On Thu, Dec 22, 2016 at 12:47 AM, Ilya Enkovich <enkovich....@gmail.com> wrote:
> 2016-12-21 22:18 GMT+03:00 Alexander Ivchenko <aivch...@gmail.com>:
>> Right.. here is this updated chunk (otherwise no difference in the patch)
>>
>> diff --git a/gcc/tree-chkp.c b/gcc/tree-chkp.c
>> index 2769682..6c7862c 100644
>> --- a/gcc/tree-chkp.c
>> +++ b/gcc/tree-chkp.c
>> @@ -3272,6 +3272,9 @@ chkp_may_narrow_to_field (tree field)
>> {
>> return DECL_SIZE (field) && TREE_CODE (DECL_SIZE (field)) == INTEGER_CST
>> && tree_to_uhwi (DECL_SIZE (field)) != 0
>> + && !(flag_chkp_flexible_struct_trailing_arrays
>> + && TREE_CODE(TREE_TYPE(field)) == ARRAY_TYPE
>> + && !DECL_CHAIN (field))
>> && (!DECL_FIELD_OFFSET (field)
>> || TREE_CODE (DECL_FIELD_OFFSET (field)) == INTEGER_CST)
>> && (!DECL_FIELD_BIT_OFFSET (field)
>
> OK.
There is array_at_struct_end_p which has a better implementation for
this (the above
considers a TYPE_DECL after the array a field).
Richard.
>>
>> 2016-12-21 21:00 GMT+03:00 Ilya Enkovich <enkovich....@gmail.com>:
>>> 2016-12-20 17:44 GMT+03:00 Alexander Ivchenko <aivch...@gmail.com>:
>>>> 2016-11-26 0:28 GMT+03:00 Ilya Enkovich <enkovich....@gmail.com>:
>>>>> 2016-11-25 15:47 GMT+03:00 Alexander Ivchenko <aivch...@gmail.com>:
>>>>>> Hi,
>>>>>>
>>>>>> The patch below addresses PR68270. could you please take a look?
>>>>>>
>>>>>> 2016-11-25 Alexander Ivchenko <aivch...@gmail.com>
>>>>>>
>>>>>> * c-family/c.opt (flag_chkp_flexible_struct_trailing_arrays):
>>>>>> Add new option.
>>>>>> * tree-chkp.c (chkp_parse_array_and_component_ref): Forbid
>>>>>> narrowing when chkp_parse_array_and_component_ref is used and
>>>>>> the ARRAY_REF points to an array in the end of the struct.
>>>>>>
>>>>>>
>>>>>>
>>>>>> diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
>>>>>> index 7d8a726..e45d6a2 100644
>>>>>> --- a/gcc/c-family/c.opt
>>>>>> +++ b/gcc/c-family/c.opt
>>>>>> @@ -1166,6 +1166,11 @@ C ObjC C++ ObjC++ LTO RejectNegative Report
>>>>>> Var(flag_chkp_narrow_to_innermost_ar
>>>>>> Forces Pointer Bounds Checker to use bounds of the innermost arrays in
>>>>>> case of
>>>>>> nested static arryas access. By default outermost array is used.
>>>>>>
>>>>>> +fchkp-flexible-struct-trailing-arrays
>>>>>> +C ObjC C++ ObjC++ LTO RejectNegative Report
>>>>>> Var(flag_chkp_flexible_struct_trailing_arrays)
>>>>>> +Allow Pointer Bounds Checker to treat all trailing arrays in structures
>>>>>> as
>>>>>> +possibly flexible.
>>>>>
>>>>> Words 'allow' and 'possibly' are confusing here. This option is about to
>>>>> force
>>>>> checker to do something, not to give him a choice.
>>>>
>>>> Fixed
>>>>
>>>>> New option has to be documented in invoke.texi. It would also be nice to
>>>>> reflect
>>>>> changes on GCC MPX wiki page.
>>>>
>>>> Done
>>>>> We have an attribute to change compiler behavior when this option is not
>>>>> set.
>>>>> But we have no way to make exceptions when this option is used. Should we
>>>>> add one?
>>>> Something like "bnd_fixed_size" ? Could work. Although the customer
>>>> request did not mention the need for that.
>>>> Can I add it in a separate patch?
>>>>
>>>
>>> Yes.
>>>
>>>>
>>>>>> +
>>>>>> fchkp-optimize
>>>>>> C ObjC C++ ObjC++ LTO Report Var(flag_chkp_optimize) Init(-1)
>>>>>> Allow Pointer Bounds Checker optimizations. By default allowed
>>>>>> diff --git a/gcc/tree-chkp.c b/gcc/tree-chkp.c
>>>>>> index 2769682..40f99c3 100644
>>>>>> --- a/gcc/tree-chkp.c
>>>>>> +++ b/gcc/tree-chkp.c
>>>>>> @@ -3425,7 +3425,9 @@ chkp_parse_array_and_component_ref (tree node,
>>>>>> tree *ptr,
>>>>>> if (flag_chkp_narrow_bounds
>>>>>> && !flag_chkp_narrow_to_innermost_arrray
>>>>>> && (!last_comp
>>>>>> - || chkp_may_narrow_to_field (TREE_OPERAND (last_comp, 1))))
>>>>>> + || (chkp_may_narrow_to_field (TREE_OPERAND (last_comp, 1))
>>>>>> + && !(flag_chkp_flexible_struct_trailing_arrays
>>>>>> + && array_at_struct_end_p (var)))))
>>>>>
>>>>> This is incorrect place for fix. Consider code
>>>>>
>>>>> struct S {
>>>>> int a;
>>>>> int b[10];
>>>>> };
>>>>>
>>>>> struct S s;
>>>>> int *p = s.b;
>>>>>
>>>>> Here you need to compute bounds for p and you want your option to take
>>>>> effect
>>>>> but in this case you won't event reach your new check because there is no
>>>>> ARRAY_REF. And even if we change it to
>>>>>
>>>>> int *p = s.b[5];
>>>>>
>>>>> then it still would be narrowed because s.b would still be written
>>>>> into 'comp_to_narrow'
>>>>> variable. Correct place for fix is in chkp_may_narrow_to_field.
>>>>
>>>> Done
>>>>
>>>>> Also you should consider fchkp-narrow-to-innermost-arrray option. Should
>>>>> it
>>>>> be more powerfull or not? I think fchkp-narrow-to-innermost-arrray
>>>>> shouldn't
>>>>> narrow to variable sized fields. BTW looks like right now
>>>>> bnd_variable_size
>>>>> attribute is ignored by fchkp-narrow-to-innermost-arrray. This is another
>>>>> problem and may be fixed in another patch though.
>>>> The way code works in chkp_parse_array_and_component_ref seems to be
>>>> exactly like you say: fchkp-narrow-to-innermost-arrray won't narrow
>>>> to variable sized fields. I will create a separate bug for
>>>> bnd_variable_size+ fchkp-narrow-to-innermost-arrray.
>>>>
>>>>> Also patch lacks tests for various situations (with option and without,
>>>>> with
>>>>> ARRAY_REF and without). In case of new attribute and fix for
>>>>> fchkp-narrow-to-innermost-arrray behavior additional tests are required.
>>>> I added three tests for flag_chkp_flexible_struct_trailing_arrays
>>>>
>>>>
>>>>
>>>> The patch is below:
>>>>
>>>> diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
>>>> index 2d47d54..21ad6aa 100644
>>>> --- a/gcc/c-family/c.opt
>>>> +++ b/gcc/c-family/c.opt
>>>> @@ -1188,7 +1188,13 @@ narrowing is on, field bounds are used.
>>>> Otherwise full object bounds are used.
>>>> fchkp-narrow-to-innermost-array
>>>> C ObjC C++ ObjC++ LTO RejectNegative Report
>>>> Var(flag_chkp_narrow_to_innermost_arrray)
>>>> Forces Pointer Bounds Checker to use bounds of the innermost arrays in
>>>> case of
>>>> -nested static arryas access. By default outermost array is used.
>>>> +nested static arrays access. By default outermost array is used.
>>>> +
>>>> +fchkp-flexible-struct-trailing-arrays
>>>> +C ObjC C++ ObjC++ LTO RejectNegative Report
>
> I also noticed this part conflicts with documentation which describes
> both positive and negative flag versions. I think we should allow
> negative version.
>
> Patch is OK with that change and proper testing.
>
> Thanks,
> Ilya
>
>>>> Var(flag_chkp_flexible_struct_trailing_arrays)
>>>> +Forces Pointer Bounds Checker to treat all trailing arrays in structures
>>>> as
>>>> +possibly flexible. By default only arrays fields with zero length or
>>>> that are
>>>> +marked with attribute bnd_variable_size are treated as flexible.
>>>>
>>>> fchkp-optimize
>>>> C ObjC C++ ObjC++ LTO Report Var(flag_chkp_optimize) Init(-1)
>>>> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
>>>> index 034ae98..2372c22a 100644
>>>> --- a/gcc/doc/invoke.texi
>>>> +++ b/gcc/doc/invoke.texi
>>>> @@ -10886,6 +10886,13 @@ Forces Pointer Bounds Checker to use narrowed
>>>> bounds for the address of the
>>>> first field in the structure. By default a pointer to the first field has
>>>> the same bounds as a pointer to the whole structure.
>>>>
>>>> +@item -fchkp-flexible-struct-trailing-arrays
>>>> +@opindex fchkp-flexible-struct-trailing-arrays
>>>> +@opindex fno-chkp-flexible-struct-trailing-arrays
>>>> +Forces Pointer Bounds Checker to treat all trailing arrays in structures
>>>> as
>>>> +possibly flexible. By default only arrays fields with zero length or
>>>> that are
>>>> +marked with attribute bnd_variable_size are treated as flexible.
>>>> +
>>>> @item -fchkp-narrow-to-innermost-array
>>>> @opindex fchkp-narrow-to-innermost-array
>>>> @opindex fno-chkp-narrow-to-innermost-array
>>>> diff --git a/gcc/testsuite/gcc.target/i386/mpx/vla-trailing-1-lbv.c
>>>> b/gcc/testsuite/gcc.target/i386/mpx/vla-trailing-1-lbv.c
>>>> new file mode 100644
>>>> index 0000000..9739920
>>>> --- /dev/null
>>>> +++ b/gcc/testsuite/gcc.target/i386/mpx/vla-trailing-1-lbv.c
>>>> @@ -0,0 +1,29 @@
>>>> +/* { dg-do run } */
>>>> +/* { dg-shouldfail "bounds violation" } */
>>>> +/* { dg-options "-fcheck-pointer-bounds -mmpx
>>>> -fchkp-flexible-struct-trailing-arrays" } */
>>>> +
>>>> +
>>>> +#define SHOULDFAIL
>>>> +
>>>> +#include "mpx-check.h"
>>>> +
>>>> +struct S
>>>> +{
>>>> + int a;
>>>> + int p[10];
>>>> +};
>>>> +
>>>> +int rd (int *p, int i)
>>>> +{
>>>> + int res = p[i];
>>>> + printf ("%d\n", res);
>>>> + return res;
>>>> +}
>>>> +
>>>> +int mpx_test (int argc, const char **argv)
>>>> +{
>>>> + struct S *s = (struct S *)alloca (sizeof(struct S) + sizeof (int)*100);
>>>> + rd (s->p, -2);
>>>> +
>>>> + return 0;
>>>> +}
>>>> diff --git a/gcc/testsuite/gcc.target/i386/mpx/vla-trailing-1-nov.c
>>>> b/gcc/testsuite/gcc.target/i386/mpx/vla-trailing-1-nov.c
>>>> new file mode 100644
>>>> index 0000000..f5c8f95
>>>> --- /dev/null
>>>> +++ b/gcc/testsuite/gcc.target/i386/mpx/vla-trailing-1-nov.c
>>>> @@ -0,0 +1,29 @@
>>>> +/* { dg-do run } */
>>>> +/* { dg-options "-fcheck-pointer-bounds -mmpx
>>>> -fchkp-flexible-struct-trailing-arrays" } */
>>>> +
>>>> +
>>>> +#include "mpx-check.h"
>>>> +
>>>> +struct S
>>>> +{
>>>> + int a;
>>>> + int p[10];
>>>> +};
>>>> +
>>>> +int rd (int *p, int i)
>>>> +{
>>>> + int res = p[i];
>>>> + printf ("%d\n", res);
>>>> + return res;
>>>> +}
>>>> +
>>>> +int mpx_test (int argc, const char **argv)
>>>> +{
>>>> + struct S *s = (struct S *)alloca (sizeof(struct S) + sizeof (int)*100);
>>>> + rd (s->p, 0);
>>>> + rd (s->p, 99);
>>>> + s->p[0];
>>>> + s->p[99];
>>>> +
>>>> + return 0;
>>>> +}
>>>> diff --git a/gcc/testsuite/gcc.target/i386/mpx/vla-trailing-1-ubv.c
>>>> b/gcc/testsuite/gcc.target/i386/mpx/vla-trailing-1-ubv.c
>>>> new file mode 100644
>>>> index 0000000..8385a5a
>>>> --- /dev/null
>>>> +++ b/gcc/testsuite/gcc.target/i386/mpx/vla-trailing-1-ubv.c
>>>> @@ -0,0 +1,29 @@
>>>> +/* { dg-do run } */
>>>> +/* { dg-shouldfail "bounds violation" } */
>>>> +/* { dg-options "-fcheck-pointer-bounds -mmpx
>>>> -fchkp-flexible-struct-trailing-arrays" } */
>>>> +
>>>> +
>>>> +#define SHOULDFAIL
>>>> +
>>>> +#include "mpx-check.h"
>>>> +
>>>> +struct S
>>>> +{
>>>> + int a;
>>>> + int p[10];
>>>> +};
>>>> +
>>>> +int rd (int *p, int i)
>>>> +{
>>>> + int res = p[i];
>>>> + printf ("%d\n", res);
>>>> + return res;
>>>> +}
>>>> +
>>>> +int mpx_test (int argc, const char **argv)
>>>> +{
>>>> + struct S *s = (struct S *)alloca (sizeof(struct S) + sizeof (int)*100);
>>>> + rd (s->p, 110);
>>>> +
>>>> + return 0;
>>>> +}
>>>> diff --git a/gcc/tree-chkp.c b/gcc/tree-chkp.c
>>>> index 2769682..6c5e541 100644
>>>> --- a/gcc/tree-chkp.c
>>>> +++ b/gcc/tree-chkp.c
>>>> @@ -3272,6 +3272,8 @@ chkp_may_narrow_to_field (tree field)
>>>> {
>>>> return DECL_SIZE (field) && TREE_CODE (DECL_SIZE (field)) == INTEGER_CST
>>>> && tree_to_uhwi (DECL_SIZE (field)) != 0
>>>> + && (!flag_chkp_flexible_struct_trailing_arrays
>>>> + || DECL_CHAIN (field))
>>>
>>> What if it's not array?
>>>
>>> Thanks,
>>> Ilya
>>>
>>>> && (!DECL_FIELD_OFFSET (field)
>>>> || TREE_CODE (DECL_FIELD_OFFSET (field)) == INTEGER_CST)
>>>> && (!DECL_FIELD_BIT_OFFSET (field)
