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Getting Started with x86 » History » Version 79

Version 78 (Alexander Kamkin, 04/06/2017 08:33 PM) → Version 79/87 (Alexander Kamkin, 04/06/2017 08:38 PM)

h1. Getting Started with x86

{{toc}}

h2. Prerequisite

MicroTESK should be [[Installation Guide|installed]].

h2. Demo Specifications

Specifications of the x86 (8086) instruction set architecture (ISA) can be found in "$MICROTESK_HOME/arch/demo/x86/model/x86.nml":http://forge.ispras.ru/projects/microtesk/repository/entry/trunk/microtesk/src/main/arch/demo/x86/model/x86.nml.

Instruction are described in [[nML Language Reference|nML]] by means of the following constructs (_move r16/r16_ is taken as an example):

## the signature
<pre><code class="c">op mov_r16r16 (dst: R16, src: R16)</code></pre>
## the assembly format
<pre><code class="c">syntax = format("mov %s, %s", dst.syntax, src.syntax)</code></pre>
## the binary encoding
<pre><code class="c">image = format("1000101111%s%s", dst.image, src.image)</code></pre>
## the semantics
<pre><code class="c">
action = {
dst = src;
...
}
</code></pre>

To compile the ISA model, run the following command:
<pre>sh $MICROTESK_HOME/bin/compile.sh x86.nml</pre>

h2. Demo Templates

Test templates for the x86 (8086) ISA can be found in "$MICROTESK_HOME/arch/demo/x86/templates":http://forge.ispras.ru/projects/microtesk/repository/entry/trunk/microtesk/src/main/arch/demo/x86/templates.

The directory contains a number of demo templates including the following ones:

{background:#f6fcff}. | "block.rb":http://forge.ispras.ru/projects/microtesk/repository/entry/trunk/microtesk/src/main/arch/demo/x86/templates/block.rb | demonstrates how to use block constructs |
| "block_random.rb":http://forge.ispras.ru/projects/microtesk/repository/entry/trunk/microtesk/src/main/arch/demo/x86/templates/block_random.rb | demonstrates how to create randomized instruction sequences using block constructs |
{background:#f6fcff}. | "euclid.rb":http://forge.ispras.ru/projects/microtesk/repository/entry/trunk/microtesk/src/main/arch/demo/x86/templates/euclid.rb | demonstrates test program simulation to predict the resulting microprocessor state |
| "random.rb":http://forge.ispras.ru/projects/microtesk/repository/entry/trunk/microtesk/src/main/arch/demo/x86/templates/random.rb | demonstrates how to randomize tests by using biases and distributions |
{background:#f6fcff}. | "random_immediate.rb":http://forge.ispras.ru/projects/microtesk/repository/entry/trunk/microtesk/src/main/arch/demo/x86/templates/random_immediate.rb | demonstrates how to randomize immediate values |
| "random_registers.rb":http://forge.ispras.ru/projects/microtesk/repository/entry/trunk/microtesk/src/main/arch/demo/x86/templates/random_registers.rb | demonstrates how to randomize registers (dependencies) |

Test templates are written in "Ruby":http://www.ruby-lang.org extended with specific [[Template_Description_Language|constructs]] (let us look at "block.rb":http://forge.ispras.ru/projects/microtesk/repository/entry/trunk/microtesk/src/main/arch/demo/x86/templates/block.rb):

# the code in the beginning includes the "x86_base.rb":http://forge.ispras.ru/projects/microtesk/repository/entry/trunk/microtesk/src/main/arch/demo/x86/templates/x86_base.rb file where a base template @X86BaseTemplate@ is defined and declares a @BlockTemplate@ template:
<pre><code class="ruby">
require_relative ''x86_base''

class BlockTemplate < X86BaseTemplate # BlockTemplate is a heir of @X86BaseTemplate@
</code></pre>
# here is a template entry point:
<pre><code class="ruby"> def run</code></pre>
# this block produces a sequence consisting of three instructions:
<pre><code class="ruby">
sequence { # sequence: {mov, sub, add}
mov_r16r16 ax, bx
sub_r16r16 cx, dx # registers: fixed
add_r16r16 r16(_), r16(_) # registers: randomized
}.run
</code></pre>
# this block produces an atomic sequence consisting of three instructions (atomic sequences are not interrupted while being merged with other ones):
<pre><code class="ruby">
atomic { # atomic sequence: {mov, add, sub}
mov_r16r16 ax, bx
add_r16r16 cx, dx
sub_r16r16 r16(_), r16(_)
}.run
</code></pre>
# this block produces three sequences each consisting of one instruction:
<pre><code class="ruby">
iterate { # sequences: {{mov}, {sub}, {add}}
mov_r16r16 ax, bx
sub_r16r16 cx, dx
add_r16r16 r16(_), r16(_)
}.run
</code></pre>
# this block produces four sequences each consisting of two instructions
~the combinator constructs the Cartesian product of the nested sets of sequences; the compositor randomly merges each tuple of the product into one sequence:~
<pre><code class="ruby">
block(:combinator => ''product'', # combinator: {({sub}, {mov}), ({sub}, {sub}), ({add}, {mov}), ({add}, {sub})}
:compositor => ''random'') { # compositor: { {mov, sub}, {sub, sub}, {add, mov}, {add, sub} }

iterate { # sequences: {{sub}, {add}}
sub_r16r16 cx, dx
add_r16r16 ax, bx
}


iterate { # sequences: {{mov}, {sub}}
mov_r16r16 ax, bx
sub_r16r16 r16(_), r16(_)
}
}.run
</code></pre>
# this block merges two sequences in a random fashion
~the combinator constructs the diagonal of the Cartesian product; the compositor randomly merges the tuples into sequences; the obfuscator reorders the sequences:~
<pre><code class="ruby">
block(:combinator => ''diagonal'', # combinator: {({sub, or}, {start, and, end})}
:compositor => ''random'', # compositor: { {sub, start, and, end, or} }
:obfuscator => ''random'') { # obfuscator: { {or, start, and, end, sub} }

sequence { # sequence: {sub, or}
sub_r16r16 bx, ax
or_r16r16 cx, dx
}

atomic { # atomic sequence: {start, add, end}
prologue { comment ''Atomic starts'' }
epilogue { comment ''Atomic ends'' }

and_r16r16 r16(_), r16(_)
}
}.run
</code></pre>

To generate a test program program(s) from a test template (in our case, from @block.rb@), run the following command:
<pre>sh $MICROTESK_HOME/bin/generate.sh x86 block.rb --code-file-prefix block --code-file-extension s -v</pre>

When generation is finished, the resulting "assembly code":http://forge.ispras.ru/attachments/download/5127/block_0000.s assembly code can be found in @$MICROTESK_HOME@.

To compile the test program, "the output file":http://forge.ispras.ru/attachments/download/5127/block_0000.s, run the following commands:
<pre>
nasm -f elf block_0000.s
ld -m i386pe -s -o block_0000 block_0000.o
</pre>

To execute resulted test cases is possible by means of the "online simulator":https://www.tutorialspoint.com/compile_assembly_online.php
!Example_block.png!