kbuild: add CONFIG_VMLINUX_MAP expert option

It can be quite useful to have ld emit a link map file, in order to
debug or verify that special sections end up where they are supposed
to, and to see what LD_DEAD_CODE_DATA_ELIMINATION manages to get rid
of.

The only reason I'm not just adding this unconditionally is that the
.map file can be rather large (several MB), and that's a waste of
space when one isn't interested in these things. Also make it depend
on CONFIG_EXPERT.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
This commit is contained in:
Rasmus Villemoes 2021-03-05 10:27:07 +01:00 коммит произвёл Masahiro Yamada
Родитель 609bbb4de4
Коммит 5cc1247204
4 изменённых файлов: 20 добавлений и 0 удалений

1
.gitignore поставляемый
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@ -59,6 +59,7 @@ modules.order
/linux
/vmlinux
/vmlinux.32
/vmlinux.map
/vmlinux.symvers
/vmlinux-gdb.py
/vmlinuz

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@ -252,6 +252,7 @@ vmlinux-*
vmlinux.aout
vmlinux.bin.all
vmlinux.lds
vmlinux.map
vmlinux.symvers
vmlinuz
voffset.h

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@ -449,6 +449,16 @@ config VMLINUX_VALIDATION
depends on STACK_VALIDATION && DEBUG_ENTRY && !PARAVIRT
default y
config VMLINUX_MAP
bool "Generate vmlinux.map file when linking"
depends on EXPERT
help
Selecting this option will pass "-Map=vmlinux.map" to ld
when linking vmlinux. That file can be useful for verifying
and debugging magic section games, and for seeing which
pieces of code get eliminated with
CONFIG_LD_DEAD_CODE_DATA_ELIMINATION.
config DEBUG_FORCE_WEAK_PER_CPU
bool "Force weak per-cpu definitions"
depends on DEBUG_KERNEL

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@ -155,6 +155,7 @@ vmlinux_link()
local output=${1}
local objects
local strip_debug
local map_option
info LD ${output}
@ -166,6 +167,10 @@ vmlinux_link()
strip_debug=-Wl,--strip-debug
fi
if [ -n "${CONFIG_VMLINUX_MAP}" ]; then
map_option="-Map=${output}.map"
fi
if [ "${SRCARCH}" != "um" ]; then
if [ -n "${CONFIG_LTO_CLANG}" ]; then
# Use vmlinux.o instead of performing the slow LTO
@ -187,6 +192,7 @@ vmlinux_link()
${LD} ${KBUILD_LDFLAGS} ${LDFLAGS_vmlinux} \
${strip_debug#-Wl,} \
-o ${output} \
${map_option} \
-T ${lds} ${objects}
else
objects="-Wl,--whole-archive \
@ -200,6 +206,7 @@ vmlinux_link()
${CC} ${CFLAGS_vmlinux} \
${strip_debug} \
-o ${output} \
${map_option:+-Wl,${map_option}} \
-Wl,-T,${lds} \
${objects} \
-lutil -lrt -lpthread
@ -303,6 +310,7 @@ cleanup()
rm -f .tmp_vmlinux*
rm -f System.map
rm -f vmlinux
rm -f vmlinux.map
rm -f vmlinux.o
}