Set up local fix for es segment register.

user/sysstat.c

@@ -8,22 +8,29 @@ See the file LICENSE for details.
 #include "library/string.h"
 #include "library/stdio.h"
 
-struct system_stats s = {0};
 
 int main(int argc, char *argv[])
 {
-	printf("a");
-	flush();
+	/*
+	This demonstrates (and fixes) a kernel bug.
+	GCC implements the initialization of the structure on the stack like this:
+            rep stos %eax,%es:(%edi)
+        However, basekernel does not automatically set up (or save) the es segment register,
+	and so the operation crashes.  The es register should be set up correctly in kernelcore,
+	saved and restored when processing interrupts/system calls, and also initialized correctly
+	using process_kstack_init.
+	*/
+
+	/* The workaround here is to explicitly set up the es register prior to using it.*/
 
-	printf("b");
-	flush();
+	asm("movl %ds, %ax");
+	asm("movl %ax, %es");
+
+	struct system_stats s = {0};
 
 	if (syscall_system_stats(&s)) {
 		return 1;
 	}
-	printf("c");
-	flush();
-
 
 	printf("System uptime: %u:%u:%u\n", s.time / (3600), (s.time % 3600) / 60, s.time % 60);
 	printf("Disk 0: %d blocks read, %d blocks written\n", s.blocks_read[0], s.blocks_written[0]);