* [PATCH] Fix UB in tree-chkp.c
@ 2017-06-19 17:43 Jakub Jelinek
2017-06-19 18:01 ` Ilya Enkovich
0 siblings, 1 reply; 2+ messages in thread
From: Jakub Jelinek @ 2017-06-19 17:43 UTC (permalink / raw)
To: Richard Biener, Ilya Enkovich, Alexander Ivchenko; +Cc: gcc-patches
Hi!
bootstrap-ubsan shows a couple of:
../../gcc/tree-chkp.c:694:37: runtime error: shift exponent 63 is too large for 32-bit type 'int'
errors.
1 << (TYPE_PRECISION (ptr_type_node) - 1)
should have been obviously
HOST_WIDE_INT_1U << (TYPE_PRECISION (ptr_type_node) - 1)
but even then, it is 1) unnecessarily complicated and expensive way
to create a pointer with just the MSB bit set and all other clear and
2) will not work if ptr_type_node has higher precision than HWI (just
theoretical possibility now)
For 1), e.g. fold_convert (ptr_type_node, integer_zero_node) is
better written as build_int_cst (ptr_type_node, 0), but still
we can actually avoid the fold_build_pointer_plus_hwi and folding
it altogether.
Bootstrapped/regtested on x86_64-linux and i686-linux (both normal
and bootstrap-ubsan), ok for trunk?
2017-07-19 Jakub Jelinek <jakub@redhat.com>
* tree-chkp.c (chkp_get_hard_register_var_fake_base_address):
Rewritten to avoid overflow for > 32-bit pointers.
--- gcc/tree-chkp.c.jj 2017-06-12 12:41:55.000000000 +0200
+++ gcc/tree-chkp.c 2017-06-19 12:57:24.670478544 +0200
@@ -690,9 +690,8 @@ chkp_erase_completed_bounds (void)
static tree
chkp_get_hard_register_var_fake_base_address ()
{
- tree base = fold_convert (ptr_type_node, integer_zero_node);
- unsigned HOST_WIDE_INT offset = 1 << (TYPE_PRECISION (ptr_type_node) - 1);
- return fold_build_pointer_plus_hwi (base, offset);
+ int prec = TYPE_PRECISION (ptr_type_node);
+ return wide_int_to_tree (ptr_type_node, wi::min_value (prec, SIGNED));
}
/* If we check bounds for a hard register variable, we cannot
Jakub
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] Fix UB in tree-chkp.c
2017-06-19 17:43 [PATCH] Fix UB in tree-chkp.c Jakub Jelinek
@ 2017-06-19 18:01 ` Ilya Enkovich
0 siblings, 0 replies; 2+ messages in thread
From: Ilya Enkovich @ 2017-06-19 18:01 UTC (permalink / raw)
To: Jakub Jelinek; +Cc: Richard Biener, Alexander Ivchenko, gcc-patches
2017-06-19 20:43 GMT+03:00 Jakub Jelinek <jakub@redhat.com>:
> Hi!
>
> bootstrap-ubsan shows a couple of:
> ../../gcc/tree-chkp.c:694:37: runtime error: shift exponent 63 is too large for 32-bit type 'int'
> errors.
>
> 1 << (TYPE_PRECISION (ptr_type_node) - 1)
> should have been obviously
> HOST_WIDE_INT_1U << (TYPE_PRECISION (ptr_type_node) - 1)
> but even then, it is 1) unnecessarily complicated and expensive way
> to create a pointer with just the MSB bit set and all other clear and
> 2) will not work if ptr_type_node has higher precision than HWI (just
> theoretical possibility now)
> For 1), e.g. fold_convert (ptr_type_node, integer_zero_node) is
> better written as build_int_cst (ptr_type_node, 0), but still
> we can actually avoid the fold_build_pointer_plus_hwi and folding
> it altogether.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux (both normal
> and bootstrap-ubsan), ok for trunk?
OK. Thanks for the fix!
Ilya
>
> 2017-07-19 Jakub Jelinek <jakub@redhat.com>
>
> * tree-chkp.c (chkp_get_hard_register_var_fake_base_address):
> Rewritten to avoid overflow for > 32-bit pointers.
>
> --- gcc/tree-chkp.c.jj 2017-06-12 12:41:55.000000000 +0200
> +++ gcc/tree-chkp.c 2017-06-19 12:57:24.670478544 +0200
> @@ -690,9 +690,8 @@ chkp_erase_completed_bounds (void)
> static tree
> chkp_get_hard_register_var_fake_base_address ()
> {
> - tree base = fold_convert (ptr_type_node, integer_zero_node);
> - unsigned HOST_WIDE_INT offset = 1 << (TYPE_PRECISION (ptr_type_node) - 1);
> - return fold_build_pointer_plus_hwi (base, offset);
> + int prec = TYPE_PRECISION (ptr_type_node);
> + return wide_int_to_tree (ptr_type_node, wi::min_value (prec, SIGNED));
> }
>
> /* If we check bounds for a hard register variable, we cannot
>
>
> Jakub
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