[PATCH 46/46] selftests/vm: add HGM UFFDIO_CONTINUE and hwpoison tests

[James Houghton]

This tests that high-granularity CONTINUEs at all sizes work
(exercising contiguous PTE sizes for arm64, when support is added). This
also tests that collapse works and hwpoison works correctly (although we
aren't yet testing high-granularity poison).

This test uses UFFD_FEATURE_EVENT_FORK + UFFD_REGISTER_MODE_WP to force
the kernel to copy page tables on fork(), exercising the changes to
copy_hugetlb_page_range().

Signed-off-by: James Houghton <jthoughton@xxxxxxxxxx>
---
 tools/testing/selftests/vm/Makefile      |   1 +
 tools/testing/selftests/vm/hugetlb-hgm.c | 455 +++++++++++++++++++++++
 2 files changed, 456 insertions(+)
 create mode 100644 tools/testing/selftests/vm/hugetlb-hgm.c

diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile
index 89c14e41bd43..4aa4ca75a471 100644
--- a/tools/testing/selftests/vm/Makefile
+++ b/tools/testing/selftests/vm/Makefile
@@ -32,6 +32,7 @@ TEST_GEN_FILES += compaction_test
 TEST_GEN_FILES += gup_test
 TEST_GEN_FILES += hmm-tests
 TEST_GEN_FILES += hugetlb-madvise
+TEST_GEN_FILES += hugetlb-hgm
 TEST_GEN_FILES += hugepage-mmap
 TEST_GEN_FILES += hugepage-mremap
 TEST_GEN_FILES += hugepage-shm
diff --git a/tools/testing/selftests/vm/hugetlb-hgm.c b/tools/testing/selftests/vm/hugetlb-hgm.c
new file mode 100644
index 000000000000..616bc40164bf
--- /dev/null
+++ b/tools/testing/selftests/vm/hugetlb-hgm.c
@@ -0,0 +1,455 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Test uncommon cases in HugeTLB high-granularity mapping:
+ *  1. Test all supported high-granularity page sizes (with MADV_COLLAPSE).
+ *  2. Test MADV_HWPOISON behavior.
+ */
+
+#define _GNU_SOURCE
+#include <fcntl.h>
+#include <sys/syscall.h>
+#include <sys/ioctl.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <sys/poll.h>
+#include <stdint.h>
+#include <string.h>
+
+#include <linux/userfaultfd.h>
+#include <linux/magic.h>
+#include <sys/mman.h>
+#include <sys/statfs.h>
+#include <errno.h>
+#include <stdbool.h>
+#include <signal.h>
+#include <pthread.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+#define PAGE_MASK ~(4096 - 1)
+
+#ifndef MADV_COLLAPSE
+#define MADV_COLLAPSE 25
+#endif
+
+#ifndef MADV_SPLIT
+#define MADV_SPLIT 26
+#endif
+
+#define PREFIX " ... "
+#define ERROR_PREFIX " !!! "
+
+enum test_status {
+	TEST_PASSED = 0,
+	TEST_FAILED = 1,
+	TEST_SKIPPED = 2,
+};
+
+static char *status_to_str(enum test_status status)
+{
+	switch (status) {
+	case TEST_PASSED:
+		return "TEST_PASSED";
+	case TEST_FAILED:
+		return "TEST_FAILED";
+	case TEST_SKIPPED:
+		return "TEST_SKIPPED";
+	default:
+		return "TEST_???";
+	}
+}
+
+int userfaultfd(int flags)
+{
+	return syscall(__NR_userfaultfd, flags);
+}
+
+int map_range(int uffd, char *addr, uint64_t length)
+{
+	struct uffdio_continue cont = {
+		.range = (struct uffdio_range) {
+			.start = (uint64_t)addr,
+			.len = length,
+		},
+		.mode = 0,
+		.mapped = 0,
+	};
+
+	if (ioctl(uffd, UFFDIO_CONTINUE, &cont) < 0) {
+		perror(ERROR_PREFIX "UFFDIO_CONTINUE failed");
+		return -1;
+	}
+	return 0;
+}
+
+int check_equal(char *mapping, size_t length, char value)
+{
+	size_t i;
+
+	for (i = 0; i < length; ++i)
+		if (mapping[i] != value) {
+			printf(ERROR_PREFIX "mismatch at %p (%d != %d)\n",
+					&mapping[i], mapping[i], value);
+			return -1;
+		}
+
+	return 0;
+}
+
+int test_continues(int uffd, char *primary_map, char *secondary_map, size_t len,
+		   bool verify)
+{
+	size_t offset = 0;
+	unsigned char iter = 0;
+	unsigned long pagesize = getpagesize();
+	uint64_t size;
+
+	for (size = len/2; size >= pagesize;
+			offset += size, size /= 2) {
+		iter++;
+		memset(secondary_map + offset, iter, size);
+		printf(PREFIX "UFFDIO_CONTINUE: %p -> %p = %d%s\n",
+				primary_map + offset,
+				primary_map + offset + size,
+				iter,
+				verify ? " (and verify)" : "");
+		if (map_range(uffd, primary_map + offset, size))
+			return -1;
+		if (verify && check_equal(primary_map + offset, size, iter))
+			return -1;
+	}
+	return 0;
+}
+
+int verify_contents(char *map, size_t len, bool last_4k_zero)
+{
+	size_t offset = 0;
+	int i = 0;
+	uint64_t size;
+
+	for (size = len/2; size > 4096; offset += size, size /= 2)
+		if (check_equal(map + offset, size, ++i))
+			return -1;
+
+	if (last_4k_zero)
+		/* expect the last 4K to be zero. */
+		if (check_equal(map + len - 4096, 4096, 0))
+			return -1;
+
+	return 0;
+}
+
+int test_collapse(char *primary_map, size_t len, bool hwpoison)
+{
+	printf(PREFIX "collapsing %p -> %p\n", primary_map, primary_map + len);
+	if (madvise(primary_map, len, MADV_COLLAPSE) < 0) {
+		if (errno == EHWPOISON && hwpoison) {
+			/* this is expected for the hwpoison test. */
+			printf(PREFIX "could not collapse due to poison\n");
+			return 0;
+		}
+		perror(ERROR_PREFIX "collapse failed");
+		return -1;
+	}
+
+	printf(PREFIX "verifying %p -> %p\n", primary_map, primary_map + len);
+	return verify_contents(primary_map, len, true);
+}
+
+static void *sigbus_addr;
+bool was_mceerr;
+bool got_sigbus;
+
+void sigbus_handler(int signo, siginfo_t *info, void *context)
+{
+	got_sigbus = true;
+	was_mceerr = info->si_code == BUS_MCEERR_AR;
+	sigbus_addr = info->si_addr;
+
+	pthread_exit(NULL);
+}
+
+void *access_mem(void *addr)
+{
+	volatile char *ptr = addr;
+
+	*ptr;
+	return NULL;
+}
+
+int test_sigbus(char *addr, bool poison)
+{
+	int ret = 0;
+	pthread_t pthread;
+
+	sigbus_addr = (void *)0xBADBADBAD;
+	was_mceerr = false;
+	got_sigbus = false;
+	ret = pthread_create(&pthread, NULL, &access_mem, addr);
+	if (ret) {
+		printf(ERROR_PREFIX "failed to create thread: %s\n",
+				strerror(ret));
+		return ret;
+	}
+
+	pthread_join(pthread, NULL);
+	if (!got_sigbus) {
+		printf(ERROR_PREFIX "didn't get a SIGBUS\n");
+		return -1;
+	} else if (sigbus_addr != addr) {
+		printf(ERROR_PREFIX "got incorrect sigbus address: %p vs %p\n",
+				sigbus_addr, addr);
+		return -1;
+	} else if (poison && !was_mceerr) {
+		printf(ERROR_PREFIX "didn't get an MCEERR?\n");
+		return -1;
+	}
+	return 0;
+}
+
+void *read_from_uffd_thd(void *arg)
+{
+	int uffd = *(int *)arg;
+	struct uffd_msg msg;
+	/* opened without O_NONBLOCK */
+	if (read(uffd, &msg, sizeof(msg)) != sizeof(msg))
+		printf(ERROR_PREFIX "reading uffd failed\n");
+
+	return NULL;
+}
+
+int read_event_from_uffd(int *uffd, pthread_t *pthread)
+{
+	int ret = 0;
+
+	ret = pthread_create(pthread, NULL, &read_from_uffd_thd, (void *)uffd);
+	if (ret) {
+		printf(ERROR_PREFIX "failed to create thread: %s\n",
+				strerror(ret));
+		return ret;
+	}
+	return 0;
+}
+
+enum test_status test_hwpoison(char *primary_map, size_t len)
+{
+	const unsigned long pagesize = getpagesize();
+	const int num_poison_checks = 512;
+	unsigned long bytes_per_check = len/num_poison_checks;
+	int i;
+
+	printf(PREFIX "poisoning %p -> %p\n", primary_map, primary_map + len);
+	if (madvise(primary_map, len, MADV_HWPOISON) < 0) {
+		perror(ERROR_PREFIX "MADV_HWPOISON failed");
+		return TEST_SKIPPED;
+	}
+
+	printf(PREFIX "checking that it was poisoned "
+	       "(%d addresses within %p -> %p)\n",
+	       num_poison_checks, primary_map, primary_map + len);
+
+	if (pagesize > bytes_per_check)
+		bytes_per_check = pagesize;
+
+	for (i = 0; i < len; i += bytes_per_check)
+		if (test_sigbus(primary_map + i, true) < 0)
+			return TEST_FAILED;
+	/* check very last byte, because we left it unmapped */
+	if (test_sigbus(primary_map + len - 1, true))
+		return TEST_FAILED;
+
+	return TEST_PASSED;
+}
+
+int test_fork(int uffd, char *primary_map, size_t len)
+{
+	int status;
+	int ret = 0;
+	pid_t pid;
+	pthread_t uffd_thd;
+
+	/*
+	 * UFFD_FEATURE_EVENT_FORK will put fork event on the userfaultfd,
+	 * which we must read, otherwise we block fork(). Setup a thread to
+	 * read that event now.
+	 *
+	 * Page fault events should result in a SIGBUS, so we expect only a
+	 * single event from the uffd (the fork event).
+	 */
+	if (read_event_from_uffd(&uffd, &uffd_thd))
+		return -1;
+
+	pid = fork();
+
+	if (!pid) {
+		/*
+		 * Because we have UFFDIO_REGISTER_MODE_WP and
+		 * UFFD_FEATURE_EVENT_FORK, the page tables should be copied
+		 * exactly.
+		 *
+		 * Check that everything except that last 4K has correct
+		 * contents, and then check that the last 4K gets a SIGBUS.
+		 */
+		printf(PREFIX "child validating...\n");
+		ret = verify_contents(primary_map, len, false) ||
+			test_sigbus(primary_map + len - 1, false);
+		ret = 0;
+		exit(ret ? 1 : 0);
+	} else {
+		/* wait for the child to finish. */
+		waitpid(pid, &status, 0);
+		ret = WEXITSTATUS(status);
+		if (!ret) {
+			printf(PREFIX "parent validating...\n");
+			/* Same check as the child. */
+			ret = verify_contents(primary_map, len, false) ||
+				test_sigbus(primary_map + len - 1, false);
+			ret = 0;
+		}
+	}
+
+	pthread_join(uffd_thd, NULL);
+	return ret;
+
+}
+
+enum test_status
+test_hgm(int fd, size_t hugepagesize, size_t len, bool hwpoison)
+{
+	int uffd;
+	char *primary_map, *secondary_map;
+	struct uffdio_api api;
+	struct uffdio_register reg;
+	struct sigaction new, old;
+	enum test_status status = TEST_SKIPPED;
+
+	if (ftruncate(fd, len) < 0) {
+		perror(ERROR_PREFIX "ftruncate failed");
+		return status;
+	}
+
+	uffd = userfaultfd(O_CLOEXEC);
+	if (uffd < 0) {
+		perror(ERROR_PREFIX "uffd not created");
+		return status;
+	}
+
+	primary_map = mmap(NULL, len, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+	if (primary_map == MAP_FAILED) {
+		perror(ERROR_PREFIX "mmap for primary mapping failed");
+		goto close_uffd;
+	}
+	secondary_map = mmap(NULL, len, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+	if (secondary_map == MAP_FAILED) {
+		perror(ERROR_PREFIX "mmap for secondary mapping failed");
+		goto unmap_primary;
+	}
+
+	printf(PREFIX "primary mapping: %p\n", primary_map);
+	printf(PREFIX "secondary mapping: %p\n", secondary_map);
+
+	api.api = UFFD_API;
+	api.features = UFFD_FEATURE_SIGBUS | UFFD_FEATURE_EXACT_ADDRESS |
+		UFFD_FEATURE_EVENT_FORK;
+	if (ioctl(uffd, UFFDIO_API, &api) == -1) {
+		perror(ERROR_PREFIX "UFFDIO_API failed");
+		goto out;
+	}
+
+	if (madvise(primary_map, len, MADV_SPLIT)) {
+		perror(ERROR_PREFIX "MADV_SPLIT failed");
+		goto out;
+	}
+
+	reg.range.start = (unsigned long)primary_map;
+	reg.range.len = len;
+	/*
+	 * Register with UFFDIO_REGISTER_MODE_WP to force fork() to copy page
+	 * tables (also need UFFD_FEATURE_EVENT_FORK, which we have).
+	 */
+	reg.mode = UFFDIO_REGISTER_MODE_MINOR | UFFDIO_REGISTER_MODE_MISSING |
+		UFFDIO_REGISTER_MODE_WP;
+	reg.ioctls = 0;
+	if (ioctl(uffd, UFFDIO_REGISTER, &reg) == -1) {
+		perror(ERROR_PREFIX "register failed");
+		goto out;
+	}
+
+	new.sa_sigaction = &sigbus_handler;
+	new.sa_flags = SA_SIGINFO;
+	if (sigaction(SIGBUS, &new, &old) < 0) {
+		perror(ERROR_PREFIX "could not setup SIGBUS handler");
+		goto out;
+	}
+
+	status = TEST_FAILED;
+
+	if (test_continues(uffd, primary_map, secondary_map, len, !hwpoison))
+		goto done;
+	if (hwpoison) {
+		/* test_hwpoison can fail with TEST_SKIPPED. */
+		enum test_status new_status = test_hwpoison(primary_map, len);
+
+		if (new_status != TEST_PASSED) {
+			status = new_status;
+			goto done;
+		}
+	} else if (test_fork(uffd, primary_map, len))
+		goto done;
+	if (test_collapse(primary_map, len, hwpoison))
+		goto done;
+
+	status = TEST_PASSED;
+
+done:
+	if (ftruncate(fd, 0) < 0) {
+		perror(ERROR_PREFIX "ftruncate back to 0 failed");
+		status = TEST_FAILED;
+	}
+
+out:
+	munmap(secondary_map, len);
+unmap_primary:
+	munmap(primary_map, len);
+close_uffd:
+	close(uffd);
+	return status;
+}
+
+int main(void)
+{
+	int fd;
+	struct statfs file_stat;
+	size_t hugepagesize;
+	size_t len;
+
+	fd = memfd_create("hugetlb_tmp", MFD_HUGETLB);
+	if (fd < 0) {
+		perror(ERROR_PREFIX "could not open hugetlbfs file");
+		return -1;
+	}
+
+	memset(&file_stat, 0, sizeof(file_stat));
+	if (fstatfs(fd, &file_stat)) {
+		perror(ERROR_PREFIX "fstatfs failed");
+		goto close;
+	}
+	if (file_stat.f_type != HUGETLBFS_MAGIC) {
+		printf(ERROR_PREFIX "not hugetlbfs file\n");
+		goto close;
+	}
+
+	hugepagesize = file_stat.f_bsize;
+	len = 2 * hugepagesize;
+	printf("HGM regular test...\n");
+	printf("HGM regular test:  %s\n",
+			status_to_str(test_hgm(fd, hugepagesize, len, false)));
+	printf("HGM hwpoison test...\n");
+	printf("HGM hwpoison test: %s\n",
+			status_to_str(test_hgm(fd, hugepagesize, len, true)));
+close:
+	close(fd);
+
+	return 0;
+}
-- 
2.39.0.314.g84b9a713c41-goog