kernel-packages team mailing list archive

[Dave Cheney <1304754@xxxxxxxxxxxxxxxxxx>]

Thanks Anton, this is great debugging.

I tried the peano experiment on my -8 (4k) kernel and it failed as
expected.

I talked to the upstream who said that ./configure should detect that
-fsplit-stack isn't supported on PPC and fall back to giving each
goroutine a full stack.

I will investigate this today.

With this said, should this bug be reassiged to gccgo (trusty) ?

On Thu, Apr 10, 2014 at 8:44 PM, Anton Blanchard <anton@xxxxxxxxx> wrote:
> Based on the fail, I took a look at how gccgo handles stacks. It relies
> on the split stack feature in gold, which doesn't appear to be
> implemented for ppc64.
>
> Running one of the go recursion testcases (attached) shows what happens
> when we run out of stack and don't have the split stack feature to save
> us:
>
> #gccgo -g -O2 -o peano peano.go
> # ./peano
> Segmentation fault
>
> And we get the setup_rt_frame error in dmesg:
>
> peano[4538]: bad frame in setup_rt_frame: 000000c20ff7f000 nip
> 0000000010001018 lr 0000000010001024
>
> As expected, we are just continually recurse without checking out stack
> pointer for overflow:
>
>    0x0000000010001008 <+8>:     cmpdi   r3,0
>    0x000000001000100c <+12>:    beq     0x10001040 <main.count+64>
>    0x0000000010001010 <+16>:    mflr    r0
>    0x0000000010001014 <+20>:    std     r0,16(r1)
>    0x0000000010001018 <+24>:    stdu    r1,-32(r1)
>    0x000000001000101c <+28>:    ld      r3,0(r3)
>    0x0000000010001020 <+32>:    bl      0x10001008 <main.count+8>
>
>
> ** Attachment added: "peano.go"
>    https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1304754/+attachment/4079310/+files/peano.go
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1304754
>
> Title:
>   gccgo compiled binaries are killed by SEGV on 64k ppc64el kernels
>
> Status in "linux" package in Ubuntu:
>   Incomplete
>
> Bug description:
>   On kernels 3.13-18 and 3.13-23 (there may be others) the kernel is
>   killing gccgo compiled binaries
>
>   [18519.444748] jujud[19277]: bad frame in setup_rt_frame:
>   0000000000000000 nip 0000000000000000 lr 0000000000000000
>   [18519.673632] init: juju-agent-ubuntu-local main process (19220)
>   killed by SEGV signal
>   [18519.673651] init: juju-agent-ubuntu-local main process ended, respawning
>
>   In powerpc/kernel/signal_64.c:
>
>   sys_rt_sigreturn is jumping to the badframe: label and executing an
>   unconditional force_sigsegv which is delivered to the userland
>   process. Like C++, gccgo tries to decode SIGSEGV as a nil pointer
>   access and blame some random function that happened to be the top
>   stack frame.
>
>   Reverting to the 3.13-08 kernel appears to resolve the issue which
>   (weakly) points the finger at the recent switch to 64k pages.
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1304754/+subscriptions

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You received this bug notification because you are a member of Kernel
Packages, which is subscribed to linux in Ubuntu.
https://bugs.launchpad.net/bugs/1304754

Title:
  gccgo compiled binaries are killed by SEGV on 64k ppc64el kernels

Status in “linux” package in Ubuntu:
  Incomplete

Bug description:
  On kernels 3.13-18 and 3.13-23 (there may be others) the kernel is
  killing gccgo compiled binaries

  [18519.444748] jujud[19277]: bad frame in setup_rt_frame:
  0000000000000000 nip 0000000000000000 lr 0000000000000000
  [18519.673632] init: juju-agent-ubuntu-local main process (19220)
  killed by SEGV signal
  [18519.673651] init: juju-agent-ubuntu-local main process ended, respawning

  In powerpc/kernel/signal_64.c:

  sys_rt_sigreturn is jumping to the badframe: label and executing an
  unconditional force_sigsegv which is delivered to the userland
  process. Like C++, gccgo tries to decode SIGSEGV as a nil pointer
  access and blame some random function that happened to be the top
  stack frame.

  Reverting to the 3.13-08 kernel appears to resolve the issue which
  (weakly) points the finger at the recent switch to 64k pages.

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1304754/+subscriptions