kbuild: link of vmlinux moved to a script

Move the final link of vmlinux to a script to improve
readability and maintainability of the code.

The Makefile fragments used to link vmlinux has over the
years seen far too many changes and the logic had become
hard to follow.

As the process by nature is serialized there was
nothing gained including this in the Makefile.

"um" has special link requirments - and the
only way to handle this was to hard-code the linking
of "um" in the script.
This was better than trying to modularize it only for the
benefit of "um" anyway.

The shell script has been improved after input from:
Arnaud Lacombe <lacombar@gmail.com>
Nick Bowler <nbowler@elliptictech.com>

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Arnaud Lacombe <lacombar@gmail.com>
Cc: Nick Bowler <nbowler@elliptictech.com>
Cc: Richard Weinberger <richard@nod.at>
Signed-off-by: Michal Marek <mmarek@suse.cz>

1 files changed, 211 insertions, 0 deletions

diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
new file mode 100644
index 000000000000..26c5b658c2d5
--- /dev/null
+++ b/scripts/link-vmlinux.sh
@@ -0,0 +1,211 @@
+#!/bin/sh
+#
+# link vmlinux
+#
+# vmlinux is linked from the objects selected by $(KBUILD_VMLINUX_INIT) and
+# $(KBUILD_VMLINUX_MAIN). Most are built-in.o files from top-level directories
+# in the kernel tree, others are specified in arch/$(ARCH)/Makefile.
+# Ordering when linking is important, and $(KBUILD_VMLINUX_INIT) must be first.
+#
+# vmlinux
+#   ^
+#   |
+#   +-< $(KBUILD_VMLINUX_INIT)
+#   |   +--< init/version.o + more
+#   |
+#   +--< $(KBUILD_VMLINUX_MAIN)
+#   |    +--< drivers/built-in.o mm/built-in.o + more
+#   |
+#   +-< ${kallsymso} (see description in KALLSYMS section)
+#
+# vmlinux version (uname -v) cannot be updated during normal
+# descending-into-subdirs phase since we do not yet know if we need to
+# update vmlinux.
+# Therefore this step is delayed until just before final link of vmlinux.
+#
+# System.map is generated to document addresses of all kernel symbols
+
+# Error out on error
+set -e
+
+# Nice output in kbuild format
+# Will be supressed by "make -s"
+info()
+{
+        if [ "${quiet}" != "silent_" ]; then
+                printf "  %-7s %s\n" ${1} ${2}
+        fi
+}
+
+# Link of vmlinux.o used for section mismatch analysis
+# ${1} output file
+modpost_link()
+{
+        ${LD} ${LDFLAGS} -r -o ${1} ${KBUILD_VMLINUX_INIT}                   \
+                --start-group ${KBUILD_VMLINUX_MAIN} --end-group
+}
+
+# Link of vmlinux
+# ${1} - optional extra .o files
+# ${2} - output file
+vmlinux_link()
+{
+        local lds="${objtree}/${KBUILD_LDS}"
+
+        if [ "${SRCARCH}" != "um" ]; then
+                ${LD} ${LDFLAGS} ${LDFLAGS_vmlinux} -o ${2}                  \
+                        -T ${lds} ${KBUILD_VMLINUX_INIT}                     \
+                        --start-group ${KBUILD_VMLINUX_MAIN} --end-group ${1}
+        else
+                ${CC} ${CFLAGS_vmlinux} -o ${2}                              \
+                        -Wl,-T,${lds} ${KBUILD_VMLINUX_INIT}                 \
+                        -Wl,--start-group                                    \
+                                 ${KBUILD_VMLINUX_MAIN}                      \
+                        -Wl,--end-group                                      \
+                        -lutil ${1}
+                rm -f linux
+        fi
+}
+
+
+# Create ${2} .o file with all symbols from the ${1} object file
+kallsyms()
+{
+        info KSYM ${2}
+        local kallsymopt;
+
+        if [ -n "${CONFIG_KALLSYMS_ALL}" ]; then
+                kallsymopt=--all-symbols
+        fi
+
+        local aflags="${KBUILD_AFLAGS} ${NOSTDINC_FLAGS}                     \
+                      ${LINUXINCLUDE} ${KBUILD_CPPFLAGS}"
+
+        ${NM} -n ${1} | \
+                scripts/kallsyms ${kallsymopt} | \
+                ${CC} ${aflags} -c -o ${2} -x assembler-with-cpp -
+}
+
+# Create map file with all symbols from ${1}
+# See mksymap for additional details
+mksysmap()
+{
+        ${CONFIG_SHELL} "${srctree}/scripts/mksysmap" ${1} ${2}
+}
+
+# Delete output files in case of error
+trap cleanup SIGHUP SIGINT SIGQUIT SIGTERM ERR
+cleanup()
+{
+        rm -f .old_version
+        rm -f .tmp_System.map
+        rm -f .tmp_kallsyms*
+        rm -f .tmp_version
+        rm -f .tmp_vmlinux*
+        rm -f System.map
+        rm -f vmlinux
+        rm -f vmlinux.o
+}
+
+#
+#
+# Use "make V=1" to debug this script
+case "${KBUILD_VERBOSE}" in
+*1*)
+        set -x
+        ;;
+esac
+
+if [ "$1" = "clean" ]; then
+        cleanup
+        exit 0
+fi
+
+# We need access to CONFIG_ symbols
+. ./.config
+
+#link vmlinux.o
+info LD vmlinux.o
+modpost_link vmlinux.o
+
+# modpost vmlinux.o to check for section mismatches
+${MAKE} -f "${srctree}/scripts/Makefile.modpost" vmlinux.o
+
+# Update version
+info GEN .version
+if [ ! -r .version ]; then
+        rm -f .version;
+        echo 1 >.version;
+else
+        mv .version .old_version;
+        expr 0$(cat .old_version) + 1 >.version;
+fi;
+
+# final build of init/
+${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init
+
+kallsymso=""
+kallsyms_vmlinux=""
+if [ -n "${CONFIG_KALLSYMS}" ]; then
+
+        # kallsyms support
+        # Generate section listing all symbols and add it into vmlinux
+        # It's a three step process:
+        # 1)  Link .tmp_vmlinux1 so it has all symbols and sections,
+        #     but __kallsyms is empty.
+        #     Running kallsyms on that gives us .tmp_kallsyms1.o with
+        #     the right size
+        # 2)  Link .tmp_vmlinux2 so it now has a __kallsyms section of
+        #     the right size, but due to the added section, some
+        #     addresses have shifted.
+        #     From here, we generate a correct .tmp_kallsyms2.o
+        # 2a) We may use an extra pass as this has been necessary to
+        #     woraround some alignment related bugs.
+        #     KALLSYMS_EXTRA_PASS=1 is used to trigger this.
+        # 3)  The correct ${kallsymso} is linked into the final vmlinux.
+        #
+        # a)  Verify that the System.map from vmlinux matches the map from
+        #     ${kallsymso}.
+
+        kallsymso=.tmp_kallsyms2.o
+        kallsyms_vmlinux=.tmp_vmlinux2
+
+        # step 1
+        vmlinux_link "" .tmp_vmlinux1
+        kallsyms .tmp_vmlinux1 .tmp_kallsyms1.o
+
+        # step 2
+        vmlinux_link .tmp_kallsyms1.o .tmp_vmlinux2
+        kallsyms .tmp_vmlinux2 .tmp_kallsyms2.o
+
+        # step 2a
+        if [ -n "${KALLSYMS_EXTRA_PASS}" ]; then
+                kallsymso=.tmp_kallsyms3.o
+                kallsyms_vmlinux=.tmp_vmlinux3
+
+                vmlinux_link .tmp_kallsyms2.o .tmp_vmlinux3
+
+                kallsyms .tmp_vmlinux3 .tmp_kallsyms3.o
+        fi
+fi
+
+info LD vmlinux
+vmlinux_link "${kallsymso}" vmlinux
+
+info SYSMAP System.map
+mksysmap vmlinux System.map
+
+# step a (see comment above)
+if [ -n "${CONFIG_KALLSYMS}" ]; then
+        mksysmap ${kallsyms_vmlinux} .tmp_System.map
+
+        if ! cmp -s System.map .tmp_System.map; then
+                echo Inconsistent kallsyms data
+                echo echo Try "make KALLSYMS_EXTRA_PASS=1" as a workaround
+                cleanup
+                exit 1
+        fi
+fi
+
+# We made a new kernel - delete old version file
+rm -f .old_version