tracing: add support for objtool mcount

This change adds build support for using objtool to generate
__mcount_loc sections.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>

diff --git a/Makefile b/Makefile
index 2233951..3189eac 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -860,6 +860,9 @@ ifdef CONFIG_FTRACE_MCOUNT_USE_CC
     endif
   endif
 endif
+ifdef CONFIG_FTRACE_MCOUNT_USE_OBJTOOL
+  CC_FLAGS_USING       += -DCC_USING_NOP_MCOUNT
+endif
 ifdef CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT
   ifdef CONFIG_HAVE_C_RECORDMCOUNT
     BUILD_C_RECORDMCOUNT := y
@@ -1236,6 +1239,10 @@ uapi-asm-generic:
 PHONY += prepare-objtool prepare-resolve_btfids
 prepare-objtool: $(objtool_target)
 ifeq ($(SKIP_STACK_VALIDATION),1)
+ifdef CONFIG_FTRACE_MCOUNT_USE_OBJTOOL
+       @echo "error: Cannot generate __mcount_loc for CONFIG_DYNAMIC_FTRACE=y, please install libelf-dev, libelf-devel or elfutils-libelf-devel" >&2
+       @false
+endif
 ifdef CONFIG_UNWINDER_ORC
        @echo "error: Cannot generate ORC metadata for CONFIG_UNWINDER_ORC=y, please install libelf-dev, libelf-devel or elfutils-libelf-devel" >&2
        @false

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 3985a31..936ccab 100644 (file)
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -60,6 +60,11 @@ config HAVE_NOP_MCOUNT
        help
          Arch supports the gcc options -pg with -mrecord-mcount and -nop-mcount
 
+config HAVE_OBJTOOL_MCOUNT
+       bool
+       help
+         Arch supports objtool --mcount
+
 config HAVE_C_RECORDMCOUNT
        bool
        help
@@ -612,10 +617,18 @@ config FTRACE_MCOUNT_USE_CC
        depends on !FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY
        depends on FTRACE_MCOUNT_RECORD
 
+config FTRACE_MCOUNT_USE_OBJTOOL
+       def_bool y
+       depends on HAVE_OBJTOOL_MCOUNT
+       depends on !FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY
+       depends on !FTRACE_MCOUNT_USE_CC
+       depends on FTRACE_MCOUNT_RECORD
+
 config FTRACE_MCOUNT_USE_RECORDMCOUNT
        def_bool y
        depends on !FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY
        depends on !FTRACE_MCOUNT_USE_CC
+       depends on !FTRACE_MCOUNT_USE_OBJTOOL
        depends on FTRACE_MCOUNT_RECORD
 
 config TRACING_MAP

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index d94fc9a..59fabd9 100644 (file)
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -238,6 +238,9 @@ endif
 ifdef CONFIG_X86_SMAP
   objtool_args += --uaccess
 endif
+ifdef CONFIG_FTRACE_MCOUNT_USE_OBJTOOL
+  objtool_args += --mcount
+endif
 
 # 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory
 # 'OBJECT_FILES_NON_STANDARD_foo.o := 'y': skip objtool checking for a file