Date: Wed, 8 Jan 2025 12:30:11 +1300
From: Tao Liu <ltao@redhat.com>
Subject: [Crash-utility] Re: [PATCH] Fix "net -a" option on Linux 6.13
        and later kernels
To: HAGIO KAZUHITO(萩尾 一仁) <k-hagio-ab@nec.com>
Cc: "devel@lists.crash-utility.osci.io"
        <devel@lists.crash-utility.osci.io>
Message-ID:
        <CAO7dBbVYFpdtgMOvtnxp4MJJB_p4GyG=2_je7yMt33H40JmZZA@mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"

Hi Kazu,

Thanks for the fix, the patch LGTM, so ack.

Thanks,
Tao Liu

On Tue, Jan 7, 2025 at 3:46 PM HAGIO KAZUHITO(萩尾　一仁) <k-hagio-ab@nec.com> wrote:
>
> From: Kazuhito Hagio <k-hagio-ab@nec.com>
>
> Kernel commit e4e3fd0a99d5 ("Merge branch 'improve-neigh_flush_dev-performance'")
> and its patch set, which are contained in Linux 6.13 and later kernels,
> removed neigh_hash_table.hash_buckets and neighbour.next members, and
> introduced neigh_hash_table.hash_heads and neighbour.hash members
> instead with the hlist implementation.
>
> Without the patch, the "net -a" option fails with the following error:
>
>   crash> net -a
>
>   net: invalid structure member offset: neigh_table_hash_buckets
>        FILE: net.c  LINE: 701  FUNCTION: dump_arp()
>   ...
>
> Signed-off-by: Kazuhito Hagio <k-hagio-ab@nec.com>
> ---
>  defs.h    |  2 ++
>  net.c     | 26 +++++++++++++++++++++-----
>  symbols.c |  2 ++
>  3 files changed, 25 insertions(+), 5 deletions(-)
>
> diff --git a/defs.h b/defs.h
> index d8d378ef94b1..8378cbab2f73 100644
> --- a/defs.h
> +++ b/defs.h
> @@ -2269,6 +2269,8 @@ struct offset_table {                    /* stash of commonly-used offsets */
>         long task_struct_thread_context_x26;
>         long task_struct_thread_context_x27;
>         long task_struct_thread_context_x28;
> +       long neigh_table_hash_heads;
> +       long neighbour_hash;
>  };
>
>  struct size_table {         /* stash of commonly-used sizes */
> diff --git a/net.c b/net.c
> index 31d3f2bf7c2f..4e14f19fc097 100644
> --- a/net.c
> +++ b/net.c
> @@ -169,6 +169,11 @@ net_init(void)
>                                 "neigh_hash_table", "hash_shift");
>                         MEMBER_OFFSET_INIT(neigh_table_hash_buckets,
>                                 "neigh_hash_table", "hash_buckets");
> +                       /* Linux 6.13 and later */
> +                       if (INVALID_MEMBER(neigh_table_hash_buckets)) {
> +                               MEMBER_OFFSET_INIT(neigh_table_hash_heads, "neigh_hash_table", "hash_heads");
> +                               MEMBER_OFFSET_INIT(neighbour_hash, "neighbour", "hash");
> +                       }
>                 } else {
>                         MEMBER_OFFSET_INIT(neigh_table_hash_buckets,
>                                 "neigh_table", "hash_buckets");
> @@ -698,9 +703,13 @@ dump_arp(void)
>                 "neigh_table key_len", FAULT_ON_ERROR);
>
>         if (VALID_MEMBER(neigh_table_nht_ptr)) {
> -               readmem(nht + OFFSET(neigh_table_hash_buckets),
> -                       KVADDR, &hash, sizeof(hash),
> -                       "neigh_hash_table hash_buckets ptr", FAULT_ON_ERROR);
> +               /* Linux 6.13 and later */
> +               if (VALID_MEMBER(neigh_table_hash_heads))
> +                       readmem(nht + OFFSET(neigh_table_hash_heads), KVADDR, &hash,
> +                               sizeof(hash), "neigh_hash_table hash_heads ptr", FAULT_ON_ERROR);
> +               else
> +                       readmem(nht + OFFSET(neigh_table_hash_buckets), KVADDR, &hash,
> +                               sizeof(hash), "neigh_hash_table hash_buckets ptr", FAULT_ON_ERROR);
>
>                 readmem(hash, KVADDR, hash_buckets, hash_bytes,
>                         "neigh_hash_table hash_buckets", FAULT_ON_ERROR);
> @@ -831,8 +840,15 @@ print_neighbour_q(ulong addr, int key_len)
>
>                 arp_state_to_flags(state);
>
> -               readmem(addr + OFFSET(neighbour_next), KVADDR,
> -                       &addr, sizeof(addr), "neighbour next", FAULT_ON_ERROR);
> +               /* Linux 6.13 and later kernels use hlist. */
> +               if (VALID_MEMBER(neighbour_hash)) {
> +                       readmem(addr + OFFSET(neighbour_hash), KVADDR, &addr,
> +                               sizeof(addr), "neighbour hash", FAULT_ON_ERROR);
> +                       if (addr)
> +                               addr -= OFFSET(neighbour_hash);
> +               } else
> +                       readmem(addr + OFFSET(neighbour_next), KVADDR, &addr,
> +                               sizeof(addr), "neighbour next", FAULT_ON_ERROR);
>         }
>
>         FREEBUF(ha_buf);
> diff --git a/symbols.c b/symbols.c
> index a3cd0f3f6e1f..0b63e11fa567 100644
> --- a/symbols.c
> +++ b/symbols.c
> @@ -11028,6 +11028,7 @@ dump_offset_table(char *spec, ulong makestruct)
>
>          fprintf(fp, "                neighbour_next: %ld\n",
>                 OFFSET(neighbour_next));
> +        fprintf(fp, "                neighbour_hash: %ld\n", OFFSET(neighbour_hash));
>          fprintf(fp, "         neighbour_primary_key: %ld\n",
>                 OFFSET(neighbour_primary_key));
>          fprintf(fp, "                  neighbour_ha: %ld\n",
> @@ -11038,6 +11039,7 @@ dump_offset_table(char *spec, ulong makestruct)
>                 OFFSET(neighbour_nud_state));
>          fprintf(fp, "      neigh_table_hash_buckets: %ld\n",
>                 OFFSET(neigh_table_hash_buckets));
> +        fprintf(fp, "        neigh_table_hash_heads: %ld\n", OFFSET(neigh_table_hash_heads));
>          fprintf(fp, "         neigh_table_hash_mask: %ld\n",
>                 OFFSET(neigh_table_hash_mask));
>          fprintf(fp, "        neigh_table_hash_shift: %ld\n",
> --
> 2.31.1