On Fri, Mar 5, 2021 at 6:27 PM Rasmus Villemoes
wrote:
>
> 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
> ---
Applied to linux-kbuild.
Thanks.
> .gitignore | 1 +
> Documentation/dontdiff | 1 +
> lib/Kconfig.debug | 10 ++
> scripts/link-vmlinux.sh | 8
> 4 files changed, 20 insertions(+)
>
> diff --git a/.gitignore b/.gitignore
> index 3af66272d6f1..3adea59847ce 100644
> --- a/.gitignore
> +++ b/.gitignore
> @@ -59,6 +59,7 @@ modules.order
> /linux
> /vmlinux
> /vmlinux.32
> +/vmlinux.map
> /vmlinux.symvers
> /vmlinux-gdb.py
> /vmlinuz
> diff --git a/Documentation/dontdiff b/Documentation/dontdiff
> index e361fc95ca29..ac42ad8d430d 100644
> --- a/Documentation/dontdiff
> +++ b/Documentation/dontdiff
> @@ -252,6 +252,7 @@ vmlinux-*
> vmlinux.aout
> vmlinux.bin.all
> vmlinux.lds
> +vmlinux.map
> vmlinux.symvers
> vmlinuz
> voffset.h
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 5ea0c1773b0a..663c1cd5018c 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -412,6 +412,16 @@ 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
> diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
> index 3b261b0f74f0..855fd4e6f03e 100755
> --- a/scripts/link-vmlinux.sh
> +++ b/scripts/link-vmlinux.sh
> @@ -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
> }
>
> --
> 2.29.2
>
--
Best Regards
Masahiro Yamada
