allow misaligned pages

Reference: /n/atom/patch/applied2013/snapmisalign
Date: Wed Jun 19 01:25:52 CES 2013
Signed-off-by: quanstro@quanstro.net

--- /sys/src/cmd/snap/read.c	Wed Jun 19 01:25:47 2013
+++ /sys/src/cmd/snap/read.c	Wed Jun 19 01:25:47 2013
@@ -4,9 +4,13 @@
 #include "snap.h"
 
 void
-panic(char *s)
+panic(char *s, ...)
 {
-	fprint(2, "%s\n", s);
+	va_list va;
+
+	va_start(va, s);
+	vfprint(2, s, va);
+	fprint(2, "\n");
 	abort();
 	exits(s);
 }
@@ -22,6 +26,11 @@
 	return plist;
 }
 
+static char dbuf[Pagesize];
+static Page fu = {
+.data = dbuf,
+};
+
 Page*
 findpage(Proc *plist, long pid, int type, uvlong off)
 {
@@ -52,8 +61,22 @@
 		return nil;
 
 	off -= s->offset;
-	if(off%Pagesize)
-		panic("bad mem offset alignment");
+	if(off%Pagesize){
+		/*panic("bad mem offset alignment %lld, %lld %lld", off, off%Pagesize, s->offset);*/
+		uvlong r, p;
+
+		r = off%Pagesize;
+		p = off/Pagesize;
+		if(p > 0){
+			memmove(fu.data, s->pg[p-1]->data+r, Pagesize-r);
+			if(debug)
+				print("memmove(x, s->pg[%lld], %lld);\n", p-1, Pagesize-r);
+		}
+		memmove(fu.data+Pagesize-r, s->pg[p]->data, r);
+		if(debug)
+			print("memmove(x+%lld, s->pg[%lld], %lld);\n", Pagesize-r, p, r);
+		return &fu;
+	}
 
 	return s->pg[off/Pagesize];
 }