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

[Pingfan Liu]

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.

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
>