Re: Regrading the .data.rel.local section size on x86-64.

[Umesh Kalappa <umesh dot kalappa0 at gmail dot com>]

Hi Andreas,

Appreciate your  input here  and thank you very much and please
consider the below case

.file   "test.c"
    .text
.Ltext0:
    .section    .data.i,"aw",@progbits
    .align 4
    .type   i, @object
    .size   i, 4
i:
    .long   10
    .section    .data.rel.local.qslab_reg_names,"aw",@progbits
    .align 32
    .type   qslab_reg_names, @object
    .size   qslab_reg_names, 128
qslab_reg_names:
    .section    .rodata
.LC0:
    .string "FPGALIB_GPIO_ID_QSLAB_LOS"
    .quad   .LC0+16
    .long   736
    .zero   4
.LC1:
    .string "FPGALIB_GPIO_ID_QSLAB_LOL0"
    .quad   .LC1+16
    .long   737
    .zero   4


and then objdump

$objdump -x test.o | more
test.o:     file format elf64-x86-64
test.o
architecture: i386:x86-64, flags 0x00000011:
HAS_RELOC, HAS_SYMS
start address 0x0000000000000000

Sections:
Idx Name          Size      VMA               LMA               File off  Algn
  0 .text         00000000  0000000000000000  0000000000000000  00000040  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
  1 .data         00000000  0000000000000000  0000000000000000  00000040  2**2
                  CONTENTS, ALLOC, LOAD, DATA
  2 .bss          00000000  0000000000000000  0000000000000000  00000040  2**2
                  ALLOC
  3 .data.i       00000004  0000000000000000  0000000000000000  00000040  2**2
                  CONTENTS, ALLOC, LOAD, DATA
  4 .data.rel.local.qslab_reg_names 00000000  0000000000000000
0000000000000000  00000060  2**5
                  CONTENTS, ALLOC, LOAD, DATA
  5 .rodata       0000013e  0000000000000000  0000000000000000  00000060  2**0
                  CONTENTS, ALLOC, LOAD, RELOC, READONLY, DATA
  6 .text.bar     0000000d  0000000000000000  0000000000000000  0000019e  2**0
                  CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE

here the data.i section inherits its size from "i" type. and note that
the .s was generated by compiler(not the hand written).

requirement here is that ,we want the section
".data.rel.local.qslab_reg_names" size  to inherit  from
qslab_reg_names object size like "data.i" section .

Any comments here ?

Thank you
~Umesh

On Mon, Mar 20, 2017 at 8:15 PM, Andreas Schwab <schwab@suse.de> wrote:
> On Mär 20 2017, Umesh Kalappa <umesh.kalappa0@gmail.com> wrote:
>
>> Here is the asm sample like
>>
>> .file   "test.c"
>>     .text
>> .Ltext0:
>>     .section    .data.rel.local.qslab_reg_names,"aw",@progbits
>>     .align 32
>>     .type   qslab_reg_names, @object
>>     .size   qslab_reg_names, 128
>> qslab_reg_names:
>>     .section    .rodata
>> .LC0:
>>     .string "FPGALIB_GPIO_ID_QSLAB_LOS"
>>     .quad   .LC0+16
>>     .long   736
>>     .zero   4
>> .LC1:
>>     .string "FPGALIB_GPIO_ID_QSLAB_LOL0"
>>     .quad   .LC1+16
>>     .long   737
>>     .zero   4
>> .LC2:
>>     .string "FPGALIB_GPIO_ID_QSLAB_LOL1"
>>     .quad   .LC2+16
>>     .long   738
>>     .zero   4
>> .LC3:
>>     .string "FPGALIB_GPIO_ID_QSLAB_LOL2"
>>     .quad   .LC3+16
>>     .long   739
>>
>> the .data.rel.local.qslab_reg_names section size ,is 128 bytes ,where
>> the qslab_reg_names is the only object in the secttion.
>
> The .size directive does not modify the size of the section, it only
> sets the size attribute of the symbol.  Since the section has no
> contents, it remains empty.  If you want to fill it with zeroes, use the
> .zero directive.
>
> Andreas.
>
> --
> Andreas Schwab, SUSE Labs, schwab@suse.de
> GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
> "And now for something completely different."