On Tue, Mar 28, 2017 at 11:57 AM, Arnd Bergmann <[email protected]> wrote: > I ran into a link error on ARM64 for lkdtm_rodata_do_nothing: > > drivers/misc/built-in.o: In function `lkdtm_rodata_do_nothing': > :(.rodata+0x68c8): relocation truncated to fit: R_AARCH64_CALL26 against > symbol `__sanitizer_cov_trace_pc' defined in .text section in > kernel/built-in.o > > I did not analyze this further, but my theory is that we would need a > trampoline > to call __sanitizer_cov_trace_pc(), but the linker (correctly) only adds > trampolines > for callers in executable sections. > > Disabling KCOV for this one file avoids the build failure with no > other practical downsides I can think of. > > The problem can only happen on kernels that contain both kcov and > lkdtm, so if we want to backport this, it should be in the earliest > version that has both (v4.8). > > Cc: Dmitry Vyukov <[email protected]> > Cc: Kees Cook <[email protected]> > Fixes: 5c9a8750a640 ("kernel: add kcov code coverage") > Fixes: 9a49a528dcf3 ("lkdtm: add function for testing .rodata section") > Signed-off-by: Arnd Bergmann <[email protected]> > --- > drivers/misc/Makefile | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile > index 4925ea8e1952..7a321047bfbe 100644 > --- a/drivers/misc/Makefile > +++ b/drivers/misc/Makefile > @@ -63,6 +63,8 @@ lkdtm-$(CONFIG_LKDTM) += lkdtm_perms.o > lkdtm-$(CONFIG_LKDTM) += lkdtm_rodata_objcopy.o > lkdtm-$(CONFIG_LKDTM) += lkdtm_usercopy.o > > +KCOV_INSTRUMENT_lkdtm_rodata.o := n > + > OBJCOPYFLAGS := > OBJCOPYFLAGS_lkdtm_rodata_objcopy.o := \ > --set-section-flags .text=alloc,readonly \ > -- > 2.9.0
Acked-by: Dmitry Vyukov <[email protected]>
