[patch] teach libkvm not to assume /dev/mem

[Aggelos Economopoulos]

This patch brings in a couple of trivial changes from freebsd that allow me to 
use kgdb on /dev/fwmem0.0 (unfortunately, when using fwmem kgdb returns 
nonsensical values for some variables, expected values for others and fails 
to access some valid addresses). It also fixes what I think is an obvious 
typo (vmfd -> pmfd).

Please apply,
Aggelos
Index: lib/libkvm/kvm.c
===================================================================
RCS file: /home/aggelos/imports/vcs/dcvs/src/lib/libkvm/kvm.c,v
retrieving revision 1.10
diff -u -r1.10 kvm.c
--- lib/libkvm/kvm.c	29 Apr 2007 01:36:04 -0000	1.10
+++ lib/libkvm/kvm.c	11 Nov 2007 15:55:14 -0000
@@ -167,6 +167,11 @@
 		_kvm_syserr(kd, kd->program, "%s", mf);
 		goto failed;
 	}
+	if (S_ISREG(st.st_mode) && st.st_size <= 0) {
+		errno = EINVAL;
+		_kvm_syserr(kd, kd->program, "empty file");
+		goto failed;
+	}
 	if (fcntl(kd->pmfd, F_SETFD, FD_CLOEXEC) < 0) {
 		_kvm_syserr(kd, kd->program, "%s", mf);
 		goto failed;
@@ -180,10 +185,6 @@
 		 */
 		if (strcmp(mf, _PATH_DEVNULL) == 0) {
 			kd->vmfd = open(_PATH_DEVNULL, O_RDONLY);
-		} else if (strcmp(mf, _PATH_MEM) != 0) {
-			_kvm_err(kd, kd->program,
-				 "%s: not physical memory device", mf);
-			goto failed;
 		} else {
 			if ((kd->vmfd = open(_PATH_KMEM, flag)) < 0) {
 				_kvm_syserr(kd, kd->program, "%s", _PATH_KMEM);
@@ -458,7 +459,7 @@
 					return NULL;
 				}
 			}
-			cc = read(kd->vmfd, &ch, 1);
+			cc = read(kd->pmfd, &ch, 1);
 			if ((ssize_t)cc < 0) {
 				_kvm_syserr(kd, 0, "kvm_readstr");
 				return NULL;