alpha: Add minimal support for software performance events

In the kernel the patch enables configuration of the perf event
option, adds the perf_event_open syscall, and includes a minimal
architecture specific asm/perf_event.h header file.
Signed-off-by: Michael Cree <mcree@orcon.net.nz>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Matt Turner <mattst88@gmail.com>

arch/alpha/Kconfig

@@ -9,6 +9,7 @@ config ALPHA
 	select HAVE_IDE
 	select HAVE_OPROFILE
 	select HAVE_SYSCALL_WRAPPERS
+	select HAVE_PERF_EVENTS
 	help
 	  The Alpha is a 64-bit general-purpose processor designed and
 	  marketed by the Digital Equipment Corporation of blessed memory,

arch/alpha/include/asm/perf_event.h

+#ifndef __ASM_ALPHA_PERF_EVENT_H
+#define __ASM_ALPHA_PERF_EVENT_H
+
+/* Alpha only supports software events through this interface. */
+static inline void set_perf_event_pending(void) { }
+
+#define PERF_EVENT_INDEX_OFFSET 0
+
+#endif /* __ASM_ALPHA_PERF_EVENT_H */

arch/alpha/include/asm/unistd.h

@@ -448,10 +448,11 @@
 #define __NR_preadv			490
 #define __NR_pwritev			491
 #define __NR_rt_tgsigqueueinfo		492
+#define __NR_perf_event_open		493
 
 #ifdef __KERNEL__
 
-#define NR_SYSCALLS			493
+#define NR_SYSCALLS			494
 
 #define __ARCH_WANT_IPC_PARSE_VERSION
 #define __ARCH_WANT_OLD_READDIR

arch/alpha/kernel/systbls.S

@@ -511,6 +511,7 @@ sys_call_table:
 	.quad sys_preadv				/* 490 */
 	.quad sys_pwritev
 	.quad sys_rt_tgsigqueueinfo
+	.quad sys_perf_event_open
 
 	.size sys_call_table, . - sys_call_table
 	.type sys_call_table, @object