On 7/17/23 13:29, Haitao Huang wrote:
...
> @@ -248,11 +258,9 @@ static struct sgx_encl_page *__sgx_encl_load_page(struct sgx_encl *encl,
> return entry;
> }
>
> - if (!(encl->secs.epc_page)) {
> - epc_page = sgx_encl_eldu(&encl->secs, NULL);
> - if (IS_ERR(epc_page))
> - return ERR_CAST(epc_page);
> - }
> + epc_page = sgx_encl_load_secs(encl);
> + if (IS_ERR(epc_page))
> + return ERR_CAST(epc_page);
>
> epc_page = sgx_encl_eldu(entry, encl->secs.epc_page);
> if (IS_ERR(epc_page))
> @@ -339,6 +347,13 @@ static vm_fault_t sgx_encl_eaug_page(struct vm_area_struct *vma,
>
> mutex_lock(&encl->lock);
>
> + epc_page = sgx_encl_load_secs(encl);
> + if (IS_ERR(epc_page)) {
> + if (PTR_ERR(epc_page) == -EBUSY)
> + vmret = VM_FAULT_NOPAGE;
> + goto err_out_unlock;
> + }
Whenever I see one of these "make sure it isn't NULL", I always jump to
asking what *keeps* it from becoming NULL again. In both cases here, I
think that's encl->lock.
A comment would be really nice here, maybe on sgx_encl_load_secs(). Maybe:
/*
* Ensure the SECS page is not swapped out. Must be called with
* encl->lock to protect _____ and ensure the SECS page is not
* swapped out again.
*/
> diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
> index 166692f2d501..4662a364ce62 100644
> --- a/arch/x86/kernel/cpu/sgx/main.c
> +++ b/arch/x86/kernel/cpu/sgx/main.c
> @@ -257,6 +257,10 @@ static void sgx_reclaimer_write(struct sgx_epc_page *epc_page,
>
> mutex_lock(&encl->lock);
>
> + /* Should not be possible */
> + if (WARN_ON(!(encl->secs.epc_page)))
> + goto out;
That comment isn't super helpful. We generally don't WARN_ON() things
that should happen. *Why* is it not possible?
