[LibOS] regression: Skip mmap test case when SGX=1

This test case passes without EDMM as all the enclave pages
are already EADDed but with EDMM, a SIGBUS is generated since
pages are only added when needed. Since SIGBUS isn't
implemented correctly for lack of memory protection, skipping
the mmap test case. Also, updated the mmap test case to remove
default default signal handler.

Signed-off-by: Vijay Dhanraj <[email protected]>

Author: vijaydhanraj

LibOS/shim/test/regression/mmap_file.c

@@ -89,10 +89,5 @@ int main(int argc, const char** argv) {
     __asm__ volatile("nop" ::: "memory");
     a[page_size] = 0xff;
 
-    if (signal(SIGBUS, SIG_DFL) == SIG_ERR) {
-        perror("signal");
-        return 1;
-    }
-
     return 0;
 }

LibOS/shim/test/regression/test_libos.py

@@ -396,7 +396,10 @@ def test_043_futex_wake_op(self):
 
         self.assertIn('Test successful!', stdout)
 
-    def test_050_mmap(self):
+    @unittest.skipIf(HAS_SGX,
+        'On SGX, SIGBUS isn\'t always implemented correctly, for lack '
+        'of memory protection. For now, some of these cases won\'t work.')
+    def test_051_mmap_sgx(self):
         stdout, _ = self.run_binary(['mmap_file'], timeout=60)
 
         # Private mmap beyond file range
@@ -409,14 +412,6 @@ def test_050_mmap(self):
         self.assertIn('mmap test 3 passed', stdout)
         self.assertIn('mmap test 4 passed', stdout)
 
-        # "test 5" and "test 8" are checked below, in test_051_mmap_sgx
-
-    @unittest.skipIf(HAS_SGX,
-        'On SGX, SIGBUS isn\'t always implemented correctly, for lack '
-        'of memory protection. For now, some of these cases won\'t work.')
-    def test_051_mmap_sgx(self):
-        stdout, _ = self.run_binary(['mmap_file'], timeout=60)
-
         # SIGBUS test
         self.assertIn('mmap test 5 passed', stdout)
         self.assertIn('mmap test 8 passed', stdout)