commit e9e08a07385e08f1a7f85c5d1e345c21c9564963 upstream.
With CONFIG_LKDTM=y and make OBJCOPY=llvm-objcopy, llvm-objcopy errors: llvm-objcopy: error: --set-section-flags=.text conflicts with --rename-section=.text=.rodata
Rather than support setting flags then renaming sections vs renaming then setting flags, it's simpler to just change both at the same time via --rename-section. Adding the load flag is required for GNU objcopy to mark .rodata Type as PROGBITS after the rename.
This can be verified with: $ readelf -S drivers/misc/lkdtm/rodata_objcopy.o ... Section Headers: [Nr] Name Type Address Offset Size EntSize Flags Link Info Align ... [ 1] .rodata PROGBITS 0000000000000000 00000040 0000000000000004 0000000000000000 A 0 0 4 ...
Which shows that .text is now renamed .rodata, the alloc flag A is set, the type is PROGBITS, and the section is not flagged as writeable W.
Cc: stable@vger.kernel.org Link: https://sourceware.org/bugzilla/show_bug.cgi?id=24554 Link: https://github.com/ClangBuiltLinux/linux/issues/448 Reported-by: Nathan Chancellor natechancellor@gmail.com Suggested-by: Alan Modra amodra@gmail.com Suggested-by: Jordan Rupprect rupprecht@google.com Suggested-by: Kees Cook keescook@chromium.org Acked-by: Kees Cook keescook@chromium.org Reviewed-by: Nathan Chancellor natechancellor@gmail.com Signed-off-by: Nick Desaulniers ndesaulniers@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- This backport is for 4.14. It should allow us to use llvm-objcopy for RELR relocations on arm64 in Android.
drivers/misc/Makefile | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile index ad0e64fdba34..76f6a4f628b3 100644 --- a/drivers/misc/Makefile +++ b/drivers/misc/Makefile @@ -69,8 +69,7 @@ KCOV_INSTRUMENT_lkdtm_rodata.o := n
OBJCOPYFLAGS := OBJCOPYFLAGS_lkdtm_rodata_objcopy.o := \ - --set-section-flags .text=alloc,readonly \ - --rename-section .text=.rodata + --rename-section .text=.rodata,alloc,readonly,load targets += lkdtm_rodata.o lkdtm_rodata_objcopy.o $(obj)/lkdtm_rodata_objcopy.o: $(obj)/lkdtm_rodata.o FORCE $(call if_changed,objcopy)