[Crash-utility] [PATCH] arm64: Use VA_BITS for page_offset calculation

[lijiang]

On Wed, Oct 27, 2021 at 11:17 AM HAGIO KAZUHITO(萩尾 一仁) <k-hagio-ab at nec.com>
wrote:

> Hi Pingfan, Lianbo,
>
> -----Original Message-----
> > On Mon, Oct 25, 2021 at 4:43 PM HAGIO KAZUHITO(萩尾 一仁)
> > <k-hagio-ab at nec.com> wrote:
> > >
> > > Hi,
> > >
> > > Here is a patch for the issue reported by Ankur.
> > > Could you help test this with your ramdumps and arm64 machines?
> > >
> > The patch looks good to me. And I will schedule a machine to have a test.
>
> Pingfan, thank you for the check and test, it's very helpful.
>
> Ankur told me that the patch was working fine.
>
> Lianbo, my understanding is that to get a raw ramdump, hardware
> functionality
>

I mean that the raw dumpfile had been generated on my machine, but it
didn't reproduce
this issue.  :-)
I guess that may be related to the  kernel '.config'.

or something is required.  But maybe you can reproduce a similar situation
> with QEMU memory dump without vmcoreinfo?  e.g. on RHEL:
>
>   # virsh dump <domain> domain.dump --memory-only
>
>
Thank you for the suggestion, Kazu.


> but you may need a kernel configured with VA_BITS=48 to reproduce and check
> the fix, I guess.
>

I can confirm that kernel has enabled the VA_BITS=48 as below:
CONFIG_ARM64_VA_BITS_48=y
CONFIG_ARM64_VA_BITS=48
Thanks.


> Thanks,
> Kazu
>
> >
> > Regards,
> > Pingfan
> > > --
> > > From 028ddf655c847c16cce23198017d2ff0169bb4de Mon Sep 17 00:00:00 2001
> > > From: Kazuhito Hagio <k-hagio-ab at nec.com>
> > > Date: Mon, 25 Oct 2021 16:53:26 +0900
> > > Subject: [PATCH] arm64: Use VA_BITS for page_offset calculation
> > >
> > > Commit 167d37e347fe ("arm64: assign page_offset with VA_BITS kernel
> > > configuration value") changed the page_offset calculation from
> > > using VA_BITS_ACTUAL to CONFIG_ARM64_VA_BITS.  This caused an error
> > > for ramdumps without vmcoreinfo like this:
> > >
> > >   crash: vmlinux and /var/tmp/ramdump_elf_XUtCMT do not match!
> > >
> > > Set the vmcoreinfo value to VA_BITS if available, and use VA_BITS
> > > for page_offset calculation instead.
> > >
> > > Also remove ARM64_FLIP_PAGE_OFFSET_ACTUAL because it's not used
> > > actually.
> > >
> > > Reported-by: Ankur Bansal <er.ankurbansal at gmail.com>
> > > Signed-off-by: Kazuhito Hagio <k-hagio-ab at nec.com>
> > > ---
> > >  arm64.c | 5 ++++-
> > >  defs.h  | 4 +---
> > >  2 files changed, 5 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/arm64.c b/arm64.c
> > > index 7069312671cf..3dcbcc642fda 100644
> > > --- a/arm64.c
> > > +++ b/arm64.c
> > > @@ -404,7 +404,7 @@ arm64_init(int when)
> > >                                 fprintf(fp, "CONFIG_ARM64_VA_BITS:
> %ld\n", ms->CONFIG_ARM64_VA_BITS);
> > >                                 fprintf(fp, "      VA_BITS_ACTUAL:
> %ld\n", ms->VA_BITS_ACTUAL);
> > >                                 fprintf(fp, "(calculated) VA_BITS:
> %ld\n", ms->VA_BITS);
> > > -                               fprintf(fp, " PAGE_OFFSET: %lx\n",
> ARM64_FLIP_PAGE_OFFSET_ACTUAL);
> > > +                               fprintf(fp, " PAGE_OFFSET: %lx\n",
> ARM64_FLIP_PAGE_OFFSET);
> > >                                 fprintf(fp, "    VA_START: %lx\n",
> ms->VA_START);
> > >                                 fprintf(fp, "     modules: %lx -
> %lx\n", ms->modules_vaddr,
> > ms->modules_end);
> > >                                 fprintf(fp, "     vmalloc: %lx -
> %lx\n", ms->vmalloc_start_addr,
> > ms->vmalloc_end);
> > > @@ -4031,6 +4031,9 @@ arm64_calc_VA_BITS(void)
> > >                                 error(FATAL, "cannot determine
> VA_BITS_ACTUAL\n");
> > >                 }
> > >
> > > +               if (machdep->machspec->CONFIG_ARM64_VA_BITS)
> > > +                       machdep->machspec->VA_BITS =
> machdep->machspec->CONFIG_ARM64_VA_BITS;
> > > +
> > >                 /*
> > >                  * The mm flip commit is introduced before 52-bits VA,
> which is before the
> > >                  * commit to export NUMBER(TCR_EL1_T1SZ)
> > > diff --git a/defs.h b/defs.h
> > > index 8b356d5e8959..971005596506 100644
> > > --- a/defs.h
> > > +++ b/defs.h
> > > @@ -3238,9 +3238,7 @@ typedef signed int s32;
> > >  #define ARM64_PAGE_OFFSET    ((0xffffffffffffffffUL) \
> > >                                         << (machdep->machspec->VA_BITS
> - 1))
> > >  /* kernels >= v5.4 the kernel VA space is flipped */
> > > -#define ARM64_FLIP_PAGE_OFFSET (-(1UL) <<
> machdep->machspec->CONFIG_ARM64_VA_BITS)
> > > -#define ARM64_FLIP_PAGE_OFFSET_ACTUAL ((0xffffffffffffffffUL) \
> > > -                                       - ((1UL) <<
> machdep->machspec->VA_BITS_ACTUAL) + 1)
> > > +#define ARM64_FLIP_PAGE_OFFSET (-(1UL) << machdep->machspec->VA_BITS)
> > >
> > >  #define ARM64_USERSPACE_TOP  ((1UL) << machdep->machspec->VA_BITS)
> > >  #define ARM64_USERSPACE_TOP_ACTUAL  ((1UL) <<
> machdep->machspec->VA_BITS_ACTUAL)
> > > --
> > > 2.27.0
> > >
>
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