linux-kernel - [PATCH v2 1/2] selftests/sgx: Use rip relative addressing for encl

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Date:   Tue, 22 Mar 2022 09:43:11 +0200
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Shuah Khan <skhan@...uxfoundation.org>
Cc:     Jarkko Sakkinen <jarkko@...nel.org>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Shuah Khan <shuah@...nel.org>,
        linux-sgx@...r.kernel.org (open list:INTEL SGX),
        linux-kselftest@...r.kernel.org (open list:KERNEL SELFTEST FRAMEWORK),
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v2 1/2] selftests/sgx: Use rip relative addressing for encl_stack

Simplify the test_encl_bootstrap.S flow by using rip-relative addressing.
Compiler does the right thing here, and this removes dependency on where
TCS entries need to be located in the binary, i.e. allows the binary layout
changed freely in the future.

Cc: Reinette Chatre <reinette.chatre@...el.com>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko@...nel.org>
---
 tools/testing/selftests/sgx/test_encl_bootstrap.S | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/tools/testing/selftests/sgx/test_encl_bootstrap.S b/tools/testing/selftests/sgx/test_encl_bootstrap.S
index 82fb0dfcbd23..1c1b5c6c4ffe 100644
--- a/tools/testing/selftests/sgx/test_encl_bootstrap.S
+++ b/tools/testing/selftests/sgx/test_encl_bootstrap.S
@@ -40,11 +40,7 @@
 	.text
 
 encl_entry:
-	# RBX contains the base address for TCS, which is the first address
-	# inside the enclave for TCS #1 and one page into the enclave for
-	# TCS #2. By adding the value of encl_stack to it, we get
-	# the absolute address for the stack.
-	lea	(encl_stack)(%rbx), %rax
+	lea	(encl_stack)(%rip), %rax
 	xchg	%rsp, %rax
 	push	%rax
 
-- 
2.35.1