On Wed, Feb 24, 2021 at 7:53 PM Rasmus Villemoes
<linux@xxxxxxxxxxxxxxxxxx> 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 hide the prompt
> behind CONFIG_EXPERT.
>
> Signed-off-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
> ---
> .gitignore | 1 +
> Makefile | 3 ++-
> lib/Kconfig.debug | 9 +++++++++
> scripts/link-vmlinux.sh | 9 +++++++++
> 4 files changed, 21 insertions(+), 1 deletion(-)
>
> diff --git a/.gitignore b/.gitignore
> index 3af66272d6f1..d3038aff4485 100644
> --- a/.gitignore
> +++ b/.gitignore
> @@ -58,6 +58,7 @@ modules.order
> /TAGS
> /linux
> /vmlinux
> +/vmlinux.map
Could you move this one line below
so that vmlinux.map is placed between
vmlinux.32 and vmlinux.symvers ?
I know this list is not sorted...
> /vmlinux.32
> /vmlinux.symvers
> /vmlinux-gdb.py
Please add this to Documentation/dontdiff as well.
> diff --git a/Makefile b/Makefile
> index b18dbc634690..be6fbd99a214 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1501,7 +1501,8 @@ endif # CONFIG_MODULES
> # Directories & files removed with 'make clean'
> CLEAN_FILES += include/ksym vmlinux.symvers \
> modules.builtin modules.builtin.modinfo modules.nsdeps \
> - compile_commands.json
> + compile_commands.json \
> + vmlinux.map
Do you need this ?
You already added this to cleanup() of scripts/link-vmlinux.sh,
which is invoked from 'make clean'.
> # Directories & files removed with 'make mrproper'
> MRPROPER_FILES += include/config include/generated \
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 5ea0c1773b0a..d6af084c11ae 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -412,6 +412,15 @@ config VMLINUX_VALIDATION
> depends on STACK_VALIDATION && DEBUG_ENTRY && !PARAVIRT
> default y
>
> +config VMLINUX_MAP
> + bool "Generate vmlinux.map file when linking" if EXPERT
Please use depends on EXPERT
because VMLINUX_MAP is not select or implied by anyone.
> + 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..bba58839db40 100755
> --- a/scripts/link-vmlinux.sh
> +++ b/scripts/link-vmlinux.sh
> @@ -166,6 +166,12 @@ vmlinux_link()
> strip_debug=-Wl,--strip-debug
> fi
>
> + if [ -n "${CONFIG_VMLINUX_MAP}" ]; then
> + map_option="-Map=${output}.map"
> + else
> + map_option=""
> + fi
> +
For consistency, please do like strip_debug, that is,
define this as a local variable, and
set the value of the 'if' case.
> if [ "${SRCARCH}" != "um" ]; then
> if [ -n "${CONFIG_LTO_CLANG}" ]; then
> # Use vmlinux.o instead of performing the slow LTO
> @@ -187,6 +193,7 @@ vmlinux_link()
> ${LD} ${KBUILD_LDFLAGS} ${LDFLAGS_vmlinux} \
> ${strip_debug#-Wl,} \
> -o ${output} \
> + ${map_option} \
> -T ${lds} ${objects}
> else
> objects="-Wl,--whole-archive \
> @@ -200,6 +207,7 @@ vmlinux_link()
> ${CC} ${CFLAGS_vmlinux} \
> ${strip_debug} \
> -o ${output} \
> + ${map_option:+-Wl,${map_option}} \
> -Wl,-T,${lds} \
> ${objects} \
> -lutil -lrt -lpthread
> @@ -303,6 +311,7 @@ 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
