With SGX1 an enclave needs to be created with its maximum memory demands pre-allocated. Pages cannot be added to an enclave after it is initialized. SGX2 introduces a new function, ENCLS[EAUG] for adding pages to an initialized enclave.
Add support for dynamically adding pages to an initialized enclave with mmap() by populating pages with EAUG. Use f_ops->populate() callback to achieve this behaviour.
Signed-off-by: Jarkko Sakkinen jarkko@kernel.org --- arch/x86/kernel/cpu/sgx/driver.c | 129 +++++++++++++++++++++++++++++++ 1 file changed, 129 insertions(+)
diff --git a/arch/x86/kernel/cpu/sgx/driver.c b/arch/x86/kernel/cpu/sgx/driver.c index aa9b8b868867..0e97e7476076 100644 --- a/arch/x86/kernel/cpu/sgx/driver.c +++ b/arch/x86/kernel/cpu/sgx/driver.c @@ -9,6 +9,7 @@ #include <asm/traps.h> #include "driver.h" #include "encl.h" +#include "encls.h"
u64 sgx_attributes_reserved_mask; u64 sgx_xfrm_reserved_mask = ~0x3; @@ -101,6 +102,133 @@ static int sgx_mmap(struct file *file, struct vm_area_struct *vma) return 0; }
+static int sgx_encl_augment_page(struct sgx_encl *encl, unsigned long offset) +{ + struct sgx_pageinfo pginfo = {0}; + struct sgx_encl_page *encl_page; + struct sgx_epc_page *epc_page; + struct sgx_va_page *va_page; + u64 secinfo_flags; + int ret; + + /* + * Ignore internal permission checking for dynamically added pages. + * They matter only for data added during the pre-initialization phase. + * The enclave decides the permissions by the means of EACCEPT, + * EACCEPTCOPY and EMODPE. + */ + secinfo_flags = SGX_SECINFO_R | SGX_SECINFO_W | SGX_SECINFO_X; + encl_page = sgx_encl_page_alloc(encl, offset, secinfo_flags); + if (IS_ERR(encl_page)) + return PTR_ERR(encl_page); + + epc_page = sgx_alloc_epc_page(encl_page, true); + if (IS_ERR(epc_page)) { + ret = PTR_ERR(epc_page); + goto err_alloc_epc_page; + } + + va_page = sgx_encl_grow(encl); + if (IS_ERR(va_page)) { + ret = PTR_ERR(va_page); + goto err_grow; + } + + mutex_lock(&encl->lock); + + /* + * Adding to encl->va_pages must be done under encl->lock. Ditto for + * deleting (via sgx_encl_shrink()) in the error path. + */ + if (va_page) + list_add(&va_page->list, &encl->va_pages); + + /* + * Insert prior to EADD in case of OOM. EADD modifies MRENCLAVE, i.e. + * can't be gracefully unwound, while failure on EADD/EXTEND is limited + * to userspace errors (or kernel/hardware bugs). + */ + ret = xa_insert(&encl->page_array, PFN_DOWN(encl_page->desc), + encl_page, GFP_KERNEL); + + /* + * If ret == -EBUSY then page was created in another flow while + * running without encl->lock + */ + if (ret) + goto err_xa_insert; + + pginfo.secs = (unsigned long)sgx_get_epc_virt_addr(encl->secs.epc_page); + pginfo.addr = encl_page->desc & PAGE_MASK; + pginfo.metadata = 0; + + ret = __eaug(&pginfo, sgx_get_epc_virt_addr(epc_page)); + if (ret) + goto err_eaug; + + encl_page->encl = encl; + encl_page->epc_page = epc_page; + encl_page->type = SGX_PAGE_TYPE_REG; + encl->secs_child_cnt++; + + sgx_mark_page_reclaimable(encl_page->epc_page); + + mutex_unlock(&encl->lock); + + return 0; + +err_eaug: + xa_erase(&encl->page_array, PFN_DOWN(encl_page->desc)); + +err_xa_insert: + sgx_encl_shrink(encl, va_page); + mutex_unlock(&encl->lock); + +err_grow: + sgx_encl_free_epc_page(epc_page); + +err_alloc_epc_page: + kfree(encl_page); + + return VM_FAULT_SIGBUS; +} + +/* + * Add new pages to the enclave sequentially with ENCLS[EAUG]. Note that + * sgx_mmap() validates that the given VMA is within the enclave range. Calling + * here sgx_encl_may_map() second time would too time consuming. + */ +static int sgx_populate(struct file *file, struct vm_area_struct *vma) +{ + unsigned long length = vma->vm_end - vma->vm_start; + struct sgx_encl *encl = file->private_data; + unsigned long start = encl->base - vma->vm_start; + unsigned long pos; + int ret; + + /* EAUG works only for initialized enclaves. */ + if (!test_bit(SGX_ENCL_INITIALIZED, &encl->flags)) + return -EINVAL; + + for (pos = 0 ; pos < length; pos += PAGE_SIZE) { + if (signal_pending(current)) { + if (!pos) + ret = -ERESTARTSYS; + + break; + } + + if (need_resched()) + cond_resched(); + + ret = sgx_encl_augment_page(encl, start + pos); + if (ret) + break; + } + + return ret; +} + static unsigned long sgx_get_unmapped_area(struct file *file, unsigned long addr, unsigned long len, @@ -133,6 +261,7 @@ static const struct file_operations sgx_encl_fops = { .compat_ioctl = sgx_compat_ioctl, #endif .mmap = sgx_mmap, + .populate = sgx_populate, .get_unmapped_area = sgx_get_unmapped_area, };