ARCv2: Implemented ftrace

Adapted ARCv3 tracing to work for ARCv2.
ARCv2 requires extra support from GCC

Signed-off-by: BrunoASMauricio <brunoasmauricio@gmail.com>

Author: BrunoASMauricio

arch/arc/Kconfig

@@ -38,8 +38,8 @@ config ARC
 	select HAVE_KERNEL_LZMA
 	select HAVE_KPROBES
 	select HAVE_KRETPROBES
-	select HAVE_FUNCTION_TRACER if ISA_ARCV3
-	select HAVE_FUNCTION_GRAPH_TRACER if ISA_ARCV3
+	select HAVE_FUNCTION_TRACER
+	select HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_MOD_ARCH_SPECIFIC
 	select HAVE_PERF_EVENTS
 	select HANDLE_DOMAIN_IRQ

arch/arc/Makefile

@@ -62,8 +62,10 @@ cflags-$(CONFIG_ARC_HAS_LL128)	+= 	-m128
 endif
 
 ifdef CONFIG_FTRACE
+ifdef CONFIG_ISA_ARCV3
 cflags-y	+= -fno-omit-frame-pointer
 endif
+endif
 
 cflags-y	+= -Wa,-I$(srctree)/arch/arc/include
 

arch/arc/kernel/Makefile

@@ -15,9 +15,6 @@ endif
 
 ifdef CONFIG_FTRACE
 
-# Currently ftrace only works on arcv3 due to ABI
-ifdef CONFIG_ISA_ARCV3
-
 # ftrace cant be traced (infinite loop)
 CFLAGS_REMOVE_ftrace.o = -pg
 CFLAGS_REMOVE_mcount.o = -pg
@@ -28,8 +25,6 @@ obj-$(CONFIG_FUNCTION_GRAPH_TRACER)    += ftrace.o
 
 endif
 
-endif
-
 obj-$(CONFIG_ISA_ARCOMPACT)		+= entry-compact.o
 obj-$(CONFIG_ISA_ARCV2)			+= entry-arcv2.o
 obj-$(CONFIG_ISA_ARCV3)			+= entry-arcv3.o

arch/arc/kernel/mcount.S

@@ -9,7 +9,7 @@
 #include <linux/init.h>
 #include <linux/linkage.h>
 #include <asm-generic/export.h>
-#include <asm/asm-macro-64-bit.h>
+#include <asm/assembler.h>
 
 .text
 ; ftrace placeholder, just return to caller
@@ -31,11 +31,9 @@ ENDPROC(ftrace_stub)
 .macro SAVE_ABI_RET
     PUSHR  r0
     PUSHR  r1
-    PUSHR  blink
 .endm
 
 .macro LOAD_ABI_RET
-    POPR blink
     POPR r1
     POPR r0
 .endm
@@ -68,21 +66,21 @@ ENTRY(_mcount)
 
     ; *ftrace_graph_return != ftrace_stub
     MOVA  r3, ftrace_graph_return
-    LD64  r3, r3
+    LDR  r3, r3
     MOVA  r4, @ftrace_stub
     brne  r3, r4, @do_ftrace_graph_caller
 
     ; *ftrace_graph_entry != *ftrace_graph_entry_stub
     MOVA  r3, @ftrace_graph_entry
-    LD64  r3, r3
+    LDR  r3, r3
     MOVA  r4, @ftrace_graph_entry_stub
     brne  r3, r4, @do_ftrace_graph_caller
 
 #endif
 
     ; *ftrace_trace_function != ftrace_stub
     MOVA r2, ftrace_trace_function
-    LD64 r2, r2
+    LDR r2, r2
 
     MOVA r3, @ftrace_stub
     brne r2, r3, @do_trace
@@ -95,9 +93,23 @@ ENDPROC(_mcount)
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 do_ftrace_graph_caller:
 
-SAVE_ABI
+#ifndef CONFIG_ISA_ARCV3
+# ABI does not allow us to infer blink location
+# ARC GCC port inserts into r1 the delta between the pushed blink and
+# the sp at call time
+# We perform calculation before any push (sp change) happens
+    ADDR  r0, r1, sp
+
+    SAVE_ABI
+
+    SUBR  r0, r0, REGSZASM
+#else
+    SAVE_ABI
+
+    ADDR r0, fp, REGSZASM
+#endif
+
 
-    ADDR r0, fp, 8
     MOVR  r1, blink
 
     MOVA  r2, @prepare_ftrace_return
@@ -117,3 +129,5 @@ SAVE_ABI
 
 LOAD_ABI
     j_s   [blink]
+
+EXPORT_SYMBOL(_mcount)