Re: [PATCH]: Make Linux use the new unified x86 watchpoint support

[Mark Kettenis <kettenis@science.uva.nl>]

   Date: Mon, 26 Mar 2001 18:14:00 -0800
   From: Michael Snyder <msnyder@cygnus.com>

   Mark Kettenis wrote:
   > 
   > FYI, I checked this in.  HJ can finally be happy now (although things
   > probably won't work correctly for multithreaded programs).

   Mark, this breaks remote i386 targets debugged from linux hosts.
   STOPPED_BY_WATCHPOINT is unconditionally defined to a function in
   i386-nat.c, but we may not be debugging a native target.

STOPPED_BY_WATCHPOINT always has been unconditionally defined.  The
only difference I can see is that with the old stuff is that I now
call perror_with_name if the ptrace call fails.

If I'm right, the attached patch should fix your problems.  I cannot
test it right now (no access to a Linux/x86 box), but if it works for
you, feel free to check it in.

More details in the reply to your other message.

Mark


Index: ChangeLog
from  Mark Kettenis  <kettenis@gnu.org>

	* i386-linux-nat.c (i386_linux_dr_get): Return 0 if ptrace call
	fails instead of calling perror_with_name.  This should fix
	debugging remote i386 targets with a native Linux/x86 GDB.  Add
	FIXME for this hack.

Index: i386-linux-nat.c
===================================================================
RCS file: /cvs/src/src/gdb/i386-linux-nat.c,v
retrieving revision 1.24
diff -u -r1.24 i386-linux-nat.c
--- i386-linux-nat.c 2001/03/21 21:22:48 1.24
+++ i386-linux-nat.c 2001/03/27 08:40:06
@@ -712,11 +712,20 @@
      one thread.  */
   tid = PIDGET (inferior_pid);
 
+  /* FIXME: kettenis/2001-03-27: Calling perror_with_name if the
+     ptrace call fails breaks debugging remote targets.  The correct
+     way to fix this is to add the hardware breakpoint and watchpoint
+     stuff to the target vectore.  For now, just return zero if the
+     ptrace call fails.  */
   errno = 0;
   value = ptrace (PT_READ_U, tid,
 		  offsetof (struct user, u_debugreg[regnum]), 0);
   if (errno != 0)
+#if 0
     perror_with_name ("Couldn't read debug register");
+#else
+    return 0;
+#endif
 
   return value;
 }