Commit 7064dc7f authored by Arnd Bergmann's avatar Arnd Bergmann Committed by Greg Kroah-Hartman

lkdtm: turn off kcov for lkdtm_rodata_do_nothing:

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).

Fixes: 5c9a8750 ("kernel: add kcov code coverage")
Fixes: 9a49a528 ("lkdtm: add function for testing .rodata section")
Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
Acked-by: default avatarDmitry Vyukov <dvyukov@google.com>
Acked-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent e22aa9d7
......@@ -61,6 +61,8 @@ 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 \
......
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