Add support for madvise(..., MADV_WILLNEED) by adding
pages with EAUG. Implement fops->fadvise() callback to
achieve this behaviour.
Note this is only done with best effort possible. If any
errors encountered or EPC is under swapping, the operation
will stop and return as normal.
Signed-off-by: Haitao Huang <haitao.huang@xxxxxxxxxxxxxxx>
---
arch/x86/kernel/cpu/sgx/driver.c | 81 ++++++++++++++++++++++++++++++++
1 file changed, 81 insertions(+)
diff --git a/arch/x86/kernel/cpu/sgx/driver.c b/arch/x86/kernel/cpu/sgx/driver.c
index aa9b8b868867..54b24897605b 100644
--- a/arch/x86/kernel/cpu/sgx/driver.c
+++ b/arch/x86/kernel/cpu/sgx/driver.c
@@ -2,6 +2,7 @@
/* Copyright(c) 2016-20 Intel Corporation. */
#include <linux/acpi.h>
+#include <linux/fadvise.h>
#include <linux/miscdevice.h>
#include <linux/mman.h>
#include <linux/security.h>
@@ -9,6 +10,7 @@
#include <asm/traps.h>
#include "driver.h"
#include "encl.h"
+#include "encls.h"
u64 sgx_attributes_reserved_mask;
u64 sgx_xfrm_reserved_mask = ~0x3;
@@ -97,10 +99,88 @@ static int sgx_mmap(struct file *file, struct vm_area_struct *vma)
vma->vm_ops = &sgx_vm_ops;
vma->vm_flags |= VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP | VM_IO;
vma->vm_private_data = encl;
+ /* Anchor vm_pgoff to the enclave base.
+ * So offset passed back to sgx_fadvise hook
+ * is relative to the enclave base
+ */
+ vma->vm_pgoff = (vma->vm_start - encl->base) >> PAGE_SHIFT;
return 0;
}
+/*
+ * Add new pages to the enclave sequentially with ENCLS[EAUG] for the WILLNEED advice.
+ * Only do this to existing VMAs in the same enclave and reject the request.
+ * Returns: 0 if EAUG done with best effort, -EINVAL if any sub-range given
+ * is not in the enclave, or enclave is not initialized..
+ */
+static int sgx_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
+{
+ struct sgx_encl *encl = file->private_data;
+ unsigned long start, end, pos;
+ int ret = -EINVAL;
+ struct vm_area_struct *vma = NULL;
+
+ /* Only support WILLNEED */
+ if (advice != POSIX_FADV_WILLNEED)
+ return -EINVAL;
+ if (!encl)
+ return -EINVAL;
+ if (!cpu_feature_enabled(X86_FEATURE_SGX2))
+ return -EINVAL;
+
+ if (offset + len < offset)
+ return -EINVAL;
+ if (encl->base + offset < encl->base)
+ return -EINVAL;
+ start = offset + encl->base;
+ end = start + len;
+ if (end < start)
+ return -EINVAL;
+ if (end > encl->base + encl->size)
+ return -EINVAL;
+
+ /* EAUG works only for initialized enclaves. */
+ if (!test_bit(SGX_ENCL_INITIALIZED, &encl->flags))
+ return -EINVAL;
+
+ mmap_read_lock(current->mm);
+
+ vma = find_vma(current->mm, start);
+ if (!vma)
+ goto unlock;
+ if (vma->vm_private_data != encl)
+ goto unlock;
+
+ pos = start;
+ if (pos < vma->vm_start || end > vma->vm_end) {
+ /* Don't allow any gaps */
+ goto unlock;
+ }
+ /* Here: vm_start <= pos < end <= vm_end */
+ while (pos < end) {
+ if (xa_load(&encl->page_array, PFN_DOWN(pos)))
+ continue;
+ if (signal_pending(current)) {
+ if (pos == start)
+ ret = -ERESTARTSYS;
+ else
+ ret = -EINTR;
+ goto unlock;
+ }
+ ret = sgx_encl_eaug_page(vma, encl, pos);
+ /* It's OK to not finish */
+ if (ret)
+ break;
+ pos = pos + PAGE_SIZE;
+ cond_resched();
+ }
+ ret = 0;
+unlock:
+ mmap_read_unlock(current->mm);
+ return ret;
+}
+
static unsigned long sgx_get_unmapped_area(struct file *file,
unsigned long addr,
unsigned long len,
@@ -133,6 +213,7 @@ static const struct file_operations sgx_encl_fops = {
.compat_ioctl = sgx_compat_ioctl,
#endif
.mmap = sgx_mmap,
+ .fadvise = sgx_fadvise,
.get_unmapped_area = sgx_get_unmapped_area,
};
--
2.25.1
