>On Sun, Jan 14, 2018 at 01:18:35PM +0200, Karim Eshapa wrote:
>> >> Use pointers to structure as arguments to function instead of coping
>> >> structures and less stack size. Also transfer TNUM(_v, _m) to
>> >> tnum.h file to be used in differnet files for creating anonymous
>> >> structures
>> >> statically.
>> >>
>> >> Signed-off-by: Karim Eshapa <karim.esh...@gmail.com>
>> ...
>> >> +/* Statically tnum constant */
>> >> +#define TNUM(_v, _m) (struct tnum){.value = _v, .mask = _m}
>> >> /* Represent a known constant as a tnum. */
>> >> struct tnum tnum_const(u64 value);
>> >> /* A completely unknown value */
>> >> @@ -26,7 +28,7 @@ struct tnum tnum_lshift(struct tnum a, u8 shift);
>> >> /* Shift a tnum right (by a fixed shift) */
>> >> struct tnum tnum_rshift(struct tnum a, u8 shift);
>> >> /* Add two tnums, return @a + @b */
>> >> -struct tnum tnum_add(struct tnum a, struct tnum b);
>> >> +void tnum_add(struct tnum *res, struct tnum *a, struct tnum *b);
>> ...
>> >> - reg_off = tnum_add(reg->var_off, tnum_const(ip_align + reg->off +
>> >> off));
>> >> + tnum_add(®_off, ®->var_off, &TNUM(ip_align + reg->off + off,
>> >> 0));
>> >> if (!tnum_is_aligned(reg_off, size)) {
>> >> char tn_buf[48];
>> >>
>> >> @@ -1023,8 +1023,7 @@ static int check_generic_ptr_alignment(struct
>> >> bpf_verifier_env *env,
>> >> /* Byte size accesses are always allowed. */
>> >> if (!strict || size == 1)
>> >> return 0;
>> >> -
>> >> - reg_off = tnum_add(reg->var_off, tnum_const(reg->off + off));
>> >> + tnum_add(®_off, ®->var_off, &TNUM(reg->off + off, 0));
>> ...
> >> - dst_reg->var_off = tnum_add(ptr_reg->var_off,
> >> off_reg->var_off);
>> >> + tnum_add(&dst_reg->var_off, &ptr_reg->var_off,
>> >> + &off_reg->var_off);
>>
>> >Is it gnu or intel style of argumnets ? where is src or dest ?
>> >Can the same pointer be used as src and as dst ? etc, etc
>> >I don't think it saves stack either.
>> >I'd rather leave things as-is.
>>
>> It's not specific style but it's recommended when passing structure
>> specially if
>> the structures have large sizes.
> and (dest, src0, src1) respectively.Although tnum structure isn't large but
> it saves
>> stack,we have 2 structure passed before calling and 1 returned to receive
>> the return value.
>1. your patch has compile time warnings
>2. it doesn't reduce stack size.
> For two functions that use tnum_add:
> adjust_ptr_min_max_vals() before and after has exactly the same.
> check_ptr_alignment() after your patch _increased_ stack size.
>3. text of verifier.o shrank 133 bytes while tnum.o increased 198
>Please do your homework next time.
>tnum code will stay as-is.
Thanks so much for your response,if there is any recommended tools
to test how your patch affect memory, performance and what's
going on because all accepted patches I sumbited was so trivial
I'll be so appreciated.
Karim,
