Re: CVS commit: src/sys/dev/pci

I'll plan on committing this sometime late next week...

+------------------+--------------------------+------------------------+
| Paul Goyette     | PGP Key fingerprint:     | E-mail addresses:      |
| (Retired)        | FA29 0E3B 35AF E8AE 6651 | paul at whooppee.com   |
| Kernel Developer | 0786 F758 55DE 53BA 7731 | pgoyette at netbsd.org |
+------------------+--------------------------+------------------------+

Index: pci_subr.c
===================================================================
RCS file: /cvsroot/src/sys/dev/pci/pci_subr.c,v
retrieving revision 1.152
diff -u -p -r1.152 pci_subr.c
--- pci_subr.c 20 Oct 2016 04:11:02 -0000 1.152
+++ pci_subr.c 28 Oct 2016 08:58:59 -0000
@@ -54,6 +54,7 @@ __KERNEL_RCSID(0, "$NetBSD: pci_subr.c,v
 #include <sys/module.h>
 #else
 #include <pci.h>
+#include <stdarg.h>
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -567,6 +568,33 @@ static const struct pci_class pci_class[
 
 DEV_VERBOSE_DEFINE(pci);
 
+/*
+ * Append a formatted string into dest without writing more than len
+ * characters (including the trailing NUL character).
+ *
+ * If vsnprintf() returns an error, *dest is unmodified.  Otherwise,
+ * *dest is updated to point to the last available character in the
+ * buffer (which is occupied by the string-terminating NUL).  It is
+ * not possible to differentiate between an output buffer that is
+ * exactly filled to capacity and one that would have overflowed.
+ */
+static void
+snappendf(char **, size_t, const char * restrict, ...) __printflike(3,4);
+
+static void
+snappendf(char **dest, size_t len, const char * restrict fmt, ...)
+{
+ va_list ap;
+ int count;
+
+ va_start(ap, fmt);
+ count = vsnprintf(*dest, len, fmt, ap);
+ va_end(ap);
+ if (count < 0 || len == 0)
+  return;
+ *dest += MIN((size_t)count, len - 1);
+}
+
 void
 pci_devinfo(pcireg_t id_reg, pcireg_t class_reg, int showclass, char *cp,
     size_t l)
@@ -612,32 +640,29 @@ pci_devinfo(pcireg_t id_reg, pcireg_t cl
   interfacep++;
  }
 
- cp += snprintf(cp, ep - cp, "%s %s", vendor, product);
+ snappendf(&cp, ep - cp, "%s %s", vendor, product);
  if (showclass) {
-  cp += snprintf(cp, ep - cp, " (");
+  snappendf(&cp, ep - cp, " (");
   if (classp->name == NULL)
-   cp += snprintf(cp, ep - cp,
-       "class 0x%02x, subclass 0x%02x", pciclass, subclass);
+   snappendf(&cp, ep - cp, "class 0x%02x, subclass 0x%02x",
+       pciclass, subclass);
   else {
    if (subclassp == NULL || subclassp->name == NULL)
-    cp += snprintf(cp, ep - cp,
-        "%s, subclass 0x%02x",
+    snappendf(&cp, ep - cp, "%s, subclass 0x%02x",
         classp->name, subclass);
    else
-    cp += snprintf(cp, ep - cp, "%s %s",
+    snappendf(&cp, ep - cp, "%s %s",
         subclassp->name, classp->name);
   }
   if ((interfacep == NULL) || (interfacep->name == NULL)) {
    if (interface != 0)
-    cp += snprintf(cp, ep - cp,
-        ", interface 0x%02x", interface);
+    snappendf(&cp, ep - cp, ", interface 0x%02x",
+        interface);
   } else if (strncmp(interfacep->name, "", 1) != 0)
-   cp += snprintf(cp, ep - cp, ", %s",
-       interfacep->name);
+   snappendf(&cp, ep - cp, ", %s", interfacep->name);
   if (revision != 0)
-   cp += snprintf(cp, ep - cp, ", revision 0x%02x",
-       revision);
-  cp += snprintf(cp, ep - cp, ")");
+   snappendf(&cp, ep - cp, ", revision 0x%02x", revision);
+  snappendf(&cp, ep - cp, ")");
  }
 }