Detect 64-bit-ness in PowerPC Book III-E

This patch is to teach both GDB and GDBServer to detect 64-bit inferior
correctly.  We find a problem that GDBServer is unable to detect on a
e5500 core processor.  Current GDBServer assumes that MSR is a 64-bit
register, but MSR is a 32-bit register in Book III-E.  This patch is
to fix this problem by checking the right bit in MSR, in order to handle
both Book III-S and Book III-E.  In order to detect Book III-S and
Book III-E, we check the PPC_FEATURE_BOOKE from the host's HWCAP (by
getauxval on glibc >= 2.16.  If getauxval doesn't exist, we implement
the fallback by parsing /proc/self/auxv), because it should an invariant
on the same machine cross different processes.

In order to share code, I add nat/ppc-linux.c for both GDB and
GDBserver side.

gdb:

2015-01-14  Yao Qi  <yao@codesourcery.com>

	* Makefile.in (ppc-linux.o): New rule.
	* config/powerpc/ppc64-linux.mh (NATDEPFILES): Add ppc-linux.o.
	* configure.ac: AC_CHECK_FUNCS(getauxval).
	* config.in: Re-generated.
	* configure: Re-generated.
	* nat/ppc-linux.h [__powerpc64__] (ppc64_64bit_inferior_p):
	Declare.
	* nat/ppc-linux.c: New file.
	* ppc-linux-nat.c (ppc_linux_target_wordsize) [__powerpc64__]:
	Call ppc64_64bit_inferior_p.

gdb/gdbserver:

2015-01-14  Yao Qi  <yao@codesourcery.com>

	* Makefile.in (SFILES): Add nat/ppc-linux.c.
	(ppc-linux.o): New rule.
	* configure.srv (powerpc*-*-linux*): Add ppc-linux.o.
	* configure.ac: AC_CHECK_FUNCS(getauxval).
	* config.in: Re-generated.
	* configure: Re-generated.
	* linux-ppc-low.c (ppc_arch_setup) [__powerpc64__]: Call
	ppc64_64bit_inferior_p

2 files changed, 81 insertions, 0 deletions

diff --git a/gdb/nat/ppc-linux.c b/gdb/nat/ppc-linux.c
new file mode 100644
index 0000000..76b3574
--- /dev/null
+++ b/gdb/nat/ppc-linux.c
@@ -0,0 +1,75 @@
+/*Copyright (C) 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 "ppc-linux.h"
+#include <elf.h>
+
+#ifdef HAVE_GETAUXVAL
+#include <sys/auxv.h>
+#endif
+
+#ifdef __powerpc64__
+
+/* Get the HWCAP from the process of GDB or GDBserver.  If success,
+   save it in *VALP.   */
+
+static void
+ppc64_host_hwcap (unsigned long *valp)
+{
+#ifdef HAVE_GETAUXVAL
+  *valp = getauxval (AT_HWCAP);
+#else
+  unsigned long data[2];
+  FILE *f = fopen ("/proc/self/auxv", "r");
+
+  if (f == NULL)
+    return;
+
+  while (fread (data, sizeof (data), 1, f) > 0)
+    {
+      if (data[0] == AT_HWCAP)
+	{
+	  *valp = data[1];
+	  break;
+	}
+    }
+
+  fclose (f);
+#endif /* HAVE_GETAUXVAL */
+}
+
+int
+ppc64_64bit_inferior_p (long msr)
+{
+  unsigned long ppc_host_hwcap = 0;
+
+  /* Get host's HWCAP to check whether the machine is Book E.  */
+  ppc64_host_hwcap (&ppc_host_hwcap);
+
+  /* We actually have a 64-bit inferior only if the certain bit of the
+     MSR is set.  The PowerISA Book III-S MSR is different from the
+     PowerISA Book III-E MSR.  The Book III-S MSR is 64 bits wide, and
+     its MSR[SF] is the bit 0 of a 64-bit value.  Book III-E MSR is 32
+     bits wide, and its MSR[CM] is the bit 0 of a 32-bit value.   */
+  if (ppc_host_hwcap & PPC_FEATURE_BOOKE)
+    return msr & 0x80000000;
+  else
+    return msr < 0;
+}
+
+#endif
diff --git a/gdb/nat/ppc-linux.h b/gdb/nat/ppc-linux.h
index 30d936f..0ff2223 100644
--- a/gdb/nat/ppc-linux.h
+++ b/gdb/nat/ppc-linux.h
@@ -82,4 +82,10 @@
 #define PTRACE_SETEVRREGS 21
 #endif
 
+#ifdef __powerpc64__
+/* Return whether the inferior is 64bit or not by checking certain bit
+   in MSR.  */
+int ppc64_64bit_inferior_p (long msr);
+#endif
+
 #endif