Messages in this thread | | | Subject | Re: [PATCH 3/5] lkdtm: add function for testing .rodata section | From | Laura Abbott <> | Date | Wed, 8 Jun 2016 09:15:23 -0700 |
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On 06/08/2016 08:46 AM, Kees Cook wrote: > On Tue, Jun 7, 2016 at 6:02 PM, Laura Abbott <labbott@redhat.com> wrote: >> On 06/07/2016 02:57 PM, Kees Cook wrote: >>> >>> This adds a function that lives in the .rodata section. The section >>> flags are corrected using objcopy since there is no way with gcc to >>> declare section flags in an architecture-agnostic way. >>> >> >> Permit me to be the bearer of bad architecture news once again. With >> arm64 cross compiler (both Fedora 6.1.1 and Linaro 5.1) >> >> CC drivers/misc/lkdtm_rodata.o >> OBJCOPY drivers/misc/lkdtm_rodata_objcopy.o >> LD drivers/misc/lkdtm.o >> drivers/misc/lkdtm_rodata_objcopy.o: file not recognized: File format not >> recognized >> scripts/Makefile.build:423: recipe for target 'drivers/misc/lkdtm.o' failed >> make[2]: *** [drivers/misc/lkdtm.o] Error 1 >> scripts/Makefile.build:440: recipe for target 'drivers/misc' failed >> make[1]: *** [drivers/misc] Error 2 >> Makefile:985: recipe for target 'drivers' failed >> make: *** [drivers] Error 2 >> >> >> As far as I can tell this is because arm64 defines OBJCOPYFLAGS and they get >> propagated to objcopy >> >> aarch64-linux-gnu-objcopy -O binary -R .note -R .note.gnu.build-id -R >> .comment >> -S --set-section-flags .text=alloc,readonly >> --rename-section .text=.rodata drivers/misc/lkdtm_rodata.o >> drivers/misc/lkdtm_rodata_objcopy.o >> >> vs x86 >> >> objcopy --set-section-flags .text=alloc,readonly --rename-section >> .text=.rodata >> drivers/misc/lkdtm_rodata.o drivers/misc/lkdtm_rodata_objcopy.o >> >> >> specifically it's the -O binary that seems to break things, the same failure >> happens on x86 as well with the the same commands. It works if I clear out >> the OBJCOPYFLAGS variable first but I don't think that's the correct way to >> fix this. >> >> Thanks, >> Laura >> >> >>> Signed-off-by: Kees Cook <keescook@chromium.org> >>> --- >>> drivers/misc/Makefile | 7 +++++++ >>> drivers/misc/lkdtm.h | 6 ++++++ >>> drivers/misc/lkdtm_core.c | 24 +++++++++++++++++------- >>> drivers/misc/lkdtm_rodata.c | 10 ++++++++++ >>> 4 files changed, 40 insertions(+), 7 deletions(-) >>> create mode 100644 drivers/misc/lkdtm.h >>> create mode 100644 drivers/misc/lkdtm_rodata.c >>> >>> diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile >>> index c3cb6ad8cc37..b2d3d68dfa22 100644 >>> --- a/drivers/misc/Makefile >>> +++ b/drivers/misc/Makefile >>> @@ -59,3 +59,10 @@ obj-$(CONFIG_CXL_BASE) += cxl/ >>> obj-$(CONFIG_PANEL) += panel.o >>> >>> lkdtm-$(CONFIG_LKDTM) += lkdtm_core.o >>> +lkdtm-$(CONFIG_LKDTM) += lkdtm_rodata_objcopy.o >>> + >>> +OBJCOPYFLAGS_lkdtm_rodata_objcopy.o := \ >>> + --set-section-flags .text=alloc,readonly \ >>> + --rename-section .text=.rodata >>> +$(obj)/lkdtm_rodata_objcopy.o: $(obj)/lkdtm_rodata.o >>> + $(call if_changed,objcopy) > > Uhhhh... How is arm64 injecting those extra flags? OBJCOPYFLAGS is > being set with := here? >
Looks like intended behavior from scripts/Makefile.lib:
# Objcopy # ---------------------------------------------------------------------------
quiet_cmd_objcopy = OBJCOPY $@ cmd_objcopy = $(OBJCOPY) $(OBJCOPYFLAGS) $(OBJCOPYFLAGS_$(@F)) $< $@
OBJCOPYFLAGS_$@ is separate from OBJCOPYFLAGS which makes sense for the original intentions although not what we want here. Some Makefile wizardry is probably needed.
> In related news I need to figure out how to get my cross-compiler > builds more well scripted... > > -Kees >
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