update more tools to use args

tools/killsnoop.bt

@@ -23,19 +23,16 @@ BEGIN
 
 tracepoint:syscalls:sys_enter_kill
 {
-	$pid = *(ctx + 16);
-	$sig = *(ctx + 24);
-	@tpid[tid] = $pid;
-	@tsig[tid] = $sig;
+	@tpid[tid] = args->pid;
+	@tsig[tid] = args->sig;
 }
 
 tracepoint:syscalls:sys_exit_kill
 /@tpid[tid]/
 {
-	$ret = *(ctx + 16);
 	time("%H:%M:%S  ");
 	printf("%-6d %-16s %-4d %-6d %d\n", pid, comm, @tsig[tid], @tpid[tid],
-	    $ret);
+	    args->ret);
 	delete(@tpid[tid]);
 	delete(@tsig[tid]);
 }

tools/statsnoop.bt

@@ -26,26 +26,22 @@ BEGIN
 
 tracepoint:syscalls:sys_enter_statfs
 {
-	$path = *(ctx + 16);
-	@filename[tid] = $path;
+	@filename[tid] = args->pathname;
 }
 
 tracepoint:syscalls:sys_enter_statx
 {
-	$file = *(ctx + 24);
-	@filename[tid] = $file;
+	@filename[tid] = args->filename;
 }
 
 tracepoint:syscalls:sys_enter_newstat
 {
-	$file = *(ctx + 16);
-	@filename[tid] = $file;
+	@filename[tid] = args->filename;
 }
 
 tracepoint:syscalls:sys_enter_newlstat
 {
-	$file = *(ctx + 16);
-	@filename[tid] = $file;
+	@filename[tid] = args->filename;
 }
 
 tracepoint:syscalls:sys_exit_statfs,

tools/writeback.bt

@@ -37,22 +37,20 @@ BEGIN
 
 tracepoint:writeback:writeback_start
 {
-	$sb_dev = *(ctx + 48) & 0xffffffff;
-	@start[$sb_dev] = nsecs;
+	@start[args->sb_dev] = nsecs;
 }
 
 tracepoint:writeback:writeback_written
 {
-	$name = str(ctx + 8);
-	$nr_pages = *(ctx + 40) & 0xffff;
-	$sb_dev = *(ctx + 48) & 0xffffffff;
-	$r = *(ctx + 68) & 0xffffffff;
+	$sb_dev = args->sb_dev;
 	$s = @start[$sb_dev];
 	delete(@start[$sb_dev]);
 	$lat = $s ? (nsecs - $s) / 1000 : 0;
 
 	time("%H:%M:%S  ");
-	printf("%-8s %-8d %-16s %d.%03d\n", $name, $nr_pages, @reason[$r],
+	printf("%-8s %-8d %-16s %d.%03d\n", args->name,
+	    args->nr_pages & 0xffff,	// TODO: explain these bitmasks
+	    @reason[args->reason & 0xffffffff],
 	    $lat / 1000, $lat % 1000);
 }