S390: Fix gdbserver support for TDB

This makes gdbserver actually provide values for the TDB registers
when the inferior was stopped in a transaction.  The change in
linux-low.c is needed to suppress the warning for an unavailable TDB.

The test case 's390-tdbregs.exp' passes with this patch and fails
without.

gdb/gdbserver/ChangeLog:

	* linux-low.c (regsets_fetch_inferior_registers): Suppress the
	warning upon ENODATA from ptrace.
	* linux-s390-low.c (s390_store_tdb): New.
	(s390_regsets): Add regset for NT_S390_TDB.

3 files changed, 30 insertions, 0 deletions

diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog
index 7818793..e65cdbd 100644
--- a/gdb/gdbserver/ChangeLog
+++ b/gdb/gdbserver/ChangeLog
@@ -1,5 +1,12 @@
 2014-12-12  Andreas Arnez  <arnez@linux.vnet.ibm.com>
 
+	* linux-low.c (regsets_fetch_inferior_registers): Suppress the
+	warning upon ENODATA from ptrace.
+	* linux-s390-low.c (s390_store_tdb): New.
+	(s390_regsets): Add regset for NT_S390_TDB.
+
+2014-12-12  Andreas Arnez  <arnez@linux.vnet.ibm.com>
+
 	* linux-low.c (regsets_store_inferior_registers): Skip regsets
 	without a fill_function.
 	* linux-s390-low.c (s390_fill_last_break): Remove.
diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c
index 5f62010..5ea9200 100644
--- a/gdb/gdbserver/linux-low.c
+++ b/gdb/gdbserver/linux-low.c
@@ -4256,6 +4256,12 @@ regsets_fetch_inferior_registers (struct regsets_info *regsets_info,
 		 this process mode.  */
 	      disable_regset (regsets_info, regset);
 	    }
+	  else if (errno == ENODATA)
+	    {
+	      /* ENODATA may be returned if the regset is currently
+		 not "active".  This can happen in normal operation,
+		 so suppress the warning in this case.  */
+	    }
 	  else
 	    {
 	      char s[256];
diff --git a/gdb/gdbserver/linux-s390-low.c b/gdb/gdbserver/linux-s390-low.c
index 9f77f30..40fb61c 100644
--- a/gdb/gdbserver/linux-s390-low.c
+++ b/gdb/gdbserver/linux-s390-low.c
@@ -310,6 +310,20 @@ s390_store_system_call (struct regcache *regcache, const void *buf)
   supply_register_by_name (regcache, "system_call", buf);
 }
 
+static void
+s390_store_tdb (struct regcache *regcache, const void *buf)
+{
+  int tdb0 = find_regno (regcache->tdesc, "tdb0");
+  int tr0 = find_regno (regcache->tdesc, "tr0");
+  int i;
+
+  for (i = 0; i < 4; i++)
+    supply_register (regcache, tdb0 + i, (const char *) buf + 8 * i);
+
+  for (i = 0; i < 16; i++)
+    supply_register (regcache, tr0 + i, (const char *) buf + 8 * (16 + i));
+}
+
 static struct regset_info s390_regsets[] = {
   { 0, 0, 0, 0, GENERAL_REGS, s390_fill_gregset, NULL },
   /* Last break address is read-only; no fill function.  */
@@ -317,6 +331,9 @@ static struct regset_info s390_regsets[] = {
     NULL, s390_store_last_break },
   { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_S390_SYSTEM_CALL, 0,
     EXTENDED_REGS, s390_fill_system_call, s390_store_system_call },
+  /* TDB is read-only.  */
+  { PTRACE_GETREGSET, -1, NT_S390_TDB, 0, EXTENDED_REGS,
+    NULL, s390_store_tdb },
   { 0, 0, 0, -1, -1, NULL, NULL }
 };