aarch64 strace decoding of 32-bit arm statfs64...

[enh]

confirmed that works for me. thanks!


On Wed, Mar 18, 2015 at 9:42 AM, Dmitry V. Levin <ldv at altlinux.org> wrote:
> On Tue, Mar 17, 2015 at 10:29:23PM -0700, enh wrote:
>> hmm. i wonder if this changed at some point? the arm64 kernel has this:
>>
>> compat_sys_statfs64_wrapper:
>>         mov     w3, #84
>>         cmp     w1, #88
>>         csel    w1, w3, w1, eq
>>         b       compat_sys_statfs64
>> ENDPROC(compat_sys_statfs64_wrapper)
>>
>> compat_sys_fstatfs64_wrapper:
>>         mov     w3, #84
>>         cmp     w1, #88
>>         csel    w1, w3, w1, eq
>>         b       compat_sys_fstatfs64
>> ENDPROC(compat_sys_fstatfs64_wrapper)
>>
>> and the arm kernel has the equivalent:
>>
>> sys_statfs64_wrapper:
>>                 teq     r1, #88
>>                 moveq   r1, #84
>>                 b       sys_statfs64
>> ENDPROC(sys_statfs64_wrapper)
>>
>> sys_fstatfs64_wrapper:
>>                 teq     r1, #88
>>                 moveq   r1, #84
>>                 b       sys_fstatfs64
>> ENDPROC(sys_fstatfs64_wrapper)
>>
>> oh, there's a comment in arch/arm/kernel/sys_oabi-compat.c:
>>
>>  * sys_statfs64:
>>  * sys_fstatfs64:
>>  *
>>  *   struct statfs64 has extra padding with EABI growing its size from
>>  *   84 to 88.  This struct is now __attribute__((packed,aligned(4)))
>>  *   with a small assembly wrapper to force the sz argument to 84 if it is 88
>>  *   to avoid copying the extra padding over user space unexpecting it.
>>
>> bionic doesn't have the packed attribute and our sizeof is 88.
>>
>> adding this in both sys_statfs64 and sys_fstatfs64 fixed things for me
>> but maybe you have a better idea?
>>
>> +#if defined ARM || defined AARCH64 /* eabi structs have padding */
>> + else if (tcp->u_arg[1] == sizeof(struct compat_statfs64) + 4)
>> + printcompat_statfs64(tcp, tcp->u_arg[2]);
>> +#endif
>
> As both sizes appear to be valid, we have no choice but to support this
> diversity.  I'm going to install this patch:
>
> --- a/statfs.c
> +++ b/statfs.c
> @@ -128,6 +128,10 @@ struct compat_statfs64 {
>    __attribute__ ((packed, aligned(4)))
>  #endif
>  ;
> +#if defined AARCH64 || defined ARM
> +/* See arch/arm/kernel/sys_oabi-compat.c for details. */
> +# define COMPAT_STATFS64_PADDED_SIZE (sizeof(struct compat_statfs64) + 4)
> +#endif
>
>  static void
>  printcompat_statfs64(struct tcb *tcp, const long addr)
> @@ -157,16 +161,19 @@ printcompat_statfs64(struct tcb *tcp, const long addr)
>         tprintf(", f_flags=%lu}", (unsigned long)statbuf.f_frsize);
>  }
>
> -int
> -sys_statfs64(struct tcb *tcp)
> +static int
> +do_statfs64_fstatfs64(struct tcb *tcp)
>  {
>         if (entering(tcp)) {
> -               printpath(tcp, tcp->u_arg[0]);
>                 tprintf(", %lu, ", tcp->u_arg[1]);
>         } else {
>                 if (tcp->u_arg[1] == sizeof(struct statfs64))
>                         printstatfs64(tcp, tcp->u_arg[2]);
> -               else if (tcp->u_arg[1] == sizeof(struct compat_statfs64))
> +               else if (tcp->u_arg[1] == sizeof(struct compat_statfs64)
> +#ifdef COMPAT_STATFS64_PADDED_SIZE
> +                        || tcp->u_arg[1] == COMPAT_STATFS64_PADDED_SIZE
> +#endif
> +                                                                       )
>                         printcompat_statfs64(tcp, tcp->u_arg[2]);
>                 else
>                         tprints("{???}");
> @@ -175,20 +182,19 @@ sys_statfs64(struct tcb *tcp)
>  }
>
>  int
> +sys_statfs64(struct tcb *tcp)
> +{
> +       if (entering(tcp))
> +               printpath(tcp, tcp->u_arg[0]);
> +       return do_statfs64_fstatfs64(tcp);
> +}
> +
> +int
>  sys_fstatfs64(struct tcb *tcp)
>  {
> -       if (entering(tcp)) {
> +       if (entering(tcp))
>                 printfd(tcp, tcp->u_arg[0]);
> -               tprintf(", %lu, ", tcp->u_arg[1]);
> -       } else {
> -               if (tcp->u_arg[1] == sizeof(struct statfs64))
> -                       printstatfs64(tcp, tcp->u_arg[2]);
> -               else if (tcp->u_arg[1] == sizeof(struct compat_statfs64))
> -                       printcompat_statfs64(tcp, tcp->u_arg[2]);
> -               else
> -                       tprints("{???}");
> -       }
> -       return 0;
> +       return do_statfs64_fstatfs64(tcp);
>  }
>  #endif /* HAVE_STRUCT_STATFS64 */
>
> --
> ldv
>
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-- 
Elliott Hughes - http://who/enh - http://jessies.org/~enh/
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