From:   Reinette Chatre <reinette.chatre@intel.com>
To:     dave.hansen@linux.intel.com, jarkko@kernel.org, tglx@linutronix.de,
        bp@alien8.de, luto@kernel.org, mingo@redhat.com,
        linux-sgx@vger.kernel.org, x86@kernel.org
Cc:     seanjc@google.com, kai.huang@intel.com, cathy.zhang@intel.com,
        cedric.xing@intel.com, haitao.huang@intel.com,
        mark.shanahan@intel.com, hpa@zytor.com,
        linux-kernel@vger.kernel.org
Subject: [PATCH 15/25] selftests/sgx: Test two different SGX2 EAUG flows
Date:   Wed,  1 Dec 2021 11:23:13 -0800
Message-Id: <cf4a1674c36f12beae71f202e3e3f5c5efcdc9bd.1638381245.git.reinette.chatre@intel.com>
In-Reply-To: <cover.1638381245.git.reinette.chatre@intel.com>
References: <cover.1638381245.git.reinette.chatre@intel.com>
MIME-Version: 1.0
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Enclave pages can be added to an initialized enclave when an address
belonging to the enclave but without a backing page is accessed from
within the enclave.

Accessing memory without a backing enclave page from within an enclave
can be in different ways:
1) Pre-emptively run ENCLU[EACCEPT]. Since the addition of a page
   always needs to be accepted by the enclave via ENCLU[EACCEPT] this
   flow is efficient since the first execution of ENCLU[EACCEPT]
   triggers the addition of the page and when execution returns to the
   same instruction the second execution would be successful as an
   acceptance of the page.

2) A direct read or write. The flow where a direct read or write
   triggers the page addition execution cannot resume from the
   instruction (read/write) that triggered the fault but instead
   the enclave needs to be entered at a different entry point to
   run needed ENCLU[EACCEPT] before execution can return to the
   original entry point and the read/write instruction that faulted.

Add tests for both flows.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
---
 tools/testing/selftests/sgx/main.c | 260 +++++++++++++++++++++++++++++
 1 file changed, 260 insertions(+)

diff --git a/tools/testing/selftests/sgx/main.c b/tools/testing/selftests/sgx/main.c
index c7c50d05e246..bc8c7d06d74c 100644
--- a/tools/testing/selftests/sgx/main.c
+++ b/tools/testing/selftests/sgx/main.c
@@ -85,6 +85,30 @@ static bool vdso_get_symtab(void *addr, struct vdso_symtab *symtab)
 	return true;
 }
 
+static inline void __cpuid(unsigned int *eax, unsigned int *ebx,
+			   unsigned int *ecx, unsigned int *edx)
+{
+	asm volatile("cpuid"
+	    : "=a" (*eax),
+	      "=b" (*ebx),
+	      "=c" (*ecx),
+	      "=d" (*edx)
+	    : "0" (*eax), "2" (*ecx)
+	    : "memory");
+}
+
+static inline int sgx2_supported(void)
+{
+	unsigned int eax, ebx, ecx, edx;
+
+	eax = SGX_CPUID;
+	ecx = 0x0;
+
+	__cpuid(&eax, &ebx, &ecx, &edx);
+
+	return eax & 0x2;
+}
+
 static unsigned long elf_sym_hash(const char *name)
 {
 	unsigned long h = 0, high;
@@ -889,4 +913,240 @@ TEST_F(enclave, epcm_permissions)
 	EXPECT_EQ(eaccept_op.ret, 0);
 }
 
+/*
+ * Test the addition of pages to an initialized enclave via writing to
+ * a page belonging to the enclave's address space but was not added
+ * during enclave creation.
+ */
+TEST_F(enclave, augment)
+{
+	struct encl_op_get_from_addr get_addr_op;
+	struct encl_op_put_to_addr put_addr_op;
+	struct encl_op_eaccept eaccept_op;
+	size_t total_size = 0;
+	void *addr;
+	int i;
+
+	if (!sgx2_supported())
+		SKIP(return, "SGX2 not supported");
+
+	ASSERT_TRUE(setup_test_encl(ENCL_HEAP_SIZE_DEFAULT, &self->encl, _metadata));
+
+	memset(&self->run, 0, sizeof(self->run));
+	self->run.tcs = self->encl.encl_base;
+
+	for (i = 0; i < self->encl.nr_segments; i++) {
+		struct encl_segment *seg = &self->encl.segment_tbl[i];
+
+		total_size += seg->size;
+	}
+
+	/*
+	 * Actual enclave size is expected to be larger than the loaded
+	 * test enclave since enclave size must be a power of 2 in bytes
+	 * and test_encl does not consume it all.
+	 */
+	EXPECT_LT(total_size + PAGE_SIZE, self->encl.encl_size);
+
+	/*
+	 * Create memory mapping for the page that will be added. New
+	 * memory mapping is for one page right after all existing
+	 * mappings.
+	 */
+	addr = mmap((void *)self->encl.encl_base + total_size, PAGE_SIZE,
+		    PROT_READ | PROT_WRITE | PROT_EXEC,
+		    MAP_SHARED | MAP_FIXED, self->encl.fd, 0);
+	EXPECT_NE(addr, MAP_FAILED);
+
+	self->run.exception_vector = 0;
+	self->run.exception_error_code = 0;
+	self->run.exception_addr = 0;
+
+	/*
+	 * Attempt to write to the new page from within enclave.
+	 * Expected to fail since page is not (yet) part of the enclave.
+	 * The first #PF will trigger the addition of the page to the
+	 * enclave, but since the new page needs an EACCEPT from within the
+	 * enclave before it can be used it would not be possible
+	 * to successfully return to the failing instruction. This is the
+	 * cause of the second #PF captured here having the SGX bit set,
+	 * it is from hardware preventing the page from being used.
+	 */
+	put_addr_op.value = MAGIC;
+	put_addr_op.addr = (unsigned long)addr;
+	put_addr_op.header.type = ENCL_OP_PUT_TO_ADDRESS;
+
+	EXPECT_EQ(ENCL_CALL(&put_addr_op, &self->run, true), 0);
+
+	EXPECT_EQ(self->run.function, ERESUME);
+	EXPECT_EQ(self->run.exception_vector, 14);
+	EXPECT_EQ(self->run.exception_addr, (unsigned long)addr);
+
+	if (self->run.exception_error_code == 0x6) {
+		munmap(addr, PAGE_SIZE);
+		SKIP(return, "Kernel does not support adding pages to initialized enclave");
+	}
+
+	EXPECT_EQ(self->run.exception_error_code, 0x8007);
+
+	self->run.exception_vector = 0;
+	self->run.exception_error_code = 0;
+	self->run.exception_addr = 0;
+
+	/* Handle AEX by running EACCEPT from new entry point. */
+	self->run.tcs = self->encl.encl_base + PAGE_SIZE;
+
+	eaccept_op.epc_addr = self->encl.encl_base + total_size;
+	eaccept_op.flags = SGX_SECINFO_R | SGX_SECINFO_W | SGX_SECINFO_REG | SGX_SECINFO_PENDING;
+	eaccept_op.ret = 0;
+	eaccept_op.header.type = ENCL_OP_EACCEPT;
+
+	EXPECT_EQ(ENCL_CALL(&eaccept_op, &self->run, true), 0);
+
+	EXPECT_EEXIT(&self->run);
+	EXPECT_EQ(self->run.exception_vector, 0);
+	EXPECT_EQ(self->run.exception_error_code, 0);
+	EXPECT_EQ(self->run.exception_addr, 0);
+	EXPECT_EQ(eaccept_op.ret, 0);
+
+	/* Can now return to main TCS to resume execution. */
+	self->run.tcs = self->encl.encl_base;
+
+	EXPECT_EQ(vdso_sgx_enter_enclave((unsigned long)&put_addr_op, 0, 0,
+					 ERESUME, 0, 0,
+					 &self->run),
+		  0);
+
+	EXPECT_EEXIT(&self->run);
+	EXPECT_EQ(self->run.exception_vector, 0);
+	EXPECT_EQ(self->run.exception_error_code, 0);
+	EXPECT_EQ(self->run.exception_addr, 0);
+
+	/*
+	 * Read memory that was just written to, confirming that data
+	 * previously written (MAGIC) is present. Only change two test
+	 * parameters, rest are same as previous test.
+	 */
+	get_addr_op.value = 0;
+	get_addr_op.addr = (unsigned long)addr;
+	get_addr_op.header.type = ENCL_OP_GET_FROM_ADDRESS;
+
+	EXPECT_EQ(ENCL_CALL(&get_addr_op, &self->run, true), 0);
+
+	EXPECT_EQ(get_addr_op.value, MAGIC);
+	EXPECT_EEXIT(&self->run);
+	EXPECT_EQ(self->run.exception_vector, 0);
+	EXPECT_EQ(self->run.exception_error_code, 0);
+	EXPECT_EQ(self->run.exception_addr, 0);
+
+	munmap(addr, PAGE_SIZE);
+}
+
+/*
+ * Test for the addition of pages to an initialized enclave via a
+ * pre-emptive run of EACCEPT on page to be added.
+ */
+TEST_F(enclave, augment_via_eaccept)
+{
+	struct encl_op_get_from_addr get_addr_op;
+	struct encl_op_put_to_addr put_addr_op;
+	struct encl_op_eaccept eaccept_op;
+	size_t total_size = 0;
+	void *addr;
+	int i;
+
+	if (!sgx2_supported())
+		SKIP(return, "SGX2 not supported");
+
+	ASSERT_TRUE(setup_test_encl(ENCL_HEAP_SIZE_DEFAULT, &self->encl, _metadata));
+
+	memset(&self->run, 0, sizeof(self->run));
+	self->run.tcs = self->encl.encl_base;
+
+	for (i = 0; i < self->encl.nr_segments; i++) {
+		struct encl_segment *seg = &self->encl.segment_tbl[i];
+
+		total_size += seg->size;
+	}
+
+	/*
+	 * Actual enclave size is expected to be larger than the loaded
+	 * test enclave since enclave size must be a power of 2 in bytes while
+	 * test_encl does not consume it all.
+	 */
+	EXPECT_LT(total_size + PAGE_SIZE, self->encl.encl_size);
+
+	/*
+	 * mmap() a page at end of existing enclave to be used for dynamic
+	 * EPC page.
+	 */
+
+	addr = mmap((void *)self->encl.encl_base + total_size, PAGE_SIZE,
+		    PROT_READ | PROT_WRITE | PROT_EXEC, MAP_SHARED | MAP_FIXED,
+		    self->encl.fd, 0);
+	EXPECT_NE(addr, MAP_FAILED);
+
+	self->run.exception_vector = 0;
+	self->run.exception_error_code = 0;
+	self->run.exception_addr = 0;
+
+	/*
+	 * Run EACCEPT on new page to trigger the #PF->EAUG->EACCEPT(again
+	 * without a #PF). All should be transparent to userspace.
+	 */
+	eaccept_op.epc_addr = self->encl.encl_base + total_size;
+	eaccept_op.flags = SGX_SECINFO_R | SGX_SECINFO_W | SGX_SECINFO_REG | SGX_SECINFO_PENDING;
+	eaccept_op.ret = 0;
+	eaccept_op.header.type = ENCL_OP_EACCEPT;
+
+	EXPECT_EQ(ENCL_CALL(&eaccept_op, &self->run, true), 0);
+
+	if (self->run.exception_vector == 14 &&
+	    self->run.exception_error_code == 4 &&
+	    self->run.exception_addr == self->encl.encl_base + total_size) {
+		munmap(addr, PAGE_SIZE);
+		SKIP(return, "Kernel does not support adding pages to initialized enclave");
+	}
+
+	EXPECT_EEXIT(&self->run);
+	EXPECT_EQ(self->run.exception_vector, 0);
+	EXPECT_EQ(self->run.exception_error_code, 0);
+	EXPECT_EQ(self->run.exception_addr, 0);
+	EXPECT_EQ(eaccept_op.ret, 0);
+
+	/*
+	 * New page should be accessible from within enclave - attempt to
+	 * write to it.
+	 */
+	put_addr_op.value = MAGIC;
+	put_addr_op.addr = (unsigned long)addr;
+	put_addr_op.header.type = ENCL_OP_PUT_TO_ADDRESS;
+
+	EXPECT_EQ(ENCL_CALL(&put_addr_op, &self->run, true), 0);
+
+	EXPECT_EEXIT(&self->run);
+	EXPECT_EQ(self->run.exception_vector, 0);
+	EXPECT_EQ(self->run.exception_error_code, 0);
+	EXPECT_EQ(self->run.exception_addr, 0);
+
+	/*
+	 * Read memory that was just written to, confirming that data
+	 * previously written (MAGIC) is present. Only change two test
+	 * parameters, rest are same as previous test.
+	 */
+	get_addr_op.value = 0;
+	get_addr_op.addr = (unsigned long)addr;
+	get_addr_op.header.type = ENCL_OP_GET_FROM_ADDRESS;
+
+	EXPECT_EQ(ENCL_CALL(&get_addr_op, &self->run, true), 0);
+
+	EXPECT_EQ(get_addr_op.value, MAGIC);
+	EXPECT_EEXIT(&self->run);
+	EXPECT_EQ(self->run.exception_vector, 0);
+	EXPECT_EQ(self->run.exception_error_code, 0);
+	EXPECT_EQ(self->run.exception_addr, 0);
+
+	munmap(addr, PAGE_SIZE);
+}
+
 TEST_HARNESS_MAIN
-- 
2.25.1