[lttng-dev] [PATCH lttng-ust] Fix: Wrong configure check for UST perf event counters context support

[Christian Babeux]

When building on non-x86 platforms, the build errors out with the following:

  CC       lttng-context-perf-counters.lo
lttng-context-perf-counters.c:95:2: error: #error "Perf event counters are only supported on x86 so far."
lttng-context-perf-counters.c: In function 'read_perf_counter':
lttng-context-perf-counters.c:114:4: warning: implicit declaration of function 'rdpmc' [-Wimplicit-function-declaration]
make[2]: *** [lttng-context-perf-counters.lo] Error 1

The configure script checks for the presence of the "perf_event.h" header to enable support for
perf events counters. However, the current implementation is only available on x86,
hence the build fails on platform where the perf header is available.

Fix this issue by detecting the architecture we are currently building and wether
to enable or not the support for perf event counters context.

Signed-off-by: Christian Babeux <christian.babeux at efficios.com>
---
 configure.ac | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/configure.ac b/configure.ac
index 76851db..4841f46 100644
--- a/configure.ac
+++ b/configure.ac
@@ -194,9 +194,23 @@ AC_CHECK_LIB([urcu-bp], [call_rcu_bp], [], [AC_MSG_ERROR([liburcu 0.6 or newer i
 
 # optional linux/perf_event.h
 AC_CHECK_HEADERS([linux/perf_event.h], [have_perf_event=yes], [])
-AM_CONDITIONAL([HAVE_PERF_EVENT], [test "x$have_perf_event" = "xyes"])
 
-if test "x$have_perf_event" = "xyes"; then
+# Perf event counters are only supported on x86 so far.
+AC_MSG_CHECKING([UST support for architecture perf event counters])
+case $host_cpu in
+changequote(,)dnl
+	i[3456]86)
+changequote([,])dnl
+	UST_SUPPORT_FOR_ARCH_PERF_EVENT_COUNTERS=yes;;
+	x86_64) UST_SUPPORT_FOR_ARCH_PERF_EVENT_COUNTERS=yes;;
+	amd64) UST_SUPPORT_FOR_ARCH_PERF_EVENT_COUNTERS=yes;;
+	*) UST_SUPPORT_FOR_ARCH_PERF_EVENT_COUNTERS=no;;
+esac
+AC_MSG_RESULT([$UST_SUPPORT_FOR_ARCH_PERF_EVENT_COUNTERS])
+
+AM_CONDITIONAL([HAVE_PERF_EVENT], [test "x$have_perf_event" = "xyes" -a "x$UST_SUPPORT_FOR_ARCH_PERF_EVENT_COUNTERS" = "xyes"])
+
+if test "x$have_perf_event" = "xyes" -a "x$UST_SUPPORT_FOR_ARCH_PERF_EVENT_COUNTERS" = "xyes"; then
 AC_DEFINE([LTTNG_UST_HAVE_PERF_EVENT], [1])
 fi
 
-- 
1.9.3