selftests/sgx: Add a new kselftest: Unclobbered_vdso_oversubscribed

Add a variation of the unclobbered_vdso test.

In the new test, create a heap for the test enclave, which has the same
size as all available Enclave Page Cache (EPC) pages in the system. This
will guarantee that all test_encl.elf pages *and* SGX Enclave Control
Structure (SECS) have been swapped out by the page reclaimer during the
load time.

This test will trigger both the page reclaimer and the page fault handler.
The page reclaimer triggered, while the heap is being created during the
load time. The page fault handler is triggered for all the required pages,
while the test case is executing.
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lkml.kernel.org/r/41f7c508eea79a3198b5014d7691903be08f9ff1.1636997631.git.reinette.chatre@intel.com

tools/testing/selftests/sgx/main.c

@@ -245,6 +245,81 @@ TEST_F(enclave, unclobbered_vdso)
 	EXPECT_EQ(self->run.user_data, 0);
 }
 
+/*
+ * A section metric is concatenated in a way that @low bits 12-31 define the
+ * bits 12-31 of the metric and @high bits 0-19 define the bits 32-51 of the
+ * metric.
+ */
+static unsigned long sgx_calc_section_metric(unsigned int low,
+					     unsigned int high)
+{
+	return (low & GENMASK_ULL(31, 12)) +
+	       ((high & GENMASK_ULL(19, 0)) << 32);
+}
+
+/*
+ * Sum total available physical SGX memory across all EPC sections
+ *
+ * Return: total available physical SGX memory available on system
+ */
+static unsigned long get_total_epc_mem(void)
+{
+	unsigned int eax, ebx, ecx, edx;
+	unsigned long total_size = 0;
+	unsigned int type;
+	int section = 0;
+
+	while (true) {
+		eax = SGX_CPUID;
+		ecx = section + SGX_CPUID_EPC;
+		__cpuid(&eax, &ebx, &ecx, &edx);
+
+		type = eax & SGX_CPUID_EPC_MASK;
+		if (type == SGX_CPUID_EPC_INVALID)
+			break;
+
+		if (type != SGX_CPUID_EPC_SECTION)
+			break;
+
+		total_size += sgx_calc_section_metric(ecx, edx);
+
+		section++;
+	}
+
+	return total_size;
+}
+
+TEST_F(enclave, unclobbered_vdso_oversubscribed)
+{
+	unsigned long total_mem;
+	struct encl_op op;
+
+	total_mem = get_total_epc_mem();
+	ASSERT_NE(total_mem, 0);
+	ASSERT_TRUE(setup_test_encl(total_mem, &self->encl, _metadata));
+
+	memset(&self->run, 0, sizeof(self->run));
+	self->run.tcs = self->encl.encl_base;
+
+	op.type = ENCL_OP_PUT;
+	op.buffer = MAGIC;
+
+	EXPECT_EQ(ENCL_CALL(&op, &self->run, false), 0);
+
+	EXPECT_EEXIT(&self->run);
+	EXPECT_EQ(self->run.user_data, 0);
+
+	op.type = ENCL_OP_GET;
+	op.buffer = 0;
+
+	EXPECT_EQ(ENCL_CALL(&op, &self->run, false), 0);
+
+	EXPECT_EQ(op.buffer, MAGIC);
+	EXPECT_EEXIT(&self->run);
+	EXPECT_EQ(self->run.user_data, 0);
+
+}
+
 TEST_F(enclave, clobbered_vdso)
 {
 	struct encl_op op;