gdb/

* Makefile.in (amd64_linux_tdep_h): New.
	(amd64-linux-nat.o, amd64-linux-tdep.o): Update.
	* amd64-linux-nat.c (amd64_linux_gregset64_reg_offset): Add
	ORIG_RAX.
	(_initialize_amd64_linux_nat): Set amd64_native_gregset64_num_regs.
	* amd64-linux-tdep.c (amd64_linux_register_name)
	(amd64_linux_register_type, amd64_linux_register_reggroup_p)
	(amd64_linux_write_pc): New.
	(amd64_linux_init_abi): Use them, and update num_regs.
	* amd64-linux-tdep.h: New file.
	* amd64-tdep.c (amd64_register_name, amd64_register_type): Make
	public.
	* amd64-tdep.h (amd64_register_name, amd64_register_type): New
	prototypes.

	* regformats/reg-x86-64-linux.dat: New file.
gdb/testsuite/
	* Makefile.in (clean): Clean reg-x86-64-linux.c.
	(reg-x86-64-linux.o, reg-x86-64-linux.c): New.
	* configure.srv (x86_64-*-linux*): Use reg-x86-64-linux.o.
	* linux-x86-64-low.c (x86_64_regmap): Include ORIG_RAX.
	(x86_64_fill_gregset, x86_64_store_gregset): Skip floating
	point registers.

gdb/amd64-linux-tdep.c

@@ -1,6 +1,6 @@
 /* Target-dependent code for GNU/Linux x86-64.
 
-   Copyright (C) 2001, 2003, 2004, 2005 Free Software Foundation, Inc.
+   Copyright (C) 2001, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
    Contributed by Jiri Smid, SuSE Labs.
 
    This file is part of GDB.
@@ -26,6 +26,9 @@
 #include "regcache.h"
 #include "osabi.h"
 #include "symtab.h"
+#include "gdbtypes.h"
+#include "reggroups.h"
+#include "amd64-linux-tdep.h"
 
 #include "gdb_string.h"
 
@@ -199,6 +202,61 @@ static int amd64_linux_sc_reg_offset[] =
   -1				/* %gs */
 };
 
+/* Replacement register functions which know about %orig_rax.  */
+
+static const char *
+amd64_linux_register_name (int reg)
+{
+  if (reg == AMD64_LINUX_ORIG_RAX_REGNUM)
+    return "orig_rax";
+
+  return amd64_register_name (reg);
+}
+
+static struct type *
+amd64_linux_register_type (struct gdbarch *gdbarch, int reg)
+{
+  if (reg == AMD64_LINUX_ORIG_RAX_REGNUM)
+    return builtin_type_int64;
+
+  return amd64_register_type (gdbarch, reg);
+}
+
+static int
+amd64_linux_register_reggroup_p (struct gdbarch *gdbarch, int regnum,
+				 struct reggroup *group)
+{ 
+  if (regnum == AMD64_LINUX_ORIG_RAX_REGNUM)
+    return (group == system_reggroup
+            || group == save_reggroup
+            || group == restore_reggroup);
+  return default_register_reggroup_p (gdbarch, regnum, group);
+}
+
+/* Set the program counter for process PTID to PC.  */
+
+static void
+amd64_linux_write_pc (CORE_ADDR pc, ptid_t ptid)
+{
+  write_register_pid (AMD64_RIP_REGNUM, pc, ptid);
+
+  /* We must be careful with modifying the program counter.  If we
+     just interrupted a system call, the kernel might try to restart
+     it when we resume the inferior.  On restarting the system call,
+     the kernel will try backing up the program counter even though it
+     no longer points at the system call.  This typically results in a
+     SIGSEGV or SIGILL.  We can prevent this by writing `-1' in the
+     "orig_rax" pseudo-register.
+
+     Note that "orig_rax" is saved when setting up a dummy call frame.
+     This means that it is properly restored when that frame is
+     popped, and that the interrupted system call will be restarted
+     when we resume the inferior on return from a function call from
+     within GDB.  In all other cases the system call will not be
+     restarted.  */
+  write_register_pid (AMD64_LINUX_ORIG_RAX_REGNUM, -1, ptid);
+}
+
 static void
 amd64_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 {
@@ -219,6 +277,13 @@ amd64_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
   set_solib_svr4_fetch_link_map_offsets
     (gdbarch, svr4_lp64_fetch_link_map_offsets);
 
+  /* Add the %orig_rax register used for syscall restarting.  */
+  set_gdbarch_write_pc (gdbarch, amd64_linux_write_pc);
+  set_gdbarch_num_regs (gdbarch, AMD64_LINUX_NUM_REGS);
+  set_gdbarch_register_name (gdbarch, amd64_linux_register_name);
+  set_gdbarch_register_type (gdbarch, amd64_linux_register_type);
+  set_gdbarch_register_reggroup_p (gdbarch, amd64_linux_register_reggroup_p);
+
   /* Enable TLS support.  */
   set_gdbarch_fetch_tls_load_module_address (gdbarch,
                                              svr4_fetch_objfile_link_map);