| 1 | Perl scripts for assembler sources
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| 2 | ==================================
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| 3 |
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| 4 | The perl scripts in this directory are my 'hack' to generate
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| 5 | multiple different assembler formats via the one original script.
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| 6 |
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| 7 | The way to use this library is to start with adding the path to this directory
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| 8 | and then include it.
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| 9 |
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| 10 | push(@INC,"perlasm","../../perlasm");
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| 11 | require "x86asm.pl";
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| 12 |
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| 13 | The first thing we do is setup the file and type of assembler
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| 14 |
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| 15 | &asm_init($ARGV[0]);
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| 16 |
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| 17 | The first argument is the 'type'. Currently
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| 18 | `cpp`, `sol`, `a.out`, `elf` or `win32`.
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| 19 | The second argument is the file name.
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| 20 |
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| 21 | The reciprocal function is
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| 22 | `&asm_finish()` which should be called at the end.
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| 23 |
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| 24 | There are two main 'packages'. `x86ms.pl`, which is the Microsoft assembler,
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| 25 | and `x86unix.pl` which is the unix (gas) version.
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| 26 |
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| 27 | Functions of interest are:
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| 28 |
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| 29 | &external_label("des_SPtrans"); declare and external variable
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| 30 | &LB(reg); Low byte for a register
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| 31 | &HB(reg); High byte for a register
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| 32 | &BP(off,base,index,scale) Byte pointer addressing
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| 33 | &DWP(off,base,index,scale) Word pointer addressing
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| 34 | &stack_push(num) Basically a 'sub esp, num*4' with extra
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| 35 | &stack_pop(num) inverse of stack_push
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| 36 | &function_begin(name,extra) Start a function with pushing of
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| 37 | edi, esi, ebx and ebp. extra is extra win32
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| 38 | external info that may be required.
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| 39 | &function_begin_B(name,extra) Same as normal function_begin but no
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| 40 | pushing.
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| 41 | &function_end(name) Call at end of function.
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| 42 | &function_end_A(name) Standard pop and ret, for use inside
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| 43 | functions.
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| 44 | &function_end_B(name) Call at end but with pop or ret.
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| 45 | &swtmp(num) Address on stack temp word.
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| 46 | &wparam(num) Parameter number num, that was push in
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| 47 | C convention. This all works over pushes
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| 48 | and pops.
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| 49 | &comment("hello there") Put in a comment.
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| 50 | &label("loop") Refer to a label, normally a jmp target.
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| 51 | &set_label("loop") Set a label at this point.
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| 52 | &data_word(word) Put in a word of data.
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| 53 |
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| 54 | So how does this all hold together? Given
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| 55 |
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| 56 | int calc(int len, int *data)
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| 57 | {
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| 58 | int i,j=0;
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| 59 |
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| 60 | for (i=0; i<len; i++)
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| 61 | {
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| 62 | j+=other(data[i]);
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| 63 | }
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| 64 | }
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| 65 |
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| 66 | So a very simple version of this function could be coded as
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| 67 |
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| 68 | push(@INC,"perlasm","../../perlasm");
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| 69 | require "x86asm.pl";
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| 70 |
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| 71 | &asm_init($ARGV[0]);
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| 72 |
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| 73 | &external_label("other");
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| 74 |
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| 75 | $tmp1= "eax";
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| 76 | $j= "edi";
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| 77 | $data= "esi";
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| 78 | $i= "ebp";
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| 79 |
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| 80 | &comment("a simple function");
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| 81 | &function_begin("calc");
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| 82 | &mov( $data, &wparam(1)); # data
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| 83 | &xor( $j, $j);
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| 84 | &xor( $i, $i);
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| 85 |
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| 86 | &set_label("loop");
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| 87 | &cmp( $i, &wparam(0));
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| 88 | &jge( &label("end"));
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| 89 |
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| 90 | &mov( $tmp1, &DWP(0,$data,$i,4));
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| 91 | &push( $tmp1);
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| 92 | &call( "other");
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| 93 | &add( $j, "eax");
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| 94 | &pop( $tmp1);
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| 95 | &inc( $i);
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| 96 | &jmp( &label("loop"));
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| 97 |
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| 98 | &set_label("end");
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| 99 | &mov( "eax", $j);
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| 100 |
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| 101 | &function_end("calc");
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| 102 |
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| 103 | &asm_finish();
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| 104 |
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| 105 | The above example is very very unoptimised but gives an idea of how
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| 106 | things work.
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| 107 |
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| 108 | There is also a cbc mode function generator in cbc.pl
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| 109 |
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| 110 | &cbc($name,
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| 111 | $encrypt_function_name,
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| 112 | $decrypt_function_name,
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| 113 | $true_if_byte_swap_needed,
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| 114 | $parameter_number_for_iv,
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| 115 | $parameter_number_for_encrypt_flag,
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| 116 | $first_parameter_to_pass,
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| 117 | $second_parameter_to_pass,
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| 118 | $third_parameter_to_pass);
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| 119 |
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| 120 | So for example, given
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| 121 |
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| 122 | void BF_encrypt(BF_LONG *data,BF_KEY *key);
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| 123 | void BF_decrypt(BF_LONG *data,BF_KEY *key);
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| 124 | void BF_cbc_encrypt(unsigned char *in, unsigned char *out, long length,
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| 125 | BF_KEY *ks, unsigned char *iv, int enc);
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| 126 |
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| 127 | &cbc("BF_cbc_encrypt","BF_encrypt","BF_encrypt",1,4,5,3,-1,-1);
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| 128 |
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| 129 | &cbc("des_ncbc_encrypt","des_encrypt","des_encrypt",0,4,5,3,5,-1);
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| 130 | &cbc("des_ede3_cbc_encrypt","des_encrypt3","des_decrypt3",0,6,7,3,4,5);
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