| Message ID | 20210224105256.1939169-1-linux@rasmusvillemoes.dk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | kbuild: add CONFIG_VMLINUX_MAP expert option | expand |
On 24/02/2021 11.52, 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 hide the prompt > behind CONFIG_EXPERT. ping
On Wed, Feb 24, 2021 at 7:53 PM Rasmus Villemoes <linux@rasmusvillemoes.dk> 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@rasmusvillemoes.dk> > --- > .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} \ > ${objects} \ > -lutil -lrt -lpthread > @@ -303,6 +311,7 @@ cleanup() > rm -f .tmp_vmlinux* > rm -f System.map > rm -f vmlinux > + rm -f vmlinux.map > rm -f vmlinux.o > } > > -- > 2.29.2 >
diff --git a/.gitignore b/.gitignore index 3af66272d6f1..d3038aff4485 100644 --- a/.gitignore +++ b/.gitignore @@ -58,6 +58,7 @@ modules.order /TAGS /linux /vmlinux +/vmlinux.map /vmlinux.32 /vmlinux.symvers /vmlinux-gdb.py diff --git a/Makefile b/Makefile index b18dbc634690..be6fbd99a214 100644 --- a/Makefile +++ b/Makefile @@ -1501,7 +1501,8 @@ endif # CONFIG_MODULES # Directories & files removed with 'make clean' CLEAN_FILES += include/ksym vmlinux.symvers \ modules.builtin modules.builtin.modinfo modules.nsdeps \ - compile_commands.json + compile_commands.json \ + vmlinux.map # Directories & files removed with 'make mrproper' MRPROPER_FILES += include/config include/generated \ diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 5ea0c1773b0a..d6af084c11ae 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -412,6 +412,15 @@ config VMLINUX_VALIDATION depends on STACK_VALIDATION && DEBUG_ENTRY && !PARAVIRT default y +config VMLINUX_MAP + bool "Generate vmlinux.map file when linking" if EXPERT + help + Selecting this option will pass "-Map=vmlinux.map" to ld + when linking vmlinux. That file can be useful for verifying + and debugging magic section games, and for seeing which + pieces of code get eliminated with + CONFIG_LD_DEAD_CODE_DATA_ELIMINATION. + config DEBUG_FORCE_WEAK_PER_CPU bool "Force weak per-cpu definitions" depends on DEBUG_KERNEL diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh index 3b261b0f74f0..bba58839db40 100755 --- a/scripts/link-vmlinux.sh +++ b/scripts/link-vmlinux.sh @@ -166,6 +166,12 @@ vmlinux_link() strip_debug=-Wl,--strip-debug fi + if [ -n "${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 }
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@rasmusvillemoes.dk> --- .gitignore | 1 + Makefile | 3 ++- lib/Kconfig.debug | 9 +++++++++ scripts/link-vmlinux.sh | 9 +++++++++ 4 files changed, 21 insertions(+), 1 deletion(-)