From: Alan Cox <alan@etchedpixels.co.uk>
Date: Fri, 21 Nov 2014 15:06:11 +0000 (+0000)
Subject: usermem: always trap NULL pointers
X-Git-Url: https://git.ndcode.org/public/gitweb.cgi?a=commitdiff_plain;h=c789eeb412a937a2b40601f122687887c721e840;p=FUZIX.git

usermem: always trap NULL pointers

Low vectors are hard due to the cp/mn emulation
---

diff --git a/Kernel/usermem.c b/Kernel/usermem.c
index fae355d6..78257d2b 100644
--- a/Kernel/usermem.c
+++ b/Kernel/usermem.c
@@ -11,7 +11,9 @@
 /* This checks to see if a user-supplied address is legitimate */
 usize_t valaddr(const char *base, usize_t size)
 {
-	if (base < (const char *)PROGBASE || base + size < base)
+	/* FIXME: for Z80 we should make this a udata field so that cp/m
+	   emulation alone can touch below 0x100 */
+	if (!base || base < (const char *)PROGBASE || base + size < base)
 		size = 0;
 	else if (base + size > (const char *)udata.u_top)
 		size = (char *)udata.u_top - base;