124 lines
3.3 KiB
Text
124 lines
3.3 KiB
Text
The perl scripts in this directory are my 'hack' to generate
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multiple different assembler formats via the one original script.
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The way to use this library is to start with adding the path to this directory
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and then include it.
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push(@INC,"perlasm","../../perlasm");
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require "x86asm.pl";
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The first thing we do is setup the file and type of assember
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&asm_init($ARGV[0],$0);
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The first argument is the 'type'. Currently
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'cpp', 'sol', 'a.out', 'elf' or 'win32'.
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Argument 2 is the file name.
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The reciprocal function is
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&asm_finish() which should be called at the end.
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There are 2 main 'packages'. x86ms.pl, which is the microsoft assembler,
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and x86unix.pl which is the unix (gas) version.
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Functions of interest are:
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&external_label("des_SPtrans"); declare and external variable
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&LB(reg); Low byte for a register
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&HB(reg); High byte for a register
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&BP(off,base,index,scale) Byte pointer addressing
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&DWP(off,base,index,scale) Word pointer addressing
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&stack_push(num) Basically a 'sub esp, num*4' with extra
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&stack_pop(num) inverse of stack_push
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&function_begin(name,extra) Start a function with pushing of
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edi, esi, ebx and ebp. extra is extra win32
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external info that may be required.
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&function_begin_B(name,extra) Same as norma function_begin but no pushing.
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&function_end(name) Call at end of function.
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&function_end_A(name) Standard pop and ret, for use inside functions
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&function_end_B(name) Call at end but with poping or 'ret'.
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&swtmp(num) Address on stack temp word.
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&wparam(num) Parameter number num, that was push
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in C convention. This all works over pushes
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and pops.
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&comment("hello there") Put in a comment.
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&label("loop") Refer to a label, normally a jmp target.
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&set_label("loop") Set a label at this point.
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&data_word(word) Put in a word of data.
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So how does this all hold together? Given
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int calc(int len, int *data)
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{
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int i,j=0;
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for (i=0; i<len; i++)
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{
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j+=other(data[i]);
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}
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}
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So a very simple version of this function could be coded as
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push(@INC,"perlasm","../../perlasm");
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require "x86asm.pl";
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&asm_init($ARGV[0],"cacl.pl");
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&external_label("other");
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$tmp1= "eax";
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$j= "edi";
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$data= "esi";
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$i= "ebp";
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&comment("a simple function");
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&function_begin("calc");
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&mov( $data, &wparam(1)); # data
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&xor( $j, $j);
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&xor( $i, $i);
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&set_label("loop");
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&cmp( $i, &wparam(0));
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&jge( &label("end"));
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&mov( $tmp1, &DWP(0,$data,$i,4));
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&push( $tmp1);
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&call( "other");
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&add( $j, "eax");
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&pop( $tmp1);
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&inc( $i);
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&jmp( &label("loop"));
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&set_label("end");
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&mov( "eax", $j);
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&function_end("calc");
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&asm_finish();
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The above example is very very unoptimised but gives an idea of how
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things work.
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There is also a cbc mode function generator in cbc.pl
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&cbc( $name,
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$encrypt_function_name,
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$decrypt_function_name,
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$true_if_byte_swap_needed,
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$parameter_number_for_iv,
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$parameter_number_for_encrypt_flag,
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$first_parameter_to_pass,
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$second_parameter_to_pass,
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$third_parameter_to_pass);
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So for example, given
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void BF_encrypt(BF_LONG *data,BF_KEY *key);
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void BF_decrypt(BF_LONG *data,BF_KEY *key);
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void BF_cbc_encrypt(unsigned char *in, unsigned char *out, long length,
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BF_KEY *ks, unsigned char *iv, int enc);
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&cbc("BF_cbc_encrypt","BF_encrypt","BF_encrypt",1,4,5,3,-1,-1);
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&cbc("des_ncbc_encrypt","des_encrypt","des_encrypt",0,4,5,3,5,-1);
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&cbc("des_ede3_cbc_encrypt","des_encrypt3","des_decrypt3",0,6,7,3,4,5);
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