riscv/ftrace: Add RECORD_MCOUNT support

Now recordmcount.pl recognizes RISC-V object files. For the mechanism to
work, we have to disable the linker relaxation.

Cc: Greentime Hu <greentime@andestech.com>
Signed-off-by: Alan Kao <alankao@andestech.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

arch/riscv/Kconfig

@@ -114,6 +114,7 @@ config ARCH_RV64I
 	select 64BIT
 	select HAVE_FUNCTION_TRACER
 	select HAVE_FUNCTION_GRAPH_TRACER
+	select HAVE_FTRACE_MCOUNT_RECORD
 
 endchoice
 

arch/riscv/Makefile

@@ -11,6 +11,9 @@
 LDFLAGS         :=
 OBJCOPYFLAGS    := -O binary
 LDFLAGS_vmlinux :=
+ifeq ($(CONFIG_DYNAMIC_FTRACE),y)
+	LDFLAGS_vmlinux := --no-relax
+endif
 KBUILD_AFLAGS_MODULE += -fPIC
 KBUILD_CFLAGS_MODULE += -fPIC
 

scripts/recordmcount.pl

@@ -376,6 +376,11 @@ if ($arch eq "x86_64") {
     $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s__mcount\$";
     $type = ".quad";
     $alignment = 8;
+} elsif ($arch eq "riscv") {
+    $function_regex = "^([0-9a-fA-F]+)\\s+<([^.0-9][0-9a-zA-Z_\\.]+)>:";
+    $mcount_regex = "^\\s*([0-9a-fA-F]+):\\sR_RISCV_CALL\\s_mcount\$";
+    $type = ".quad";
+    $alignment = 2;
 } else {
     die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD";
 }