diff --git a/arch/x86/entry/vdso/vsgx_enter_enclave.S b/arch/x86/entry/vdso/vsgx_enter_enclave.S
index 34cee2b0ef09..be7e467e1efb 100644
--- a/arch/x86/entry/vdso/vsgx_enter_enclave.S
+++ b/arch/x86/entry/vdso/vsgx_enter_enclave.S
@@ -15,66 +15,6 @@
 .code64
 .section .text, "ax"
 
-/**
- * __vdso_sgx_enter_enclave() - Enter an SGX enclave
- * @leaf:	ENCLU leaf, must be EENTER or ERESUME
- * @tcs:	TCS, must be non-NULL
- * @e:		Optional struct sgx_enclave_exception instance
- * @handler:	Optional enclave exit handler
- *
- * **Important!**  __vdso_sgx_enter_enclave() is **NOT** compliant with the
- * x86-64 ABI, i.e. cannot be called from standard C code.
- *
- * Input ABI:
- *  @leaf	%eax
- *  @tcs	8(%rsp)
- *  @e 		0x10(%rsp)
- *  @handler	0x18(%rsp)
- *
- * Output ABI:
- *  @ret	%eax
- *
- * All general purpose registers except RAX, RBX and RCX are passed as-is to
- * the enclave. RAX, RBX and RCX are consumed by EENTER and ERESUME and are
- * loaded with @leaf, asynchronous exit pointer, and @tcs respectively.
- *
- * RBP and the stack are used to anchor __vdso_sgx_enter_enclave() to the
- * pre-enclave state, e.g. to retrieve @e and @handler after an enclave exit.
- * All other registers are available for use by the enclave and its runtime,
- * e.g. an enclave can push additional data onto the stack (and modify RSP) to
- * pass information to the optional exit handler (see below).
- *
- * Most exceptions reported on ENCLU, including those that occur within the
- * enclave, are fixed up and reported synchronously instead of being delivered
- * via a standard signal. Debug Exceptions (#DB) and Breakpoints (#BP) are
- * never fixed up and are always delivered via standard signals. On synchrously
- * reported exceptions, -EFAULT is returned and details about the exception are
- * recorded in @e, the optional sgx_enclave_exception struct.
-
- * If an exit handler is provided, the handler will be invoked on synchronous
- * exits from the enclave and for all synchronously reported exceptions. In
- * latter case, @e is filled prior to invoking the handler.
- *
- * The exit handler's return value is interpreted as follows:
- *  >0:		continue, restart __vdso_sgx_enter_enclave() with @ret as @leaf
- *   0:		success, return @ret to the caller
- *  <0:		error, return @ret to the caller
- *
- * The exit handler may transfer control, e.g. via longjmp() or C++ exception,
- * without returning to __vdso_sgx_enter_enclave().
- *
- * Return:
- *  0 on success,
- *  -EINVAL if ENCLU leaf is not allowed,
- *  -EFAULT if an exception occurs on ENCLU or within the enclave
- *  -errno for all other negative values returned by the userspace exit handler
- */
-#ifdef SGX_KERNEL_DOC
-/* C-style function prototype to coerce kernel-doc into parsing the comment. */
-int __vdso_sgx_enter_enclave(int leaf, void *tcs,
-			     struct sgx_enclave_exception *e,
-			     sgx_enclave_exit_handler_t handler);
-#endif
 SYM_FUNC_START(__vdso_sgx_enter_enclave)
 	/* Prolog */
 	.cfi_startproc
@@ -83,7 +23,10 @@ SYM_FUNC_START(__vdso_sgx_enter_enclave)
 	.cfi_rel_offset		%rbp, 0
 	mov	%rsp, %rbp
 	.cfi_def_cfa_register	%rbp
+	push	%rbx
+	.cfi_rel_offset		%rbx, -8
 
+	mov	%ecx, %eax
 .Lenter_enclave:
 	/* EENTER <= leaf <= ERESUME */
 	cmp	$EENTER, %eax
@@ -109,6 +52,7 @@ SYM_FUNC_START(__vdso_sgx_enter_enclave)
 	jne	.Linvoke_userspace_handler
 
 .Lout:
+	pop	%rbx
 	leave
 	.cfi_def_cfa		%rsp, 8
 	ret
diff --git a/arch/x86/include/uapi/asm/sgx.h b/arch/x86/include/uapi/asm/sgx.h
index e196cfd44b70..3760e5d5dc0c 100644
--- a/arch/x86/include/uapi/asm/sgx.h
+++ b/arch/x86/include/uapi/asm/sgx.h
@@ -111,4 +111,65 @@ typedef int (*sgx_enclave_exit_handler_t)(long rdi, long rsi, long rdx,
 					  void *tcs, int ret,
 					  struct sgx_enclave_exception *e);
 
+/**
+ * __vdso_sgx_enter_enclave() - Enter an SGX enclave
+ * @rdi:	Pass-through value for RDI
+ * @rsi:	Pass-through value for RSI
+ * @rdx:	Pass-through value for RDX
+ * @leaf:	ENCLU leaf, must be EENTER or ERESUME
+ * @r8:		Pass-through value for R8
+ * @r9:		Pass-through value for R9
+ * @tcs:	TCS, must be non-NULL
+ * @e:		Optional struct sgx_enclave_exception instance
+ * @handler:	Optional enclave exit handler
+ *
+ * NOTE: __vdso_sgx_enter_enclave() does not ensure full compliance with the
+ * x86-64 ABI, e.g. doesn't explicitly clear EFLAGS.DF after EEXIT.  Except for
+ * non-volatile general purpose registers, preserving/setting state in
+ * accordance with the x86-64 ABI is the responsibility of the enclave and its
+ * runtime, i.e. __vdso_sgx_enter_enclave() cannot be called from C code
+ * without careful consideration by both the enclave and its runtime.
+ *
+ * All general purpose registers except RAX, RBX and RCX are passed as-is to
+ * the enclave.  RAX, RBX and RCX are consumed by EENTER and ERESUME and are
+ * loaded with @leaf, asynchronous exit pointer, and @tcs respectively.
+ *
+ * RBP and the stack are used to anchor __vdso_sgx_enter_enclave() to the
+ * pre-enclave state, e.g. to retrieve @e and @handler after an enclave exit.
+ * All other registers are available for use by the enclave and its runtime,
+ * e.g. an enclave can push additional data onto the stack (and modify RSP) to
+ * pass information to the optional exit handler (see below).
+ *
+ * Most exceptions reported on ENCLU, including those that occur within the
+ * enclave, are fixed up and reported synchronously instead of being delivered
+ * via a standard signal. Debug Exceptions (#DB) and Breakpoints (#BP) are
+ * never fixed up and are always delivered via standard signals. On synchrously
+ * reported exceptions, -EFAULT is returned and details about the exception are
+ * recorded in @e, the optional sgx_enclave_exception struct.
+
+ * If an exit handler is provided, the handler will be invoked on synchronous
+ * exits from the enclave and for all synchronously reported exceptions. In
+ * latter case, @e is filled prior to invoking the handler.
+ *
+ * The exit handler's return value is interpreted as follows:
+ *  >0:		continue, restart __vdso_sgx_enter_enclave() with @ret as @leaf
+ *   0:		success, return @ret to the caller
+ *  <0:		error, return @ret to the caller
+ *
+ * The exit handler may transfer control, e.g. via longjmp() or C++ exception,
+ * without returning to __vdso_sgx_enter_enclave().
+ *
+ * Return:
+ *  0 on success,
+ *  -EINVAL if ENCLU leaf is not allowed,
+ *  -EFAULT if an exception occurs on ENCLU or within the enclave
+ *  -errno for all other negative values returned by the userspace exit handler
+ */
+typedef int (*vdso_sgx_enter_enclave_t)(unsigned long rdi, unsigned long rsi,
+					unsigned long rdx, unsigned int leaf,
+					unsigned long r8,  unsigned long r9,
+					void *tcs,
+					struct sgx_enclave_exception *e,
+					sgx_enclave_exit_handler_t handler);
+
 #endif /* _UAPI_ASM_X86_SGX_H */
diff --git a/tools/testing/selftests/sgx/call.S b/tools/testing/selftests/sgx/call.S
index c37f55a607c8..77131e83db42 100644
--- a/tools/testing/selftests/sgx/call.S
+++ b/tools/testing/selftests/sgx/call.S
@@ -37,7 +37,6 @@ sgx_call_vdso:
 	.cfi_adjust_cfa_offset	8
 	push	0x48(%rsp)
 	.cfi_adjust_cfa_offset	8
-	mov	$2, %eax
 	call	*eenter(%rip)
 	add	$0x20, %rsp
 	.cfi_adjust_cfa_offset	-0x20
diff --git a/tools/testing/selftests/sgx/defines.h b/tools/testing/selftests/sgx/defines.h
index 1802cace7527..be8969922804 100644
--- a/tools/testing/selftests/sgx/defines.h
+++ b/tools/testing/selftests/sgx/defines.h
@@ -15,6 +15,7 @@
 #define __packed __attribute__((packed))
 
 #include "../../../../arch/x86/kernel/cpu/sgx/arch.h"
+#include "../../../../arch/x86/include/asm/enclu.h"
 #include "../../../../arch/x86/include/uapi/asm/sgx.h"
 
 #endif /* DEFINES_H */
diff --git a/tools/testing/selftests/sgx/main.c b/tools/testing/selftests/sgx/main.c
index 9238cce47f77..f6bb40f22884 100644
--- a/tools/testing/selftests/sgx/main.c
+++ b/tools/testing/selftests/sgx/main.c
@@ -171,7 +171,7 @@ int main(int argc, char *argv[], char *envp[])
 
 	eenter = addr + eenter_sym->st_value;
 
-	sgx_call_vdso((void *)&MAGIC, &result, 0, NULL, NULL, NULL,
+	sgx_call_vdso((void *)&MAGIC, &result, 0, EENTER, NULL, NULL,
 		      (void *)encl.encl_base, &exception, NULL);
 	if (result != MAGIC)
 		goto err;
diff --git a/tools/testing/selftests/sgx/main.h b/tools/testing/selftests/sgx/main.h
index 6e1ae292bd25..999422cc7343 100644
--- a/tools/testing/selftests/sgx/main.h
+++ b/tools/testing/selftests/sgx/main.h
@@ -32,7 +32,7 @@ bool encl_load(const char *path, struct encl *encl);
 bool encl_measure(struct encl *encl);
 bool encl_build(struct encl *encl);
 
-int sgx_call_vdso(void *rdi, void *rsi, long rdx, void *rcx, void *r8, void *r9,
+int sgx_call_vdso(void *rdi, void *rsi, long rdx, u32 leaf, void *r8, void *r9,
 		  void *tcs, struct sgx_enclave_exception *ei, void *cb);
 
 #endif /* MAIN_H */
