New site

We moved to a new home.

http://hackingbits.github.io/

See you there.

How to find out the current (in use) XServer DISPLAY number!

Well, just the hack of the day.

$ ps u | awk -v tty=$(cat /sys/class/tty/tty0/active) '$0 ~ tty { print $2  }' | while read pid && [[ "$display" == "" ]]; do  display="$(awk -v RS='\0' -F= '$1=="DISPLAY" { print $2 }' /proc/$pid/environ)"; if [ "$display" != "" ]; then echo "$display"; fi; done 2>/dev/null

:0

Can you improve it? So tell me how. o/

The discussion about the theme on Quora and Linkedin.

__________________________

Edited with improvement:

http://www.commandlinefu.com/commands/view/14259/find-out-the-active-xorg-server-display-number-from-outside

$ for p in $(pgrep -t $(cat /sys/class/tty/tty0/active)); do d=$(awk -v RS='0' -F= '$1=="DISPLAY" { print $2 }' /proc/$p/environ 2>/dev/null); [[ -n $d ]] && break; done; echo $d

A book to study C, or NOT!

As promised I'm back to talk about the Programming in C (4th Edition) book. Well, I'll paste my amazon's review, to be short.

"When I started this reading soon I became absorbed by the formation of the writer's words. Unfortunately that feeling did not persist throughout the work. I still read until functions chapter, but the book is not renewed in style. There's much prolonged talk for bit subjects... For me a boring approach. The author uses many almost useless, in day-to-day, mathematical examples. A beginner will give up of C language or seek another book that is more aimed.

I still prefer the Expert C Programming: Deep C Secrets by Peter van der Linden that invites you to understand language with real facts about C, and The C Programming Language by the creators of the Language that despite being old and summarized, informs the reader about the language accurately."

It's yours choice.

Cheers.

A book to study C

I received my copy of Programming in C (4th Edition) (Developer's Library) from Pearson today.

The book is dense with 548 pages and, at first glance, a great resource for beginners and advanced C coders. I'll let you know more about my reading. Just wait.

Odd ways to zeroing some x86_64 registers

Hi there! Here are some ways (retrocompatible instructions [1-2] and xmm) to fill registers with zero (NULL) bytes without have any zero bytes in bytecode.

400091:    6a 01                    pushq  $0x1
400093:    58                       pop    %rax
400094:    ff c8                    dec    %eax
Zeroing (1) %RAX at 5 bytes cost (very known indeed).


40008b:    97                       xchg   %eax,%edi
40008c:    48 c1 c8 20              ror    $0x20,%rax
400090:    97                       xchg   %eax,%edi
Zeroing (1) %RDI at 6 bytes cost.


40008b:    92                       xchg   %eax,%edx
40008c:    48 99                    cqto
Zeroing (1) %RDX at 3 bytes cost.


40008b:    92                       xchg   %eax,%edx
40008c:    48 99                    cqto
40008e:    52                       push   %rdx
40008f:    58                       pop    %rax
Zeroing (2) %RDX e %RAX at 5 bytes cost.


40008b:    48 31 ff                 xor    %rdi,%rdi
40008e:    48 f7 e7                 mul    %rdi
Zeroing (3) %RAX, %RDX e %RDI at 6 bytes cost (however, widely known).


40008b:    97                       xchg   %eax,%edi
40008c:    48 c1 c8 20              ror    $0x20,%rax
400090:    f7 e7                    mul    %edi
400092:    50                       push   %rax
400093:    5f                       pop    %rdi
Zeroing (3) %RAX, %RDX e %RDI at 9 bytes cost.


400090:    c5 fc 77                 vzeroall
400093:    66 48 0f 7e c2           movq   %xmm0,%rdx
Zeroing (1) general-purpose reg %RDX and (all) YMM at 8 bytes cost.


400090:    66 0f df c0              pandn  %xmm0,%xmm0
400094:    66 48 0f 7e c2           movq   %xmm0,%rdx
Zeroing (1) general-purpose reg %RDX and (1) %XMM0 at 9 bytes cost.


400090:    50                       push   %rax
400091:    5a                       pop    %rdx
400092:    48 f7 d2                 not    %rdx
400095:    48 21 d0                 and    %rdx,%rax
Zeroing (1) %RAX at 8 bytes cost.


400097:    52                       push   %rdx
400098:    58                       pop    %rax
400099:    f7 d0                    not    %eax
40009b:    21 c2                    and    %eax,%edx
Zeroing (1) %RDX at 6 bytes cost.


Use them at will.


[1] - How NOP nearly became a non-NOP on AMD64
[2] - x86oddities

Você Fiscal!!! Eleições...

Temos a oportunidade de sermos fiscais de verdade nas próximas eleições. Para isso, o mínimo que podemos fazer, neste momento, é contribuir com o Projeto Você Fiscal (Diego Aranha) e divulgá-lo o máximo possível.

http://www.catarse.me/pt/VoceFiscal

Eu, no momento, não acredito na discussão política atual; antes, ao meu ver, teríamos que discutir o homem em si, para só depois adentrarmos na sua política. Contudo, a iniciativa do Diego Aranha é fantástica, pois nos permite acompanhar de perto esse processo até então obscuro.

Compartilhem!!!

Uzumaki.el - a simple Emacs buffers cycler

I always complained about the buffer switching procedures in Emacs. So I decided to create my own method to do that, and it rocks (to me ;D ).

Check it: https://github.com/geyslan/uzumaki/

And it's also available through MELPA archive: http://melpa.milkbox.net/#/uzumaki

If you do like it, or don't, feel free to do pull requests on git.