Re: [PATCH v2 2/3] cobalt/rtdm: Prepare for new signature of mm_get_unmapped_area() in 6.19

On 24.02.26 17:02, Florian Bezdeka wrote:
> On Fri, 2026-02-20 at 16:25 +0100, Jan Kiszka wrote:
>> On 20.02.26 12:27, Florian Bezdeka wrote:
>>> Since 6.19 the signature of mm_get_unmapped_area() has one parameter
>>> less. The (previously) first struct mm_struct *mm parameter has been
>>> removed.
>>>
>>> Signed-off-by: Florian Bezdeka <[email protected]>
>>> ---
>>>  kernel/cobalt/rtdm/drvlib.c | 8 ++++++--
>>>  1 file changed, 6 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/kernel/cobalt/rtdm/drvlib.c b/kernel/cobalt/rtdm/drvlib.c
>>> index 86788743fe47b228662ef16831b4281ddefd04ff..0258100db5bbcc04880ddc71632b7992e50168dc 100644
>>> --- a/kernel/cobalt/rtdm/drvlib.c
>>> +++ b/kernel/cobalt/rtdm/drvlib.c
>>> @@ -1907,8 +1907,12 @@ driver_get_unmapped_area(struct file *filp,
>>>  
>>>  #ifdef CONFIG_MMU
>>>  	/* Run default handler. */
>>> -	return mm_get_unmapped_area(current->mm, filp, addr, len, pgoff,
>>> -				    flags);
>>> +#if LINUX_VERSION_CODE < KERNEL_VERSION(6,19,0)
>>> +	return mm_get_unmapped_area(current->mm, filp, addr, len, pgoff, flags);
>>> +#else
>>> +	return mm_get_unmapped_area(filp, addr, len, pgoff, flags);
>>> +#endif
>>
>> -> wrappers.h, extending the existing logic there, using the latest
>> pattern here.
>>
> 
> Just realized that this function has more history in wrapping:
> 
> #if LINUX_VERSION_CODE < KERNEL_VERSION(6,10,0)
> #define mm_get_unmapped_area(__mm, __filp, __addr, __len, __pgoff, __flags) \
> 	(__mm)->get_unmapped_area(__filp, __addr, __len, __pgoff, __flags)
> #endif
> 
> Kernel versions < 6.19 will need 6 parameters, >= 6.19 will need 5. The
> callers of the wrapper macro must agree in the number of parameters.
> 
> As we cannot touch other callers (Linux code), we have to align the
> caller to the kernel version. I'm running out of ideas here...
> 

The wrapper will only affect Xenomai users, thus does not need to worry
about other code in the kernel.

I'm not quite sure I understand the problem now, why you cannot
translate the inline wrapping above into a xenomai-generic one that
expands the 5-args call to 6 (using current->mm).

Jan

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