diff mbox series

[v3] lkdtm: support llvm-objcopy

Message ID 20190515182441.30990-1-ndesaulniers@google.com
State Accepted
Commit e9e08a07385e08f1a7f85c5d1e345c21c9564963
Headers show
Series [v3] lkdtm: support llvm-objcopy | expand

Commit Message

Nick Desaulniers May 15, 2019, 6:24 p.m. UTC 
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>

---
Changes from v2 -> v3:
* correct Nathan's email address and collect his reviewed by.
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

Comments

Nathan Chancellor May 17, 2019, 4:06 a.m. UTC | #1 
On Fri, May 17, 2019 at 12:10:02AM +0000, Sasha Levin wrote:
> Hi,

> 

> [This is an automated email]

> 

> This commit has been processed because it contains a -stable tag.

> The stable tag indicates that it's relevant for the following trees: all


Nick, the stable tag should probably specify 4.8+ since the commit it
fixes came in during 4.8-rc1.

Cc: stable@vger.kernel.org # 4.8+

Might also help to add:

Fixes: 9a49a528dcf3 ("lkdtm: add function for testing .rodata section")

> 

> The bot has tested the following trees: v5.1.2, v5.0.16, v4.19.43, v4.14.119, v4.9.176, v4.4.179, v3.18.140.

> 

> v5.1.2: Build OK!

> v5.0.16: Build OK!

> v4.19.43: Build OK!

> v4.14.119: Failed to apply! Possible dependencies:

>     039a1c42058d ("lkdtm: Relocate code to subdirectory")


However, it will still need a manual backport because of the lack of
this commit. I've attached the current patch backported for reference,
the git am flags '-3 -p4 --directory=drivers/misc' help get it proper
then the conflict is rather easy to resolve.

Thanks,
Nathan
Nathan Chancellor May 17, 2019, 4:09 a.m. UTC | #2 
On Thu, May 16, 2019 at 09:06:13PM -0700, Nathan Chancellor wrote:
> On Fri, May 17, 2019 at 12:10:02AM +0000, Sasha Levin wrote:

> > Hi,

> > 

> > [This is an automated email]

> > 

> > This commit has been processed because it contains a -stable tag.

> > The stable tag indicates that it's relevant for the following trees: all

> 

> Nick, the stable tag should probably specify 4.8+ since the commit it

> fixes came in during 4.8-rc1.

> 

> Cc: stable@vger.kernel.org # 4.8+

> 

> Might also help to add:

> 

> Fixes: 9a49a528dcf3 ("lkdtm: add function for testing .rodata section")

> 

> > 

> > The bot has tested the following trees: v5.1.2, v5.0.16, v4.19.43, v4.14.119, v4.9.176, v4.4.179, v3.18.140.

> > 

> > v5.1.2: Build OK!

> > v5.0.16: Build OK!

> > v4.19.43: Build OK!

> > v4.14.119: Failed to apply! Possible dependencies:

> >     039a1c42058d ("lkdtm: Relocate code to subdirectory")

> 

> However, it will still need a manual backport because of the lack of

> this commit. I've attached the current patch backported for reference,


Would help if I actually did this... :^)

> the git am flags '-3 -p4 --directory=drivers/misc' help get it proper

> then the conflict is rather easy to resolve.

> 

> Thanks,

> Nathan
From 10c0a74a8d92669b91b66efe6b72550fc24e8e7d Mon Sep 17 00:00:00 2001
From: Nick Desaulniers <ndesaulniers@google.com>

Date: Wed, 15 May 2019 11:24:41 -0700
Subject: [PATCH] lkdtm: support llvm-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 <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: Nathan Chancellor <natechancellor@gmail.com>

---
 drivers/misc/Makefile | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index c3c8624f4d95..805835c2b99b 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -70,8 +70,7 @@ 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)
-- 
2.22.0.rc0
diff mbox series

Patch

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)