[PATCH 2/2] S390: Fix gdbserver support for TDB

[Andreas Arnez <arnez@linux.vnet.ibm.com>]

This makes gdbserver actually provide values for the TDB registers
when the inferior was stopped in a transaction.  The changes in
linux-low.c are needed for treating an unavailable TDB correctly and
without warnings.  The test case 's390-tdbregs.exp' passes with this
patch and fails without.

gdb/gdbserver/ChangeLog:

	* linux-low.c (regsets_fetch_inferior_registers): Treat ENODATA
	from ptrace as if a zeroed buffer was returned.
	(regsets_store_inferior_registers): Skip regsets without a
	fill_function.
	* linux-s390-low.c (s390_fill_last_break): Remove.
	(s390_store_tdb): New.
	(s390_regsets): Set fill_function to NULL for NT_S390_LAST_BREAK.
	Add regset for NT_S390_TDB.
	(s390_arch_setup): Use regset's size instead of fill_function for
	loop end condition.
---
 gdb/gdbserver/linux-low.c      |   11 +++++++++-
 gdb/gdbserver/linux-s390-low.c |   45 +++++++++++++++++++++++++++++++---------
 2 files changed, 45 insertions(+), 11 deletions(-)

diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c
index 01f11b7..5d1d9e1 100644
--- a/gdb/gdbserver/linux-low.c
+++ b/gdb/gdbserver/linux-low.c
@@ -4263,6 +4263,14 @@ regsets_fetch_inferior_registers (struct regsets_info *regsets_info,
 	      free (buf);
 	      continue;
 	    }
+	  else if (errno == ENODATA)
+	    {
+	      /* ENODATA may be returned if the regset is currently
+		 not "active".  Provide a zeroed buffer and assume
+		 that the store_function deals with this
+		 appropriately.  */
+	      memset (buf, 0, regset->size);
+	    }
 	  else
 	    {
 	      char s[256];
@@ -4300,7 +4308,8 @@ regsets_store_inferior_registers (struct regsets_info *regsets_info,
       void *buf, *data;
       int nt_type, res;
 
-      if (regset->size == 0 || regset_disabled (regsets_info, regset))
+      if (regset->size == 0 || regset_disabled (regsets_info, regset)
+	  || regset->fill_function == NULL)
 	{
 	  regset ++;
 	  continue;
diff --git a/gdb/gdbserver/linux-s390-low.c b/gdb/gdbserver/linux-s390-low.c
index 79fa6c0..4b547aa 100644
--- a/gdb/gdbserver/linux-s390-low.c
+++ b/gdb/gdbserver/linux-s390-low.c
@@ -290,12 +290,6 @@ s390_fill_gregset (struct regcache *regcache, void *buf)
 /* Fill and store functions for extended register sets.  */
 
 static void
-s390_fill_last_break (struct regcache *regcache, void *buf)
-{
-  /* Last break address is read-only.  */
-}
-
-static void
 s390_store_last_break (struct regcache *regcache, const void *buf)
 {
   const char *p;
@@ -316,13 +310,44 @@ 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;
+
+  if (*(const unsigned char *) buf != 0x01)
+    {
+      /* Invalid/unrecognized TDB format.  Invalidate.  */
+      for (i = 0; i < 4; i++)
+	supply_register (regcache, tdb0 + i, NULL);
+
+      for (i = 0; i < 16; i++)
+	supply_register (regcache, tr0 + i, NULL);
+
+      return;
+    }
+
+  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; do not attempt PTRACE_SETREGSET.  */
-  { PTRACE_GETREGSET, PTRACE_GETREGSET, NT_S390_LAST_BREAK, 0,
-    EXTENDED_REGS, s390_fill_last_break, s390_store_last_break },
+  /* Last break address is read-only; no fill function.  */
+  { PTRACE_GETREGSET, -1, NT_S390_LAST_BREAK, 0, EXTENDED_REGS,
+    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 }
 };
 
@@ -485,7 +510,7 @@ s390_arch_setup (void)
 #endif
 
   /* Update target_regsets according to available register sets.  */
-  for (regset = s390_regsets; regset->fill_function != NULL; regset++)
+  for (regset = s390_regsets; regset->size >= 0; regset++)
     if (regset->get_request == PTRACE_GETREGSET)
       switch (regset->nt_type)
 	{
-- 
1.7.9.5