[ltt-dev] [UST PATCH] armv5 archs require write alignment

[Jason Wessel]

Reads and writes to unsigned int 32 bit numbers must be address
aligned or the l2 cache can return junk in the high order 16 bits on
reads.

This patch activates the original work done for alignment in ltt for
the UST code.  The config.ac changes will isolate the use of alignment
to the known arch type with the problem.

Signed-off-by: Jason Wessel <jason.wessel at windriver.com>
---
 configure.ac       |   26 ++++++++++++++++++++++++++
 include/ust/core.h |    6 +++---
 2 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/configure.ac b/configure.ac
index 8ca32ff..d05b18c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -10,6 +10,7 @@ AM_INIT_AUTOMAKE([foreign])
 m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([yes])])
 AC_CONFIG_SRCDIR([ustctl/ustctl.c])
 AC_CONFIG_HEADERS([config.h])
+AH_TEMPLATE([HAVE_EFFICIENT_UNALIGNED_ACCESS], [Use efficient unaligned access.])
 
 # Checks for programs.
 AC_PROG_CC
@@ -108,6 +109,7 @@ changequote([,])dnl
 	ppc64) LIBFORMAT="elf64-powerpc" ;;
 	s390) LIBFORMAT="elf32-s390" ;;
 	s390x) LIBFORMAT="elf64-s390" ;;
+        armv5) LIBFORMAT="elf32-littlearm"; NO_UNALIGNED_ACCESS=1 ;;
 	arm) LIBFORMAT="elf32-littlearm" ;;
 	mips*) LIBFORMAT="" ;;
 	*) AC_MSG_ERROR([unable to detect library format (unsupported architecture ($host_cpu)?)]) ;;
@@ -115,6 +117,30 @@ esac
 AC_SUBST(LIBFORMAT)
 AC_MSG_RESULT($LIBFORMAT)
 
+if test "x$host_cpu" = "xarm" ; then
+AC_MSG_CHECKING([checking for armv5])
+AC_TRY_COMPILE(
+[
+],
+[
+#ifndef __ARM_ARCH_5TEJ__
+#error "no arm5 here"
+#endif
+],
+[
+	AC_MSG_RESULT([yes])
+	NO_UNALIGNED_ACCESS=1
+]
+,
+[
+	AC_MSG_RESULT([no])
+]
+)
+fi
+if test x$NO_UNALIGNED_ACCESS = x ; then
+AC_DEFINE([HAVE_EFFICIENT_UNALIGNED_ACCESS], [1])
+fi
+
 AC_CONFIG_FILES([
 	Makefile
 	doc/Makefile
diff --git a/include/ust/core.h b/include/ust/core.h
index e781a3a..4a2c6e5 100644
--- a/include/ust/core.h
+++ b/include/ust/core.h
@@ -23,7 +23,7 @@
 #define likely(x)	__builtin_expect(!!(x), 1)
 #define unlikely(x)	__builtin_expect(!!(x), 0)
 
-#if defined(CONFIG_LTT) && defined(CONFIG_LTT_ALIGNMENT)
+#ifndef HAVE_EFFICIENT_UNALIGNED_ACCESS
 
 /*
  * Calculate the offset needed to align the type.
@@ -42,7 +42,7 @@ static inline int ltt_get_alignment(void)
 	return sizeof(void *);
 }
 
-#else
+#else /* HAVE_EFFICIENT_UNALIGNED_ACCESS */
 
 static inline unsigned int ltt_align(size_t align_drift,
 		 size_t size_of_type)
@@ -56,7 +56,7 @@ static inline int ltt_get_alignment(void)
 {
 	return 0;
 }
-#endif /* defined(CONFIG_LTT) && defined(CONFIG_LTT_ALIGNMENT) */
+#endif /* HAVE_EFFICIENT_UNALIGNED_ACCESS */
 
 
 /* ARRAYS */
-- 
1.7.1