Before this commit, there are two strange bugs:
1. No backtraces are displayed on panic by Rust; and,
2. Thread local storage in Rust sometimes causes panics.
It turns out that the the root cause of the two bugs are the same: Occlum's
patch to Intel SGX SDK that informs SDK about the stack range of the currnet
LibOS user-level thread. The problem about this patch is that it modifies some
fundamental data structures and Rust SGX SDK does not know the modification.
This causes Rust SGX SDK to panic in certain conditions.
To resolve the conflict for good, this commit gets rid of the patch to Intel
SGX SDK by updating SDK's stack ranges upon user/kernel switch.
1. Use arch_prctl to replace RDFSBASE/WRFSBASE
Ptrace can't get right value if WRFSBASE is called which
will make debugger fail in simulation mode. Use arch_prctl
to replace these instructions in simulation mode.
2. Disable the busy thread in exit_group test
exit_group doesn't have a real implementation yet but test
under SGX simulation mode give core dump for exit_group test.
Disable the busy loop thread and the core dump disappear.
3. Add SDK lib path to LD_LIBRARY_PATH
Linker sometims can't find urts_sim and uae_service_sim when
running. Explicitly add path to LD_LIBRARY_PATH when running
occlum command.
Signed-off-by: sanqian.hcy <sanqian.hcy@antfin.com>
There are two types of stacks: the kernel ones and the user ones. The kernel
stacks are used by Occlum and managed by Intel SGX SDK itself, while the user
stacks are used by the threads created and managed by Occlum. These user stacks
are transparent to Intel SGX SDK so far.
The problem is that Intel SGX SDK needs to be aware of the user stacks.
SGX exception handlers will check whether the rsp value---when the exception
happened---is within the stack of the current SGX thread. If the check fails,
the registered exception handler will not be triggered. But when exceptions are
triggered by the threads running upon Occlum, the rsp value points to the user
stacks, which Intel SGX SDK are completely unware of. So the check always
fails.
Therefore, we extend Intel SGX SDK with two new APIs:
int sgx_enable_user_stack(size_t stack_base, size_t stack_limit);
void sgx_disable_user_stack(void);
And this commit uses the two APIs to inform Intel SGX SDK about the
Occlum-managed stacks. And the rsp checks in SGX exception handlers will
check whether rsp is within the user stacks.
