Re: [Crash-utility] [PATCH] arm64: Use VA_BITS for page_offset calculation
Hi Pingfan, Lianbo,
-----Original Message-----
On Mon, Oct 25, 2021 at 4:43 PM HAGIO KAZUHITO(萩尾 一仁)
<k-hagio-ab(a)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
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
but you may need a kernel configured with VA_BITS=48 to reproduce and check
the fix, I guess.
Thanks,
Kazu
Regards,
Pingfan
> --
> From 028ddf655c847c16cce23198017d2ff0169bb4de Mon Sep 17 00:00:00 2001
> From: Kazuhito Hagio <k-hagio-ab(a)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(a)gmail.com>
> Signed-off-by: Kazuhito Hagio <k-hagio-ab(a)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
>