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Diffstat (limited to 'devel/perlasm/readme')
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diff --git a/devel/perlasm/readme b/devel/perlasm/readme new file mode 100644 index 0000000000..f02bbee75a --- /dev/null +++ b/devel/perlasm/readme @@ -0,0 +1,124 @@ +The perl scripts in this directory are my 'hack' to generate +multiple different assembler formats via the one origional script. + +The way to use this library is to start with adding the path to this directory +and then include it. + +push(@INC,"perlasm","../../perlasm"); +require "x86asm.pl"; + +The first thing we do is setup the file and type of assember + +&asm_init($ARGV[0],$0); + +The first argument is the 'type'. Currently +'cpp', 'sol', 'a.out', 'elf' or 'win32'. +Argument 2 is the file name. + +The reciprocal function is +&asm_finish() which should be called at the end. + +There are 2 main 'packages'. x86ms.pl, which is the microsoft assembler, +and x86unix.pl which is the unix (gas) version. + +Functions of interest are: +&external_label("des_SPtrans"); declare and external variable +&LB(reg); Low byte for a register +&HB(reg); High byte for a register +&BP(off,base,index,scale) Byte pointer addressing +&DWP(off,base,index,scale) Word pointer addressing +&stack_push(num) Basically a 'sub esp, num*4' with extra +&stack_pop(num) inverse of stack_push +&function_begin(name,extra) Start a function with pushing of + edi, esi, ebx and ebp. extra is extra win32 + external info that may be required. +&function_begin_B(name,extra) Same as norma function_begin but no pushing. +&function_end(name) Call at end of function. +&function_end_A(name) Standard pop and ret, for use inside functions +&function_end_B(name) Call at end but with poping or 'ret'. +&swtmp(num) Address on stack temp word. +&wparam(num) Parameter number num, that was push + in C convention. This all works over pushes + and pops. +&comment("hello there") Put in a comment. +&label("loop") Refer to a label, normally a jmp target. +&set_label("loop") Set a label at this point. +&data_word(word) Put in a word of data. + +So how does this all hold together? Given + +int calc(int len, int *data) + { + int i,j=0; + + for (i=0; i<len; i++) + { + j+=other(data[i]); + } + } + +So a very simple version of this function could be coded as + + push(@INC,"perlasm","../../perlasm"); + require "x86asm.pl"; + + &asm_init($ARGV[0],"cacl.pl"); + + &external_label("other"); + + $tmp1= "eax"; + $j= "edi"; + $data= "esi"; + $i= "ebp"; + + &comment("a simple function"); + &function_begin("calc"); + &mov( $data, &wparam(1)); # data + &xor( $j, $j); + &xor( $i, $i); + + &set_label("loop"); + &cmp( $i, &wparam(0)); + &jge( &label("end")); + + &mov( $tmp1, &DWP(0,$data,$i,4)); + &push( $tmp1); + &call( "other"); + &add( $j, "eax"); + &pop( $tmp1); + &inc( $i); + &jmp( &label("loop")); + + &set_label("end"); + &mov( "eax", $j); + + &function_end("calc"); + + &asm_finish(); + +The above example is very very unoptimised but gives an idea of how +things work. + +There is also a cbc mode function generator in cbc.pl + +&cbc( $name, + $encrypt_function_name, + $decrypt_function_name, + $true_if_byte_swap_needed, + $parameter_number_for_iv, + $parameter_number_for_encrypt_flag, + $first_parameter_to_pass, + $second_parameter_to_pass, + $third_parameter_to_pass); + +So for example, given +void BF_encrypt(BF_LONG *data,BF_KEY *key); +void BF_decrypt(BF_LONG *data,BF_KEY *key); +void BF_cbc_encrypt(unsigned char *in, unsigned char *out, long length, + BF_KEY *ks, unsigned char *iv, int enc); + +&cbc("BF_cbc_encrypt","BF_encrypt","BF_encrypt",1,4,5,3,-1,-1); + +&cbc("des_ncbc_encrypt","des_encrypt","des_encrypt",0,4,5,3,5,-1); +&cbc("des_ede3_cbc_encrypt","des_encrypt3","des_decrypt3",0,6,7,3,4,5); + |