2 files changed, 8 insertions(+), 2 deletions(-)

M pc/trap.c
M port/alloc.c

@@ 537,6 537,10 @@ syscall(Ureg* ureg)
 	if((ureg->cs & 0xFFFF) != UESEL)
 		panic("syscall: cs 0x%4.4luX\n", ureg->cs);
 
+	/* check syscall has an empty kernel stack */
+	if(up->kstack + KSTACK - (char*)ureg > 512)
+		panic("syscall: stack %ld\n", up->kstack + KSTACK - (char*)ureg);
+
 	m->syscall++;
 	up->insyscall = 1;
 	up->pc = ureg->pc;

@@ 189,12 189,14 @@ malloc(ulong size)
 	void *v;
 
 	v = poolalloc(mainmem, size+Npadlong*sizeof(ulong));
-	if(Npadlong && v != nil) {
+	if(v == nil)
+		return nil;
+	if(Npadlong){
 		v = (ulong*)v+Npadlong;
 		setmalloctag(v, getcallerpc(&size));
 		setrealloctag(v, 0);
-		memset(v, 0, size);
 	}
+	memset(v, 0, size);
 	return v;
 }