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Subject[tip: x86/sgx] selftests/sgx: Introduce dynamic entry point
The following commit has been merged into the x86/sgx branch of tip:

Commit-ID: 7eb4370152beb2f1e25543088bce2e3f0621ab81
Gitweb: https://git.kernel.org/tip/7eb4370152beb2f1e25543088bce2e3f0621ab81
Author: Reinette Chatre <reinette.chatre@intel.com>
AuthorDate: Tue, 10 May 2022 11:09:01 -07:00
Committer: Dave Hansen <dave.hansen@linux.intel.com>
CommitterDate: Thu, 07 Jul 2022 10:13:04 -07:00

selftests/sgx: Introduce dynamic entry point

The test enclave (test_encl.elf) is built with two initialized
Thread Control Structures (TCS) included in the binary. Both TCS are
initialized with the same entry point, encl_entry, that correctly
computes the absolute address of the stack based on the stack of each
TCS that is also built into the binary.

A new TCS can be added dynamically to the enclave and requires to be
initialized with an entry point used to enter the enclave. Since the
existing entry point, encl_entry, assumes that the TCS and its stack
exists at particular offsets within the binary it is not able to handle
a dynamically added TCS and its stack.

Introduce a new entry point, encl_dyn_entry, that initializes the
absolute address of that thread's stack to the address immediately
preceding the TCS itself. It is now possible to dynamically add a
contiguous memory region to the enclave with the new stack preceding
the new TCS. With the new TCS initialized with encl_dyn_entry as entry
point the absolute address of the stack is computed correctly on entry.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Jarkko Sakkinen <jarkko@kernel.org>
Link: https://lkml.kernel.org/r/93e9c420dedf5f773ba6965c18245bc7d62aca83.1652137848.git.reinette.chatre@intel.com
---
tools/testing/selftests/sgx/test_encl_bootstrap.S | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/tools/testing/selftests/sgx/test_encl_bootstrap.S b/tools/testing/selftests/sgx/test_encl_bootstrap.S
index 82fb0df..03ae0f5 100644
--- a/tools/testing/selftests/sgx/test_encl_bootstrap.S
+++ b/tools/testing/selftests/sgx/test_encl_bootstrap.S
@@ -45,6 +45,12 @@ encl_entry:
# TCS #2. By adding the value of encl_stack to it, we get
# the absolute address for the stack.
lea (encl_stack)(%rbx), %rax
+ jmp encl_entry_core
+encl_dyn_entry:
+ # Entry point for dynamically created TCS page expected to follow
+ # its stack directly.
+ lea -1(%rbx), %rax
+encl_entry_core:
xchg %rsp, %rax
push %rax

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