[PATCH RFC v2 5/7] mm: selftests: Add shmem memory failure test

[Lisa Wang <wyihan@google.com>]

Add a shmem memory failure selftest to test the shmem memory failure is
correct after modifying shmem return value.

Test that
+ madvise() call returns 0 at the first time
+ trigger a SIGBUS when the poisoned shmem page is fault-in again.

Signed-off-by: Lisa Wang <wyihan@google.com>
---
 tools/testing/selftests/mm/Makefile                |  3 +
 tools/testing/selftests/mm/run_vmtests.sh          |  1 +
 .../selftests/mm/shmem_memory_failure_test.c       | 98 ++++++++++++++++++++++
 3 files changed, 102 insertions(+)

diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile
index 7a5de4e9bf52..ac033851c9eb 100644
--- a/tools/testing/selftests/mm/Makefile
+++ b/tools/testing/selftests/mm/Makefile
@@ -72,6 +72,7 @@ TEST_GEN_FILES += madv_populate
 TEST_GEN_FILES += map_fixed_noreplace
 TEST_GEN_FILES += map_hugetlb
 TEST_GEN_FILES += map_populate
+TEST_GEN_FILES += shmem_memory_failure_test
 ifneq (,$(filter $(ARCH),arm64 riscv riscv64 x86 x86_64 loongarch32 loongarch64))
 TEST_GEN_FILES += memfd_secret
 endif
@@ -259,6 +260,8 @@ $(OUTPUT)/migration: LDLIBS += -lnuma
 
 $(OUTPUT)/rmap: LDLIBS += -lnuma
 
+$(OUTPUT)/shmem_memory_failure_test: CFLAGS += -I$(top_srcdir)/tools/include
+
 local_config.mk local_config.h: check_config.sh
 	CC="$(CC)" CFLAGS="$(CFLAGS)" ./check_config.sh
 
diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh
index afdcfd0d7cef..58fb959a7936 100755
--- a/tools/testing/selftests/mm/run_vmtests.sh
+++ b/tools/testing/selftests/mm/run_vmtests.sh
@@ -402,6 +402,7 @@ CATEGORY="hugetlb" run_test ./hugetlb-soft-offline
 echo "$nr_hugepages_tmp" > /proc/sys/vm/nr_hugepages
 echo "$enable_soft_offline" > /proc/sys/vm/enable_soft_offline
 CATEGORY="hugetlb" run_test ./hugetlb-read-hwpoison
+CATEGORY="mmap" run_test ./shmem_memory_failure_test
 fi
 
 if [ $VADDR64 -ne 0 ]; then
diff --git a/tools/testing/selftests/mm/shmem_memory_failure_test.c b/tools/testing/selftests/mm/shmem_memory_failure_test.c
new file mode 100644
index 000000000000..44752024a7fc
--- /dev/null
+++ b/tools/testing/selftests/mm/shmem_memory_failure_test.c
@@ -0,0 +1,98 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * This test makes sure when memory failure happens, shmem can handle
+ * successfully.
+ */
+#include <linux/compiler.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <signal.h>
+#include <setjmp.h>
+#include <errno.h>
+#include "kselftest.h"
+#include "vm_util.h"
+
+static sigjmp_buf sigbuf;
+
+static void signal_handler(int sig, siginfo_t *info, void *ucontext)
+{
+	siglongjmp(sigbuf, 1);
+}
+
+static void set_signal_handler(int sig, void (*handler)(int, siginfo_t *, void *))
+{
+	struct sigaction sa = {};
+
+	sa.sa_sigaction = handler;
+	sa.sa_flags = SA_SIGINFO;
+	sigemptyset(&sa.sa_mask);
+	if (sigaction(sig, &sa, NULL) == -1)
+		ksft_exit_fail_msg("Failed to set SIGBUS handler: %s\n", strerror(errno));
+}
+
+static unsigned long addr_to_pfn(char *addr)
+{
+	int pagemap_fd;
+	unsigned long pfn;
+
+	pagemap_fd = open("/proc/self/pagemap", O_RDONLY);
+	if (pagemap_fd < 0)
+		ksft_exit_fail_msg("Failed to open /proc/self/pagemap: %s\n", strerror(errno));
+	pfn = pagemap_get_pfn(pagemap_fd, addr);
+	close(pagemap_fd);
+
+	return pfn;
+}
+
+static void test_shmem_memory_failure(size_t total_size, size_t page_size)
+{
+	unsigned long memory_failure_pfn;
+	char *memory_failure_mem;
+	char *memory_failure_addr;
+	int fd;
+
+	fd = memfd_create("shmem_hwpoison_test", 0);
+	if (fd < 0)
+		ksft_exit_skip("memfd_create failed: %s\n", strerror(errno));
+
+	if (ftruncate(fd, total_size) < 0)
+		ksft_exit_fail_msg("ftruncate failed: %s\n", strerror(errno));
+
+	memory_failure_mem = mmap(NULL, total_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+	if (memory_failure_mem == MAP_FAILED)
+		ksft_exit_fail_msg("mmap failed: %s\n", strerror(errno));
+	memory_failure_addr = memory_failure_mem + page_size;
+	READ_ONCE(memory_failure_addr[0]);
+	memory_failure_pfn = addr_to_pfn(memory_failure_addr);
+
+	if (madvise(memory_failure_addr, page_size, MADV_HWPOISON) != 0)
+		ksft_exit_fail_msg("MADV_HWPOISON failed: %s\n", strerror(errno));
+
+	if (sigsetjmp(sigbuf, 1) == 0) {
+		READ_ONCE(memory_failure_addr[0]);
+		ksft_test_result_fail("Read from poisoned page should have triggered SIGBUS\n");
+	} else {
+		ksft_test_result_pass("SIGBUS triggered as expected on poisoned page\n");
+	}
+
+	munmap(memory_failure_mem, total_size);
+	close(fd);
+	if (unpoison_memory(memory_failure_pfn) < 0)
+		ksft_exit_fail_msg("unpoison_memory failed: %s\n", strerror(errno));
+}
+
+int main(int argc, char *argv[])
+{
+	const size_t pagesize = getpagesize();
+
+	ksft_print_header();
+	ksft_set_plan(1);
+
+	set_signal_handler(SIGBUS, signal_handler);
+	test_shmem_memory_failure(pagesize * 4, pagesize);
+	ksft_finished();
+}

-- 
2.53.0.959.g497ff81fa9-goog