On Mon, Mar 28, 2022 at 02:49:04PM -0700, Reinette Chatre wrote:
Hi Jarkko,
On 3/22/2022 12:43 AM, Jarkko Sakkinen wrote:
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@intel.com Cc: Dave Hansen dave.hansen@linux.intel.com Signed-off-by: Jarkko Sakkinen jarkko@kernel.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
The goal of the above snippet is to set RSP to ensure that each thread has its own stack.
Since EENTER computes RIP as EnclaveBase + TCS.OENTRY, by using offset from RIP this would result in all TCS with OENTRY of encl_entry to use the same stack, no?
Could you please consider the following as an alternative: https://lore.kernel.org/lkml/65c137c875bd4da675eaba35316ff43d7cfd52f8.164427...
The idea in that patch is that a new TCS would always need to be accompanied by a dedicated stack so, at least for testing purposes, the TCS and stack can be dynamically allocated together with the TCS page following its stack. This seems much simpler to me and also makes the following patch unnecessary.
There's no better alternative than use rip. Compiler will fix it up.
So, no, I won't consider that. This a dead obvious change.
BR, Jarkko