Re: [drm-misc:drm-misc-next 4/11] drivers/gpu/drm/drm_gem.c:1261:10: error: call to undeclared function 'mm_get_unmapped_area'; ISO C99 and later do not support implicit function declarations

[Boris Brezillon <boris.brezillon@collabora.com>]

On Tue, 9 Dec 2025 23:58:10 +0800
kernel test robot <lkp@intel.com> wrote:

> tree:   https://gitlab.freedesktop.org/drm/misc/kernel.git drm-misc-next
> head:   0823bd894278e4c0f1acb8f3a8a3c67745e6d1f6
> commit: 99bda20d6d4cac30ed6d357658d8bc328c3b27d9 [4/11] drm/gem: Introduce drm_gem_get_unmapped_area() fop
> config: arm-randconfig-003-20251209 (https://download.01.org/0day-ci/archive/20251209/202512092338.ylY8zET6-lkp@intel.com/config)
> compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project 6ec8c4351cfc1d0627d1633b02ea787bd29c77d8)
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251209/202512092338.ylY8zET6-lkp@intel.com/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202512092338.ylY8zET6-lkp@intel.com/
> 
> All errors (new ones prefixed by >>):
> 
> >> drivers/gpu/drm/drm_gem.c:1261:10: error: call to undeclared function 'mm_get_unmapped_area'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]  
>     1261 |                 return mm_get_unmapped_area(current->mm, filp, uaddr, len, 0,
>          |                        ^
>    drivers/gpu/drm/drm_gem.c:1261:10: note: did you mean '__get_unmapped_area'?
>    include/linux/mm.h:3441:1: note: '__get_unmapped_area' declared here
>     3441 | __get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
>          | ^
>    1 error generated.
> 
> 
> vim +/mm_get_unmapped_area +1261 drivers/gpu/drm/drm_gem.c
> 
>   1229	
>   1230	/**
>   1231	 * drm_gem_get_unmapped_area - get memory mapping region routine for GEM objects
>   1232	 * @filp: DRM file pointer
>   1233	 * @uaddr: User address hint
>   1234	 * @len: Mapping length
>   1235	 * @pgoff: Offset (in pages)
>   1236	 * @flags: Mapping flags
>   1237	 *
>   1238	 * If a driver supports GEM object mapping, before ending up in drm_gem_mmap(),
>   1239	 * mmap calls on the DRM file descriptor will first try to find a free linear
>   1240	 * address space large enough for a mapping. Since GEM objects are backed by
>   1241	 * shmem buffers, this should preferably be handled by the shmem virtual memory
>   1242	 * filesystem which can appropriately align addresses to huge page sizes when
>   1243	 * needed.
>   1244	 *
>   1245	 * Look up the GEM object based on the offset passed in (vma->vm_pgoff will
>   1246	 * contain the fake offset we created) and call shmem_get_unmapped_area() with
>   1247	 * the right file pointer.
>   1248	 *
>   1249	 * If a GEM object is not available at the given offset or if the caller is not
>   1250	 * granted access to it, fall back to mm_get_unmapped_area().
>   1251	 */
>   1252	unsigned long drm_gem_get_unmapped_area(struct file *filp, unsigned long uaddr,
>   1253						unsigned long len, unsigned long pgoff,
>   1254						unsigned long flags)
>   1255	{
>   1256		struct drm_gem_object *obj;
>   1257		unsigned long ret;
>   1258	
>   1259		obj = drm_gem_object_lookup_at_offset(filp, pgoff, len >> PAGE_SHIFT);
>   1260		if (IS_ERR(obj) || !obj->filp || !obj->filp->f_op->get_unmapped_area)
> > 1261			return mm_get_unmapped_area(current->mm, filp, uaddr, len, 0,  
>   1262						    flags);

Hm, smells like a build without CONFIG_MMU=n. I guess we need some
#ifdef CONFIG_MMU around drm_gem_get_unmapped_area() definitions.

>   1263	
>   1264		ret = obj->filp->f_op->get_unmapped_area(obj->filp, uaddr, len, 0,
>   1265							 flags);
>   1266	
>   1267		drm_gem_object_put(obj);
>   1268	
>   1269		return ret;
>   1270	}
>   1271	EXPORT_SYMBOL_GPL(drm_gem_get_unmapped_area);
>   1272	
>