some documentation and fixing

2 files changed, 49 insertions, 2 deletions

diff --git a/crenshaw/README b/crenshaw/README
index 56b01f6..b2414fc 100644
--- a/crenshaw/README
+++ b/crenshaw/README
@@ -1,4 +1,5 @@
 debugging
+---------
 
 set disassemble-next-line on 
 display $eax
@@ -9,10 +10,20 @@ start
 si
 
 run in emulator (also for unit testing)
+---------------
 
-gcc -Wall -std=c99 -o emul emul.c -lunicorn -pthread
+Non-ELF, linear layout, start address 0x01000000,
+stack starts at 0x01800000 growing downwards.
+No segments or protections for now.
+
+gcc -g -Wall -std=c99 -o emul emul.c -lunicorn -lcapstone -pthread
+fpc main.pas 
+./main < test.prog > test.asm
+nasm -o test.bin -f bin test.asm
+./emul test.bin
 
 links
+-----
 
 https://en.wikibooks.org/wiki/68000_Assembly
 https://en.wikipedia.org/wiki/X86_instruction_listings
@@ -21,3 +32,39 @@ file:///media/sd/compilertests/doc/Intel 80x86 Assembly Language OpCodes.html#di
 https://github.com/Rewzilla/asemu.git
 http://www.unicorn-engine.org/
 http://www.capstone-engine.org/
+
+findings
+--------
+
+tutor2:
+
+the expression and data stacks should be better explained and
+linked to the abstract description of the algorithm.
+
+tutor3, local variables:
+
+local variables can be addresses after the code, letting
+the assembler fill in the dword ptr [X] addresses. The
+compiler merely adds [X] references and X: dw 0 labels and
+data initializers.
+
+https://stackoverflow.com/questions/18447627/what-is-pc-relative-addressing-and-how-can-i-use-it-in-masm
+
+emulate the (PC) relative addressing of the MIPS:
+
+CALL x
+x:
+  ; Now address "x" is on the stack
+  POP EDI
+  ; Now EDI contains address of "x"
+  ; Now we can do (pseudo-)PC-Relative addressing:
+  MOV EAX,[EDI+1234]
+
+but we still have to calculate relative addresses.  
+
+There is no initializer yet, so we can just address the initialized
+variable in the expression for now.
+
+=> there is a tradeoff here, how much do we do in the compiler, how
+   much in the assember, linker
+   
diff --git a/crenshaw/main.pas b/crenshaw/main.pas
index 55189a7..654d547 100644
--- a/crenshaw/main.pas
+++ b/crenshaw/main.pas
@@ -202,7 +202,7 @@ end;
 procedure Variables;
 var i : integer;
 begin
-	for i := 0 to nof_names do begin
+	for i := 0 to nof_names-1 do begin
 		EmitLabel(names[i]);
 		EmitLn('dw 0');
 	end;