On Wed, May 15, 2019 at 11:12:04AM -0700, 'Nick Desaulniers' via Clang Built Linux wrote:
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 nathanchance@gmail.com
Doesn't look like this got updated. I don't want to make you send a v3 just for that though since it's purely cosmetic and adding my tag below will ensure I get copied on any backports and such.
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 Signed-off-by: Nick Desaulniers ndesaulniers@google.com
Reviewed-by: Nathan Chancellor natechancellor@gmail.com
Changes from v1 -> v2:
- add load flag, as per Kees and Alan.
- update commit message to mention reason for load flag.
- add Kees' and Alan's suggested by.
- carry Kees' Ack.
- cc stable.
drivers/misc/lkdtm/Makefile | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/drivers/misc/lkdtm/Makefile b/drivers/misc/lkdtm/Makefile index 951c984de61a..fb10eafe9bde 100644 --- a/drivers/misc/lkdtm/Makefile +++ b/drivers/misc/lkdtm/Makefile @@ -15,8 +15,7 @@ KCOV_INSTRUMENT_rodata.o := n OBJCOPYFLAGS := OBJCOPYFLAGS_rodata_objcopy.o := \
--set-section-flags .text=alloc,readonly \--rename-section .text=.rodata
--rename-section .text=.rodata,alloc,readonly,loadtargets += rodata.o rodata_objcopy.o $(obj)/rodata_objcopy.o: $(obj)/rodata.o FORCE $(call if_changed,objcopy) -- 2.21.0.1020.gf2820cf01a-goog