ftrace, ia64: IA64 dynamic ftrace support

IA64 dynamic ftrace support.
The original _mcount stub for each function is like:
	alloc r40=ar.pfs,12,8,0
	mov r43=r0;;
	mov r42=b0
	mov r41=r1
	nop.i 0x0
	br.call.sptk.many b0 = _mcount;;

The patch convert it to below for nop:
	[MII] nop.m 0x0
	mov r3=ip
	nop.i 0x0
	[MLX] nop.m 0x0
	nop.x 0x0;;
This isn't completely nop, as there is one instuction 'mov r3=ip', but
it should be light and harmless for code follow it.

And below is for call
	[MII] nop.m 0x0
	mov r3=ip
	nop.i 0x0
	[MLX] nop.m 0x0
	brl.many .;;
In this way, only one instruction is changed to convert code between nop
and call. This should meet dyn-ftrace's requirement.
But this requires CPU support brl instruction, so dyn-ftrace isn't
supported for old Itanium system. Assume there are quite few such old
system running.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 5 insertions, 0 deletions

diff --git a/arch/ia64/kernel/Makefile b/arch/ia64/kernel/Makefile
index c381ea954892..ab6e7ec0bba3 100644
--- a/arch/ia64/kernel/Makefile
+++ b/arch/ia64/kernel/Makefile
@@ -2,6 +2,10 @@
 # Makefile for the linux kernel.
 #
 
+ifdef CONFIG_DYNAMIC_FTRACE
+CFLAGS_REMOVE_ftrace.o = -pg
+endif
+
 extra-y := head.o init_task.o vmlinux.lds
 
 obj-y := acpi.o entry.o efi.o efi_stub.o gate-data.o fsys.o ia64_ksyms.o irq.o irq_ia64.o       \
@@ -28,6 +32,7 @@ obj-$(CONFIG_IA64_CYCLONE)	+= cyclone.o
 obj-$(CONFIG_CPU_FREQ)          += cpufreq/
 obj-$(CONFIG_IA64_MCA_RECOVERY) += mca_recovery.o
 obj-$(CONFIG_KPROBES)           += kprobes.o jprobes.o
+obj-$(CONFIG_DYNAMIC_FTRACE)    += ftrace.o
 obj-$(CONFIG_KEXEC)             += machine_kexec.o relocate_kernel.o crash.o
 obj-$(CONFIG_CRASH_DUMP)        += crash_dump.o
 obj-$(CONFIG_IA64_UNCACHED_ALLOCATOR)   += uncached.o