[Crash-utility] Adding a new command rbtree

[qiaonuohan]

Modified. I remain the "-N" option. But for radix tree on RHEL5 or 
below, the height does not exist. So "-N" is not supported for radix 
tree on these version.

At 2012-5-30 3:56, Dave Anderson wrote:
>
>
> ----- Original Message -----
>>
>>
>> ----- Original Message -----
>
>> As it turns out, the radix tree problem I reported seems to be an issue
>> associated with the kernel version.
>
>> But when I try the same thing on a RHEL5 kernel, it always fails like
>> this:
>>
>> crash>  tree -t radix -r address_space.page_tree ffff81012eab2e00
>> radix_tree_node at ffff81011f9932e8
>> struct radix_tree_node {
>>    count = 0x6,
>>    slots = {0xffff810103c06490, 0xffff810103c1c760,
>>    0xffff810103c58580, 0xffff810103bfb750, 0xffff810103e84cd8,
>>    0xffff810103bf8b5
>> 8, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
>> 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
>> 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
>> 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0
>> , 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0},
>>    tags = {{0x0}, {0x0}}
>> }
>> tree: height 1536 is greater than height_to_maxindex[]
>>                   index 12
>> crash>
>
> The reason that the command fails on RHEL5 is due to this part of
> your patch:
>
>     3766 void rdtree_iteration(ulong node_p, struct tree_data *td, char * ppos, ulong indexnum)
>     3767 {
>     3768         uint height;
>     3769         ulong slot;
>     3770         int index;
>     3771         int i;
>     3772         char pos[BUFSIZE];
>     3773
>     3774         if (indexnum != -1)
>     3775                 sprintf(pos, "%s/%ld", ppos, indexnum);
>     3776         else
>     3777                 sprintf(pos, "%s", ppos);
>     3778
>     3779         readmem(node_p + MEMBER_OFFSET("radix_tree_node", "height"), KVADDR,
>     3780&height, sizeof(uint), "radix_tree_node height", FAULT_ON_ERROR);
>     3781
>     3782         if (height>  ARRAY_LENGTH(height_to_maxindex)) {
>     3783                 fprintf(fp, "radix_tree_node at %lx\n", node_p);
>     3784                 dump_struct("radix_tree_node", node_p, RADIX(16));
>     3785                 error(FATAL, "height %d is greater than height_to_maxindex[] \
>     3786                         index %ld\n", height, ARRAY_LENGTH(height_to_maxindex));
>     3787         }
>
> In line 3779, you calculate "height" using: MEMBER_OFFSET("radix_tree_node", "height")
> which returns -1, because RHEL5's radix_tree_node does not have a "height" member:
>
>    crash>  radix_tree_node
>    struct radix_tree_node {
>        unsigned int count;
>        void *slots[64];
>        long unsigned int tags[2][1];
>    }
>    SIZE: 536
>    crash>
>
> In RHEL6, a radix_tree_node structure does have a "height" member:
>
>    crash>  radix_tree_node
>    struct radix_tree_node {
>        unsigned int height;
>        unsigned int count;
>        struct rcu_head rcu_head;
>        void *slots[64];
>        long unsigned int tags[3][1];
>    }
>    SIZE: 560
>    crash>
>
> In any case, I now see that your patch uses MEMBER_OFFSET(...) in 4 places:
>
> $ grep MEMBER_OFFSET 0001-add-a-new-command-tree.patch
> +       readmem(node_p + MEMBER_OFFSET("radix_tree_node", "height"), KVADDR,
> +               readmem(td->start + MEMBER_OFFSET("rb_root", "rb_node"), KVADDR,
> +       readmem(node_p+MEMBER_OFFSET("rb_node", "rb_left"), KVADDR,&left_p,
> +       readmem(node_p+MEMBER_OFFSET("rb_node", "rb_right"), KVADDR,&right_p,
> $
>
> which is not acceptable, because it hides these kinds of programming errors.
>
> For each of the 4 structure members above, add them to the offset_table[] array,
> initialize them with MEMBER_OFFSET_INIT(), and use OFFSET(...) instead of
> MEMBER_OFFSET().  Then if your code is incorrect as above, it will fail
> immediately and show a meaningful error message.
>
> Dave
>
>
>
> --
> Crash-utility mailing list
> Crash-utility at redhat.com
> https://www.redhat.com/mailman/listinfo/crash-utility
>
>


-- 
--
Regards
Qiao Nuohan


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