linux-kernel - Re: Crash in -next due to 'objtool: Improve detection of BUG() and other dead ends'

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Date:   Mon, 27 Feb 2017 16:21:14 -0600
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: Crash in -next due to 'objtool: Improve detection of BUG() and
 other dead ends'

On Mon, Feb 27, 2017 at 12:59:23PM -0800, Guenter Roeck wrote:
> Hi,
> 
> my qemu tests for mips64 in -next fail as follows.
> 
> ...
> VFS: Mounted root (ext3 filesystem) on device 8:0.
> Freeing unused kernel memory: 304K
> This architecture does not have kernel memory protection.
> Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000a
> 
> ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000a
> 
> There is no symbol traceback, and I don't see any other (obvious) error
> message.  bisect points to commit 'objtool: Improve detection of BUG()
> and other dead ends'; reverting that patch fixes the problem.
> Bisect log is attached below.
> 
> The script used to run the test as well as the root file system is available
> at https://github.com/groeck/linux-build-test/tree/master/rootfs/mips64
> 
> A complete log is available at
> http://kerneltests.org/builders/qemu-mips64-next/builds/592/steps/qemubuildcommand/logs/stdio

Hi Guenter,

This failure doesn't make much sense.  Objtool (and the reported bad
patch) are x86-only and should have nothing to do with mips64.  Would it
be possible for you to double check the error?

Otherwise I could try to recreate.  Do you have a recommendation for a
mips cross-compiler?  (preferably something that's already built and that
might work on Fedora)

> ---
> # bad: [ed7b11e565c736828f0b793f596a4ca20efee747] Add linux-next specific files for 20170227
> # good: [c470abd4fde40ea6a0846a2beab642a578c0b8cd] Linux 4.10
> git bisect start 'HEAD' 'v4.10'
> # good: [caa59428971d5ad81d19512365c9ba580d83268c] Merge tag 'staging-4.11-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging
> git bisect good caa59428971d5ad81d19512365c9ba580d83268c
> # good: [d5500a074741b78b7f778b4ab3415d5ecdcda0a7] Merge tag 'usercopy-v4.11-rc1.fix' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux
> git bisect good d5500a074741b78b7f778b4ab3415d5ecdcda0a7
> # good: [5d8a00eee2ed2e548a5d21b0edf495f3f7bf8bb4] Merge tag 'clk-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/clk/linux
> git bisect good 5d8a00eee2ed2e548a5d21b0edf495f3f7bf8bb4
> # good: [017bfb6c372fa793cdb09828597a464fa24e0ea7] Merge remote-tracking branch 'jfs/jfs-next'
> git bisect good 017bfb6c372fa793cdb09828597a464fa24e0ea7
> # bad: [e2a95a3fe9e9586df29e8d673dc8cdd36ed6158b] Merge remote-tracking branch 'edac/linux_next'
> git bisect bad e2a95a3fe9e9586df29e8d673dc8cdd36ed6158b
> # good: [736e441efdafdbf0bb32732d87e00b8ba7f75260] Merge remote-tracking branch 'thermal/next'
> git bisect good 736e441efdafdbf0bb32732d87e00b8ba7f75260
> # good: [5bd695c24b294b482d86d352a4a0c7ba2059dcff] Merge remote-tracking branch 'block/for-next'
> git bisect good 5bd695c24b294b482d86d352a4a0c7ba2059dcff
> # good: [690962e72babac64c8240071e106d2c3e8d08306] Merge remote-tracking branch 'spi/for-next'
> git bisect good 690962e72babac64c8240071e106d2c3e8d08306
> # bad: [462a53b1a2f984a8c8c0aade1c461ce9ea156d5b] Merge branch 'perf/urgent'
> git bisect bad 462a53b1a2f984a8c8c0aade1c461ce9ea156d5b
> # good: [bb963e16507ca7670f0bb47ccaada8874b2ba6a1] perf utils: Check verbose flag properly
> git bisect good bb963e16507ca7670f0bb47ccaada8874b2ba6a1
> # good: [7bbba0eb1af34694868d028b80475981f90e6bee] perf/core: Fix perf_event_enable_on_exec() timekeeping (again)
> git bisect good 7bbba0eb1af34694868d028b80475981f90e6bee
> # bad: [1db159781cc7df093085ccaddc022beaaa9dd990] Merge branch 'core/urgent'
> git bisect bad 1db159781cc7df093085ccaddc022beaaa9dd990
> # bad: [d1091c7fa3d52ebce4dd3f15d04155b3469b2f90] objtool: Improve detection of BUG() and other dead ends
> git bisect bad d1091c7fa3d52ebce4dd3f15d04155b3469b2f90
> # good: [9f0c18aec620bc9d82268b3cb937568dd07b43ff] objtool: Fix CONFIG_STACK_VALIDATION=y warning for out-of-tree modules
> git bisect good 9f0c18aec620bc9d82268b3cb937568dd07b43ff
> # first bad commit: [d1091c7fa3d52ebce4dd3f15d04155b3469b2f90] objtool: Improve detection of BUG() and other dead ends

-- 
Josh