On 11/7/21 10:06 AM, Jarkko Sakkinen wrote:
On Thu, Nov 04, 2021 at 03:38:55PM -0700, Dave Hansen wrote:
On 11/3/21 4:22 PM, Jarkko Sakkinen wrote:
--- a/arch/x86/kernel/cpu/sgx/encl.c +++ b/arch/x86/kernel/cpu/sgx/encl.c @@ -22,6 +22,7 @@ static int __sgx_encl_eldu(struct sgx_encl_page *encl_page, { unsigned long va_offset = encl_page->desc & SGX_ENCL_PAGE_VA_OFFSET_MASK; struct sgx_encl *encl = encl_page->encl;
- struct inode *inode = file_inode(encl->backing); struct sgx_pageinfo pginfo; struct sgx_backing b; pgoff_t page_index;
@@ -60,6 +61,9 @@ static int __sgx_encl_eldu(struct sgx_encl_page *encl_page, sgx_encl_put_backing(&b, false);
- /* Free the backing memory. */
- shmem_truncate_range(inode, PFN_PHYS(page_index), PFN_PHYS(page_index) + PAGE_SIZE - 1);
- return ret;
}
This also misses tearing down the backing storage if it is in place at sgx_encl_release().
Hmm... sgx_encl_release() does fput(). Isn't that enough to tear it down, or does it require explicit truncate, i.e. something like
shmem_truncate_range(file_inode(encl->backing), encl->base, encl->size - 1);
That's true, the page cache should all be torn down along with the fput(). *But*, it would be a very nice property if the backing storage was empty by this point. It essentially ensures that no enclave-runtime cases missed truncating the backing storage away.
Does a entry->epc_page==NULL page in there guarantee that it has backing storage?
Yes, it is an invariant. That what I was thinking to use for PCMD: iterate 32 pages and check if they have a faulted page.
I think the rule should be that entry->epc_page==NULL enclave pages have backing storage. All entry->epc_page!=NULL do *not* have backing storage.