On Sun, Mar 17, 2019 at 11:14:48PM +0200, Jarkko Sakkinen wrote:
> Add VMA callbacks for ptrace() that can be used with debug enclaves.
> With debug enclaves data can be read and write the memory word at a time
> by using ENCLS(EDBGRD) and ENCLS(EDBGWR) leaf instructions.
>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
> ---
> arch/x86/kernel/cpu/sgx/encl.c | 97 ++++++++++++++++++++++++++++++++++
> 1 file changed, 97 insertions(+)
>
> diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c
> index 1b8874699dd3..5b5fc933ee19 100644
> --- a/arch/x86/kernel/cpu/sgx/encl.c
> +++ b/arch/x86/kernel/cpu/sgx/encl.c
> @@ -256,10 +256,107 @@ static unsigned int sgx_vma_fault(struct vm_fault *vmf)
> return ret;
> }
>
> +static int sgx_edbgrd(struct sgx_encl *encl, struct sgx_encl_page *page,
> + unsigned long addr, void *data)
> +{
> + unsigned long offset;
> + int ret;
> +
> + offset = addr & ~PAGE_MASK;
> +
> + if ((page->desc & SGX_ENCL_PAGE_TCS) &&
> + offset > offsetof(struct sgx_tcs, gs_limit))
> + return -ECANCELED;
> +
> + ret = __edbgrd(sgx_epc_addr(page->epc_page) + offset, data);
> + if (ret)
> + return -EIO;
> +
> + return 0;
> +}
> +
> +static int sgx_edbgwr(struct sgx_encl *encl, struct sgx_encl_page *page,
> + unsigned long addr, void *data)
> +{
> + unsigned long offset;
> + int ret;
> +
> + offset = addr & ~PAGE_MASK;
> +
> + /* Writing anything else than flags will cause #GP */
> + if ((page->desc & SGX_ENCL_PAGE_TCS) &&
> + offset != offsetof(struct sgx_tcs, flags))
> + return -ECANCELED;
> +
> + ret = __edbgwr(sgx_epc_addr(page->epc_page) + offset, data);
> + if (ret)
> + return -EIO;
> +
> + return 0;
> +}
> +
> +static int sgx_vma_access(struct vm_area_struct *vma, unsigned long addr,
> + void *buf, int len, int write)
> +{
> + struct sgx_encl *encl = vma->vm_private_data;
> + struct sgx_encl_page *entry = NULL;
> + unsigned long align;
> + char data[sizeof(unsigned long)];
> + int offset;
> + int cnt;
> + int ret = 0;
> + int i;
> +
> + /* If process was forked, VMA is still there but vm_private_data is set
> + * to NULL.
> + */
> + if (!encl)
> + return -EFAULT;
> +
> + if (!(encl->flags & SGX_ENCL_DEBUG) ||
> + !(encl->flags & SGX_ENCL_INITIALIZED) ||
> + (encl->flags & SGX_ENCL_DEAD))
> + return -EFAULT;
> +
> + for (i = 0; i < len; i += cnt) {
> + entry = sgx_encl_reserve_page(encl, (addr + i) & PAGE_MASK);
Taking a lock indirectly via sgx_encl_reserve_page() and releasing it
directly via mutex_unlock() is a bit difficult to follow, having a helper
to pair up with sgx_encl_reserve_page() would be more readable. Open
coding sgx_encl_reserve_page() would probably be even better since this
is the only user AFAICT.
All that being said, I prefer the old approach of marking the page RESERVED
instead of holding the enclave's lock, even though it was slightly more
complex.
> + if (IS_ERR(entry)) {
> + ret = PTR_ERR(entry);
> + break;
> + }
> +
> + align = ALIGN_DOWN(addr + i, sizeof(unsigned long));
> + offset = (addr + i) & (sizeof(unsigned long) - 1);
> + cnt = sizeof(unsigned long) - offset;
> + cnt = min(cnt, len - i);
> +
> + ret = sgx_edbgrd(encl, entry, align, data);
> + if (ret)
> + goto out;
> +
> + if (write) {
> + memcpy(data + offset, buf + i, cnt);
> + ret = sgx_edbgwr(encl, entry, align, data);
> + if (ret)
> + goto out;
> + } else
> + memcpy(buf + i, data + offset, cnt);
> +
> +out:
> + mutex_unlock(&encl->lock);
> +
> + if (ret)
> + break;
> + }
> +
> + return ret < 0 ? ret : i;
> +}
> +
> const struct vm_operations_struct sgx_vm_ops = {
> .close = sgx_vma_close,
> .open = sgx_vma_open,
> .fault = sgx_vma_fault,
> + .access = sgx_vma_access,
> };
> EXPORT_SYMBOL_GPL(sgx_vm_ops);
>
> --
> 2.19.1
>
