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authorArne Schwabe <arne@rfc2549.org>2012-04-16 19:21:14 +0200
committerArne Schwabe <arne@rfc2549.org>2012-04-16 19:21:14 +0200
commit3e4d8f433239c40311037616b1b8833a06651ae0 (patch)
tree98ab7fce0d011d34677b0beb762d389cb5c39199 /openssl/crypto/perlasm/readme
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+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);
+