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From: Florian Weimer <fweimer@redhat.com>
To: Adhemerval Zanella via Libc-alpha <libc-alpha@sourceware.org>
Cc: Fangrui Song <maskray@google.com>,
	 Carlos O'Donell <carlos@redhat.com>,
	"H.J. Lu" <hjl.tools@gmail.com>,
	 Adhemerval Zanella <adhemerval.zanella@linaro.org>,
	 Rich Felker <dalias@libc.org>
Subject: Re: Can DT_RELR catch up glibc 2.35?
Date: Wed, 17 Nov 2021 23:12:30 +0100	[thread overview]
Message-ID: <8735nu2zzl.fsf@oldenburg.str.redhat.com> (raw)
In-Reply-To: <e9dd6c87-318d-8645-6a9e-46fda37cffb2@linaro.org> (Adhemerval Zanella via Libc-alpha's message of "Tue, 16 Nov 2021 18:07:40 -0300")

* Adhemerval Zanella via Libc-alpha:

> Afaik kernel does not pass such information on auxv vector (we might ask
> for a AT_EHDR eventually) so a potential fix will cost us some extra 
> syscalls on every program execution (to read and check the ELF Header with 
> similar test done on open_verify()).

We need a change to the auxiliary vector to make this reliable.

AT_PHDR - sizeof (ElfW(Ehdr)) is not a replacement for AT_EHDR because I
don't think the program headers must come immediately after the ELF
header.  Otherwise, we wouldn't need both e_phoff and e_ehsize.

> So I think the best course of action for this issue is indeed fix EI_ABIVERSION
> and make DT_RELR a new 'libc-abis' entry.  We might backport the EI_ABIVERSION
> fix to some older releases, and distros that want to use DT_RELR
> should do also.

I agree.  Waiting for the proposed flags in gABI to appear does not seem
attractive to me.

Thanks,
Florian


  parent reply	other threads:[~2021-11-17 22:12 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-12  7:47 Fangrui Song
2021-11-16 21:07 ` Adhemerval Zanella
2021-11-17  0:26   ` H.J. Lu
2021-11-17 12:46     ` Adhemerval Zanella
2021-11-17 13:14       ` H.J. Lu
2021-11-18  0:30         ` Fangrui Song
2021-11-18  9:45           ` Florian Weimer
2021-11-18 23:27             ` Fangrui Song
2021-11-19 11:51               ` Adhemerval Zanella
2021-11-24  1:10               ` Sam James
2021-11-19 19:18           ` Rich Felker
2021-11-17 22:12   ` Florian Weimer [this message]
2021-11-18 12:45     ` Adhemerval Zanella

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