[Crash-utility] 答复: [External Mail]Re: zram decompress support for gcore/crash-utility

Wed Apr 15 05:25:57 UTC 2020

Hi,Hatayama

Since zram page not a existing page,so we can't use vtop find exactly physical address,so gcore have  to make a little change for this.gcore patch i've already sent in previous mail

I've answered your question in the previous email about exactly kernel commit in aarch64 stack,please refer to below change
The latest two changes are attached,please review.

commit 34be98f4944f99076f049a6806fc5f5207a755d3
Author: Ard Biesheuvel <ard.biesheuvel at linaro.org>
Date:   Thu Jul 20 17:15:45 2017 +0100

    arm64: kernel: remove {THREAD,IRQ_STACK}_START_SP

    For historical reasons, we leave the top 16 bytes of our task and IRQ
    stacks unused, a practice used to ensure that the SP can always be
    masked to find the base of the current stack (historically, where
    thread_info could be found).

    However, this is not necessary, as:

    * When an exception is taken from a task stack, we decrement the SP by
      S_FRAME_SIZE and stash the exception registers before we compare the
      SP against the task stack. In such cases, the SP must be at least
      S_FRAME_SIZE below the limit, and can be safely masked to determine
      whether the task stack is in use.

    * When transitioning to an IRQ stack, we'll place a dummy frame onto the
      IRQ stack before enabling asynchronous exceptions, or executing code
      we expect to trigger faults. Thus, if an exception is taken from the
      IRQ stack, the SP must be at least 16 bytes below the limit.

    * We no longer mask the SP to find the thread_info, which is now found
      via sp_el0. Note that historically, the offset was critical to ensure
      that cpu_switch_to() found the correct stack for new threads that
      hadn't yet executed ret_from_fork().

    Given that, this initial offset serves no purpose, and can be removed.
    This brings us in-line with other architectures (e.g. x86) which do not
    rely on this masking.

    Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
    [Mark: rebase, kill THREAD_START_SP, commit msg additions]
    Signed-off-by: Mark Rutland <mark.rutland at arm.com>
    Reviewed-by: Will Deacon <will.deacon at arm.com>
    Tested-by: Laura Abbott <labbott at redhat.com>
    Cc: Catalin Marinas <catalin.marinas at arm.com>
    Cc: James Morse <james.morse at arm.com>

________________________________
From: d.hatayama at fujitsu.com <d.hatayama at fujitsu.com>
Sent: Tuesday, April 14, 2020 20:16
To: 赵乾利; Dave Anderson
Cc: Discussion list for crash utility usage, maintenance and development
Subject: Re: 答复: [External Mail]Re: [Crash-utility] zram decompress support for gcore/crash-utility

Zhao,

I don't find latest patch for gcore command, but looking at the commit
b12bdd36cf7caad24957c0b8c030001321ab2df4 in crash utility,
try_zram_decompress() is called after uvtop() in the final design,
not uvtop() being replaced by readmem(UVADDR), which can more easilly be
into the gcore source code. Please send a new patch based on the latest
design. It's very helpful if you share test set for this ZRAM support work.

Also, for the other independent aarch64 patch, as I already requested,
please tell me the kernel commit that made the corresponding change
on Aaarch64 kernel statck data structure, which I need it to check whether your
patch is correct or not and to file it for maintenance purpose.

________________________________
差出人: 赵乾利 <zhaoqianli at xiaomi.com>
送信日時: 2020年4月13日 22:41
宛先: Dave Anderson <anderson at redhat.com>
CC: Hatayama, Daisuke/畑山 大輔 <d.hatayama at fujitsu.com>; Discussion list for crash utility usage, maintenance and development <crash-utility at redhat.com>
件名: Re: 答复: [External Mail]Re: [Crash-utility] zram decompress support for gcore/crash-utility

Hi, hatayama

May I ask about how the patch of support the zram in gcore?support in crash is ready.
Is there anything else I can do for you?

________________________________________
From: Dave Anderson <anderson at redhat.com>
Sent: Monday, April 13, 2020 20:17
To: 赵乾利
Cc: d hatayama; Discussion list for crash utility usage, maintenance and development
Subject: Re: 答复: [External Mail]Re: [Crash-utility] zram decompress support for gcore/crash-utility

----- Original Message -----
>
> Make the mistake cause by patch update....
> please re-check the new patch

In the interest of expediency, I went ahead and made a few cosmetic changes to
the comments and error message strings, and queued the patch for crash-7.2.9:

  https://github.com/crash-utility/crash/commit/b12bdd36cf7caad24957c0b8c030001321ab2df4

Thanks,
  Dave

> ________________________________________
> From: Dave Anderson <anderson at redhat.com>
> Sent: Friday, April 10, 2020 22:57
> To: 赵乾利
> Cc: d hatayama; Discussion list for crash utility usage, maintenance and
> development
> Subject: Re: 答复: [External Mail]Re: [Crash-utility] zram decompress support
> for gcore/crash-utility
>
> ----- Original Message -----
> > I got little problem to compile 32-bit on my x86-64 host..
> >  96 /usr/bin/ld: skipping incompatible
> >  /usr/lib/gcc/x86_64-linux-gnu/4.8/libgcc.a when searching for -lgcc
> >  97 /usr/bin/ld: cannot find -lgcc
> >  98 /usr/bin/ld: skipping incompatible
> >  /usr/lib/gcc/x86_64-linux-gnu/4.8/libgcc_s.so when searching for -lgcc_s
> >  99 /usr/bin/ld: cannot find -lgcc_s
> >
> > I think i have fixed the build warning,but failed rebuild in 32-bit since
> > above error,please help confirm,and move log to try_zram_decompress,please
> > check the attachment.
>
> The patch now compiles OK, but my first simple test shows that something
> is obviously wrong with the patch.
>
> Here are a set of user-space addresses that have been swapped out to disk:
>
>   crash> set 1
>       PID: 1
>   COMMAND: "systemd"
>      TASK: ffff92a13a1e8000  [THREAD_INFO: ffff92a13a260000]
>       CPU: 2
>     STATE: TASK_INTERRUPTIBLE
>   crash> vm -p | grep SWAP
>   55d917fb5000  SWAP: /dev/dm-2  OFFSET: 55827
>   55d917fb7000  SWAP: /dev/dm-2  OFFSET: 55828
>   55d917fc2000  SWAP: /dev/dm-2  OFFSET: 121359
>   55d917fc6000  SWAP: /dev/dm-2  OFFSET: 88579
>   55d917fcb000  SWAP: /dev/dm-2  OFFSET: 88581
>   55d917fcc000  SWAP: /dev/dm-2  OFFSET: 88582
>   55d917fcd000  SWAP: /dev/dm-2  OFFSET: 88583
>   55d917fce000  SWAP: /dev/dm-2  OFFSET: 104963
>   55d917fcf000  SWAP: /dev/dm-2  OFFSET: 104964
>   ...
>
> Obviously any read of the addresses above should fail, but each
> read returns successfully, and each read is screwing up the internal
> buffering scheme:
>
>   crash> rd -u 55d917fb5000
>       55d917fb5000:  0000000000000000                    ........
>   WARNING: malloc/free mismatch (53/54)
>   crash> rd -u 55d917fb7000
>       55d917fb7000:  0000000000000000                    ........
>   WARNING: malloc/free mismatch (53/55)
>   crash> rd -u 55d917fc2000
>       55d917fc2000:  0000000000000000                    ........
>   WARNING: malloc/free mismatch (53/56)
>   crash> rd -u 55d917fc6000
>       55d917fc6000:  0000000000000000                    ........
>   WARNING: malloc/free mismatch (53/57)
>   crash>
>
> Dave
>
>
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