Fix ppc_collect/supply_ptrace_register() routines

This patch fixes the routines to collect and supply ptrace registers on ppc64le
gdbserver. Originally written for big endian arch, they were causing several
issues on little endian. With this fix, the number of unexpected failures in
the testsuite dropped from 263 to 72 on ppc64le.

gdb/gdbserver/ChangeLog

	* linux-ppc-low.c (ppc_collect_ptrace_register): Adjust routine to take
	endianness into account.
	(ppc_supply_ptrace_register): Likewise.

2 files changed, 42 insertions, 9 deletions

diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog
index 3fb143c..c860daf 100644
--- a/gdb/gdbserver/ChangeLog
+++ b/gdb/gdbserver/ChangeLog
@@ -1,3 +1,9 @@
+2014-09-08  Edjunior Barbosa Machado  <emachado@linux.vnet.ibm.com>
+
+	* linux-ppc-low.c (ppc_collect_ptrace_register): Adjust routine to take
+	endianness into account.
+	(ppc_supply_ptrace_register): Likewise.
+
 2014-09-03  James Hogan  <james.hogan@imgtec.com>
 
 	* linux-mips-low.c (mips_read_description): Reset errno to 0 prior
diff --git a/gdb/gdbserver/linux-ppc-low.c b/gdb/gdbserver/linux-ppc-low.c
index d743311..8fd4b38 100644
--- a/gdb/gdbserver/linux-ppc-low.c
+++ b/gdb/gdbserver/linux-ppc-low.c
@@ -202,25 +202,52 @@ ppc_cannot_fetch_register (int regno)
 static void
 ppc_collect_ptrace_register (struct regcache *regcache, int regno, char *buf)
 {
-  int size = register_size (regcache->tdesc, regno);
-
   memset (buf, 0, sizeof (long));
 
-  if (size < sizeof (long))
-    collect_register (regcache, regno, buf + sizeof (long) - size);
+  if (__BYTE_ORDER == __LITTLE_ENDIAN)
+    {
+      /* Little-endian values always sit at the left end of the buffer.  */
+      collect_register (regcache, regno, buf);
+    }
+  else if (__BYTE_ORDER == __BIG_ENDIAN)
+    {
+      /* Big-endian values sit at the right end of the buffer.  In case of
+         registers whose sizes are smaller than sizeof (long), we must use a
+         padding to access them correctly.  */
+      int size = register_size (regcache->tdesc, regno);
+
+      if (size < sizeof (long))
+	collect_register (regcache, regno, buf + sizeof (long) - size);
+      else
+	collect_register (regcache, regno, buf);
+    }
   else
-    collect_register (regcache, regno, buf);
+    perror_with_name ("Unexpected byte order");
 }
 
 static void
 ppc_supply_ptrace_register (struct regcache *regcache,
 			    int regno, const char *buf)
 {
-  int size = register_size (regcache->tdesc, regno);
-  if (size < sizeof (long))
-    supply_register (regcache, regno, buf + sizeof (long) - size);
+  if (__BYTE_ORDER == __LITTLE_ENDIAN)
+    {
+      /* Little-endian values always sit at the left end of the buffer.  */
+      supply_register (regcache, regno, buf);
+    }
+  else if (__BYTE_ORDER == __BIG_ENDIAN)
+    {
+      /* Big-endian values sit at the right end of the buffer.  In case of
+         registers whose sizes are smaller than sizeof (long), we must use a
+         padding to access them correctly.  */
+      int size = register_size (regcache->tdesc, regno);
+
+      if (size < sizeof (long))
+	supply_register (regcache, regno, buf + sizeof (long) - size);
+      else
+	supply_register (regcache, regno, buf);
+    }
   else
-    supply_register (regcache, regno, buf);
+    perror_with_name ("Unexpected byte order");
 }