[Crash-utility] [PATCH v5 0/3] Improve kaslr_offset detection

[lijiang]

在 2020年11月11日 13:17, HAGIO KAZUHITO(萩尾　一仁) 写道:
> Hi Alexey,
> 
> -----Original Message-----
>> v5 change: added ack by Lianbo Jiang.
>>
>> v4 changes: fixed GCC warnings reported by Kazu.
> 
> Thanks for the update.
> 
>>
>> Alexey Makhalov (3):
>>   calc_kaslr_offset: try all CPUs
>>   calc_kaslr_offset: 5-level paging support
> 
> I tested the patchset on a qemu memory dump with 5-level paging (la57)
> and crash failed during starting session:
> 
>   crash: read error: physical address: 125a0c000  type: "p4d page"
> 
Thank you for checking this error, Kazu.

I did not make the test for this patch because it was marked as Verified as below:
Patch #2: new patch. 5 level paging support. Verified.

Seems that making the test myself is a good way to check for errors ASAP.

Thanks.
Lianbo

> It seems that it needs something like:
> 
> diff --git a/kaslr_helper.c b/kaslr_helper.c
> index f13b7ff0850b..b9fef825a290 100644
> --- a/kaslr_helper.c
> +++ b/kaslr_helper.c
> @@ -671,6 +671,8 @@ calc_kaslr_offset(ulong *ko, ulong *pb)
>                         machdep->machspec->physical_mask_shift = __PHYSICAL_MASK_SHIFT_5LEVEL;
>                         machdep->machspec->pgdir_shift = PGDIR_SHIFT_5LEVEL;
>                         machdep->machspec->ptrs_per_pgd = PTRS_PER_PGD_5LEVEL;
> +                       if ((machdep->machspec->p4d = (char *)malloc(PAGESIZE())) == NULL)
> +                               error(FATAL, "cannot malloc p4d space.");
>                 } else {
>                         machdep->machspec->physical_mask_shift = __PHYSICAL_MASK_SHIFT_2_6;
>                         machdep->machspec->pgdir_shift = PGDIR_SHIFT;
> diff --git a/x86_64.c b/x86_64.c
> index 0acef2b04faf..939c8a9fddd4 100644
> --- a/x86_64.c
> +++ b/x86_64.c
> @@ -356,9 +356,11 @@ x86_64_init(int when)
>                         machdep->machspec->physical_mask_shift = __PHYSICAL_MASK_SHIFT_5LEVEL;
>                         machdep->machspec->pgdir_shift = PGDIR_SHIFT_5LEVEL;
>                         machdep->machspec->ptrs_per_pgd = PTRS_PER_PGD_5LEVEL;
> -                       if ((machdep->machspec->p4d = (char *)malloc(PAGESIZE())) == NULL)
> -                               error(FATAL, "cannot malloc p4d space.");
> -                       machdep->machspec->last_p4d_read = 0;
> +                       if (!machdep->machspec->p4d) {
> +                               if ((machdep->machspec->p4d = (char *)malloc(PAGESIZE())) == NULL)
> +                                       error(FATAL, "cannot malloc p4d space.");
> +                               machdep->machspec->last_p4d_read = 0;
> +                       }
>                         machdep->uvtop = x86_64_uvtop_level4;  /* 5-level is optional per-task */
>                         machdep->kvbase = (ulong)PAGE_OFFSET;
>                         machdep->identity_map_base = (ulong)PAGE_OFFSET;
> 
> With this, tested OK.
> If this looks good, I can fix 2/3 when merging, or you can repost.
> 
> Thanks,
> Kazu
> 
>>   kaslr: get offset by walking page tree
>>
>>  defs.h         |   8 +-
>>  diskdump.c     |   6 +
>>  kaslr_helper.c | 434 ++++++++++++++++++++++++++++++++++++++++++---------------
>>  netdump.c      |   6 +
>>  sadump.c       |  37 +----
>>  symbols.c      |   5 +-
>>  vmware_vmss.c  |  15 +-
>>  7 files changed, 359 insertions(+), 152 deletions(-)
>>
>> --
>> 2.11.0
>