On 10/10/2019 5:40 PM, Sean Christopherson wrote:
Swap @ret and @ursp in the callback prototype so that the output from
the vDSO itself, @ret and @e, are grouped together. Having the first
N parameters all share a type also makes the prototype easier to parse
by (some) humans. And, passing @ursp via register saves one whole
MOV instruction!
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
---
arch/x86/entry/vdso/vsgx_enter_enclave.S | 16 +++++++---------
arch/x86/include/uapi/asm/sgx.h | 10 +++++-----
2 files changed, 12 insertions(+), 14 deletions(-)
diff --git a/arch/x86/entry/vdso/vsgx_enter_enclave.S b/arch/x86/entry/vdso/vsgx_enter_enclave.S
index 3dd22780b7ef..94f613b53b13 100644
--- a/arch/x86/entry/vdso/vsgx_enter_enclave.S
+++ b/arch/x86/entry/vdso/vsgx_enter_enclave.S
@@ -134,23 +134,21 @@ ENTRY(__vdso_sgx_enter_enclave)
jmp .Lhandle_exit
.Linvoke_userspace_handler:
+ /* Pass the untrusted RSP (at exit) to the callback via %rcx. */
+ mov %rsp, %rcx
+
/*
- * Align stack per x86_64 ABI. Save the original %rsp in %rbx to be
- * restored after the callback returns. Note, %rsp needs to be 16-byte
- * aligned _after_ pushing the three parameters on the stack.
+ * Align stack per x86_64 ABI. Note, %rsp needs to be 16-byte aligned
+ * _after_ pushing the three parameters on the stack.
*/
- mov %rsp, %rbx
Per x86_64 ABI, %rcx is _not_ preserved across function call. How are
you going to restore the stack after callback returns?
and $-0x10, %rsp
sub $0x8, %rsp
Usually compilers would just use a 1-byte "push" instead of a 4-byte
"sub" instruction here.
- /* Push @e, u_rsp and @tcs as parameters to the callback. */
+ /* Push @e, the "return" value and @tcs as params to the callback. */
push 0x18(%rbp)
- push %rbx
+ push %rax
push 0x10(%rbp)
- /* Pass the "return" value to the callback via %rcx. */
- mov %eax, %ecx
-
/* Clear RFLAGS.DF per x86_64 ABI */
cld
diff --git a/arch/x86/include/uapi/asm/sgx.h b/arch/x86/include/uapi/asm/sgx.h
index 255392f5054f..95f69f938b58 100644
--- a/arch/x86/include/uapi/asm/sgx.h
+++ b/arch/x86/include/uapi/asm/sgx.h
@@ -88,16 +88,16 @@ struct sgx_enclave_exception {
* @rdi: RDI at the time of enclave exit
* @rsi: RSI at the time of enclave exit
* @rdx: RDX at the time of enclave exit
- * @ret: 0 on success (EEXIT), -EFAULT on an exception
+ * @ursp: RSP at the time of enclave exit (untrusted stack)
* @r8: R8 at the time of enclave exit
* @r9: R9 at the time of enclave exit
* @tcs: Thread Control Structure used to enter enclave
- * @ursp: RSP at the time of enclave exit
+ * @ret: 0 on success (EEXIT), -EFAULT on an exception
* @e: Pointer to struct sgx_enclave_exception (as provided by caller)
*/
-typedef int (*sgx_enclave_exit_handler_t)(long rdi, long rsi, long rdx, int ret,
- long r8, long r9, void *tcs,
- long ursp,
+typedef int (*sgx_enclave_exit_handler_t)(long rdi, long rsi, long rdx,
+ long ursp, long r8, long r9,
+ void *tcs, int ret,
struct sgx_enclave_exception *e);
#endif /* _UAPI_ASM_X86_SGX_H */
