Move low-level Linux x86 debug register code to a shared file

This commit moves the now-identical low-level Linux x86 debug register
code from gdb/x86-linux-nat.c and gdb/gdbserver/linux-x86-low.c into a
new shared file gdb/nat/x86-linux-dregs.c.

gdb/ChangeLog:

	* nat/x86-linux-dregs.h: New file.
	* nat/x86-linux-dregs.c: Likewise.
	* Makefile.in (HFILES_NO_SRCDIR): Add nat/x86-linux-dregs.h.
	(x86-linux-dregs.o): New rule.
	* config/i386/linux.mh (NATDEPFILES): Add x86-linux-dregs.o.
	* config/i386/linux64.mh (NATDEPFILES): Likewise.
	* x86-linux-nat.c: Include nat/x86-linux-dregs.h.
	(u_debugreg_offset): Moved to nat/x86-linux-dregs.c.
	(x86_linux_dr_get): Likewise.
	(x86_linux_dr_set): Likewise.
	(x86_linux_dr_get_addr): Likewise.
	(x86_linux_dr_get_control): Likewise.
	(x86_linux_dr_get_status): Likewise.
	(update_debug_registers_callback): Likewise.
	(x86_linux_dr_set_control): Likewise.
	(x86_linux_dr_set_addr): Likewise.
	(x86_linux_update_debug_registers): Likewise.

gdb/gdbserver/ChangeLog:

	* Makefile.in (x86-linux-dregs.o): New rule.
	* configure.srv: Add x86-linux-dregs.o to relevant targets.
	* linux-x86-low.c: Include nat/x86-linux-dregs.h.
	(u_debugreg_offset): Moved to nat/x86-linux-dregs.c.
	(x86_linux_dr_get): Likewise.
	(x86_linux_dr_set): Likewise.
	(update_debug_registers_callback): Likewise.
	(x86_linux_dr_set_addr): Likewise.
	(x86_linux_dr_get_addr): Likewise.
	(x86_linux_dr_set_control): Likewise.
	(x86_linux_dr_get_control): Likewise.
	(x86_linux_dr_get_status): Likewise.
	(x86_linux_update_debug_registers): Likewise.

2 files changed, 236 insertions, 0 deletions

diff --git a/gdb/nat/x86-linux-dregs.c b/gdb/nat/x86-linux-dregs.c
new file mode 100644
index 0000000..9389803
--- /dev/null
+++ b/gdb/nat/x86-linux-dregs.c
@@ -0,0 +1,183 @@
+/* Low-level debug register code for GNU/Linux x86 (i386 and x86-64).
+
+   Copyright (C) 1999-2015 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include "common-defs.h"
+#include <sys/ptrace.h>
+#include <sys/user.h>
+#include "target/waitstatus.h"
+#include "nat/x86-linux.h"
+#include "nat/x86-dregs.h"
+#include "nat/x86-linux-dregs.h"
+
+/* Return the offset of REGNUM in the u_debugreg field of struct
+   user.  */
+
+static int
+u_debugreg_offset (int regnum)
+{
+  return (offsetof (struct user, u_debugreg)
+	  + sizeof (((struct user *) 0)->u_debugreg[0]) * regnum);
+}
+
+/* Get debug register REGNUM value from the LWP specified by PTID.  */
+
+static unsigned long
+x86_linux_dr_get (ptid_t ptid, int regnum)
+{
+  int tid;
+  unsigned long value;
+
+  gdb_assert (ptid_lwp_p (ptid));
+  tid = ptid_get_lwp (ptid);
+
+  errno = 0;
+  value = ptrace (PTRACE_PEEKUSER, tid, u_debugreg_offset (regnum), 0);
+  if (errno != 0)
+    perror_with_name (_("Couldn't read debug register"));
+
+  return value;
+}
+
+/* Set debug register REGNUM to VALUE in the LWP specified by PTID.  */
+
+static void
+x86_linux_dr_set (ptid_t ptid, int regnum, unsigned long value)
+{
+  int tid;
+
+  gdb_assert (ptid_lwp_p (ptid));
+  tid = ptid_get_lwp (ptid);
+
+  errno = 0;
+  ptrace (PTRACE_POKEUSER, tid, u_debugreg_offset (regnum), value);
+  if (errno != 0)
+    perror_with_name (_("Couldn't write debug register"));
+}
+
+/* Callback for iterate_over_lwps.  Mark that our local mirror of
+   LWP's debug registers has been changed, and cause LWP to stop if
+   it isn't already.  Values are written from our local mirror to
+   the actual debug registers immediately prior to LWP resuming.  */
+
+static int
+update_debug_registers_callback (struct lwp_info *lwp, void *arg)
+{
+  lwp_set_debug_registers_changed (lwp, 1);
+
+  if (!lwp_is_stopped (lwp))
+    linux_stop_lwp (lwp);
+
+  /* Continue the iteration.  */
+  return 0;
+}
+
+/* See nat/x86-linux-dregs.h.  */
+
+CORE_ADDR
+x86_linux_dr_get_addr (int regnum)
+{
+  gdb_assert (DR_FIRSTADDR <= regnum && regnum <= DR_LASTADDR);
+
+  return x86_linux_dr_get (current_lwp_ptid (), regnum);
+}
+
+/* See nat/x86-linux-dregs.h.  */
+
+void
+x86_linux_dr_set_addr (int regnum, CORE_ADDR addr)
+{
+  ptid_t pid_ptid = pid_to_ptid (ptid_get_pid (current_lwp_ptid ()));
+
+  gdb_assert (DR_FIRSTADDR <= regnum && regnum <= DR_LASTADDR);
+
+  iterate_over_lwps (pid_ptid, update_debug_registers_callback, NULL);
+}
+
+/* See nat/x86-linux-dregs.h.  */
+
+unsigned long
+x86_linux_dr_get_control (void)
+{
+  return x86_linux_dr_get (current_lwp_ptid (), DR_CONTROL);
+}
+
+/* See nat/x86-linux-dregs.h.  */
+
+void
+x86_linux_dr_set_control (unsigned long control)
+{
+  ptid_t pid_ptid = pid_to_ptid (ptid_get_pid (current_lwp_ptid ()));
+
+  iterate_over_lwps (pid_ptid, update_debug_registers_callback, NULL);
+}
+
+/* See nat/x86-linux-dregs.h.  */
+
+unsigned long
+x86_linux_dr_get_status (void)
+{
+  return x86_linux_dr_get (current_lwp_ptid (), DR_STATUS);
+}
+
+/* See nat/x86-linux-dregs.h.  */
+
+void
+x86_linux_update_debug_registers (struct lwp_info *lwp)
+{
+  ptid_t ptid = ptid_of_lwp (lwp);
+  int clear_status = 0;
+
+  gdb_assert (lwp_is_stopped (lwp));
+
+  if (lwp_debug_registers_changed (lwp))
+    {
+      struct x86_debug_reg_state *state
+	= x86_debug_reg_state (ptid_get_pid (ptid));
+      int i;
+
+      /* Prior to Linux kernel 2.6.33 commit
+	 72f674d203cd230426437cdcf7dd6f681dad8b0d, setting DR0-3 to
+	 a value that did not match what was enabled in DR_CONTROL
+	 resulted in EINVAL.  To avoid this we zero DR_CONTROL before
+	 writing address registers, only writing DR_CONTROL's actual
+	 value once all the addresses are in place.  */
+      x86_linux_dr_set (ptid, DR_CONTROL, 0);
+
+      ALL_DEBUG_ADDRESS_REGISTERS (i)
+	if (state->dr_ref_count[i] > 0)
+	  {
+	    x86_linux_dr_set (ptid, i, state->dr_mirror[i]);
+
+	    /* If we're setting a watchpoint, any change the inferior
+	       has made to its debug registers needs to be discarded
+	       to avoid x86_stopped_data_address getting confused.  */
+	    clear_status = 1;
+	  }
+
+      /* If DR_CONTROL is supposed to be zero then it's already set.  */
+      if (state->dr_control_mirror != 0)
+	x86_linux_dr_set (ptid, DR_CONTROL, state->dr_control_mirror);
+
+      lwp_set_debug_registers_changed (lwp, 0);
+    }
+
+  if (clear_status
+      || lwp_stop_reason (lwp) == TARGET_STOPPED_BY_WATCHPOINT)
+    x86_linux_dr_set (ptid, DR_STATUS, 0);
+}
diff --git a/gdb/nat/x86-linux-dregs.h b/gdb/nat/x86-linux-dregs.h
new file mode 100644
index 0000000..063e508
--- /dev/null
+++ b/gdb/nat/x86-linux-dregs.h
@@ -0,0 +1,53 @@
+/* Low-level debug register code for GNU/Linux x86 (i386 and x86-64).
+
+   Copyright (C) 1999-2015 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef X86_LINUX_DREGS_H
+#define X86_LINUX_DREGS_H
+
+/* Return the address stored in the current inferior's debug register
+   REGNUM.  */
+
+extern CORE_ADDR x86_linux_dr_get_addr (int regnum);
+
+/* Store ADDR in debug register REGNUM of all LWPs of the current
+   inferior.  */
+
+extern void x86_linux_dr_set_addr (int regnum, CORE_ADDR addr);
+
+/* Return the value stored in the current inferior's debug control
+   register.  */
+
+extern unsigned long x86_linux_dr_get_control (void);
+
+/* Store CONTROL in the debug control registers of all LWPs of the
+   current inferior.  */
+
+extern void x86_linux_dr_set_control (unsigned long control);
+
+/* Return the value stored in the current inferior's debug status
+   register.  */
+
+extern unsigned long x86_linux_dr_get_status (void);
+
+/* Update the thread's debug registers if the values in our local
+   mirror have been changed.  */
+
+extern void x86_linux_update_debug_registers (struct lwp_info *lwp);
+
+#endif /* X86_LINUX_DREGS_H */