* [4.14 PATCH] lkdtm: support llvm-objcopy
@ 2019-08-12 21:17 Nick Desaulniers
2019-08-13 6:09 ` Greg Kroah-Hartman
0 siblings, 1 reply; 2+ messages in thread
From: Nick Desaulniers @ 2019-08-12 21:17 UTC (permalink / raw)
To: stable
Cc: pcc, Nick Desaulniers, Nathan Chancellor, Alan Modra,
Jordan Rupprect, Kees Cook, Greg Kroah-Hartman
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)
--
2.23.0.rc1.153.gdeed80330f-goog
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [4.14 PATCH] lkdtm: support llvm-objcopy
2019-08-12 21:17 [4.14 PATCH] lkdtm: support llvm-objcopy Nick Desaulniers
@ 2019-08-13 6:09 ` Greg Kroah-Hartman
0 siblings, 0 replies; 2+ messages in thread
From: Greg Kroah-Hartman @ 2019-08-13 6:09 UTC (permalink / raw)
To: Nick Desaulniers
Cc: stable, pcc, Nathan Chancellor, Alan Modra, Jordan Rupprect, Kees Cook
On Mon, Aug 12, 2019 at 02:17:50PM -0700, Nick Desaulniers wrote:
> This backport is for 4.14. It should allow us to use llvm-objcopy for
> RELR relocations on arm64 in Android.
I don't object to this, but the odds that you are actually using the
lkdtm driver on Android systems is pretty slim :)
thanks,
greg k-h
^ permalink raw reply [flat|nested] 2+ messages in thread
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