switch some tools to use args

tools/bitesize.bt

@@ -20,8 +20,7 @@ BEGIN
 
 tracepoint:block:block_rq_issue
 {
-	$b = *(ctx+28) & 0x3ffff;
-	@[comm] = hist($b);
+	@[comm] = hist(args->bytes);
 }
 
 END

tools/execsnoop.bt

@@ -22,10 +22,9 @@ BEGIN
 
 tracepoint:syscalls:sys_enter_execve
 {
-	$argv = ctx + 24; // workaround until #32
 	$now = nsecs;
 	printf("%-10u %-5d ", ($now - @epoch) / 1000000, pid);
-	join(*$argv);
+	join(args->argv);
 }
 
 END

tools/opensnoop.bt

@@ -22,14 +22,13 @@ BEGIN
 
 tracepoint:syscalls:sys_enter_open
 {
-	$file = *(ctx + 16);
-	@filename[tid] = $file;
+	@filename[tid] = args->filename;
 }
 
 tracepoint:syscalls:sys_exit_open
 /@filename[tid]/
 {
-	$ret = *(ctx + 16);
+	$ret = args->ret;
 	$fd = $ret > 0 ? $ret : -1;
 	$errno = $ret > 0 ? 0 : - $ret;
 

tools/syscount.bt

@@ -20,8 +20,7 @@ BEGIN
 
 tracepoint:raw_syscalls:sys_enter
 {
-	$id = *(ctx + 8); // workaround until #32
-	@syscall[$id] = count();
+	@syscall[args->id] = count();
 	@process[comm] = count();
 }