From: Philipp Rudo <email@example.com> To: Alexander Egorenkov <firstname.lastname@example.org> Cc: email@example.com, firstname.lastname@example.org, email@example.com Subject: Re: [PATCH 1/1] s390/kexec: handle R_390_PLT32DBL reloc entries in arch_kexec_do_relocs() Date: Thu, 9 Dec 2021 12:00:37 +0100 [thread overview] Message-ID: <20211209120037.050e3db1@rhtmp> (raw) In-Reply-To: <firstname.lastname@example.org> Hi Alexander, On Wed, 08 Dec 2021 18:42:05 +0100 Alexander Egorenkov <email@example.com> wrote: > Hi Philipp, > > Philipp Rudo <firstname.lastname@example.org> writes: > > > Hi Alexander, > > > > thanks for taking care of this so fast! > > > > My personal approach was slightly different (see below). The idea > > behind this was that arch_kexec_do_relocs is also used by others which > > might have a PLT. For them your approach would mean an ABI breakage. On > > the other hand in case the other users have the same problem they would > > need to handle it for themselves. Not sure what's the better approach. > > > > I'm also fine with your proposal for the fix. > > If i'm not mistaken, arch_kexec_do_relocs() is used in decompressor and > for purgatory at the moment, and both should have all relocs resolved. > Do we have more users of arch_kexec_do_relocs() ? That was the reason i > added the fix to arch_kexec_do_relocs(). no, there are no other users of arch_kexec_do_relocs other than kexec_file and kaslr at the moment. From a technical perspective your patch was totally fine for todays use cases. My concern was more for a potential future user. But maybe I was a little bit overcautious... > Now i'm actually wondering why we don't have any issues with > decompressor, probably because we do the final link where all > PLT-relative addresses are fixed. Because i see plenty of R_390_PLT32DBL > in startup.o e.g. IIUC, the culprit is the '-r' option in the LDFLAGS. With this option the output can be used again as input _for ld_. The way I interpret this is that ld can (and apparently does) use any internal convention without complying with the ABI when this option is given. kaslr doesn't use '-r' but a combination of -fPIE (CFLAGS) and -pie (LDFLAGS) so they are not affected by ld's internal behavior. Maybe it's worth investigating in the long run if the purgatory could be build with -fPIE/-pie as well. Thanks Philipp
prev parent reply other threads:[~2021-12-09 11:00 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-12-08 10:58 Alexander Egorenkov 2021-12-08 13:59 ` Philipp Rudo 2021-12-08 17:42 ` Alexander Egorenkov 2021-12-09 11:00 ` Philipp Rudo [this message]
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