[PATCH v2] gdb: btrace: fix build errors on older glibc builds

[Mike Frysinger <vapier at gentoo dot org>]

It is possible to have a build of glibc where SYS_perf_event_open is not
defined (because when the glibc was compiled, the syscall did not exist),
but have newer kernel headers installed so that linux/perf_event.h is
available.  In this setup, you get a build failure:

./common/linux-btrace.c: In function 'kernel_supports_btrace':
./common/linux-btrace.c:316:23: error: 'SYS_perf_event_open' undeclared (first use in this function)

Update the ifdef check to also see if the syscall is available.

URL: https://bugs.gentoo.org/473522
Reported-by: William Throwe <wtt6@cornell.edu>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>

gdb/:
2013-09-12  Mike Frysinger  <vapier@gentoo.org>

	* common/linux-btrace.c: Move sys/syscall.h out of the
	HAVE_LINUX_PERF_EVENT_H check and wrap it in HAVE_SYS_SYSCALL_H.
	Also check for SYS_perf_event_open before attempting to buid.

gdbserver/:
2013-09-12  Mike Frysinger  <vapier@gentoo.org>

	* configure.ac (AC_CHECK_HEADERS): Add sys/syscall.h
	* config.in, configure: Regenerated.
---
v2
	- update gdbserver to search for sys/syscall.h too

 gdb/common/linux-btrace.c  | 7 +++++--
 gdb/gdbserver/config.in    | 3 +++
 gdb/gdbserver/configure    | 2 +-
 gdb/gdbserver/configure.ac | 2 +-
 4 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/gdb/common/linux-btrace.c b/gdb/common/linux-btrace.c
index b874c84..7e20745 100644
--- a/gdb/common/linux-btrace.c
+++ b/gdb/common/linux-btrace.c
@@ -33,13 +33,16 @@
 #include "gdb_wait.h"
 #include "i386-cpuid.h"
 
-#if HAVE_LINUX_PERF_EVENT_H
+#ifdef HAVE_SYS_SYSCALL_H
+#include <sys/syscall.h>
+#endif
+
+#if HAVE_LINUX_PERF_EVENT_H && defined(SYS_perf_event_open)
 
 #include <errno.h>
 #include <string.h>
 #include <stdint.h>
 #include <unistd.h>
-#include <sys/syscall.h>
 #include <sys/mman.h>
 #include <sys/user.h>
 #include <sys/ptrace.h>
diff --git a/gdb/gdbserver/config.in b/gdb/gdbserver/config.in
index 7f23a31..1154df2 100644
--- a/gdb/gdbserver/config.in
+++ b/gdb/gdbserver/config.in
@@ -199,6 +199,9 @@
 /* Define to 1 if you have the <sys/stat.h> header file. */
 #undef HAVE_SYS_STAT_H
 
+/* Define to 1 if you have the <sys/syscall.h> header file. */
+#undef HAVE_SYS_SYSCALL_H 1
+
 /* Define to 1 if you have the <sys/types.h> header file. */
 #undef HAVE_SYS_TYPES_H
 
diff --git a/gdb/gdbserver/configure b/gdb/gdbserver/configure
index 193aedc..55dba84 100755
--- a/gdb/gdbserver/configure
+++ b/gdb/gdbserver/configure
@@ -4873,7 +4873,7 @@ $as_echo "$as_me: running $SHELL $ac_sub_configure $ac_sub_configure_args --cach
   cd "$ac_popdir"
 
 
-for ac_header in sgtty.h termio.h termios.h sys/reg.h string.h 		 proc_service.h sys/procfs.h thread_db.h linux/elf.h 		 stdlib.h 		 errno.h fcntl.h signal.h sys/file.h malloc.h 		 sys/ioctl.h netinet/in.h sys/socket.h netdb.h 		 netinet/tcp.h arpa/inet.h sys/wait.h wait.h sys/un.h 		 linux/perf_event.h
+for ac_header in sgtty.h termio.h termios.h sys/reg.h string.h 		 proc_service.h sys/procfs.h thread_db.h linux/elf.h 		 stdlib.h 		 errno.h fcntl.h signal.h sys/file.h malloc.h 		 sys/ioctl.h netinet/in.h sys/socket.h netdb.h 		 netinet/tcp.h arpa/inet.h sys/wait.h wait.h sys/un.h 		 linux/perf_event.h sys/syscall.h
 do :
   as_ac_Header=`$as_echo "ac_cv_header_$ac_header" | $as_tr_sh`
 ac_fn_c_check_header_mongrel "$LINENO" "$ac_header" "$as_ac_Header" "$ac_includes_default"
diff --git a/gdb/gdbserver/configure.ac b/gdb/gdbserver/configure.ac
index 456a1f7..c167508 100644
--- a/gdb/gdbserver/configure.ac
+++ b/gdb/gdbserver/configure.ac
@@ -84,7 +84,7 @@ AC_CHECK_HEADERS(sgtty.h termio.h termios.h sys/reg.h string.h dnl
 		 errno.h fcntl.h signal.h sys/file.h malloc.h dnl
 		 sys/ioctl.h netinet/in.h sys/socket.h netdb.h dnl
 		 netinet/tcp.h arpa/inet.h sys/wait.h wait.h sys/un.h dnl
-		 linux/perf_event.h)
+		 linux/perf_event.h sys/syscall.h)
 AC_CHECK_FUNCS(pread pwrite pread64 readlink fdwalk pipe2)
 AC_REPLACE_FUNCS(vasprintf vsnprintf)
 
-- 
1.8.3.2