Re: [PATCH v4] tee: Use iov_iter to better support shared buffer registration
From: Arnaud POULIQUEN
Date: Thu Nov 30 2023 - 04:08:43 EST
On 11/30/23 08:54, Sumit Garg wrote:
> On Wed, 29 Nov 2023 at 22:15, Arnaud Pouliquen
> <arnaud.pouliquen@xxxxxxxxxxx> wrote:
>>
>> Currently it's not possible to register kernel buffers with TEE
>> which are allocated via vmalloc.
>>
>> Use iov_iter and associated helper functions to manage the page
>> registration for all type of memories.
>>
>> Suggested-by: Christoph Hellwig <hch@xxxxxxxxxxxxx>
>> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@xxxxxxxxxxx>
>> ---
>> Update from V3 to V4:
>> - improve commit message,
>> - use import_ubuf() instead of iov_iter_init(),
>> - move shm_get_kernel_pages in register_shm_helper,
>> - put back untagged_addr in register_shm_helper(),
>> - move the comment related to pin pages from shm_get_kernel_pages()
>> to register_shm_helper().
>>
>> Update from V2 to V3:
>> - break lines longer than 80 columns.
>>
>> Update from V1 to V2:
>> - replace ITER_SOURCE by ITER_DEST flag in tee_shm_register_user_buf(),
>> - replace IS_ERR_OR NULL(shm) by IS_ERR(shm) in tee_shm_register_user_buf().
>>
>> V1:
>> The support of buffer registration allocated with vmalloc is no more
>> available since c83900393aa1 ("tee: Remove vmalloc page support").
>>
>> This patch is an alternative to a revert and resulted from a discussion
>> with Christopher Hellwig [1].
>>
>> This patch has been tested using xtest tool in optee qemu environment [2]
>> and using the series related to the remoteproc tee that should be
>> proposed soon [3].
>>
>> References:
>> [1] https://lore.kernel.org/linux-arm-kernel/18a8528d-7d9d-6ed0-0045-5ee47dd39fb2@xxxxxxxxxxx/T/#m8ec683c44fcd9b69c2aee42eaed0793afac9dd18in
>> [2] https://optee.readthedocs.io/en/latest/building/devices/qemu.html#build-instructions
>> [3] https://lore.kernel.org/linux-arm-kernel/18a8528d-7d9d-6ed0-0045-5ee47dd39fb2@xxxxxxxxxxx/T/#maca0a1fc897aadd54c7deac432e11473fe970d1d
>> ---
>> drivers/tee/tee_shm.c | 83 ++++++++++++++++++++++++-------------------
>> 1 file changed, 46 insertions(+), 37 deletions(-)
>>
>> diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c
>> index 673cf0359494..ac73e8143233 100644
>> --- a/drivers/tee/tee_shm.c
>> +++ b/drivers/tee/tee_shm.c
>> @@ -22,23 +22,12 @@ static void shm_put_kernel_pages(struct page **pages, size_t page_count)
>> put_page(pages[n]);
>> }
>>
>> -static int shm_get_kernel_pages(unsigned long start, size_t page_count,
>> - struct page **pages)
>> +static void shm_get_kernel_pages(struct page **pages, size_t page_count)
>> {
>> - struct page *page;
>> size_t n;
>>
>> - if (WARN_ON_ONCE(is_vmalloc_addr((void *)start) ||
>> - is_kmap_addr((void *)start)))
>> - return -EINVAL;
>> -
>> - page = virt_to_page((void *)start);
>> - for (n = 0; n < page_count; n++) {
>> - pages[n] = page + n;
>> + for (n = 0; n < page_count; n++)
>> get_page(pages[n]);
>> - }
>> -
>> - return page_count;
>> }
>>
>> static void release_registered_pages(struct tee_shm *shm)
>> @@ -214,13 +203,14 @@ struct tee_shm *tee_shm_alloc_priv_buf(struct tee_context *ctx, size_t size)
>> EXPORT_SYMBOL_GPL(tee_shm_alloc_priv_buf);
>>
>> static struct tee_shm *
>> -register_shm_helper(struct tee_context *ctx, unsigned long addr,
>> - size_t length, u32 flags, int id)
>> +register_shm_helper(struct tee_context *ctx, struct iov_iter *iter, u32 flags,
>> + int id)
>> {
>> struct tee_device *teedev = ctx->teedev;
>> struct tee_shm *shm;
>> - unsigned long start;
>> - size_t num_pages;
>> + unsigned long start, addr;
>> + size_t num_pages, off;
>> + ssize_t len;
>> void *ret;
>> int rc;
>>
>> @@ -245,31 +235,38 @@ register_shm_helper(struct tee_context *ctx, unsigned long addr,
>> shm->flags = flags;
>> shm->ctx = ctx;
>> shm->id = id;
>> - addr = untagged_addr(addr);
>> + addr = untagged_addr((unsigned long)iter_iov_addr(iter));
>> start = rounddown(addr, PAGE_SIZE);
>> - shm->offset = addr - start;
>> - shm->size = length;
>> - num_pages = (roundup(addr + length, PAGE_SIZE) - start) / PAGE_SIZE;
>> + num_pages = iov_iter_npages(iter, INT_MAX);
>> + if (!num_pages) {
>> + ret = ERR_PTR(-ENOMEM);
>> + goto err_ctx_put;
>> + }
>> +
>> shm->pages = kcalloc(num_pages, sizeof(*shm->pages), GFP_KERNEL);
>> if (!shm->pages) {
>> ret = ERR_PTR(-ENOMEM);
>> goto err_free_shm;
>> }
>>
>> - if (flags & TEE_SHM_USER_MAPPED)
>> - rc = pin_user_pages_fast(start, num_pages, FOLL_WRITE,
>> - shm->pages);
>> - else
>> - rc = shm_get_kernel_pages(start, num_pages, shm->pages);
>> - if (rc > 0)
>> - shm->num_pages = rc;
>> - if (rc != num_pages) {
>> - if (rc >= 0)
>> - rc = -ENOMEM;
>> - ret = ERR_PTR(rc);
>> - goto err_put_shm_pages;
>> + len = iov_iter_extract_pages(iter, &shm->pages, LONG_MAX, num_pages, 0,
>> + &off);
>> + if (unlikely(len <= 0)) {
>> + ret = len ? ERR_PTR(len) : ERR_PTR(-ENOMEM);
>> + goto err_free_shm_pages;
>> }
>>
>> + /*
>> + * iov_iter_extract_kvec_pages does not get reference on the pages,
>> + * get a pin on them.
>
> I think you meant: "get a reference on them". But I don't see the
> value of this comment since iov_iter_extract_kvec_pages() already has
> been commented properly as follows:
>
> /*
> * Extract a list of virtually contiguous pages from an ITER_KVEC iterator.
> * This does not get references on the pages, nor does it get a pin on them.
> */
>
I spent some time debugging this part. Since we use the same API for both user
and kernel buffers, we wouldn't expect to have any specific actions to take.
Therefore, I thought it would be helpful to add a comment explaining the reason
for this specific code, rather than go deeper into iov_iter to understand it.
But if you don't see the value, I can remove the comment.
>> + */
>> + if (iov_iter_is_kvec(iter))
>> + shm_get_kernel_pages(shm->pages, num_pages);
>> +
>> + shm->offset = off;
>> + shm->size = len;
>> + shm->num_pages = num_pages;
>> +
>> rc = teedev->desc->ops->shm_register(ctx, shm, shm->pages,
>> shm->num_pages, start);
>> if (rc) {
>> @@ -279,10 +276,11 @@ register_shm_helper(struct tee_context *ctx, unsigned long addr,
>>
>> return shm;
>> err_put_shm_pages:
>> - if (flags & TEE_SHM_USER_MAPPED)
>> + if (!iov_iter_is_kvec(iter))
>> unpin_user_pages(shm->pages, shm->num_pages);
>> else
>> shm_put_kernel_pages(shm->pages, shm->num_pages);
>> +err_free_shm_pages:
>> kfree(shm->pages);
>> err_free_shm:
>> kfree(shm);
>> @@ -307,8 +305,9 @@ struct tee_shm *tee_shm_register_user_buf(struct tee_context *ctx,
>> u32 flags = TEE_SHM_USER_MAPPED | TEE_SHM_DYNAMIC;
>> struct tee_device *teedev = ctx->teedev;
>> struct tee_shm *shm;
>> + struct iov_iter iter;
>> void *ret;
>> - int id;
>> + int id, err;
>>
>> if (!access_ok((void __user *)addr, length))
>> return ERR_PTR(-EFAULT);
>> @@ -319,7 +318,11 @@ struct tee_shm *tee_shm_register_user_buf(struct tee_context *ctx,
>> if (id < 0)
>> return ERR_PTR(id);
>>
>> - shm = register_shm_helper(ctx, addr, length, flags, id);
>> + err = import_ubuf(ITER_DEST, (void __user *)addr, length, &iter);
>
> As I mentioned in a previous review, import_ubuf() already does the
> access_ok() check, so we don't need the extra access_ok() check above.
> Also, you should move import_ubuf() to be the first invocation within
> this API.
My apologies, I re-added import_ubuf() during testing to debug an issue and
forgot to
remove it afterwards.
Thanks and regards,
Arnaud
>
> -Sumit
>
>> + if (err)
>> + return ERR_PTR(err);
>> +
>> + shm = register_shm_helper(ctx, &iter, flags, id);
>> if (IS_ERR(shm)) {
>> mutex_lock(&teedev->mutex);
>> idr_remove(&teedev->idr, id);
>> @@ -352,8 +355,14 @@ struct tee_shm *tee_shm_register_kernel_buf(struct tee_context *ctx,
>> void *addr, size_t length)
>> {
>> u32 flags = TEE_SHM_DYNAMIC;
>> + struct kvec kvec;
>> + struct iov_iter iter;
>> +
>> + kvec.iov_base = addr;
>> + kvec.iov_len = length;
>> + iov_iter_kvec(&iter, ITER_DEST, &kvec, 1, length);
>>
>> - return register_shm_helper(ctx, (unsigned long)addr, length, flags, -1);
>> + return register_shm_helper(ctx, &iter, flags, -1);
>> }
>> EXPORT_SYMBOL_GPL(tee_shm_register_kernel_buf);
>>
>> --
>> 2.25.1
>>