linux-kernel - [PATCH 4/4] selftests/sgx: Fix compiler optimizations in test enclave

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Message-Id: <20230720221623.9530-5-jo.vanbulck@cs.kuleuven.be>
Date:   Fri, 21 Jul 2023 00:16:23 +0200
From:   Jo Van Bulck <jo.vanbulck@...kuleuven.be>
To:     jarkko@...nel.org, linux-sgx@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     dave.hansen@...ux.intel.com,
        Jo Van Bulck <jo.vanbulck@...kuleuven.be>
Subject: [PATCH 4/4] selftests/sgx: Fix compiler optimizations in test enclave

Relocate encl_op_array entries at runtime relative to the enclave base to
ensure correct function pointer when compiling the test enclave with -Os.

Declare the secinfo struct as volatile to prevent compiler optimizations
from passing an unaligned pointer to ENCLU.

Signed-off-by: Jo Van Bulck <jo.vanbulck@...kuleuven.be>
---
 tools/testing/selftests/sgx/test_encl.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/sgx/test_encl.c b/tools/testing/selftests/sgx/test_encl.c
index ea24cdf9e..b580c37f3 100644
--- a/tools/testing/selftests/sgx/test_encl.c
+++ b/tools/testing/selftests/sgx/test_encl.c
@@ -105,7 +105,8 @@ static inline void assert_inside_enclave(uint64_t arg, size_t len)
 static void do_encl_emodpe(void *_op)
 {
 	struct encl_op_emodpe op;
-	struct sgx_secinfo secinfo __aligned(sizeof(struct sgx_secinfo)) = {0};
+	/* declare secinfo volatile to preserve alignment */
+	volatile struct __aligned(sizeof(struct sgx_secinfo)) sgx_secinfo secinfo = {0};
 
 	copy_inside_enclave(&op, _op, sizeof(op));
 	assert_inside_enclave(op.epc_addr, PAGE_SIZE);
@@ -122,8 +123,9 @@ static void do_encl_emodpe(void *_op)
 static void do_encl_eaccept(void *_op)
 {
 	struct encl_op_eaccept op;
-	struct sgx_secinfo secinfo __aligned(sizeof(struct sgx_secinfo)) = {0};
 	int rax;
+	/* declare secinfo volatile to preserve alignment */
+	volatile struct __aligned(sizeof(struct sgx_secinfo)) sgx_secinfo secinfo = {0};
 
 	copy_inside_enclave(&op, _op, sizeof(op));
 	assert_inside_enclave(op.epc_addr, PAGE_SIZE);
@@ -222,7 +224,7 @@ static void do_encl_op_nop(void *_op)
 
 void encl_body(void *rdi,  void *rsi)
 {
-	const void (*encl_op_array[ENCL_OP_MAX])(void *) = {
+	static const void (*encl_op_array[ENCL_OP_MAX])(void *) = {
 		do_encl_op_put_to_buf,
 		do_encl_op_get_from_buf,
 		do_encl_op_put_to_addr,
@@ -237,5 +239,5 @@ void encl_body(void *rdi,  void *rsi)
 	copy_inside_enclave(&op, rdi, sizeof(op));
 
 	if (op.type < ENCL_OP_MAX)
-		(*encl_op_array[op.type])(rdi);
+		(*(get_enclave_base() + encl_op_array[op.type]))(rdi);
 }
-- 
2.34.1