Re: [PATCH v7 22/27] binfmt_elf: Extract .note.gnu.property from an ELF file

On Tue, 2019-06-11 at 12:41 +0100, Dave Martin wrote:

On Mon, Jun 10, 2019 at 07:24:43PM +0200, Florian Weimer wrote:

quoted

* Yu-cheng Yu:

quoted

To me, looking at PT_GNU_PROPERTY and not trying to support anything is a
logical choice.  And it breaks only a limited set of toolchains.

I will simplify the parser and leave this patch as-is for anyone who wants
to
back-port.  Are there any objections or concerns?

Red Hat Enterprise Linux 8 does not use PT_GNU_PROPERTY and is probably
the largest collection of CET-enabled binaries that exists today.

For clarity, RHEL is actively parsing these properties today?

quoted

My hope was that we would backport the upstream kernel patches for CET,
port the glibc dynamic loader to the new kernel interface, and be ready
to run with CET enabled in principle (except that porting userspace
libraries such as OpenSSL has not really started upstream, so many
processes where CET is particularly desirable will still run without
it).

I'm not sure if it is a good idea to port the legacy support if it's not
part of the mainline kernel because it comes awfully close to creating
our own private ABI.

I guess we can aim to factor things so that PT_NOTE scanning is
available as a fallback on arches for which the absence of
PT_GNU_PROPERTY is not authoritative.

We can probably check PT_GNU_PROPERTY first, and fallback (based on ld-linux
version?) to PT_NOTE scanning?

Yu-cheng