Re: [PATCH] lkdtm: Fix content of section containing lkdtm_rodata_do_nothing()

On Fri, Oct 08, 2021 at 11:09:47AM -0700, Nick Desaulniers wrote:

On Fri, Oct 8, 2021 at 9:59 AM Christophe Leroy
[off-list ref] wrote:

quoted

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")

Thanks for the patch; sorry I broke this.
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

Hah! Whoops; sorry I don't have an inverted version of this test! I
should have caught this when it broke. :|

-Kees

-- 
Kees Cook