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Message-Id: <20201009161338.657380-6-samitolvanen@google.com>
Date: Fri,  9 Oct 2020 09:13:14 -0700
From: Sami Tolvanen <samitolvanen@...gle.com>
To: Masahiro Yamada <masahiroy@...nel.org>, Will Deacon <will@...nel.org>, 
	Steven Rostedt <rostedt@...dmis.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	"Paul E. McKenney" <paulmck@...nel.org>, Kees Cook <keescook@...omium.org>, 
	Nick Desaulniers <ndesaulniers@...gle.com>, clang-built-linux@...glegroups.com, 
	kernel-hardening@...ts.openwall.com, linux-arch@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-kbuild@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org, x86@...nel.org, 
	Sami Tolvanen <samitolvanen@...gle.com>
Subject: [PATCH v5 05/29] 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@...gle.com>
---
 Makefile             | 12 ++++++++++--
 kernel/trace/Kconfig | 13 +++++++++++++
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index 434da9fcbf3c..fb2cf557d3ca 100644
--- a/Makefile
+++ b/Makefile
@@ -850,6 +850,9 @@ 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
@@ -1209,11 +1212,16 @@ uapi-asm-generic:
 PHONY += prepare-objtool prepare-resolve_btfids
 prepare-objtool: $(objtool_target)
 ifeq ($(SKIP_STACK_VALIDATION),1)
+objtool-lib-prompt := "please install libelf-dev, libelf-devel or elfutils-libelf-devel"
+ifdef CONFIG_FTRACE_MCOUNT_USE_OBJTOOL
+	@echo "error: Cannot generate __mcount_loc for CONFIG_DYNAMIC_FTRACE=y, $(objtool-lib-prompt)" >&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
+	@echo "error: Cannot generate ORC metadata for CONFIG_UNWINDER_ORC=y, $(objtool-lib-prompt)" >&2
 	@false
 else
-	@echo "warning: Cannot use CONFIG_STACK_VALIDATION=y, please install libelf-dev, libelf-devel or elfutils-libelf-devel" >&2
+	@echo "warning: Cannot use CONFIG_STACK_VALIDATION=y, $(objtool-lib-prompt)" >&2
 endif
 endif
 
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 927ad004888a..89263210ab26 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -51,6 +51,11 @@ 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
@@ -605,10 +610,18 @@ 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
-- 
2.28.0.1011.ga647a8990f-goog

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