[PATCH v5 05/29] tracing: add support for objtool mcount

Sami Tolvanen
2020-10-09T16:15:01Z

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

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