Re: [PATCH v13 14/20] drm/amdgpu, arm64: untag user pointers in amdgpu_ttm_tt_get_user_pages

On 22/03/2019 15:59, Catalin Marinas wrote:

On Wed, Mar 20, 2019 at 03:51:28PM +0100, Andrey Konovalov wrote:

...

This patch is a part of a series that extends arm64 kernel ABI to allow to pass tagged user pointers (with the top byte set to something else other than 0x00) as syscall arguments.

amdgpu_ttm_tt_get_user_pages() uses provided user pointers for vma lookups, which can only by done with untagged pointers.

Untag user pointers in this function.

Signed-off-by: Andrey Konovalov andreyknvl@google.com

drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c index 73e71e61dc99..891b027fa33b 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c @@ -751,10 +751,11 @@ int amdgpu_ttm_tt_get_user_pages(struct ttm_tt *ttm, struct page **pages) * check that we only use anonymous memory to prevent problems * with writeback */

• unsigned long end = gtt->userptr + ttm->num_pages * PAGE_SIZE;
  

• unsigned long userptr = untagged_addr(gtt->userptr);
  

• unsigned long end = userptr + ttm->num_pages * PAGE_SIZE;
  

  struct vm_area_struct *vma;

• vma = find_vma(mm, gtt->userptr);
  

• vma = find_vma(mm, userptr);
  

  if (!vma || vma->vm_file || vma->vm_end < end) { up_read(&mm->mmap_sem); return -EPERM;

I tried to track this down but I failed to see whether user could provide an tagged pointer here (under the restrictions as per Vincenzo's ABI document).

->userptr is set by radeon_ttm_tt_set_userptr(), itself called from radeon_gem_userptr_ioctl(). Any page-aligned value is allowed.

Kevin