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From: "nsz at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug dynamic-link/23293] aarch64: getauxval is broken when run as
 ld.so ./exe and ld.so adjusts argv on the stack
Date: Thu, 25 Jun 2020 15:34:42 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D23293

Szabolcs Nagy <nsz at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |nsz at gcc dot gnu.org

--- Comment #4 from Szabolcs Nagy <nsz at gcc dot gnu.org> ---
(In reply to Florian Weimer from comment #3)
> (In reply to Michael Hudson-Doyle from comment #2)
> > I've just run into this because it causes a glibc test failure when
> > libnss-systemd is enabled
> > (https://bugs.launchpad.net/ubuntu/+source/glibc/+bug/1869364).
> >=20
> > Would a fix be for _dl_start_user to update _dl_auxv in the same way it
> > updates _dl_argv? Or is that just naive (start up code confuses me!)
>=20
> I think this should work. There does not seems to be anything that stores
> the address if auxv entries, only values read from the vector.

it may work, but i think _dl_start_user stack handling should
not be updated, it should be removed: the logic is backwards:

most targets have fragile asm for the rtld start code to shuffle
around entries on the stack, but such shuffling can be done in c
in the generic code (e.g. in dl_main).

this would also fix the (imo security) bug that the protection
of dl data is not consistent across targets (DL_ARGV_NOT_RELRO).

and all this mess is for saving a few cycles on targets where
you don't need to do the shuffling. i think the generic code
should work for all targets and those who wish to optimize
add some hacks (e.g. ifdef out the shuffling), not the other
way around.

i didnt get the chance to clean this up yet, so it's not fixed.

--=20
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