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selftests/sgx: Test two different SGX2 EAUG flows
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 <[email protected]> Signed-off-by: Dave Hansen <[email protected]> Acked-by: Jarkko Sakkinen <[email protected]> Link: https://lkml.kernel.org/r/0c321e0e32790ac1de742ce5017a331e6d902ac1.1652137848.git.reinette.chatre@intel.com
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‎tools/testing/selftests/sgx/main.c

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Original file line numberDiff line numberDiff line change
@@ -86,6 +86,15 @@ static bool vdso_get_symtab(void *addr, struct vdso_symtab *symtab)
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return true;
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}
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static inline int sgx2_supported(void)
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{
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unsigned int eax, ebx, ecx, edx;
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__cpuid_count(SGX_CPUID, 0x0, eax, ebx, ecx, edx);
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return eax & 0x2;
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}
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static unsigned long elf_sym_hash(const char *name)
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{
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unsigned long h = 0, high;
@@ -840,4 +849,245 @@ TEST_F(enclave, epcm_permissions)
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EXPECT_EQ(self->run.exception_addr, 0);
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}
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/*
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* Test the addition of pages to an initialized enclave via writing to
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* a page belonging to the enclave's address space but was not added
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* during enclave creation.
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*/
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TEST_F(enclave, augment)
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{
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struct encl_op_get_from_addr get_addr_op;
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struct encl_op_put_to_addr put_addr_op;
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struct encl_op_eaccept eaccept_op;
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size_t total_size = 0;
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void *addr;
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int i;
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if (!sgx2_supported())
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SKIP(return, "SGX2 not supported");
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ASSERT_TRUE(setup_test_encl(ENCL_HEAP_SIZE_DEFAULT, &self->encl, _metadata));
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memset(&self->run, 0, sizeof(self->run));
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self->run.tcs = self->encl.encl_base;
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for (i = 0; i < self->encl.nr_segments; i++) {
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struct encl_segment *seg = &self->encl.segment_tbl[i];
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total_size += seg->size;
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}
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/*
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* Actual enclave size is expected to be larger than the loaded
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* test enclave since enclave size must be a power of 2 in bytes
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* and test_encl does not consume it all.
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*/
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EXPECT_LT(total_size + PAGE_SIZE, self->encl.encl_size);
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/*
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* Create memory mapping for the page that will be added. New
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* memory mapping is for one page right after all existing
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* mappings.
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* Kernel will allow new mapping using any permissions if it
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* falls into the enclave's address range but not backed
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* by existing enclave pages.
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*/
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addr = mmap((void *)self->encl.encl_base + total_size, PAGE_SIZE,
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PROT_READ | PROT_WRITE | PROT_EXEC,
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MAP_SHARED | MAP_FIXED, self->encl.fd, 0);
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EXPECT_NE(addr, MAP_FAILED);
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self->run.exception_vector = 0;
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self->run.exception_error_code = 0;
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self->run.exception_addr = 0;
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/*
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* Attempt to write to the new page from within enclave.
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* Expected to fail since page is not (yet) part of the enclave.
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* The first #PF will trigger the addition of the page to the
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* enclave, but since the new page needs an EACCEPT from within the
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* enclave before it can be used it would not be possible
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* to successfully return to the failing instruction. This is the
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* cause of the second #PF captured here having the SGX bit set,
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* it is from hardware preventing the page from being used.
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*/
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put_addr_op.value = MAGIC;
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put_addr_op.addr = (unsigned long)addr;
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put_addr_op.header.type = ENCL_OP_PUT_TO_ADDRESS;
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EXPECT_EQ(ENCL_CALL(&put_addr_op, &self->run, true), 0);
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EXPECT_EQ(self->run.function, ERESUME);
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EXPECT_EQ(self->run.exception_vector, 14);
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EXPECT_EQ(self->run.exception_addr, (unsigned long)addr);
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if (self->run.exception_error_code == 0x6) {
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munmap(addr, PAGE_SIZE);
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SKIP(return, "Kernel does not support adding pages to initialized enclave");
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}
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EXPECT_EQ(self->run.exception_error_code, 0x8007);
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self->run.exception_vector = 0;
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self->run.exception_error_code = 0;
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self->run.exception_addr = 0;
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/* Handle AEX by running EACCEPT from new entry point. */
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self->run.tcs = self->encl.encl_base + PAGE_SIZE;
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eaccept_op.epc_addr = self->encl.encl_base + total_size;
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eaccept_op.flags = SGX_SECINFO_R | SGX_SECINFO_W | SGX_SECINFO_REG | SGX_SECINFO_PENDING;
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eaccept_op.ret = 0;
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eaccept_op.header.type = ENCL_OP_EACCEPT;
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EXPECT_EQ(ENCL_CALL(&eaccept_op, &self->run, true), 0);
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EXPECT_EEXIT(&self->run);
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EXPECT_EQ(self->run.exception_vector, 0);
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EXPECT_EQ(self->run.exception_error_code, 0);
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EXPECT_EQ(self->run.exception_addr, 0);
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EXPECT_EQ(eaccept_op.ret, 0);
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/* Can now return to main TCS to resume execution. */
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self->run.tcs = self->encl.encl_base;
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EXPECT_EQ(vdso_sgx_enter_enclave((unsigned long)&put_addr_op, 0, 0,
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ERESUME, 0, 0,
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&self->run),
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0);
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EXPECT_EEXIT(&self->run);
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EXPECT_EQ(self->run.exception_vector, 0);
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EXPECT_EQ(self->run.exception_error_code, 0);
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EXPECT_EQ(self->run.exception_addr, 0);
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/*
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* Read memory from newly added page that was just written to,
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* confirming that data previously written (MAGIC) is present.
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*/
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get_addr_op.value = 0;
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get_addr_op.addr = (unsigned long)addr;
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get_addr_op.header.type = ENCL_OP_GET_FROM_ADDRESS;
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EXPECT_EQ(ENCL_CALL(&get_addr_op, &self->run, true), 0);
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EXPECT_EQ(get_addr_op.value, MAGIC);
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EXPECT_EEXIT(&self->run);
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EXPECT_EQ(self->run.exception_vector, 0);
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EXPECT_EQ(self->run.exception_error_code, 0);
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EXPECT_EQ(self->run.exception_addr, 0);
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munmap(addr, PAGE_SIZE);
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}
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/*
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* Test for the addition of pages to an initialized enclave via a
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* pre-emptive run of EACCEPT on page to be added.
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*/
987+
TEST_F(enclave, augment_via_eaccept)
988+
{
989+
struct encl_op_get_from_addr get_addr_op;
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struct encl_op_put_to_addr put_addr_op;
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struct encl_op_eaccept eaccept_op;
992+
size_t total_size = 0;
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void *addr;
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int i;
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if (!sgx2_supported())
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SKIP(return, "SGX2 not supported");
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ASSERT_TRUE(setup_test_encl(ENCL_HEAP_SIZE_DEFAULT, &self->encl, _metadata));
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1001+
memset(&self->run, 0, sizeof(self->run));
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self->run.tcs = self->encl.encl_base;
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for (i = 0; i < self->encl.nr_segments; i++) {
1005+
struct encl_segment *seg = &self->encl.segment_tbl[i];
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total_size += seg->size;
1008+
}
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/*
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* Actual enclave size is expected to be larger than the loaded
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* test enclave since enclave size must be a power of 2 in bytes while
1013+
* test_encl does not consume it all.
1014+
*/
1015+
EXPECT_LT(total_size + PAGE_SIZE, self->encl.encl_size);
1016+
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/*
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* mmap() a page at end of existing enclave to be used for dynamic
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* EPC page.
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*
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* Kernel will allow new mapping using any permissions if it
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* falls into the enclave's address range but not backed
1023+
* by existing enclave pages.
1024+
*/
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addr = mmap((void *)self->encl.encl_base + total_size, PAGE_SIZE,
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PROT_READ | PROT_WRITE | PROT_EXEC, MAP_SHARED | MAP_FIXED,
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self->encl.fd, 0);
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EXPECT_NE(addr, MAP_FAILED);
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self->run.exception_vector = 0;
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self->run.exception_error_code = 0;
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self->run.exception_addr = 0;
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/*
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* Run EACCEPT on new page to trigger the #PF->EAUG->EACCEPT(again
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* without a #PF). All should be transparent to userspace.
1038+
*/
1039+
eaccept_op.epc_addr = self->encl.encl_base + total_size;
1040+
eaccept_op.flags = SGX_SECINFO_R | SGX_SECINFO_W | SGX_SECINFO_REG | SGX_SECINFO_PENDING;
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eaccept_op.ret = 0;
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eaccept_op.header.type = ENCL_OP_EACCEPT;
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EXPECT_EQ(ENCL_CALL(&eaccept_op, &self->run, true), 0);
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if (self->run.exception_vector == 14 &&
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self->run.exception_error_code == 4 &&
1048+
self->run.exception_addr == self->encl.encl_base + total_size) {
1049+
munmap(addr, PAGE_SIZE);
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SKIP(return, "Kernel does not support adding pages to initialized enclave");
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}
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1053+
EXPECT_EEXIT(&self->run);
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EXPECT_EQ(self->run.exception_vector, 0);
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EXPECT_EQ(self->run.exception_error_code, 0);
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EXPECT_EQ(self->run.exception_addr, 0);
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EXPECT_EQ(eaccept_op.ret, 0);
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/*
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* New page should be accessible from within enclave - attempt to
1061+
* write to it.
1062+
*/
1063+
put_addr_op.value = MAGIC;
1064+
put_addr_op.addr = (unsigned long)addr;
1065+
put_addr_op.header.type = ENCL_OP_PUT_TO_ADDRESS;
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1067+
EXPECT_EQ(ENCL_CALL(&put_addr_op, &self->run, true), 0);
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EXPECT_EEXIT(&self->run);
1070+
EXPECT_EQ(self->run.exception_vector, 0);
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EXPECT_EQ(self->run.exception_error_code, 0);
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EXPECT_EQ(self->run.exception_addr, 0);
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/*
1075+
* Read memory from newly added page that was just written to,
1076+
* confirming that data previously written (MAGIC) is present.
1077+
*/
1078+
get_addr_op.value = 0;
1079+
get_addr_op.addr = (unsigned long)addr;
1080+
get_addr_op.header.type = ENCL_OP_GET_FROM_ADDRESS;
1081+
1082+
EXPECT_EQ(ENCL_CALL(&get_addr_op, &self->run, true), 0);
1083+
1084+
EXPECT_EQ(get_addr_op.value, MAGIC);
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EXPECT_EEXIT(&self->run);
1086+
EXPECT_EQ(self->run.exception_vector, 0);
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EXPECT_EQ(self->run.exception_error_code, 0);
1088+
EXPECT_EQ(self->run.exception_addr, 0);
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1090+
munmap(addr, PAGE_SIZE);
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}
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TEST_HARNESS_MAIN

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