b8

commit 25c37ed37df02632f9dfd84aaf3c96ecc17d6888
parent d4bda8e59ffc61c65dcf4b42099d9bc71b7df46b
Author: Léo Villeveygoux <leo.villeveygoux@etu.u-bordeaux.fr>
Date:   Fri, 16 Jun 2017 17:04:52 +0200

more precise binary layout

Diffstat:
M
b8.c
 | 
27
+++++++++++++++++++--------
M
mem.txt
 | 
16
++++++++++++++--
M
test.asm
 | 
11
+++++++----

3 files changed, 40 insertions(+), 14 deletions(-)
diff --git a/b8.c b/b8.c
@@ -5,25 +5,36 @@
 #include <stdlib.h>
 #include <stdio.h>
 
+#define CHECK_STD_ERROR(predicate, name) do{\
+	if(predicate){\
+		perror(name);\
+		exit(1);\
+	}\
+}while(0)
+
 char buf[0x40000] __attribute__ ((section ("mem_chunk"))) = {0};
 
 int main(int argc, char *argv[]){
-	int (*f)(void) = NULL;
+	void (*cart_fun)(void) = NULL;
 
-	if(argc < 2)
+	if(argc < 2) {
+		fprintf(stderr, "Usage: %s file.bin\n", argv[0]);
 		return 1;
+	}
 
 	int fd = open(argv[1], O_RDONLY);
-	if(fd == -1) perror("open");
+	CHECK_STD_ERROR(fd == -1, "open");
         
 	int ret = mprotect(&buf, 4096, PROT_READ|PROT_WRITE|PROT_EXEC);
-	if(ret) perror("mprotect");
+	CHECK_STD_ERROR(ret, "mprotect");
+
+	int rdsize = read(fd, buf, 0x20000);
+	CHECK_STD_ERROR(rdsize == -1, "read");
 
-	int rdsize = read(fd, buf, 27);
-	if(rdsize != 27) perror("read");
+	cart_fun = (void*)buf+0x20;
 
-	f = (void*)buf;
+	cart_fun();
 
-	printf("%d\n",*(int*)f());
+	printf("%d\n",(int)buf[0x20000]);
 	return 0;
 }
diff --git a/mem.txt b/mem.txt
@@ -4,7 +4,19 @@
 
 0x20000 ---------
 
-  cart mapping
+  cart mapping,
+  header:
+
+  0x20000 -------
+  
+    "#!/usr/bin/env b8\n",
+    0, ...
+
+  0x20020 -------
+
+  entry point,  
+
+  cart content
 
 0x40000 ---------
   
@@ -21,6 +33,6 @@
 
 0x51000 ---------
 
-  out PCM
+  out PCM buffer
 
 0x52f40 ---------
diff --git a/test.asm b/test.asm
@@ -1,8 +1,10 @@
 org 0x20000
 bits 32
 
-call f
-ret
+header: db '#!/usr/bin/env b8', 0x0a
+times 32-$+header db 0x0
+
+jmp f
 nop
 nop
 nop
@@ -10,12 +12,13 @@ nop
 nop
 
 f:
-mov eax, lol
+mov eax, [lol]
+mov [0x40000], eax
 ret
 nop
 nop
 
-lol dd 42
+lol db 42
 nop
 nop
 nop