[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:     1bd02c4f1a351989ee57a0735db1a0652238f991
Gitweb:        https://git.kernel.org/tip/1bd02c4f1a351989ee57a0735db1a0652238f991
Author:        Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate:    Wed, 18 Mar 2020 13:33:54 +01:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Wed, 22 Apr 2020 23:10:07 +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
---
 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 0b5cf05..3263b43 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