[oss] [Lab 02][Task 5] mark .data as executable

[Alex Teaca]

Hi Lucian,

Yes, the 'section .data exec' in the .asm file works for me too.
But this solution assumes that you are compiling with the nasm an .asm
file, right ?

The idea was to be able to do this thing by starting from a C source. And
converting
from .s file obtained with the gcc compiler into an .asm file is not very
natural and easy.
I think the syntax for the gcc compiler applied to the .s file
should be: `.section .data,"x", at progbits`, but the compiler does not like
it and will warn:

main.s: Assembler messages:
main.s:2: Warning: ignoring changed section attributes for .data

I mean, if you want the stack executable and add in the .s file '.section
.note.GNU-stack,"x", at progbits'
works, but for .data section does not.

Thanks, Alex


On Sun, Oct 26, 2014 at 11:08 AM, Lucian Mogosanu <lucian.mogosanu at cs.pub.ro
> wrote:

> On Sat, Oct 25, 2014 at 05:06:17PM +0300, Alex Teaca wrote:
> > Also, I tried to compile with -S flag, and update the task5.s with
> > ".section .data,"awx", at progbits"
> > but, when I compile, I get
> >
> > gcc -C task5.s
> > test5.s: Assembler messages:
> > test5.s:5: Warning: ignoring changed section attributes for .data
> >
> > and the .data section remains WA.
>
> I managed to make .data executable with NASM, with a little help from the
> documentation [1]: I added the `exec` directive to .data on hello.asm, and
> now
> readelf -S gives me the following output:
>
> ---
> There are 15 section headers, starting at offset 0x2d4:
>
> Section Headers:
> [...]
>   [ 9] .text             PROGBITS        08048190 000190 00000a 00  AX  0
>  0 16
>   [10] .eh_frame         PROGBITS        0804819c 00019c 000000 00   A  0
>  0  4
>   [11] .dynamic          DYNAMIC         0804919c 00019c 0000a0 08  WA  4
>  0  4
>   [12] .got.plt          PROGBITS        0804923c 00023c 000010 04  WA  0
>  0  4
>   [13] .data             PROGBITS        0804924c 00024c 00000e 00 WAX  0
>  0  4
> [...]
> ---
>
> Does that work for you?
>
> [1]: http://www.nasm.us/doc/nasmdoc7.html#section-7.9.2
>
> Lucian
> _______________________________________________
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