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    Subject[PATCH 5.10 032/563] lkdtm: Fix content of section containing lkdtm_rodata_do_nothing()
    Date
    From: Christophe Leroy <christophe.leroy@csgroup.eu>

    commit bc93a22a19eb2b68a16ecf04cdf4b2ed65aaf398 upstream.

    On a kernel without CONFIG_STRICT_KERNEL_RWX, running EXEC_RODATA
    test leads to "Illegal instruction" failure.

    Looking at the content of rodata_objcopy.o, we see that the
    function content zeroes only:

    Disassembly of section .rodata:

    0000000000000000 <.lkdtm_rodata_do_nothing>:
    0: 00 00 00 00 .long 0x0

    Add the contents flag in order to keep the content of the section
    while renaming it.

    Disassembly of section .rodata:

    0000000000000000 <.lkdtm_rodata_do_nothing>:
    0: 4e 80 00 20 blr

    Fixes: e9e08a07385e ("lkdtm: support llvm-objcopy")
    Cc: stable@vger.kernel.org
    Cc: Kees Cook <keescook@chromium.org>
    Cc: Arnd Bergmann <arnd@arndb.de>
    Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Cc: Nick Desaulniers <ndesaulniers@google.com>
    Cc: Nathan Chancellor <nathan@kernel.org>
    Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
    Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
    Signed-off-by: Kees Cook <keescook@chromium.org>
    Link: https://lore.kernel.org/r/8900731fbc05fb8b0de18af7133a8fc07c3c53a1.1633712176.git.christophe.leroy@csgroup.eu
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/misc/lkdtm/Makefile | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/drivers/misc/lkdtm/Makefile
    +++ b/drivers/misc/lkdtm/Makefile
    @@ -16,7 +16,7 @@ KCOV_INSTRUMENT_rodata.o := n

    OBJCOPYFLAGS :=
    OBJCOPYFLAGS_rodata_objcopy.o := \
    - --rename-section .noinstr.text=.rodata,alloc,readonly,load
    + --rename-section .noinstr.text=.rodata,alloc,readonly,load,contents
    targets += rodata.o rodata_objcopy.o
    $(obj)/rodata_objcopy.o: $(obj)/rodata.o FORCE
    $(call if_changed,objcopy)

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