Don't return stale data from fbsd_pid_to_exec_file for kernel processes.

For processes without an associated executable (such as kernel processes),
the kern.proc.pathname.<pid> system control node returns a length of zero
without modifying the user's buffer.  Detect this case and return NULL
rather than the previous contents of the static buffer 'buf'.

gdb/ChangeLog:

	* fbsd-nat.c (fbsd_pid_to_exec_file) [KERN_PROC_PATHNAME]: Return
	NULL for an empty pathname.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index e7f3cc2..3752a3b 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,10 @@
 2018-01-09  John Baldwin  <jhb@FreeBSD.org>
 
+       * fbsd-nat.c (fbsd_pid_to_exec_file) [KERN_PROC_PATHNAME]: Return
+       NULL for an empty pathname.
+
+2018-01-09  John Baldwin  <jhb@FreeBSD.org>
+
        * fbsd-tdep.c (KVE_STRUCTSIZE, KVE_START, KVE_END, KVE_OFFSET)
        (KVE_FLAGS, KVE_PROTECTION, KVE_PATH, KINFO_VME_PROT_READ)
        (KINFO_VME_PROT_WRITE, KINFO_VME_PROT_EXEC, KINFO_VME_FLAG_COW)

diff --git a/gdb/fbsd-nat.c b/gdb/fbsd-nat.c
index ec4eed9..d0aaf89 100644 (file)
--- a/gdb/fbsd-nat.c
+++ b/gdb/fbsd-nat.c
@@ -63,7 +63,10 @@ fbsd_pid_to_exec_file (struct target_ops *self, int pid)
   mib[3] = pid;
   buflen = sizeof buf;
   if (sysctl (mib, 4, buf, &buflen, NULL, 0) == 0)
-    return buf;
+    /* The kern.proc.pathname.<pid> sysctl returns a length of zero
+       for processes without an associated executable such as kernel
+       processes.  */
+    return buflen == 0 ? NULL : buf;
 #endif
 
   xsnprintf (name, PATH_MAX, "/proc/%d/exe", pid);