From: Kees Cook <keescook@chromium.org>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Nathan Chancellor <natechancellor@gmail.com>,
clang-built-linux <clang-built-linux@googlegroups.com>,
Nathan Chancellor <nathanchance@gmail.com>,
Jordan Rupprect <rupprecht@google.com>,
Arnd Bergmann <arnd@arndb.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] lkdtm: support llvm-objcopy
Date: Wed, 15 May 2019 09:42:56 -0700 [thread overview]
Message-ID: <201905150935.3AFE8CC68B@keescook> (raw)
In-Reply-To: <CAKwvOdn2ESh+-T8=YFT=W=gjZHPpCY8QJVS7ytPHM04tN1v13g@mail.gmail.com>
On Tue, May 14, 2019 at 01:24:37PM -0700, Nick Desaulniers wrote:
> On Tue, May 14, 2019 at 11:11 AM Kees Cook <keescook@chromium.org> wrote:
> >
> > On Mon, May 13, 2019 at 04:50:05PM -0700, Nick Desaulniers wrote:
> > > On Mon, May 13, 2019 at 4:29 PM Nathan Chancellor
> > > <natechancellor@gmail.com> wrote:
> > > >
> > > > On Mon, May 13, 2019 at 03:21:09PM -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.
>
> I'm not sure I want to call it a bug in the initial implementation. I've filed:
> https://sourceware.org/bugzilla/show_bug.cgi?id=24554 for
> clarification. Jordan, I hope you can participate in any discussion
> there?
Based on the hint from Alan Modra, it seems PROGBITS/NOBITS can be
controlled with the presence/absence of the "load" section flag. This
appears to work for both BFD and LLVM:
$ objcopy --rename-section .text=.rodata,alloc,readonly,load rodata.o rodata_objcopy.o
$ readelf -WS rodata_objcopy.o | grep \.rodata
[ 1] .rodata PROGBITS 0000000000000000 000040 000002 00 A 0 0 16
$ llvm-objcopy --rename-section .text=.rodata,alloc,readonly,load rodata.o rodata_objcopy.o
$ readelf -WS rodata_objcopy.o | grep \.rodata
[ 1] .rodata PROGBITS 0000000000000000 000040 000002 00 A 0 0 16
So, that's an easy change that could be folded into the original version
of this patch (no need for my two-phase work-around).
--
Kees Cook
next prev parent reply other threads:[~2019-05-15 16:43 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-13 22:21 [PATCH] lkdtm: support llvm-objcopy Nick Desaulniers
2019-05-13 22:26 ` Nick Desaulniers
2019-05-13 23:04 ` Kees Cook
2019-05-13 23:29 ` Nathan Chancellor
2019-05-13 23:38 ` Jordan Rupprecht
2019-05-13 23:47 ` Nathan Chancellor
2019-05-13 23:50 ` Nick Desaulniers
2019-05-14 18:10 ` Kees Cook
2019-05-14 20:24 ` Nick Desaulniers
2019-05-15 16:42 ` Kees Cook [this message]
2019-05-15 17:37 ` Nick Desaulniers
2019-05-15 18:12 ` [PATCH v2] " Nick Desaulniers
2019-05-15 18:19 ` Nathan Chancellor
2019-05-15 18:24 ` [PATCH v3] " Nick Desaulniers
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