[PATCH v4 09/13] kbuild/objtool: Add objtool-vmlinux.o pass

[Peter Zijlstra <peterz@infradead.org>]

Now that objtool is capable of processing vmlinux.o and actually has
something useful to do there, (conditionally) add it to the final link
pass.

This will increase build time by a few seconds.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 lib/Kconfig.debug       |    5 +++++
 scripts/link-vmlinux.sh |   24 ++++++++++++++++++++++++
 2 files changed, 29 insertions(+)

--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -379,6 +379,11 @@ config STACK_VALIDATION
 	  For more information, see
 	  tools/objtool/Documentation/stack-validation.txt.
 
+config VMLINUX_VALIDATION
+	bool
+	depends on STACK_VALIDATION && DEBUG_ENTRY && !PARAVIRT
+	default y
+
 config DEBUG_FORCE_WEAK_PER_CPU
 	bool "Force weak per-cpu definitions"
 	depends on DEBUG_KERNEL
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -55,6 +55,29 @@ modpost_link()
 	${LD} ${KBUILD_LDFLAGS} -r -o ${1} ${objects}
 }
 
+objtool_link()
+{
+	local objtoolopt;
+
+	if [ -n "${CONFIG_VMLINUX_VALIDATION}" ]; then
+		objtoolopt="check"
+		if [ -z "${CONFIG_FRAME_POINTER}" ]; then
+			objtoolopt="${objtoolopt} --no-fp"
+		fi
+		if [ -n "${CONFIG_GCOV_KERNEL}" ]; then
+			objtoolopt="${objtoolopt} --no-unreachable"
+		fi
+		if [ -n "${CONFIG_RETPOLINE}" ]; then
+			objtoolopt="${objtoolopt} --retpoline"
+		fi
+		if [ -n "${CONFIG_X86_SMAP}" ]; then
+			objtoolopt="${objtoolopt} --uaccess"
+		fi
+		info OBJTOOL ${1}
+		tools/objtool/objtool ${objtoolopt} ${1}
+	fi
+}
+
 # Link of vmlinux
 # ${1} - output file
 # ${2}, ${3}, ... - optional extra .o files
@@ -244,6 +267,7 @@ ${MAKE} -f "${srctree}/scripts/Makefile.
 #link vmlinux.o
 info LD vmlinux.o
 modpost_link vmlinux.o
+objtool_link vmlinux.o
 
 # modpost vmlinux.o to check for section mismatches
 ${MAKE} -f "${srctree}/scripts/Makefile.modpost" MODPOST_VMLINUX=1