linux-kselftest-next-5.14-rc1

This Kselftest update for Linux 5.14-rc1 consists of fixes to
 existing tests and framework:
 
 -- migrate sgx test to kselftest harness
 -- add new test cases to sgx test
 -- ftrace test fix event-no-pid on 1-core machine
 -- splice test adjust for handler fallback removal
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Merge tag 'linux-kselftest-next-5.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest

Pull Kselftest update from Shuah Khan:
 "Fixes to existing tests and framework:

   - migrate sgx test to kselftest harness

   - add new test cases to sgx test

   - ftrace test fix event-no-pid on 1-core machine

   - splice test adjust for handler fallback removal"

* tag 'linux-kselftest-next-5.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest:
  selftests/sgx: remove checks for file execute permissions
  selftests/ftrace: fix event-no-pid on 1-core machine
  selftests/sgx: Refine the test enclave to have storage
  selftests/sgx: Add EXPECT_EEXIT() macro
  selftests/sgx: Dump enclave memory map
  selftests/sgx: Migrate to kselftest harness
  selftests/sgx: Rename 'eenter' and 'sgx_call_vdso'
  selftests: timers: rtcpie: skip test if default RTC device does not exist
  selftests: lib.mk: Also install "config" and "settings"
  selftests: splice: Adjust for handler fallback removal
  selftests/tls: Add {} to avoid static checker warning
  selftests/resctrl: Fix incorrect parsing of option "-t"

tools/testing/selftests/ftrace/test.d/event/event-no-pid.tc

@@ -57,6 +57,10 @@ enable_events() {
     echo 1 > tracing_on
 }
 
+other_task() {
+    sleep .001 || usleep 1 || sleep 1
+}
+
 echo 0 > options/event-fork
 
 do_reset
@@ -94,6 +98,9 @@ child=$!
 echo "child = $child"
 wait $child
 
+# Be sure some other events will happen for small systems (e.g. 1 core)
+other_task
+
 echo 0 > tracing_on
 
 cnt=`count_pid $mypid`

tools/testing/selftests/lib.mk

@@ -100,6 +100,7 @@ define INSTALL_RULE
 	$(eval INSTALL_LIST = $(TEST_CUSTOM_PROGS)) $(INSTALL_SINGLE_RULE)
 	$(eval INSTALL_LIST = $(TEST_GEN_PROGS_EXTENDED)) $(INSTALL_SINGLE_RULE)
 	$(eval INSTALL_LIST = $(TEST_GEN_FILES)) $(INSTALL_SINGLE_RULE)
+	$(eval INSTALL_LIST = $(wildcard config settings)) $(INSTALL_SINGLE_RULE)
 endef
 
 install: all

tools/testing/selftests/net/tls.c

@@ -444,8 +444,9 @@ TEST_F(tls, sendmsg_large)
 		EXPECT_EQ(sendmsg(self->cfd, &msg, 0), send_len);
 	}
 
-	while (recvs++ < sends)
+	while (recvs++ < sends) {
 		EXPECT_NE(recv(self->fd, mem, send_len, 0), -1);
+	}
 
 	free(mem);
 }

tools/testing/selftests/resctrl/README

@@ -47,7 +47,7 @@ Parameter '-h' shows usage information.
 
 usage: resctrl_tests [-h] [-b "benchmark_cmd [options]"] [-t test list] [-n no_of_bits]
         -b benchmark_cmd [options]: run specified benchmark for MBM, MBA and CMT default benchmark is builtin fill_buf
-        -t test list: run tests specified in the test list, e.g. -t mbm, mba, cmt, cat
+        -t test list: run tests specified in the test list, e.g. -t mbm,mba,cmt,cat
         -n no_of_bits: run cache tests using specified no of bits in cache bit mask
         -p cpu_no: specify CPU number to run the test. 1 is default
         -h: help

tools/testing/selftests/resctrl/resctrl_tests.c

@@ -40,7 +40,7 @@ static void cmd_help(void)
 	printf("\t-b benchmark_cmd [options]: run specified benchmark for MBM, MBA and CMT\n");
 	printf("\t   default benchmark is builtin fill_buf\n");
 	printf("\t-t test list: run tests specified in the test list, ");
-	printf("e.g. -t mbm, mba, cmt, cat\n");
+	printf("e.g. -t mbm,mba,cmt,cat\n");
 	printf("\t-n no_of_bits: run cache tests using specified no of bits in cache bit mask\n");
 	printf("\t-p cpu_no: specify CPU number to run the test. 1 is default\n");
 	printf("\t-h: help\n");
@@ -173,7 +173,7 @@ int main(int argc, char **argv)
 
 					return -1;
 				}
-				token = strtok(NULL, ":\t");
+				token = strtok(NULL, ",");
 			}
 			break;
 		case 'p':

tools/testing/selftests/sgx/call.S

@@ -5,8 +5,8 @@
 
 	.text
 
-	.global sgx_call_vdso
-sgx_call_vdso:
+	.global sgx_enter_enclave
+sgx_enter_enclave:
 	.cfi_startproc
 	push	%r15
 	.cfi_adjust_cfa_offset	8
@@ -27,7 +27,7 @@ sgx_call_vdso:
 	.cfi_adjust_cfa_offset	8
 	push	0x38(%rsp)
 	.cfi_adjust_cfa_offset	8
-	call	*eenter(%rip)
+	call	*vdso_sgx_enter_enclave(%rip)
 	add	$0x10, %rsp
 	.cfi_adjust_cfa_offset	-0x10
 	pop	%rbx

tools/testing/selftests/sgx/defines.h

@@ -18,4 +18,14 @@
 #include "../../../../arch/x86/include/asm/enclu.h"
 #include "../../../../arch/x86/include/uapi/asm/sgx.h"
 
+enum encl_op_type {
+	ENCL_OP_PUT,
+	ENCL_OP_GET,
+};
+
+struct encl_op {
+	uint64_t type;
+	uint64_t buffer;
+};
+
 #endif /* DEFINES_H */

tools/testing/selftests/sgx/load.c

@@ -150,16 +150,6 @@ bool encl_load(const char *path, struct encl *encl)
 		goto err;
 	}
 
-	/*
-	 * This just checks if the /dev file has these permission
-	 * bits set.  It does not check that the current user is
-	 * the owner or in the owning group.
-	 */
-	if (!(sb.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH))) {
-		fprintf(stderr, "no execute permissions on device file %s\n", device_path);
-		goto err;
-	}
-
 	ptr = mmap(NULL, PAGE_SIZE, PROT_READ, MAP_SHARED, fd, 0);
 	if (ptr == (void *)-1) {
 		perror("mmap for read");
@@ -169,13 +159,13 @@ bool encl_load(const char *path, struct encl *encl)
 
 #define ERR_MSG \
 "mmap() succeeded for PROT_READ, but failed for PROT_EXEC.\n" \
-" Check that current user has execute permissions on %s and \n" \
-" that /dev does not have noexec set: mount | grep \"/dev .*noexec\"\n" \
+" Check that /dev does not have noexec set:\n" \
+" \tmount | grep \"/dev .*noexec\"\n" \
 " If so, remount it executable: mount -o remount,exec /dev\n\n"
 
 	ptr = mmap(NULL, PAGE_SIZE, PROT_EXEC, MAP_SHARED, fd, 0);
 	if (ptr == (void *)-1) {
-		fprintf(stderr, ERR_MSG, device_path);
+		fprintf(stderr, ERR_MSG);
 		goto err;
 	}
 	munmap(ptr, PAGE_SIZE);
@@ -239,9 +229,6 @@ bool encl_load(const char *path, struct encl *encl)
 		seg->offset = (phdr->p_offset & PAGE_MASK) - src_offset;
 		seg->size = (phdr->p_filesz + PAGE_SIZE - 1) & PAGE_MASK;
 
-		printf("0x%016lx 0x%016lx 0x%02x\n", seg->offset, seg->size,
-		       seg->prot);
-
 		j++;
 	}
 

tools/testing/selftests/sgx/main.c

@@ -17,11 +17,11 @@
 #include <sys/types.h>
 #include <sys/auxv.h>
 #include "defines.h"
+#include "../kselftest_harness.h"
 #include "main.h"
-#include "../kselftest.h"
 
 static const uint64_t MAGIC = 0x1122334455667788ULL;
-vdso_sgx_enter_enclave_t eenter;
+vdso_sgx_enter_enclave_t vdso_sgx_enter_enclave;
 
 struct vdso_symtab {
 	Elf64_Sym *elf_symtab;
@@ -107,85 +107,51 @@ static Elf64_Sym *vdso_symtab_get(struct vdso_symtab *symtab, const char *name)
 	return NULL;
 }
 
-bool report_results(struct sgx_enclave_run *run, int ret, uint64_t result,
-		  const char *test)
-{
-	bool valid = true;
-
-	if (ret) {
-		printf("FAIL: %s() returned: %d\n", test, ret);
-		valid = false;
-	}
-
-	if (run->function != EEXIT) {
-		printf("FAIL: %s() function, expected: %u, got: %u\n", test, EEXIT,
-		       run->function);
-		valid = false;
-	}
-
-	if (result != MAGIC) {
-		printf("FAIL: %s(), expected: 0x%lx, got: 0x%lx\n", test, MAGIC,
-		       result);
-		valid = false;
-	}
-
-	if (run->user_data) {
-		printf("FAIL: %s() user data, expected: 0x0, got: 0x%llx\n",
-		       test, run->user_data);
-		valid = false;
-	}
-
-	return valid;
-}
-
-static int user_handler(long rdi, long rsi, long rdx, long ursp, long r8, long r9,
-			struct sgx_enclave_run *run)
-{
-	run->user_data = 0;
-	return 0;
-}
-
-int main(int argc, char *argv[])
-{
-	struct sgx_enclave_run run;
-	struct vdso_symtab symtab;
-	Elf64_Sym *eenter_sym;
-	uint64_t result = 0;
+FIXTURE(enclave) {
 	struct encl encl;
+	struct sgx_enclave_run run;
+};
+
+FIXTURE_SETUP(enclave)
+{
+	Elf64_Sym *sgx_enter_enclave_sym = NULL;
+	struct vdso_symtab symtab;
+	struct encl_segment *seg;
+	char maps_line[256];
+	FILE *maps_file;
 	unsigned int i;
 	void *addr;
-	int ret;
 
-	memset(&run, 0, sizeof(run));
-
-	if (!encl_load("test_encl.elf", &encl)) {
-		encl_delete(&encl);
+	if (!encl_load("test_encl.elf", &self->encl)) {
+		encl_delete(&self->encl);
 		ksft_exit_skip("cannot load enclaves\n");
 	}
 
-	if (!encl_measure(&encl))
+	for (i = 0; i < self->encl.nr_segments; i++) {
+		seg = &self->encl.segment_tbl[i];
+
+		TH_LOG("0x%016lx 0x%016lx 0x%02x", seg->offset, seg->size, seg->prot);
+	}
+
+	if (!encl_measure(&self->encl))
 		goto err;
 
-	if (!encl_build(&encl))
+	if (!encl_build(&self->encl))
 		goto err;
 
 	/*
 	 * An enclave consumer only must do this.
 	 */
-	for (i = 0; i < encl.nr_segments; i++) {
-		struct encl_segment *seg = &encl.segment_tbl[i];
+	for (i = 0; i < self->encl.nr_segments; i++) {
+		struct encl_segment *seg = &self->encl.segment_tbl[i];
 
-		addr = mmap((void *)encl.encl_base + seg->offset, seg->size,
-			    seg->prot, MAP_SHARED | MAP_FIXED, encl.fd, 0);
-		if (addr == MAP_FAILED) {
-			perror("mmap() segment failed");
-			exit(KSFT_FAIL);
-		}
+		addr = mmap((void *)self->encl.encl_base + seg->offset, seg->size,
+			    seg->prot, MAP_SHARED | MAP_FIXED, self->encl.fd, 0);
+		EXPECT_NE(addr, MAP_FAILED);
+		if (addr == MAP_FAILED)
+			goto err;
 	}
 
-	memset(&run, 0, sizeof(run));
-	run.tcs = encl.encl_base;
-
 	/* Get vDSO base address */
 	addr = (void *)getauxval(AT_SYSINFO_EHDR);
 	if (!addr)
@@ -194,37 +160,134 @@ int main(int argc, char *argv[])
 	if (!vdso_get_symtab(addr, &symtab))
 		goto err;
 
-	eenter_sym = vdso_symtab_get(&symtab, "__vdso_sgx_enter_enclave");
-	if (!eenter_sym)
+	sgx_enter_enclave_sym = vdso_symtab_get(&symtab, "__vdso_sgx_enter_enclave");
+	if (!sgx_enter_enclave_sym)
 		goto err;
 
-	eenter = addr + eenter_sym->st_value;
+	vdso_sgx_enter_enclave = addr + sgx_enter_enclave_sym->st_value;
 
-	ret = sgx_call_vdso((void *)&MAGIC, &result, 0, EENTER, NULL, NULL, &run);
-	if (!report_results(&run, ret, result, "sgx_call_vdso"))
-		goto err;
+	memset(&self->run, 0, sizeof(self->run));
+	self->run.tcs = self->encl.encl_base;
 
+	maps_file = fopen("/proc/self/maps", "r");
+	if (maps_file != NULL)  {
+		while (fgets(maps_line, sizeof(maps_line), maps_file) != NULL) {
+			maps_line[strlen(maps_line) - 1] = '\0';
 
-	/* Invoke the vDSO directly. */
-	result = 0;
-	ret = eenter((unsigned long)&MAGIC, (unsigned long)&result, 0, EENTER,
-		     0, 0, &run);
-	if (!report_results(&run, ret, result, "eenter"))
-		goto err;
+			if (strstr(maps_line, "/dev/sgx_enclave"))
+				TH_LOG("%s", maps_line);
+		}
 
-	/* And with an exit handler. */
-	run.user_handler = (__u64)user_handler;
-	run.user_data = 0xdeadbeef;
-	ret = eenter((unsigned long)&MAGIC, (unsigned long)&result, 0, EENTER,
-		     0, 0, &run);
-	if (!report_results(&run, ret, result, "user_handler"))
-		goto err;
-
-	printf("SUCCESS\n");
-	encl_delete(&encl);
-	exit(KSFT_PASS);
+		fclose(maps_file);
+	}
 
 err:
-	encl_delete(&encl);
-	exit(KSFT_FAIL);
+	if (!sgx_enter_enclave_sym)
+		encl_delete(&self->encl);
+
+	ASSERT_NE(sgx_enter_enclave_sym, NULL);
 }
+
+FIXTURE_TEARDOWN(enclave)
+{
+	encl_delete(&self->encl);
+}
+
+#define ENCL_CALL(op, run, clobbered) \
+	({ \
+		int ret; \
+		if ((clobbered)) \
+			ret = vdso_sgx_enter_enclave((unsigned long)(op), 0, 0, \
+						     EENTER, 0, 0, (run)); \
+		else \
+			ret = sgx_enter_enclave((void *)(op), NULL, 0, EENTER, NULL, NULL, \
+						(run)); \
+		ret; \
+	})
+
+#define EXPECT_EEXIT(run) \
+	do { \
+		EXPECT_EQ((run)->function, EEXIT); \
+		if ((run)->function != EEXIT) \
+			TH_LOG("0x%02x 0x%02x 0x%016llx", (run)->exception_vector, \
+			       (run)->exception_error_code, (run)->exception_addr); \
+	} while (0)
+
+TEST_F(enclave, unclobbered_vdso)
+{
+	struct encl_op op;
+
+	op.type = ENCL_OP_PUT;
+	op.buffer = MAGIC;
+
+	EXPECT_EQ(ENCL_CALL(&op, &self->run, false), 0);
+
+	EXPECT_EEXIT(&self->run);
+	EXPECT_EQ(self->run.user_data, 0);
+
+	op.type = ENCL_OP_GET;
+	op.buffer = 0;
+
+	EXPECT_EQ(ENCL_CALL(&op, &self->run, false), 0);
+
+	EXPECT_EQ(op.buffer, MAGIC);
+	EXPECT_EEXIT(&self->run);
+	EXPECT_EQ(self->run.user_data, 0);
+}
+
+TEST_F(enclave, clobbered_vdso)
+{
+	struct encl_op op;
+
+	op.type = ENCL_OP_PUT;
+	op.buffer = MAGIC;
+
+	EXPECT_EQ(ENCL_CALL(&op, &self->run, true), 0);
+
+	EXPECT_EEXIT(&self->run);
+	EXPECT_EQ(self->run.user_data, 0);
+
+	op.type = ENCL_OP_GET;
+	op.buffer = 0;
+
+	EXPECT_EQ(ENCL_CALL(&op, &self->run, true), 0);
+
+	EXPECT_EQ(op.buffer, MAGIC);
+	EXPECT_EEXIT(&self->run);
+	EXPECT_EQ(self->run.user_data, 0);
+}
+
+static int test_handler(long rdi, long rsi, long rdx, long ursp, long r8, long r9,
+			struct sgx_enclave_run *run)
+{
+	run->user_data = 0;
+
+	return 0;
+}
+
+TEST_F(enclave, clobbered_vdso_and_user_function)
+{
+	struct encl_op op;
+
+	self->run.user_handler = (__u64)test_handler;
+	self->run.user_data = 0xdeadbeef;
+
+	op.type = ENCL_OP_PUT;
+	op.buffer = MAGIC;
+
+	EXPECT_EQ(ENCL_CALL(&op, &self->run, true), 0);
+
+	EXPECT_EEXIT(&self->run);
+	EXPECT_EQ(self->run.user_data, 0);
+
+	op.type = ENCL_OP_GET;
+	op.buffer = 0;
+
+	EXPECT_EQ(ENCL_CALL(&op, &self->run, true), 0);
+
+	EXPECT_EQ(op.buffer, MAGIC);
+	EXPECT_EEXIT(&self->run);
+	EXPECT_EQ(self->run.user_data, 0);
+}
+
+TEST_HARNESS_MAIN

tools/testing/selftests/sgx/main.h

@@ -35,7 +35,7 @@ bool encl_load(const char *path, struct encl *encl);
 bool encl_measure(struct encl *encl);
 bool encl_build(struct encl *encl);
 
-int sgx_call_vdso(void *rdi, void *rsi, long rdx, u32 function, void *r8, void *r9,
-		  struct sgx_enclave_run *run);
+int sgx_enter_enclave(void *rdi, void *rsi, long rdx, u32 function, void *r8, void *r9,
+		      struct sgx_enclave_run *run);
 
 #endif /* MAIN_H */

tools/testing/selftests/sgx/test_encl.c

@@ -4,6 +4,8 @@
 #include <stddef.h>
 #include "defines.h"
 
+static uint8_t encl_buffer[8192] = { 1 };
+
 static void *memcpy(void *dest, const void *src, size_t n)
 {
 	size_t i;
@@ -14,7 +16,20 @@ static void *memcpy(void *dest, const void *src, size_t n)
 	return dest;
 }
 
-void encl_body(void *rdi, void *rsi)
+void encl_body(void *rdi,  void *rsi)
 {
-	memcpy(rsi, rdi, 8);
+	struct encl_op *op = (struct encl_op *)rdi;
+
+	switch (op->type) {
+	case ENCL_OP_PUT:
+		memcpy(&encl_buffer[0], &op->buffer, 8);
+		break;
+
+	case ENCL_OP_GET:
+		memcpy(&op->buffer, &encl_buffer[0], 8);
+		break;
+
+	default:
+		break;
+	}
 }

tools/testing/selftests/sgx/test_encl.lds

@@ -18,9 +18,10 @@ SECTIONS
 	.text : {
 		*(.text*)
 		*(.rodata*)
+		FILL(0xDEADBEEF);
+		. = ALIGN(4096);
 	} : text
 
-	. = ALIGN(4096);
 	.data : {
 		*(.data*)
 	} : data

tools/testing/selftests/splice/short_splice_read.sh

@@ -1,21 +1,87 @@
 #!/bin/sh
 # SPDX-License-Identifier: GPL-2.0
+#
+# Test for mishandling of splice() on pseudofilesystems, which should catch
+# bugs like 11990a5bd7e5 ("module: Correctly truncate sysfs sections output")
+#
+# Since splice fallback was removed as part of the set_fs() rework, many of these
+# tests expect to fail now. See https://lore.kernel.org/lkml/202009181443.C2179FB@keescook/
 set -e
 
+DIR=$(dirname "$0")
+
 ret=0
 
+expect_success()
+{
+	title="$1"
+	shift
+
+	echo "" >&2
+	echo "$title ..." >&2
+
+	set +e
+	"$@"
+	rc=$?
+	set -e
+
+	case "$rc" in
+	0)
+		echo "ok: $title succeeded" >&2
+		;;
+	1)
+		echo "FAIL: $title should work" >&2
+		ret=$(( ret + 1 ))
+		;;
+	*)
+		echo "FAIL: something else went wrong" >&2
+		ret=$(( ret + 1 ))
+		;;
+	esac
+}
+
+expect_failure()
+{
+	title="$1"
+	shift
+
+	echo "" >&2
+	echo "$title ..." >&2
+
+	set +e
+	"$@"
+	rc=$?
+	set -e
+
+	case "$rc" in
+	0)
+		echo "FAIL: $title unexpectedly worked" >&2
+		ret=$(( ret + 1 ))
+		;;
+	1)
+		echo "ok: $title correctly failed" >&2
+		;;
+	*)
+		echo "FAIL: something else went wrong" >&2
+		ret=$(( ret + 1 ))
+		;;
+	esac
+}
+
 do_splice()
 {
 	filename="$1"
 	bytes="$2"
 	expected="$3"
+	report="$4"
 
-	out=$(./splice_read "$filename" "$bytes" | cat)
+	out=$("$DIR"/splice_read "$filename" "$bytes" | cat)
 	if [ "$out" = "$expected" ] ; then
-		echo "ok: $filename $bytes"
+		echo "      matched $report" >&2
+		return 0
 	else
-		echo "FAIL: $filename $bytes"
-		ret=1
+		echo "      no match: '$out' vs $report" >&2
+		return 1
 	fi
 }
 
@@ -23,34 +89,45 @@ test_splice()
 {
 	filename="$1"
 
+	echo "  checking $filename ..." >&2
+
 	full=$(cat "$filename")
+	rc=$?
+	if [ $rc -ne 0 ] ; then
+		return 2
+	fi
+
 	two=$(echo "$full" | grep -m1 . | cut -c-2)
 
 	# Make sure full splice has the same contents as a standard read.
-	do_splice "$filename" 4096 "$full"
+	echo "    splicing 4096 bytes ..." >&2
+	if ! do_splice "$filename" 4096 "$full" "full read" ; then
+		return 1
+	fi
 
 	# Make sure a partial splice see the first two characters.
-	do_splice "$filename" 2 "$two"
+	echo "    splicing 2 bytes ..." >&2
+	if ! do_splice "$filename" 2 "$two" "'$two'" ; then
+		return 1
+	fi
+
+	return 0
 }
 
-# proc_single_open(), seq_read()
-test_splice /proc/$$/limits
-# special open, seq_read()
-test_splice /proc/$$/comm
+### /proc/$pid/ has no splice interface; these should all fail.
+expect_failure "proc_single_open(), seq_read() splice" test_splice /proc/$$/limits
+expect_failure "special open(), seq_read() splice" test_splice /proc/$$/comm
 
-# proc_handler, proc_dointvec_minmax
-test_splice /proc/sys/fs/nr_open
-# proc_handler, proc_dostring
-test_splice /proc/sys/kernel/modprobe
-# proc_handler, special read
-test_splice /proc/sys/kernel/version
+### /proc/sys/ has a splice interface; these should all succeed.
+expect_success "proc_handler: proc_dointvec_minmax() splice" test_splice /proc/sys/fs/nr_open
+expect_success "proc_handler: proc_dostring() splice" test_splice /proc/sys/kernel/modprobe
+expect_success "proc_handler: special read splice" test_splice /proc/sys/kernel/version
 
+### /sys/ has no splice interface; these should all fail.
 if ! [ -d /sys/module/test_module/sections ] ; then
-	modprobe test_module
+	expect_success "test_module kernel module load" modprobe test_module
 fi
-# kernfs, attr
-test_splice /sys/module/test_module/coresize
-# kernfs, binattr
-test_splice /sys/module/test_module/sections/.init.text
+expect_failure "kernfs attr splice" test_splice /sys/module/test_module/coresize
+expect_failure "kernfs binattr splice" test_splice /sys/module/test_module/sections/.init.text
 
 exit $ret

tools/testing/selftests/timers/rtcpie.c

@@ -18,6 +18,8 @@
 #include <stdlib.h>
 #include <errno.h>
 
+#include "../kselftest.h"
+
 /*
  * This expects the new RTC class driver framework, working with
  * clocks that will often not be clones of what the PC-AT had.
@@ -35,8 +37,14 @@ int main(int argc, char **argv)
 	switch (argc) {
 	case 2:
 		rtc = argv[1];
-		/* FALLTHROUGH */
+		break;
 	case 1:
+		fd = open(default_rtc, O_RDONLY);
+		if (fd == -1) {
+			printf("Default RTC %s does not exist. Test Skipped!\n", default_rtc);
+			exit(KSFT_SKIP);
+		}
+		close(fd);
 		break;
 	default:
 		fprintf(stderr, "usage:  rtctest [rtcdev] [d]\n");