Re: [PATCH 2/7] scripts: modpost: increase buf_printf's buffer size

["Alexandre Courbot" <acourbot@nvidia.com>]

Hi Gary,

On Fri May 1, 2026 at 10:02 PM JST, Gary Guo wrote:
> On Thu Apr 30, 2026 at 3:55 PM BST, Alexandre Courbot wrote:
>> Rust tends to produce long symbol names; when trying to export symbols
>> from nova-core for nova-drm to link to, the 500 bytes of the internal
>> buffer used for symbol name formatting are not enough, making modpost
>> fail.
>>
>> Fix this by increasing the size of the buffer used to format the symbols
>> to 1024 bytes. It is a stack buffer, but modpost is a user-space program
>> so that shouldn't be a problem.
>
> I think we should make sure all constants related to symbol names match.
> KSYM_NAME_LEN is 512 so this should just be that.

Do you mean we should use `KSYM_NAME_LEN` for the size of `tmp`? The
formatted strings can be longer than the symbol name alone (see the
example below which wraps it into `KSYMTAB_FUNC()`), so this should
probably be `KSYM_NAME_LEN + something` if we align to it.

>
> The only case that I've been hit with very long symbol names so far is doc tests.
> Can you provide an example of the case where you're hit with very long symbol
> names in Nova? In many cases they're just functions that are supposed to be
> inlined but isn't.

Here is an example string that doesn't make it, it doesn't seem related
to doctests but also doesn't occur on all configs:

ERROR: modpost: buf_printf output was truncated for string
KSYMTAB_FUNC(_RINvXs5_NtNtCs1EKtwoKEMO2_6kernel5alloc4kboxINtB6_3BoxINtNtNtCs1peUGmbrgHn_4core3mem12maybe_uninit11MaybeUninitINtNtBa_9auxiliary16RegistrationDataNtNtCs6wA3Ay79aUn_9nova_core6driver7AuxDataEENtNtB8_9allocator7KmallocEINtCsfxcgfq7FLKi_8pin_init12InPlaceWriteB1L_E14write_pin_initNtNtBa_5error5ErrorINtNtB3x_10___internal11InitClosureNCINvYIBH_B1L_B34_EINtNtBa_4init11InPlaceInitB1L_E8pin_initB4t_IB4N_NCINvMsd_B1O_INtB1O_12RegistrationINtNtNtBa_5types6for_lt15UnsafeForLtImplDG_INtB72_:
608 bytes needed, 500 available