Use kinfo_getfile to implement fdwalk on FreeBSD.

kinfo_getfile() requires a couple of system calls to fetch the list of
open file descriptors.  This can be much cheaper than invoking fstat
on all of the values from 0 to the open file resource limit maximum.

gdb/ChangeLog:

	* common/filestuff.c [HAVE_KINFO_GETFILE]: Include headers.
	(fdwalk) [HAVE_KINFO_GETFILE]: Use kinfo_getfile.

1 files changed, 24 insertions, 0 deletions

diff --git a/gdb/common/filestuff.c b/gdb/common/filestuff.c
index 0db5c69..f4d5e38 100644
--- a/gdb/common/filestuff.c
+++ b/gdb/common/filestuff.c
@@ -36,6 +36,11 @@
 #define HAVE_SOCKETS 1
 #endif
 
+#ifdef HAVE_KINFO_GETFILE
+#include <sys/user.h>
+#include <libutil.h>
+#endif
+
 #ifdef HAVE_SYS_RESOURCE_H
 #include <sys/resource.h>
 #endif /* HAVE_SYS_RESOURCE_H */
@@ -108,6 +113,25 @@ fdwalk (int (*func) (void *, int), void *arg)
     }
   /* We may fall through to the next case.  */
 #endif
+#ifdef HAVE_KINFO_GETFILE
+  int nfd;
+  gdb::unique_xmalloc_ptr<struct kinfo_file[]> fdtbl
+    (kinfo_getfile (getpid (), &nfd));
+  if (fdtbl != NULL)
+    {
+      for (int i = 0; i < nfd; i++)
+	{
+	  if (fdtbl[i].kf_fd >= 0)
+	    {
+	      int result = func (arg, fdtbl[i].kf_fd);
+	      if (result != 0)
+		return result;
+	    }
+	}
+      return 0;
+    }
+  /* We may fall through to the next case.  */
+#endif
 
   {
     int max, fd;