.h and langhooks.h.
> (ubsan_encode_value): Pass BITINT_TYPE values which fit into pointer
> size converted to pointer sized integer, pass BITINT_TYPE values
> which fit into TImode (if supported) or DImode as those integer types
> or otherwise for now punt (pass 0).
> (ubsan_type_descriptor): Handle BITINT_TYPE. For pstyle of
> UBSAN_PRINT_FORCE_INT use TK_Integer (0x) mode with a
> TImode/DImode precision rather than TK_Unknown used otherwise for
> large/huge BITINT_TYPEs.
> (instrument_si_overflow): Instrument BITINT_TYPE operations even when
> they don't have mode precision.
> * ubsan.h (enum ubsan_print_style): New enumerator.
> gcc/c-family/
> * c-ubsan.cc (ubsan_instrument_shift): Use UBSAN_PRINT_FORCE_INT
> for type0 type descriptor.
>
> --- gcc/ubsan.cc.jj 2023-08-08 15:54:35.443599459 +0200
> +++ gcc/ubsan.cc 2023-08-08 16:12:02.329939798 +0200
> @@ -50,6 +50,8 @@ along with GCC; see the file COPYING3.
> #include "gimple-fold.h"
> #include "varasm.h"
> #include "realmpfr.h"
> +#include "target.h"
> +#include "langhooks.h"
>
> /* Map from a tree to a VAR_DECL tree. */
>
> @@ -125,6 +127,25 @@ tree
> ubsan_encode_value (tree t, enum ubsan_encode_value_phase phase)
> {
>tree type = TREE_TYPE (t);
> + if (TREE_CODE (type) == BITINT_TYPE)
> +{
> + if (TYPE_PRECISION (type) <= POINTER_SIZE)
> + {
> + type = pointer_sized_int_node;
> + t = fold_build1 (NOP_EXPR, type, t);
> + }
> + else
> + {
> + scalar_int_mode arith_mode
> + = (targetm.scalar_mode_supported_p (TImode) ? TImode : DImode);
> + if (TYPE_PRECISION (type) > GET_MODE_PRECISION (arith_mode))
> + return build_zero_cst (pointer_sized_int_node);
> + type
> + = build_nonstandard_integer_type (GET_MODE_PRECISION (arith_mode),
> + TYPE_UNSIGNED (type));
> + t = fold_build1 (NOP_EXPR, type, t);
> + }
> +}
>scalar_mode mode = SCALAR_TYPE_MODE (type);
>const unsigned int bitsize = GET_MODE_BITSIZE (mode);
>if (bitsize <= POINTER_SIZE)
> @@ -355,14 +376,32 @@ ubsan_type_descriptor (tree type, enum u
> {
>/* See through any typedefs. */
>type = TYPE_MAIN_VARIANT (type);
> + tree type3 = type;
> + if (pstyle == UBSAN_PRINT_FORCE_INT)
> +{
> + /* Temporary hack for -fsanitize=shift with _BitInt(129) and more.
> + libubsan crashes if it is not TK_Integer type. */
> + if (TREE_CODE (type) == BITINT_TYPE)
> + {
> + scalar_int_mode arith_mode
> + = (targetm.scalar_mode_supported_p (TImode)
> +? TImode : DImode);
> + if (TYPE_PRECISION (type) > GET_MODE_PRECISION (arith_mode))
> + type3 = build_qualified_type (type, TYPE_QUAL_CONST);
> + }
> + if (type3 == type)
> + pstyle = UBSAN_PRINT_NORMAL;
> +}
>
> - tree decl = decl_for_type_lookup (type);
> + tree decl = decl_for_type_lookup (type3);
>/* It is possible that some of the earlier created DECLs were found
> unused, in that case they weren't emitted and varpool_node::get
> returns NULL node on them. But now we really need them. Thus,
> renew them here. */
>if (decl != NULL_TREE && varpool_node::get (decl))
> -return build_fold_addr_expr (decl);
> +{
> + return build_fold_addr_expr (decl);
> +}
>
>tree dtype = ubsan_get_type_descriptor_type ();
>tree type2 = type;
> @@ -370,6 +409,7 @@ ubsan_type_descriptor (tree type, enum u
>pretty_printer pretty_name;
>unsigned char deref_depth = 0;
>unsigned short tkind, tinfo;
> + char tname_bitint[sizeof ("unsigned _BitInt(2147483647)")];
>
>/* Get the name of the type, or the name of the pointer type. */
>if (pstyle == UBSAN_PRINT_POINTER)
> @@ -403,8 +443,18 @@ ubsan_type_descriptor (tree type, enum u
> }
>
>if (tname == NULL)
> -/* We weren't able to determine the type
[PATCH 7/12] ubsan: _BitInt -fsanitize=undefined support [PR102989]
Hi!
The following patch introduces some -fsanitize=undefined support for _BitInt,
but some of the diagnostics is limited by lack of proper support in the
library.
I've filed https://github.com/llvm/llvm-project/issues/64100 to request
proper support, for now some of the diagnostics might have less or more
confusing or inaccurate wording but UB should still be diagnosed when it
happens.
2023-08-09 Jakub Jelinek
PR c/102989
gcc/
* internal-fn.cc (expand_ubsan_result_store): Add LHS, MODE and
DO_ERROR arguments. For non-mode precision BITINT_TYPE results
check if all padding bits up to mode precision are zeros or sign
bit copies and if not, jump to DO_ERROR.
(expand_addsub_overflow, expand_neg_overflow, expand_mul_overflow):
Adjust expand_ubsan_result_store callers.
* ubsan.cc: Include target.h and langhooks.h.
(ubsan_encode_value): Pass BITINT_TYPE values which fit into pointer
size converted to pointer sized integer, pass BITINT_TYPE values
which fit into TImode (if supported) or DImode as those integer types
or otherwise for now punt (pass 0).
(ubsan_type_descriptor): Handle BITINT_TYPE. For pstyle of
UBSAN_PRINT_FORCE_INT use TK_Integer (0x) mode with a
TImode/DImode precision rather than TK_Unknown used otherwise for
large/huge BITINT_TYPEs.
(instrument_si_overflow): Instrument BITINT_TYPE operations even when
they don't have mode precision.
* ubsan.h (enum ubsan_print_style): New enumerator.
gcc/c-family/
* c-ubsan.cc (ubsan_instrument_shift): Use UBSAN_PRINT_FORCE_INT
for type0 type descriptor.
--- gcc/ubsan.cc.jj 2023-08-08 15:54:35.443599459 +0200
+++ gcc/ubsan.cc2023-08-08 16:12:02.329939798 +0200
@@ -50,6 +50,8 @@ along with GCC; see the file COPYING3.
#include "gimple-fold.h"
#include "varasm.h"
#include "realmpfr.h"
+#include "target.h"
+#include "langhooks.h"
/* Map from a tree to a VAR_DECL tree. */
@@ -125,6 +127,25 @@ tree
ubsan_encode_value (tree t, enum ubsan_encode_value_phase phase)
{
tree type = TREE_TYPE (t);
+ if (TREE_CODE (type) == BITINT_TYPE)
+{
+ if (TYPE_PRECISION (type) <= POINTER_SIZE)
+ {
+ type = pointer_sized_int_node;
+ t = fold_build1 (NOP_EXPR, type, t);
+ }
+ else
+ {
+ scalar_int_mode arith_mode
+ = (targetm.scalar_mode_supported_p (TImode) ? TImode : DImode);
+ if (TYPE_PRECISION (type) > GET_MODE_PRECISION (arith_mode))
+ return build_zero_cst (pointer_sized_int_node);
+ type
+ = build_nonstandard_integer_type (GET_MODE_PRECISION (arith_mode),
+ TYPE_UNSIGNED (type));
+ t = fold_build1 (NOP_EXPR, type, t);
+ }
+}
scalar_mode mode = SCALAR_TYPE_MODE (type);
const unsigned int bitsize = GET_MODE_BITSIZE (mode);
if (bitsize <= POINTER_SIZE)
@@ -355,14 +376,32 @@ ubsan_type_descriptor (tree type, enum u
{
/* See through any typedefs. */
type = TYPE_MAIN_VARIANT (type);
+ tree type3 = type;
+ if (pstyle == UBSAN_PRINT_FORCE_INT)
+{
+ /* Temporary hack for -fsanitize=shift with _BitInt(129) and more.
+libubsan crashes if it is not TK_Integer type. */
+ if (TREE_CODE (type) == BITINT_TYPE)
+ {
+ scalar_int_mode arith_mode
+ = (targetm.scalar_mode_supported_p (TImode)
+ ? TImode : DImode);
+ if (TYPE_PRECISION (type) > GET_MODE_PRECISION (arith_mode))
+ type3 = build_qualified_type (type, TYPE_QUAL_CONST);
+ }
+ if (type3 == type)
+ pstyle = UBSAN_PRINT_NORMAL;
+}
- tree decl = decl_for_type_lookup (type);
+ tree decl = decl_for_type_lookup (type3);
/* It is possible that some of the earlier created DECLs were found
unused, in that case they weren't emitted and varpool_node::get
returns NULL node on them. But now we really need them. Thus,
renew them here. */
if (decl != NULL_TREE && varpool_node::get (decl))
-return build_fold_addr_expr (decl);
+{
+ return build_fold_addr_expr (decl);
+}
tree dtype = ubsan_get_type_descriptor_type ();
tree type2 = type;
@@ -370,6 +409,7 @@ ubsan_type_descriptor (tree type, enum u
pretty_printer pretty_name;
unsigned char deref_depth = 0;
unsigned short tkind, tinfo;
+ char tname_bitint[sizeof ("unsigned _BitInt(2147483647)")];
/* Get the name of the type, or the name of the pointer type. */
if (pstyle == UBSAN_PRINT_POINTER)
@@ -403,8 +443,18 @@ ubsan_type_descriptor (tree type, enum u
}
if (tname == NULL)
-/* We weren't able to determine the type name. */
-tname = "";
+{
+ if (TREE_CODE (type2) == BITINT_TYPE)
+ {
+ snprintf (tname_bitint, sizeof (tname_bitint),
+ "%s_BitInt(%d)", TYPE_UNSIGNED (type2) ? "unsigned " : "",
+
