x86: add pagetables test suite

For the moment, we validate the flags on all RAM pages,
ensure that NULL is never mapped, and show that dumping
page tables doesn't crash.

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>

tests/arch/x86/pagetables/CMakeLists.txt

@@ -0,0 +1,13 @@
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.13.1)
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(pagetables)
+
+FILE(GLOB app_sources src/*.c)
+target_sources(app PRIVATE ${app_sources})
+
+target_include_directories(app PRIVATE
+  ${ZEPHYR_BASE}/kernel/include
+  ${ZEPHYR_BASE}/arch/${ARCH}/include
+  )

tests/arch/x86/pagetables/prj.conf

@@ -0,0 +1,4 @@
+CONFIG_ZTEST=y
+CONFIG_TEST_HW_STACK_PROTECTION=n
+CONFIG_TEST_USERSPACE=y
+CONFIG_EXCEPTION_DEBUG=y

tests/arch/x86/pagetables/src/main.c

@@ -0,0 +1,153 @@
+/*
+ * Copyright (c) 2020 Intel Corporation.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @file
+ * x86-specific tests for MMU features and page tables
+ */
+
+#include <zephyr.h>
+#include <ztest.h>
+#include <tc_util.h>
+#include <arch/x86/mmustructs.h>
+#include <x86_mmu.h>
+#include <linker/linker-defs.h>
+
+#define VM_BASE		((uint8_t *)CONFIG_KERNEL_VM_BASE)
+#define VM_LIMIT	(VM_BASE + KB((size_t)CONFIG_SRAM_SIZE))
+
+#ifdef CONFIG_X86_64
+#define PT_LEVEL	3
+#elif CONFIG_X86_PAE
+#define PT_LEVEL	2
+#else
+#define PT_LEVEL	1
+#endif
+
+/* Set of flags whose state we will check. Ignore Accessed/Dirty
+ * At leaf level PS bit indicates PAT, but regardless we don't set it
+ */
+#define FLAGS_MASK	(MMU_P | MMU_RW | MMU_US | MMU_PWT | MMU_PCD | \
+			 MMU_G | MMU_PS | MMU_XD)
+
+#define LPTR(name, suffix)	((uint8_t *)&_CONCAT(name, suffix))
+#define LSIZE(name, suffix)	((size_t)&_CONCAT(name, suffix))
+#define IN_REGION(name, virt) \
+	(virt >= LPTR(name, _start) && \
+	 virt < (LPTR(name, _start) + LSIZE(name, _size)))
+
+#ifdef CONFIG_X86_64
+extern char _locore_start[];
+extern char _locore_size[];
+extern char _lorodata_start[];
+extern char _lorodata_size[];
+#endif
+
+#ifdef CONFIG_COVERAGE_GCOV
+extern char __gcov_bss_start[];
+extern char __gcov_bss_size[];
+#endif
+
+/**
+ * Test that MMU flags on RAM virtual address range are set properly
+ *
+ * @ingroup kernel_memprotect_tests
+ */
+void test_ram_perms(void)
+{
+	uint8_t *pos;
+
+	for (pos = VM_BASE; pos < VM_LIMIT; pos += CONFIG_MMU_PAGE_SIZE) {
+		int level;
+		pentry_t entry, flags, expected;
+
+		if (pos == NULL) {
+			/* We have another test specifically for NULL page */
+			continue;
+		}
+
+		z_x86_pentry_get(&level, &entry, z_x86_page_tables_get(), pos);
+
+		zassert_true((entry & MMU_P) != 0,
+			     "non-present RAM entry");
+		zassert_equal(level, PT_LEVEL, "bigpage found");
+		flags = entry & FLAGS_MASK;
+
+		if (!IS_ENABLED(CONFIG_SRAM_REGION_PERMISSIONS)) {
+			expected = MMU_P | MMU_RW;
+		} else if (IN_REGION(_image_text, pos)) {
+			expected = MMU_P | MMU_US;
+		} else if (IN_REGION(_image_rodata, pos)) {
+			expected = MMU_P | MMU_US | MMU_XD;
+#ifdef CONFIG_COVERAGE_GCOV
+		} else if (IN_REGION(__gcov_bss, pos)) {
+			expected = MMU_P | MMU_RW | MMU_US | MMU_XD;
+#endif
+#ifdef CONFIG_X86_64
+		} else if (IN_REGION(_locore, pos)) {
+			if (IS_ENABLED(CONFIG_X86_KPTI)) {
+				expected = MMU_P | MMU_US;
+			} else {
+				expected = MMU_P;
+			}
+		} else if (IN_REGION(_lorodata, pos)) {
+			if (IS_ENABLED(CONFIG_X86_KPTI)) {
+				expected = MMU_P | MMU_US | MMU_XD;
+			} else {
+				expected = MMU_P | MMU_XD;
+			}
+#endif /* CONFIG_X86_64 */
+		} else {
+			/* We forced CONFIG_HW_STACK_PROTECTION off otherwise
+			 * guard pages will have RW cleared. We can relax this
+			 * once we start memory-mapping stacks.
+			 */
+			expected = MMU_P | MMU_RW | MMU_XD;
+		}
+
+		zassert_equal(flags, expected,
+				"bad flags " PRI_ENTRY " at %p",
+				flags, pos);
+	}
+
+}
+
+/**
+ * Test that the NULL virtual page is always non-present
+ *
+ * @ingroup kernel_memprotect_tests
+ */
+void test_null_map(void)
+{
+	int level;
+	pentry_t entry;
+
+	/* The NULL page must always be non-present */
+	z_x86_pentry_get(&level, &entry, z_x86_page_tables_get(), NULL);
+	zassert_true((entry & MMU_P) == 0, "present NULL entry");
+}
+
+/**
+ * Dump kernel's page tables to console
+ *
+ * We don't verify any specific output, but this shouldn't crash
+ *
+ * @ingroup kernel_memprotect_tests
+ */
+void test_dump_ptables(void)
+{
+	z_x86_dump_page_tables(z_x86_page_tables_get());
+}
+
+void test_main(void)
+{
+	ztest_test_suite(x86_pagetables,
+			 ztest_unit_test(test_ram_perms),
+			 ztest_unit_test(test_null_map),
+			 ztest_unit_test(test_dump_ptables)
+			 );
+	ztest_run_test_suite(x86_pagetables);
+}

tests/arch/x86/pagetables/testcase.yaml

@@ -0,0 +1,5 @@
+tests:
+  arch.x86.pagetables:
+    arch_whitelist: x86
+    tags: userspace mmu
+    filter: CONFIG_MMU