From d1ff0dba241643c5daf6a755af0d384058b90898 Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Thu, 25 Apr 2002 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 2002-04-25

---
 pc/trap.c    | 4 ++++
 port/alloc.c | 6 ++++--
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/pc/trap.c b/pc/trap.c
index c8d2bccd21f79faf99315ada6f736066f74aab97..a3f103f8c1565b4ff369d94294e5d2ac7adb75b9 100644
--- a/pc/trap.c
+++ b/pc/trap.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;
diff --git a/port/alloc.c b/port/alloc.c
index 36246894d02c053efadcfb729ea8b5facd6f4550..9eadefa17eb314e8adbc02869108c2a45e12b318 100644
--- a/port/alloc.c
+++ b/port/alloc.c
@@ -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;
 }