From: "Martin Storsjö" <martin@martin.st>
To: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: nickc@redhat.com, binutils@sourceware.org,
linux-arm-kernel@lists.infradead.org, linux@armlinux.org.uk,
linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH v2] arm: detect buggy binutils when in thumb2 mode
Date: Thu, 23 Nov 2017 14:01:44 +0200 (EET) [thread overview]
Message-ID: <alpine.DEB.2.20.1711231358420.12424@cone.martin.st> (raw)
In-Reply-To: <20171123115021.25213-1-Jason@zx2c4.com>
On Thu, 23 Nov 2017, Jason A. Donenfeld wrote:
> On older versions of binutils, \sym points to an aligned address. On
> newer versions of binutils, \sym sometimes points to the unaligned thumb
> address in certain circumstances. In order to homogenize this behavior,
> rather than adding 1, we could simply OR in 1, so that already unaligned
> instructions don't change. While that works, the downside is that we have
> to add an `orr` instruction to a fast path. The assembler can't do this at
> assemble time via "|1" because "invalid operands (.text and *ABS* sections)
> for `|'". A better solution would be to have consistent binutils behavior,
> but that ship has sailed.
>
> So, this commit adds a detection mechanism, which began as a small thing
> from Russell King that I then rewrote to use pure bash instead of
> shelling out, so that it doesn't slow down the build process. The detection
> mechanism _could_ be used to modify the assembly we generate, but for now
> it's just being used to catch buggy binutils and abort the build process in
> that case.
>
> The rest of this commit message contains all of the relevant information
> about the boot bug when compiled in thumb2 mode.
>
> My tests concerned these versions:
> broken: GNU ld (Gentoo 2.29.1 p3) 2.29.1
> working: GNU ld (GNU Binutils for Ubuntu) 2.26.1
FWIW, this issue stems from this change:
https://sourceware.org/bugzilla/show_bug.cgi?id=21458
The same issue caused problems in libavcodec as well, where we chose to
work around the issue in this fashion:
https://git.libav.org/?p=libav.git;a=commitdiff;h=9dde6ab06c48f9447cd16f39bee33569cddb7be4;hp=547db1eaecd597031165a2bf637acaaacde52788
Related debian bug report, with a different workaround:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=870622
(In libav, we chose the workaround since the .eqv one suggested in the
debian bug report didn't really work well with assemblers for other
platforms.)
// Martin
WARNING: multiple messages have this Message-ID (diff)
From: martin@martin.st (Martin Storsjö)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2] arm: detect buggy binutils when in thumb2 mode
Date: Thu, 23 Nov 2017 14:01:44 +0200 (EET) [thread overview]
Message-ID: <alpine.DEB.2.20.1711231358420.12424@cone.martin.st> (raw)
In-Reply-To: <20171123115021.25213-1-Jason@zx2c4.com>
On Thu, 23 Nov 2017, Jason A. Donenfeld wrote:
> On older versions of binutils, \sym points to an aligned address. On
> newer versions of binutils, \sym sometimes points to the unaligned thumb
> address in certain circumstances. In order to homogenize this behavior,
> rather than adding 1, we could simply OR in 1, so that already unaligned
> instructions don't change. While that works, the downside is that we have
> to add an `orr` instruction to a fast path. The assembler can't do this at
> assemble time via "|1" because "invalid operands (.text and *ABS* sections)
> for `|'". A better solution would be to have consistent binutils behavior,
> but that ship has sailed.
>
> So, this commit adds a detection mechanism, which began as a small thing
> from Russell King that I then rewrote to use pure bash instead of
> shelling out, so that it doesn't slow down the build process. The detection
> mechanism _could_ be used to modify the assembly we generate, but for now
> it's just being used to catch buggy binutils and abort the build process in
> that case.
>
> The rest of this commit message contains all of the relevant information
> about the boot bug when compiled in thumb2 mode.
>
> My tests concerned these versions:
> broken: GNU ld (Gentoo 2.29.1 p3) 2.29.1
> working: GNU ld (GNU Binutils for Ubuntu) 2.26.1
FWIW, this issue stems from this change:
https://sourceware.org/bugzilla/show_bug.cgi?id=21458
The same issue caused problems in libavcodec as well, where we chose to
work around the issue in this fashion:
https://git.libav.org/?p=libav.git;a=commitdiff;h=9dde6ab06c48f9447cd16f39bee33569cddb7be4;hp=547db1eaecd597031165a2bf637acaaacde52788
Related debian bug report, with a different workaround:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=870622
(In libav, we chose the workaround since the .eqv one suggested in the
debian bug report didn't really work well with assemblers for other
platforms.)
// Martin
next prev parent reply other threads:[~2017-11-23 12:59 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-21 17:27 [PATCH] arm: ensure symbol is a thumb symbol in new binutils Jason A. Donenfeld
2017-11-21 17:27 ` Jason A. Donenfeld
2017-11-21 17:38 ` Russell King - ARM Linux
2017-11-21 17:38 ` Russell King - ARM Linux
2017-11-21 17:46 ` Jason A. Donenfeld
2017-11-21 17:46 ` Jason A. Donenfeld
2017-11-21 17:49 ` Russell King - ARM Linux
2017-11-21 17:49 ` Russell King - ARM Linux
2017-11-22 23:34 ` Jason A. Donenfeld
2017-11-22 23:34 ` Jason A. Donenfeld
2017-11-23 10:35 ` Russell King - ARM Linux
2017-11-23 10:35 ` Russell King - ARM Linux
2017-11-23 10:47 ` Fwd: " Jason A. Donenfeld
2017-11-23 10:47 ` Jason A. Donenfeld
2017-11-23 11:48 ` [PATCH] arm: detect buggy binutils when in thumb2 mode Jason A. Donenfeld
2017-11-23 11:48 ` Jason A. Donenfeld
2017-11-23 11:50 ` [PATCH v2] " Jason A. Donenfeld
2017-11-23 11:50 ` Jason A. Donenfeld
2017-11-23 12:01 ` Martin Storsjö [this message]
2017-11-23 12:01 ` Martin Storsjö
2017-11-23 14:02 ` Fwd: [PATCH] arm: ensure symbol is a thumb symbol in new binutils Russell King - ARM Linux
2017-11-23 14:02 ` Russell King - ARM Linux
2017-11-23 14:26 ` Ard Biesheuvel
2017-11-23 14:26 ` Ard Biesheuvel
2017-11-23 14:26 ` Ard Biesheuvel
[not found] ` <765227b5-981d-0cea-c831-73cfe2f58721@redhat.com>
[not found] ` <aaf57bb5-13e6-852c-0f67-f72aedef0e79@gmail.com>
[not found] ` <254af731-459b-1f1d-2d93-27c5a91e7bfb@redhat.com>
2018-05-31 21:16 ` [Buildroot] " Romain Naour
2018-06-01 8:28 ` Christophe PRIOUZEAU
[not found] ` <2a8151c1-644e-a6b0-9a21-2c570ac7000b@redhat.com>
2018-06-05 8:52 ` Christophe PRIOUZEAU
[not found] ` <ec2b0134-6c4a-53ff-4ae2-69c3f0646ded@redhat.com>
2018-06-05 14:11 ` Christophe PRIOUZEAU
[not found] ` <1d8f302b-5ece-9921-b930-8c4bca61743e@redhat.com>
2018-06-11 14:47 ` Christophe PRIOUZEAU
[not found] ` <1d8f302b-5ece-9921-b930-8c4bca61743e@redhat. com>
[not found] ` <CAJA7tRbsNa7oTS-1sLs0WpA74RZr0R-v=sCyQxbDam5Gb7fYHA@mail.gmail.com>
[not found] ` <be2db8d4-7c12-2706-5084-322aa659c3bc@redhat.com>
2018-06-18 15:04 ` Christophe PRIOUZEAU
2018-06-18 18:29 ` Romain Naour
[not found] ` <062a421f-a669-fc1c-91e0-88cf73794414@redhat.com>
2018-06-19 12:27 ` Christophe PRIOUZEAU
2018-01-16 8:43 ` Chen-Yu Tsai
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