[tip: objtool/core] kbuild/objtool: Add objtool-vmlinux.o pass

[tip-bot2 for Peter Zijlstra]

The following commit has been merged into the objtool/core branch of tip:

Commit-ID:     6804c1afd794c8135351faaa69e1503ee11393ac
Gitweb:        https://git.kernel.org/tip/6804c1afd794c8135351faaa69e1503ee11393ac
Author:        Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate:    Wed, 18 Mar 2020 13:33:54 +01:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Wed, 22 Apr 2020 10:53:51 +02:00

kbuild/objtool: Add objtool-vmlinux.o pass

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@xxxxxxxxxxxxx>
Reviewed-by: Miroslav Benes <mbenes@xxxxxxx>
Reviewed-by: Alexandre Chartre <alexandre.chartre@xxxxxxxxxx>
Acked-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20200416115119.287494491@xxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 lib/Kconfig.debug       |  5 +++++
 scripts/link-vmlinux.sh | 24 ++++++++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 21d9c5f..977b5a1 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -369,6 +369,11 @@ 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
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index d09ab4a..3adef49 100755
--- 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
@@ -251,6 +274,7 @@ ${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init need-builtin=1
 #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