[RFC PATCH v1 1/1] linux: mm_types: allow to modified the vm_flags in vm_area_struct

From: Vincenzo Palazzo
Date: Sun Mar 12 2023 - 18:43:05 EST

With 6.3-rc1 is not possible to build the following drivers

- nvidia, that the compilation returns the following errors

/var/lib/dkms/nvidia/525.89.02/build/nvidia/nv-mmap.c: In function ‘nvidia_mmap_numa’:
/var/lib/dkms/nvidia/525.89.02/build/nvidia/nv-mmap.c:455:19: error: assignment of read-only member ‘vm_flags’
455 | vma->vm_flags |= VM_MIXEDMAP;
| ^~
/var/lib/dkms/nvidia/525.89.02/build/nvidia/nv-mmap.c: In function ‘nvidia_mmap_helper’:
/var/lib/dkms/nvidia/525.89.02/build/nvidia/nv-mmap.c:599:23: error: assignment of read-only member ‘vm_flags’
599 | vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND;
| ^~
/var/lib/dkms/nvidia/525.89.02/build/nvidia/nv-mmap.c:666:23: error: assignment of read-only member ‘vm_flags’
666 | vma->vm_flags |= (VM_IO | VM_LOCKED | VM_RESERVED);
| ^~
/var/lib/dkms/nvidia/525.89.02/build/nvidia/nv-mmap.c:667:23: error: assignment of read-only member ‘vm_flags’
667 | vma->vm_flags |= (VM_DONTEXPAND | VM_DONTDUMP);
| ^~
/var/lib/dkms/nvidia/525.89.02/build/nvidia/nv-mmap.c:673:23: error: assignment of read-only member ‘vm_flags’
673 | vma->vm_flags &= ~VM_WRITE;
| ^~
/var/lib/dkms/nvidia/525.89.02/build/nvidia/nv-mmap.c:674:23: error: assignment of read-only member ‘vm_flags’
674 | vma->vm_flags &= ~VM_MAYWRITE;
| ^~
/var/lib/dkms/nvidia/525.89.02/build/nvidia/nv-mmap.c: In function ‘nv_encode_caching’:
/var/lib/dkms/nvidia/525.89.02/build/nvidia/nv-mmap.c:353:16: warning: this statement may fall through [-Wimplicit-fallthrough=]
353 | if (NV_ALLOW_CACHING(memory_type))
| ^
/var/lib/dkms/nvidia/525.89.02/build/nvidia/nv-mmap.c:356:9: note: here
356 | default:
| ^~~~~~~
make[2]: *** [scripts/Makefile.build:252: /var/lib/dkms/nvidia/525.89.02/build/nvidia/nv-mmap.o] Error 1
make[2]: *** Waiting for unfinished jobs....
make[1]: *** [Makefile:2028: /var/lib/dkms/nvidia/525.89.02/build] Error 2
make[1]: Leaving directory '/home/vincenzopalazzo/gittea/linux'
make: *** [Makefile:82: modules] Error 2
------

- vboxhost/7.0.6_OSE where the build fails with the following errors
DKMS make.log for vboxhost-7.0.6_OSE for kernel 6.3.0-rc1-00231-g511e7733223b (x86_64)
Sat Mar 11 04:21:34 PM UTC 2023
CC [M] /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxnetflt/linux/VBoxNetFlt-linux.o
CC [M] /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxnetadp/linux/VBoxNetAdp-linux.o
CC [M] /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxnetflt/VBoxNetFlt.o
CC [M] /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/linux/SUPDrv-linux.o
CC [M] /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/SUPDrv.o
CC [M] /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxnetadp/VBoxNetAdp.o
CC [M] /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/SUPDrvGip.o
CC [M] /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxnetflt/SUPR0IdcClient.o
CC [M] /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/SUPDrvSem.o
CC [M] /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxnetflt/SUPR0IdcClientComponent.o
CC [M] /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxnetflt/linux/SUPR0IdcClient-linux.o
CC [M] /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/SUPDrvTracer.o
CC [M] /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/SUPLibAll.o
CC [M] /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/common/string/strformatrt.o
CC [M] /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/combined-agnostic1.o
CC [M] /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/combined-agnostic2.o
CC [M] /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/combined-os-specific.o
LD [M] /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxnetadp/vboxnetadp.o
In file included from /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/combined-os-specific.c:43:
/var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/r0drv/linux/memobj-r0drv-linux.c: In function ‘rtR0MemObjNativeLockUser’:
/var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/r0drv/linux/memobj-r0drv-linux.c:1404:39: error: assignment of read-only member ‘vm_flags’
1404 | papVMAs[rc]->vm_flags |= VM_DONTCOPY | VM_LOCKED;
| ^~
/var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/r0drv/linux/memobj-r0drv-linux.c: In function ‘rtR0MemObjNativeMapUser’:
/var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/r0drv/linux/memobj-r0drv-linux.c:1876:35: error: assignment of read-only member ‘vm_flags’
1876 | vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
| ^~
make[2]: *** [scripts/Makefile.build:252: /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/combined-os-specific.o] Error 1
make[2]: *** Waiting for unfinished jobs....
LD [M] /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxnetflt/vboxnetflt.o
make[1]: *** [scripts/Makefile.build:494: /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv] Error 2
make: *** [Makefile:2028: /var/lib/dkms/vboxhost/7.0.6_OSE/build] Error 2
-----

The commands that I use to build these drivers are:

- sudo dkms install --no-depmod nvidia/525.89.02 -k 6.3.0-rc1-00231-g511e7733223b
- sudo dkms install --no-depmod vboxhost/7.0.6_OSE -k 6.3.0-rc1-00231-g511e7733223b

The following commit reverts the const constraint that was added in [1],
and also I tested this patch on my system and all started again as
6.2.2.

[1] https://lore.kernel.org/all/20230126193752.297968-3-surenb@xxxxxxxxxx/T/#u

Signed-off-by: Vincenzo Palazzo <vincenzopalazzodev@xxxxxxxxx>
---
include/linux/mm_types.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 0722859c3647..a354eb60c7e8 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -497,7 +497,7 @@ struct vm_area_struct {
* To modify use vm_flags_{init|reset|set|clear|mod} functions.
*/
union {
- const vm_flags_t vm_flags;
+ vm_flags_t vm_flags;
vm_flags_t __private __vm_flags;
};

--
2.39.2