[PATCH 9/9] [GDBserver] hostio.c: Fallback to packet buffer size if PATH_MAX is not available.

[Pedro Alves <palves@redhat.com>]

PATH_MAX is not defined on systems which have no limit on filename
length, such as GNU/Hurd.  As designed, the hostio RSP packets carry
the paths as parameters in the request/reply packets, which themselves
have an upper size limit, so lifting the filename limit completely
would require a redesign with new hostio packets.  While that doesn't
happen, we can at least support filename lengths as long as the packet
buffer can fit.

gdb/
2013-06-27  Pedro Alves  <palves@redhat.com>

	* hostio.c (HOSTIO_PATH_MAX): Define.
	(require_filename, handle_open, handle_unlink, handle_readlink):
	Use it.
---
 gdb/gdbserver/hostio.c |   16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/gdb/gdbserver/hostio.c b/gdb/gdbserver/hostio.c
index df94d31..031bb54 100644
--- a/gdb/gdbserver/hostio.c
+++ b/gdb/gdbserver/hostio.c
@@ -50,6 +50,14 @@ safe_fromhex (char a, int *nibble)
   return 0;
 }
 
+/* Filenames are hex encoded, so the maximum we can handle is half the
+   packet buffer size.  Cap to PATH_MAX, if it is shorter.  */
+#if !defined (PATH_MAX) || (PATH_MAX > (PBUFSIZ / 2))
+#  define HOSTIO_PATH_MAX (PBUFSIZ / 2)
+#else
+#  define HOSTIO_PATH_MAX PATH_MAX
+#endif
+
 static int
 require_filename (char **pp, char *filename)
 {
@@ -64,7 +72,7 @@ require_filename (char **pp, char *filename)
       int nib1, nib2;
 
       /* Don't allow overflow.  */
-      if (count >= PATH_MAX - 1)
+      if (count >= HOSTIO_PATH_MAX - 1)
 	return -1;
 
       if (safe_fromhex (p[0], &nib1)
@@ -266,7 +274,7 @@ fileio_open_flags_to_host (int fileio_open_flags, int *open_flags_p)
 static void
 handle_open (char *own_buf)
 {
-  char filename[PATH_MAX];
+  char filename[HOSTIO_PATH_MAX];
   char *p;
   int fileio_flags, mode, flags, fd;
   struct fd_list *new_fd;
@@ -442,7 +450,7 @@ handle_close (char *own_buf)
 static void
 handle_unlink (char *own_buf)
 {
-  char filename[PATH_MAX];
+  char filename[HOSTIO_PATH_MAX];
   char *p;
   int ret;
 
@@ -470,7 +478,7 @@ static void
 handle_readlink (char *own_buf, int *new_packet_len)
 {
 #if defined (HAVE_READLINK)
-  char filename[PATH_MAX], linkname[PATH_MAX];
+  char filename[HOSTIO_PATH_MAX], linkname[HOSTIO_PATH_MAX];
   char *p;
   int ret, bytes_sent;