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>
diff --git a/arch/ia64/kernel/entry.S b/arch/ia64/kernel/entry.S
index c2f7d79..e0be92a 100644
--- a/arch/ia64/kernel/entry.S
+++ b/arch/ia64/kernel/entry.S
@@ -1406,6 +1406,56 @@
END(unw_init_running)
#ifdef CONFIG_FUNCTION_TRACER
+#ifdef CONFIG_DYNAMIC_FTRACE
+GLOBAL_ENTRY(_mcount)
+ br ftrace_stub
+END(_mcount)
+
+.here:
+ br.ret.sptk.many b0
+
+GLOBAL_ENTRY(ftrace_caller)
+ alloc out0 = ar.pfs, 8, 0, 4, 0
+ mov out3 = r0
+ ;;
+ mov out2 = b0
+ add r3 = 0x20, r3
+ mov out1 = r1;
+ br.call.sptk.many b0 = ftrace_patch_gp
+ //this might be called from module, so we must patch gp
+ftrace_patch_gp:
+ movl gp=__gp
+ mov b0 = r3
+ ;;
+.global ftrace_call;
+ftrace_call:
+{
+ .mlx
+ nop.m 0x0
+ movl r3 = .here;;
+}
+ alloc loc0 = ar.pfs, 4, 4, 2, 0
+ ;;
+ mov loc1 = b0
+ mov out0 = b0
+ mov loc2 = r8
+ mov loc3 = r15
+ ;;
+ adds out0 = -MCOUNT_INSN_SIZE, out0
+ mov out1 = in2
+ mov b6 = r3
+
+ br.call.sptk.many b0 = b6
+ ;;
+ mov ar.pfs = loc0
+ mov b0 = loc1
+ mov r8 = loc2
+ mov r15 = loc3
+ br ftrace_stub
+ ;;
+END(ftrace_caller)
+
+#else
GLOBAL_ENTRY(_mcount)
movl r2 = ftrace_stub
movl r3 = ftrace_trace_function;;
@@ -1435,6 +1485,7 @@
br ftrace_stub
;;
END(_mcount)
+#endif
GLOBAL_ENTRY(ftrace_stub)
mov r3 = b0