On 29.09.17 16:06, Mark Rutland wrote:
On Thu, Sep 28, 2017 at 09:04:04PM +0300, Volodymyr Babchuk wrote:
From: Volodymyr Babchuk vlad.babchuk@gmail.com
This change adds ops for shm_(un)register functions in tee interface. Client application can use these functions to (un)register an own shared buffer in OP-TEE address space. This allows zero copy data sharing between Normal and Secure Worlds.
Please note that while those functions were added to optee code, it does not report to userspace that those functions are available. OP-TEE code does not set TEE_GEN_CAP_REG_MEM flag. This flag will be enabled only after all other features of dynamic shared memory will be implemented in subsequent patches.
While it's not adveritsed to the user, AFAICT the user could still invoke these via ioctls, right?
Is there a problem if the user were to do so, or is it simply not useful without the other features?
Yes, user can invoke this via ioctl. And this buffer will be registeredin OP-TEE. But user will not be able to use this registered buffer, because optee driver does not know how to handle references to registered buffers.
This is a complex feature and I tried to split it into different commits to ease up review.
Probably, I can remove + .shm_register = optee_shm_register, + .shm_unregister = optee_shm_unregister,
from this patch, so user will be not able to call this functions at all. How do you thing? Should I do this?
+int optee_shm_register(struct tee_context *ctx, struct tee_shm *shm,
struct page **pages, size_t num_pages)+{
- pages_array = optee_allocate_pages_array(num_pages);
- if (!pages_array)
return -ENOMEM;
- msg_arg->params->u.tmem.buf_ptr = virt_to_phys(pages_array) |
tee_shm_get_page_offset(shm);This doesn't look right. Why is the shm page offset being orred-in to the pages_array physical address? They're completely separate objects.
They present the same registered shared buffer. You have a list of pages and offset from the first page. Strictly speaking this is not buf_ptr anymore, but it is named so...
This is a part of OP-TEE ABI. We considered different approaches at [1]. This fits into general ABI design.
[1] https://github.com/OP-TEE/optee_os/pull/1232#issuecomment-301851514