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Subject[PATCH v12 12/13] platform/x86: ptrace() support for the SGX driver
Date
Implemented VMA callbacks in order to ptrace() 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@linux.intel.com>
---
drivers/platform/x86/intel_sgx/sgx_encl.c | 2 +-
drivers/platform/x86/intel_sgx/sgx_vma.c | 116 ++++++++++++++++++++++
2 files changed, 117 insertions(+), 1 deletion(-)

diff --git a/drivers/platform/x86/intel_sgx/sgx_encl.c b/drivers/platform/x86/intel_sgx/sgx_encl.c
index e3d7fa885489..20cd9ff7dd75 100644
--- a/drivers/platform/x86/intel_sgx/sgx_encl.c
+++ b/drivers/platform/x86/intel_sgx/sgx_encl.c
@@ -954,7 +954,7 @@ int sgx_encl_load_page(struct sgx_encl_page *encl_page,
ret = __eldu(&pginfo, epc_ptr, va_ptr + va_offset);
if (ret) {
sgx_err(encl, "ELDU returned %d\n", ret);
- ret = -EFAULT;
+ ret = ENCLS_TO_ERR(ret);
}

kunmap_atomic((void *)(unsigned long)(pginfo.pcmd - pcmd_offset));
diff --git a/drivers/platform/x86/intel_sgx/sgx_vma.c b/drivers/platform/x86/intel_sgx/sgx_vma.c
index cc0993b4fd40..3a856e40c82c 100644
--- a/drivers/platform/x86/intel_sgx/sgx_vma.c
+++ b/drivers/platform/x86/intel_sgx/sgx_vma.c
@@ -51,8 +51,124 @@ static int sgx_vma_fault(struct vm_fault *vmf)
return VM_FAULT_SIGBUS;
}

+static int sgx_edbgrd(struct sgx_encl *encl, struct sgx_encl_page *page,
+ unsigned long addr, void *data)
+{
+ unsigned long offset;
+ void *ptr;
+ int ret;
+
+ offset = addr & ~PAGE_MASK;
+
+ if ((page->desc & SGX_ENCL_PAGE_TCS) &&
+ offset > offsetof(struct sgx_tcs, gslimit))
+ return -ECANCELED;
+
+ ptr = sgx_get_page(page->epc_page);
+ ret = __edbgrd((unsigned long)ptr + offset, data);
+ sgx_put_page(ptr);
+ if (ret) {
+ sgx_dbg(encl, "EDBGRD returned %d\n", ret);
+ return ENCLS_TO_ERR(ret);
+ }
+
+ return 0;
+}
+
+static int sgx_edbgwr(struct sgx_encl *encl, struct sgx_encl_page *page,
+ unsigned long addr, void *data)
+{
+ unsigned long offset;
+ void *ptr;
+ 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;
+
+ ptr = sgx_get_page(page->epc_page);
+ ret = __edbgwr((unsigned long)ptr + offset, data);
+ sgx_put_page(ptr);
+ if (ret) {
+ sgx_dbg(encl, "EDBGWR returned %d\n", ret);
+ return ENCLS_TO_ERR(ret);
+ }
+
+ 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) {
+ if (!entry || !((addr + i) & (PAGE_SIZE - 1))) {
+ if (entry)
+ entry->desc &= ~SGX_ENCL_PAGE_RESERVED;
+
+ entry = sgx_fault_page(vma, (addr + i) & PAGE_MASK,
+ true);
+ if (IS_ERR(entry)) {
+ ret = PTR_ERR(entry);
+ entry = NULL;
+ break;
+ }
+ }
+
+ /* Locking is not needed because only immutable fields of the
+ * page are accessed and page itself is reserved so that it
+ * cannot be swapped out in the middle.
+ */
+
+ 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)
+ break;
+ if (write) {
+ memcpy(data + offset, buf + i, cnt);
+ ret = sgx_edbgwr(encl, entry, align, data);
+ if (ret)
+ break;
+ }
+ else
+ memcpy(buf + i,data + offset, cnt);
+ }
+
+ if (entry)
+ entry->desc &= ~SGX_ENCL_PAGE_RESERVED;
+
+ return (ret < 0 && ret != -ECANCELED) ? 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,
};
--
2.17.1
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