Re: [PATCH bpf-next v3 2/3] selftests/bpf: support array presets in veristat

[Mykyta Yatsenko <mykyta.yatsenko5@gmail.com>]

On 6/11/25 01:45, Eduard Zingerman wrote:
> On Tue, 2025-06-10 at 20:08 +0100, Mykyta Yatsenko wrote:
>> From: Mykyta Yatsenko <yatsenko@meta.com>
>>
>> Implement support for presetting values for array elements in
>> veristat.
>> For example:
>> ```
>> sudo ./veristat set_global_vars.bpf.o -G "arr[3] = 1"
>> ```
>> Arrays of structures and structure of arrays work, but each
>> individual
>> scalar value has to be set separately: `foo[1].bar[2] = value`.
>>
>> Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
>> ---
> A few nits regarding error reporting:
>
>    ./veristat -q -G ptr_arr[10]=0 set_global_vars.bpf.o
>    Unsupported array element type for variable ptr_arr. Only int, enum, struct, union are supported
>                                                                                                   ^^^
> 											 missing dot
>
>    ./veristat -G arr[[10]]=0 set_global_vars.bpf.o
>    Could not parse 'arr[[10]]'Failed to parse global variable presets: arr[[10]]=0
>    ^^^^^^^^^                ^^^                                                  ^^^
>    Can't ?		   dot or comma                                 missing dot
>
>    ./veristat -q -G "struct1[0] = 0" set_global_vars.bpf.o
>    Setting value for type Struct is not supported
>                                             ^^^^^^^^^
> 					   report full_name here?
>
> I applied a diff as in the attachment, to see what offsets are being assigned.
> Looks like this shows a bug:
>
>    ./veristat  -q -G "struct1[0].filler = 42" set_global_vars.bpf.o > /dev/null
>    setting struct1[0].filler: offset 54, kind int, value 42
>
> Shouldn't offset be 2 in this case?
>
> (maybe print such info in debug (-d) mode?)
>
> Unrelated to this patch, but still a bug:
>
>    # Catches range error:
>    ./veristat -q -G "struct1[0].filler2 = 100500" set_global_vars.bpf.o
>    Variable unsigned short value 100500 is out of range [0; 65535]
>    # Does not range error:
>    ./veristat -q -G "struct1[0].filler2 = -1" set_global_vars.bpf.o
Thanks for taking a look and checking few testcases.
I'll fix this one in the next patch, along with the error messages.
>    ... success ...
>
> [...]