From: Quentin Casasnovas <quentin.casasnovas@oracle.com>
To: Guenter Roeck <linux@roeck-us.net>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>,
linux-next@vger.kernel.org, linux-kernel@vger.kernel.org,
Quentin Casasnovas <quentin.casasnovas@oracle.com>,
Rusty Russell <rusty@rustcorp.com.au>
Subject: Re: linux-next: Tree for Apr 14 (crash due to modpost patch)
Date: Tue, 14 Apr 2015 18:36:03 +0200 [thread overview]
Message-ID: <20150414163603.GD2925@chrystal.uk.oracle.com> (raw)
In-Reply-To: <20150414161114.GA18420@roeck-us.net>
On Tue, Apr 14, 2015 at 09:11:14AM -0700, Guenter Roeck wrote:
> On Tue, Apr 14, 2015 at 06:42:44PM +1000, Stephen Rothwell wrote:
> > Hi all,
> >
> > Please do not add any v4.2 material to your linux-next included trees
> > until after v4.1-rc1 is released.
> >
> > Changes since 20150413:
> >
> > Dropped tree: idle (complex conflict)
> >
> > The arm-soc tree still had its build failure for which I reverted
> > a commit.
> >
> > The vfs tree gained conflicts against the ext4 and xfs trees.
> >
> > The pm tree lost its build failure.
> >
> > The idle tree gained a complex conflict against the pm tree so I dropped
> > it for today.
> >
> > The irqchip tree lost its build failure.
> >
> > The ftrace tree gained a conflict against the net-next tree.
> >
> > The rcu tree stilll had its build failure for which I reverted a commit.
> >
> > The xen-tip tree gained a build failure so I used the version from
> > next-20150410.
> >
> > Non-merge commits (relative to Linus' tree): 9605
> > 8774 files changed, 407882 insertions(+), 199408 deletions(-)
> >
> This version results in a modpost crash when building a score target.
>
> /bin/sh: line 1: 18057 Floating point exception(core dumped) scripts/mod/modpost -o ./Module.symvers -S vmlinux.o
> scripts/Makefile.modpost:97: recipe for target 'vmlinux.o' failed
> make[1]: *** [vmlinux.o] Error 136
> Makefile:949: recipe for target 'vmlinux' failed
> make: *** [vmlinux] Error 2
>
> Culprit is commit 52dc0595d540 ("modpost: handle relocations mismatch in
> __ex_table.). That patch has a number of problems.
>
> + if (!extable_entry_size && cur == start + 1 &&
> + strcmp("__ex_table", sec) == 0)
> + extable_entry_size = r->r_offset * 2;
>
> Debugging shows that "cur - start" can be anywhere in multiples of 8
> (arm, score) to 24 (alpha). I have never seen it to be 1. As a result,
> extable_entry_size will never be set, or at least not for the
> architectures I looked at.
Derp sorry about this :(
I moved that "cur == start + 1" test from section_rel[a]() to here but
completely missed to properly cast before doing the pointer arithmetics.
>
> +static inline bool is_extable_fault_address(Elf_Rela *r)
> +{
> + if (!extable_entry_size == 0)
> + fatal("extable_entry size hasn't been discovered!\n");
>
> "!extable_entry_size == 0" is true if extable_entry_size is not 0.
> Presumably that was supposed to be "if (extable_entry_size == 0)"
> or "if (!extable_entry_size)".
>
> + return ((r->r_offset == 0) ||
> + (r->r_offset % extable_entry_size == 0));
>
> So this code will execute if extable_entry_size==0, predictably causing
> the observed crash.
>
> I still don't know why this is triggered when building a score image.
> It appears that some __ex_table entry causes the problem. Which may or
> may not be a problem. Personally I think it is a bit rude to abort
> compilation because of it.
>
It is rude and I'm really sorry about this, I had only tested this on
x86_64 and sparc.
Should I send a tentative fix or will you do it since you've done all the
hard work? In any case thanks for the detailed analysis.
Quentin
next prev parent reply other threads:[~2015-04-14 16:33 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-14 8:42 linux-next: Tree for Apr 14 Stephen Rothwell
2015-04-14 16:11 ` linux-next: Tree for Apr 14 (crash due to modpost patch) Guenter Roeck
2015-04-14 16:36 ` Quentin Casasnovas [this message]
2015-04-14 16:50 ` Guenter Roeck
2015-04-15 8:54 ` [PATCH 0/2] Tentative fix for the divide-by-zero on score/paris/ Quentin Casasnovas
2015-04-15 8:54 ` [PATCH 1/2] modpost: fix inverted logic in is_extable_fault_address() Quentin Casasnovas
2015-04-15 8:54 ` [PATCH 2/2] modpost: fix extable entry size calculation Quentin Casasnovas
2015-04-15 13:26 ` [PATCH 0/2] Tentative fix for the divide-by-zero on score/paris/ Guenter Roeck
2015-04-15 13:46 ` Quentin Casasnovas
2015-04-15 15:31 ` Guenter Roeck
2015-04-15 16:49 ` Quentin Casasnovas
2015-04-15 21:19 ` Quentin Casasnovas
2015-04-15 21:32 ` Guenter Roeck
2015-04-16 1:43 ` Guenter Roeck
2015-04-16 3:49 ` Rusty Russell
2015-04-16 8:21 ` Quentin Casasnovas
2015-04-16 12:47 ` Guenter Roeck
2015-04-16 13:58 ` Quentin Casasnovas
2015-04-18 5:52 ` Guenter Roeck
2015-04-19 11:47 ` Quentin Casasnovas
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20150414163603.GD2925@chrystal.uk.oracle.com \
--to=quentin.casasnovas@oracle.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-next@vger.kernel.org \
--cc=linux@roeck-us.net \
--cc=rusty@rustcorp.com.au \
--cc=sfr@canb.auug.org.au \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).