| Message ID | 20190515181204.20859-1-ndesaulniers@google.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v2] lkdtm: support llvm-objcopy | expand |
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,load > targets += rodata.o rodata_objcopy.o > $(obj)/rodata_objcopy.o: $(obj)/rodata.o FORCE > $(call if_changed,objcopy) > -- > 2.21.0.1020.gf2820cf01a-goog >
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,load targets += rodata.o rodata_objcopy.o $(obj)/rodata_objcopy.o: $(obj)/rodata.o FORCE $(call if_changed,objcopy)
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> 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> --- 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(-) -- 2.21.0.1020.gf2820cf01a-goog