io_uring provides a simple mechanism to test long-term, R/W GUP pins -- via fixed buffers -- and can be used to verify that GUP pins stay in sync with the pages in the page table even if a page would temporarily get mapped R/O or concurrent fork() could accidentially end up sharing pinned pages with the child.
Note that this essentially re-introduces local_config support that was removed recently in commit 6f83d6c74ea5 ("Kselftests: remove support of libhugetlbfs from kselftests").
Signed-off-by: David Hildenbrand david@redhat.com --- tools/testing/selftests/vm/Makefile | 21 ++- tools/testing/selftests/vm/anon_cow.c | 190 +++++++++++++++++++++ tools/testing/selftests/vm/check_config.sh | 31 ++++ 3 files changed, 241 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/vm/check_config.sh
diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile index bc759534ec28..7931b84040ed 100644 --- a/tools/testing/selftests/vm/Makefile +++ b/tools/testing/selftests/vm/Makefile @@ -1,7 +1,9 @@ # SPDX-License-Identifier: GPL-2.0 # Makefile for vm selftests
-LOCAL_HDRS += $(top_srcdir)/mm/gup_test.h +LOCAL_HDRS += $(selfdir)/vm/local_config.h $(top_srcdir)/mm/gup_test.h + +include local_config.mk
uname_M := $(shell uname -m 2>/dev/null || echo not) MACHINE ?= $(shell echo $(uname_M) | sed -e 's/aarch64.*/arm64/' -e 's/ppc64.*/ppc64/') @@ -150,8 +152,25 @@ warn_32bit_failure: endif endif
+# ANON_COW_EXTRA_LIBS may get set in local_config.mk, or it may be left empty. +$(OUTPUT)/anon_cow: LDLIBS += $(ANON_COW_EXTRA_LIBS) + $(OUTPUT)/mlock-random-test $(OUTPUT)/memfd_secret: LDLIBS += -lcap
$(OUTPUT)/ksm_tests: LDLIBS += -lnuma
$(OUTPUT)/migration: LDLIBS += -lnuma + +local_config.mk local_config.h: check_config.sh + /bin/sh ./check_config.sh $(CC) + +EXTRA_CLEAN += local_config.mk local_config.h + +ifeq ($(ANON_COW_EXTRA_LIBS),) +all: warn_missing_liburing + +warn_missing_liburing: + @echo ; \ + echo "Warning: missing liburing support. Some COW tests will be skipped." ; \ + echo +endif diff --git a/tools/testing/selftests/vm/anon_cow.c b/tools/testing/selftests/vm/anon_cow.c index 06fd046bf1f2..369b3e15647d 100644 --- a/tools/testing/selftests/vm/anon_cow.c +++ b/tools/testing/selftests/vm/anon_cow.c @@ -19,6 +19,11 @@ #include <sys/mman.h> #include <sys/wait.h>
+#include "local_config.h" +#ifdef LOCAL_CONFIG_HAVE_LIBURING +#include <liburing.h> +#endif /* LOCAL_CONFIG_HAVE_LIBURING */ + #include "../kselftest.h" #include "vm_util.h"
@@ -334,6 +339,170 @@ static void test_vmsplice_after_fork(char *mem, size_t size) do_test_vmsplice_in_parent(mem, size, false); }
+#ifdef LOCAL_CONFIG_HAVE_LIBURING +static void do_test_iouring(char *mem, size_t size, bool use_fork) +{ + struct comm_pipes comm_pipes; + struct io_uring_cqe *cqe; + struct io_uring_sqe *sqe; + struct io_uring ring; + size_t cur, total; + struct iovec iov; + char *buf, *tmp; + int ret, fd; + FILE *file; + + ret = setup_comm_pipes(&comm_pipes); + if (ret) { + ksft_test_result_fail("pipe() failed\n"); + return; + } + + file = tmpfile(); + if (!file) { + ksft_test_result_fail("tmpfile() failed\n"); + goto close_comm_pipes; + } + fd = fileno(file); + assert(fd); + + tmp = malloc(size); + if (!tmp) { + ksft_test_result_fail("malloc() failed\n"); + goto close_file; + } + + /* Skip on errors, as we might just lack kernel support. */ + ret = io_uring_queue_init(1, &ring, 0); + if (ret < 0) { + ksft_test_result_skip("io_uring_queue_init() failed\n"); + goto free_tmp; + } + + /* + * Register the range as a fixed buffer. This will FOLL_WRITE | FOLL_PIN + * | FOLL_LONGTERM the range. + * + * Skip on errors, as we might just lack kernel support or might not + * have sufficient MEMLOCK permissions. + */ + iov.iov_base = mem; + iov.iov_len = size; + ret = io_uring_register_buffers(&ring, &iov, 1); + if (ret) { + ksft_test_result_skip("io_uring_register_buffers() failed\n"); + goto queue_exit; + } + + if (use_fork) { + /* + * fork() and keep the child alive until we're done. Note that + * we expect the pinned page to not get shared with the child. + */ + ret = fork(); + if (ret < 0) { + ksft_test_result_fail("fork() failed\n"); + goto unregister_buffers; + } else if (!ret) { + write(comm_pipes.child_ready[1], "0", 1); + while (read(comm_pipes.parent_ready[0], &buf, 1) != 1) + ; + exit(0); + } + + while (read(comm_pipes.child_ready[0], &buf, 1) != 1) + ; + } else { + /* + * Map the page R/O into the page table. Enable softdirty + * tracking to stop the page from getting mapped R/W immediately + * again by mprotect() optimizations. Note that we don't have an + * easy way to test if that worked (the pagemap does not export + * if the page is mapped R/O vs. R/W). + */ + ret = mprotect(mem, size, PROT_READ); + clear_softdirty(); + ret |= mprotect(mem, size, PROT_READ | PROT_WRITE); + if (ret) { + ksft_test_result_fail("mprotect() failed\n"); + goto unregister_buffers; + } + } + + /* + * Modify the page and write page content as observed by the fixed + * buffer pin to the file so we can verify it. + */ + memset(mem, 0xff, size); + sqe = io_uring_get_sqe(&ring); + if (!sqe) { + ksft_test_result_fail("io_uring_get_sqe() failed\n"); + goto quit_child; + } + io_uring_prep_write_fixed(sqe, fd, mem, size, 0, 0); + + ret = io_uring_submit(&ring); + if (ret < 0) { + ksft_test_result_fail("io_uring_submit() failed\n"); + goto quit_child; + } + + ret = io_uring_wait_cqe(&ring, &cqe); + if (ret < 0) { + ksft_test_result_fail("io_uring_wait_cqe() failed\n"); + goto quit_child; + } + + if (cqe->res != size) { + ksft_test_result_fail("write_fixed failed\n"); + goto quit_child; + } + io_uring_cqe_seen(&ring, cqe); + + /* Read back the file content to the temporary buffer. */ + total = 0; + while (total < size) { + cur = pread(fd, tmp + total, size - total, total); + if (cur < 0) { + ksft_test_result_fail("pread() failed\n"); + goto quit_child; + } + total += cur; + } + + /* Finally, check if we read what we expected. */ + ksft_test_result(!memcmp(mem, tmp, size), + "Longterm R/W pin is reliable\n"); + +quit_child: + if (use_fork) { + write(comm_pipes.parent_ready[1], "0", 1); + wait(&ret); + } +unregister_buffers: + io_uring_unregister_buffers(&ring); +queue_exit: + io_uring_queue_exit(&ring); +free_tmp: + free(tmp); +close_file: + fclose(file); +close_comm_pipes: + close_comm_pipes(&comm_pipes); +} + +static void test_iouring_ro(char *mem, size_t size) +{ + do_test_iouring(mem, size, false); +} + +static void test_iouring_fork(char *mem, size_t size) +{ + do_test_iouring(mem, size, true); +} + +#endif /* LOCAL_CONFIG_HAVE_LIBURING */ + typedef void (*test_fn)(char *mem, size_t size);
static void do_run_with_base_page(test_fn fn, bool swapout) @@ -660,6 +829,27 @@ static const struct test_case test_cases[] = { "vmsplice() + unmap in parent after fork()", test_vmsplice_after_fork, }, +#ifdef LOCAL_CONFIG_HAVE_LIBURING + /* + * Take a R/W longterm pin and then map the page R/O into the page + * table to trigger a write fault on next access. When modifying the + * page, the page content must be visible via the pin. + */ + { + "R/O-mapping a page registered as iouring fixed buffer", + test_iouring_ro, + }, + /* + * Take a R/W longterm pin and then fork() a child. When modifying the + * page, the page content must be visible via the pin. We expect the + * pinned page to not get shared with the child. + */ + { + "fork() with an iouring fixed buffer", + test_iouring_fork, + }, + +#endif /* LOCAL_CONFIG_HAVE_LIBURING */ };
static void run_test_case(struct test_case const *test_case) diff --git a/tools/testing/selftests/vm/check_config.sh b/tools/testing/selftests/vm/check_config.sh new file mode 100644 index 000000000000..9a44c6520925 --- /dev/null +++ b/tools/testing/selftests/vm/check_config.sh @@ -0,0 +1,31 @@ +#!/bin/sh +# SPDX-License-Identifier: GPL-2.0 +# +# Probe for libraries and create header files to record the results. Both C +# header files and Makefile include fragments are created. + +OUTPUT_H_FILE=local_config.h +OUTPUT_MKFILE=local_config.mk + +tmpname=$(mktemp) +tmpfile_c=${tmpname}.c +tmpfile_o=${tmpname}.o + +# liburing +echo "#include <sys/types.h>" > $tmpfile_c +echo "#include <liburing.h>" >> $tmpfile_c +echo "int func(void) { return 0; }" >> $tmpfile_c + +CC=${1:?"Usage: $0 <compiler> # example compiler: gcc"} +$CC -c $tmpfile_c -o $tmpfile_o >/dev/null 2>&1 + +if [ -f $tmpfile_o ]; then + echo "#define LOCAL_CONFIG_HAVE_LIBURING 1" > $OUTPUT_H_FILE + echo "ANON_COW_EXTRA_LIBS = -luring" > $OUTPUT_MKFILE +else + echo "// No liburing support found" > $OUTPUT_H_FILE + echo "# No liburing support found, so:" > $OUTPUT_MKFILE + echo "ANON_COW_EXTRA_LIBS = " >> $OUTPUT_MKFILE +fi + +rm ${tmpname}.*