From: William Roberts <bill.c.roberts@gmail.com>
To: Stephen Smalley <stephen.smalley.work@gmail.com>
Cc: SElinux list <selinux@vger.kernel.org>,
Ulrich Drepper <drepper@redhat.com>,
Ondrej Mosnacek <omosnace@redhat.com>,
Petr Lautrbach <plautrba@redhat.com>,
William Roberts <william.c.roberts@intel.com>
Subject: Re: [PATCH 2/3] Makefile: add -fno-semantic-interposition
Date: Fri, 28 Feb 2020 07:59:03 -0600 [thread overview]
Message-ID: <CAFftDdrNcbOWGa-o3TaeagF1TL7NnFxk2Osm_rembw+HH1wACw@mail.gmail.com> (raw)
In-Reply-To: <CAEjxPJ7bLsGHQ4-wz19ntft=GYvWMLL5bZd8hAimbu1hzc5+Ew@mail.gmail.com>
On Fri, Feb 28, 2020 at 7:50 AM Stephen Smalley
<stephen.smalley.work@gmail.com> wrote:
>
> On Thu, Feb 27, 2020 at 6:01 PM <bill.c.roberts@gmail.com> wrote:
> >
> > From: William Roberts <william.c.roberts@intel.com>
> >
> > Add -fno-semantic-interposition to CFLAGS. This will restore
> > the DSO infrastructures protections to insure internal callers
> > of exported symbols call into libselinux and not something laoding first
> > in the library list.
> >
> > Clang has this enabled by default.
> >
> > Signed-off-by: William Roberts <william.c.roberts@intel.com>
>
> I'm fine with this but since Nicolas pointed out the option of using
> -Bsymbolic to
> the linker as an alternative to hidden_def/hidden_proto in
> https://github.com/SELinuxProject/selinux/issues/204#issuecomment-591092288
> I was wondering how they differ. I guess -Bsymbolic only affects the
> linker while -fno-semantic-interposition
> permits the compiler to further optimize the code.
That's my understanding of the difference as well. -B is only link
time, so the compiler can't
really optimize the calls, but IIUC the compiler can only optimize
whats in the compilation
unit, so it can only optimize call sites for calls within the compilation unit.
-B also only works for elf builds, so we would conditionally need to
modify LDFLAGS based
on host type. The compiler option is just a clang/gcc split, which is
already there. To go
to symbolic we would have to conditionally set that... a tad bit more work :-p
next prev parent reply other threads:[~2020-02-28 13:59 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-27 23:01 libselinux: drop dso.h bill.c.roberts
2020-02-27 23:01 ` [PATCH 1/3] dso: drop hidden_proto and hidden_def bill.c.roberts
2020-02-27 23:01 ` [PATCH 2/3] Makefile: add -fno-semantic-interposition bill.c.roberts
2020-02-28 13:51 ` Stephen Smalley
2020-02-28 13:59 ` William Roberts [this message]
2020-03-01 20:32 ` Nicolas Iooss
2020-03-02 16:41 ` [V4] libselinux: drop dso.h bill.c.roberts
2020-03-02 16:41 ` [PATCH v4 1/4] dso: drop hidden_proto and hidden_def bill.c.roberts
2020-03-02 16:41 ` [PATCH v4 2/4] Makefile: add -fno-semantic-interposition bill.c.roberts
2020-03-02 16:41 ` [PATCH v4 3/4] Makefile: add linker script to minimize exports bill.c.roberts
2020-03-02 16:41 ` [PATCH v4 4/4] libselinux: drop symbols from map bill.c.roberts
2020-03-03 18:58 ` [V4] libselinux: drop dso.h Stephen Smalley
2020-03-04 12:26 ` Ondrej Mosnacek
2020-03-04 13:48 ` William Roberts
2020-03-04 13:15 ` Petr Lautrbach
2020-03-05 12:42 ` Petr Lautrbach
2020-03-05 16:12 ` William Roberts
2020-03-05 19:09 ` William Roberts
2020-03-11 18:14 ` Stephen Smalley
2020-03-12 14:05 ` William Roberts
2020-02-27 23:01 ` [PATCH 3/3] Makefile: add linker script to minimize exports bill.c.roberts
2020-02-28 13:36 ` Stephen Smalley
2020-02-28 13:38 ` William Roberts
2020-02-28 14:05 ` [V2] libselinux: drop dso.h bill.c.roberts
2020-02-28 14:05 ` [PATCH v2 1/4] dso: drop hidden_proto and hidden_def bill.c.roberts
2020-02-28 14:05 ` [PATCH v2 2/4] Makefile: add -fno-semantic-interposition bill.c.roberts
2020-02-28 14:05 ` [PATCH v2 3/4] Makefile: add linker script to minimize exports bill.c.roberts
2020-02-28 14:05 ` [PATCH v2 4/4] libselinux: drop symbols from map bill.c.roberts
2020-02-28 15:39 ` Stephen Smalley
2020-02-28 15:40 ` William Roberts
2020-02-28 15:48 ` [V3] libselinux: drop dso.h bill.c.roberts
2020-02-28 15:48 ` [PATCH v3 1/4] dso: drop hidden_proto and hidden_def bill.c.roberts
2020-02-28 15:48 ` [PATCH v3 2/4] Makefile: add -fno-semantic-interposition bill.c.roberts
2020-02-28 15:48 ` [PATCH v3 3/4] Makefile: add linker script to minimize exports bill.c.roberts
[not found] ` <CAEjxPJ7CuMf5QeW_jjEonRN=kfcpTV8c4UnUMyEjyb2hee1YXg@mail.gmail.com>
[not found] ` <CAFftDdpeP39qvXNTe06EWkc3Kp_TMu5bGOf8WN6Q-k2Cehn_3w@mail.gmail.com>
2020-02-28 19:05 ` Stephen Smalley
2020-03-01 20:04 ` Nicolas Iooss
2020-02-28 15:48 ` [PATCH v3 4/4] libselinux: drop symbols from map bill.c.roberts
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