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 <[email protected]> --- .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 /vmlinux.32 /vmlinux.symvers /vmlinux-gdb.py 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 # 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 + 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 + 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
