kbuild: rust: keep Rust objects out of Clang LTO with inline helpersgrafted

Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit
`objtool` errors such as:

    vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a:
    can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd

The reason is that in such builds, the Clang invocation that compiles
the combined Rust plus helpers bitcode emits LLVM bitcode (again) --
the final code generation happens in the linker's LTO step, which the
`-mllvm` trap options passed to Clang do not reach.

This, in turn, means that unreachable traps are missing, and the
impossible paths do not merely fallthrough to the next symbol, but past
the end of their own section, since LTO builds place each function in
its own section.

Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always
emits machine code directly, with the traps in place.

Assisted-by: LLM
Cc: Gary Guo <gary@garyguo.net>
Cc: Boqun Feng <boqun@kernel.org>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Matthew Maurer <mmaurer@google.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust")
Acked-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

4 files changed, 521 insertions, 0 deletions

diff --git a/tools/testing/selftests/rtc/.gitignore b/tools/testing/selftests/rtc/.gitignore
new file mode 100644
index 000000000..a2afe7994
--- /dev/null
+++ b/tools/testing/selftests/rtc/.gitignore
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+rtctest
diff --git a/tools/testing/selftests/rtc/Makefile b/tools/testing/selftests/rtc/Makefile
new file mode 100644
index 000000000..547c244a2
--- /dev/null
+++ b/tools/testing/selftests/rtc/Makefile
@@ -0,0 +1,9 @@
+# SPDX-License-Identifier: GPL-2.0
+CFLAGS += -O3 -Wl,-no-as-needed -Wall -I$(top_srcdir)/usr/include
+LDLIBS += -lrt -lpthread -lm
+
+TEST_GEN_PROGS = rtctest
+
+TEST_FILES := settings
+
+include ../lib.mk
diff --git a/tools/testing/selftests/rtc/rtctest.c b/tools/testing/selftests/rtc/rtctest.c
new file mode 100644
index 000000000..8047d9879
--- /dev/null
+++ b/tools/testing/selftests/rtc/rtctest.c
@@ -0,0 +1,509 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Real Time Clock Driver Test Program
+ *
+ * Copyright (c) 2018 Alexandre Belloni <alexandre.belloni@bootlin.com>
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <linux/rtc.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/ioctl.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <time.h>
+#include <unistd.h>
+
+#include "kselftest_harness.h"
+
+#define NUM_UIE 3
+#define ALARM_DELTA 3
+#define READ_LOOP_DURATION_SEC 30
+#define READ_LOOP_SLEEP_MS 11
+
+static char *rtc_file = "/dev/rtc0";
+
+enum rtc_alarm_state {
+	RTC_ALARM_UNKNOWN,
+	RTC_ALARM_ENABLED,
+	RTC_ALARM_DISABLED,
+	RTC_ALARM_RES_MINUTE,
+};
+
+FIXTURE(rtc) {
+	int fd;
+};
+
+FIXTURE_SETUP(rtc) {
+	self->fd = open(rtc_file, O_RDONLY);
+}
+
+FIXTURE_TEARDOWN(rtc) {
+	close(self->fd);
+}
+
+TEST_F(rtc, date_read) {
+	int rc;
+	struct rtc_time rtc_tm;
+
+	if (self->fd == -1 && errno == ENOENT)
+		SKIP(return, "Skipping test since %s does not exist", rtc_file);
+	ASSERT_NE(-1, self->fd);
+
+	/* Read the RTC time/date */
+	rc = ioctl(self->fd, RTC_RD_TIME, &rtc_tm);
+	ASSERT_NE(-1, rc);
+
+	TH_LOG("Current RTC date/time is %02d/%02d/%02d %02d:%02d:%02d.",
+	       rtc_tm.tm_mday, rtc_tm.tm_mon + 1, rtc_tm.tm_year + 1900,
+	       rtc_tm.tm_hour, rtc_tm.tm_min, rtc_tm.tm_sec);
+}
+
+static time_t rtc_time_to_timestamp(struct rtc_time *rtc_time)
+{
+	struct tm tm_time = {
+	       .tm_sec = rtc_time->tm_sec,
+	       .tm_min = rtc_time->tm_min,
+	       .tm_hour = rtc_time->tm_hour,
+	       .tm_mday = rtc_time->tm_mday,
+	       .tm_mon = rtc_time->tm_mon,
+	       .tm_year = rtc_time->tm_year,
+	};
+
+	return mktime(&tm_time);
+}
+
+static void nanosleep_with_retries(long ns)
+{
+	struct timespec req = {
+		.tv_sec = 0,
+		.tv_nsec = ns,
+	};
+	struct timespec rem;
+
+	while (nanosleep(&req, &rem) != 0) {
+		req.tv_sec = rem.tv_sec;
+		req.tv_nsec = rem.tv_nsec;
+	}
+}
+
+static enum rtc_alarm_state get_rtc_alarm_state(int fd, int need_seconds)
+{
+	struct rtc_param param = { 0 };
+	int rc;
+
+	/* Validate kernel reflects unsupported RTC alarm state */
+	param.param = RTC_PARAM_FEATURES;
+	param.index = 0;
+	rc = ioctl(fd, RTC_PARAM_GET, &param);
+	if (rc < 0)
+		return RTC_ALARM_UNKNOWN;
+
+	if ((param.uvalue & _BITUL(RTC_FEATURE_ALARM)) == 0)
+		return RTC_ALARM_DISABLED;
+
+	/* Check if alarm has desired granularity */
+	if (need_seconds && (param.uvalue & _BITUL(RTC_FEATURE_ALARM_RES_MINUTE)))
+		return RTC_ALARM_RES_MINUTE;
+
+	return RTC_ALARM_ENABLED;
+}
+
+TEST_F_TIMEOUT(rtc, date_read_loop, READ_LOOP_DURATION_SEC + 2) {
+	int rc;
+	long iter_count = 0;
+	struct rtc_time rtc_tm;
+	time_t start_rtc_read, prev_rtc_read;
+
+	if (self->fd == -1 && errno == ENOENT)
+		SKIP(return, "Skipping test since %s does not exist", rtc_file);
+	ASSERT_NE(-1, self->fd);
+
+	TH_LOG("Continuously reading RTC time for %ds (with %dms breaks after every read).",
+	       READ_LOOP_DURATION_SEC, READ_LOOP_SLEEP_MS);
+
+	rc = ioctl(self->fd, RTC_RD_TIME, &rtc_tm);
+	ASSERT_NE(-1, rc);
+	start_rtc_read = rtc_time_to_timestamp(&rtc_tm);
+	prev_rtc_read = start_rtc_read;
+
+	do  {
+		time_t rtc_read;
+
+		rc = ioctl(self->fd, RTC_RD_TIME, &rtc_tm);
+		ASSERT_NE(-1, rc);
+
+		rtc_read = rtc_time_to_timestamp(&rtc_tm);
+		/* Time should not go backwards */
+		ASSERT_LE(prev_rtc_read, rtc_read);
+		/* Time should not increase more then 1s at a time */
+		ASSERT_GE(prev_rtc_read + 1, rtc_read);
+
+		/* Sleep 11ms to avoid killing / overheating the RTC */
+		nanosleep_with_retries(READ_LOOP_SLEEP_MS * 1000000);
+
+		prev_rtc_read = rtc_read;
+		iter_count++;
+	} while (prev_rtc_read <= start_rtc_read + READ_LOOP_DURATION_SEC);
+
+	TH_LOG("Performed %ld RTC time reads.", iter_count);
+}
+
+TEST_F_TIMEOUT(rtc, uie_read, NUM_UIE + 2) {
+	int i, rc, irq = 0;
+	unsigned long data;
+
+	if (self->fd == -1 && errno == ENOENT)
+		SKIP(return, "Skipping test since %s does not exist", rtc_file);
+	ASSERT_NE(-1, self->fd);
+
+	/* Turn on update interrupts */
+	rc = ioctl(self->fd, RTC_UIE_ON, 0);
+	if (rc == -1) {
+		ASSERT_EQ(EINVAL, errno);
+		TH_LOG("skip update IRQs not supported.");
+		return;
+	}
+
+	for (i = 0; i < NUM_UIE; i++) {
+		/* This read will block */
+		rc = read(self->fd, &data, sizeof(data));
+		ASSERT_NE(-1, rc);
+		irq++;
+	}
+
+	EXPECT_EQ(NUM_UIE, irq);
+
+	rc = ioctl(self->fd, RTC_UIE_OFF, 0);
+	ASSERT_NE(-1, rc);
+}
+
+TEST_F(rtc, uie_select) {
+	int i, rc, irq = 0;
+	unsigned long data;
+
+	if (self->fd == -1 && errno == ENOENT)
+		SKIP(return, "Skipping test since %s does not exist", rtc_file);
+	ASSERT_NE(-1, self->fd);
+
+	/* Turn on update interrupts */
+	rc = ioctl(self->fd, RTC_UIE_ON, 0);
+	if (rc == -1) {
+		ASSERT_EQ(EINVAL, errno);
+		TH_LOG("skip update IRQs not supported.");
+		return;
+	}
+
+	for (i = 0; i < NUM_UIE; i++) {
+		struct timeval tv = { .tv_sec = 2 };
+		fd_set readfds;
+
+		FD_ZERO(&readfds);
+		FD_SET(self->fd, &readfds);
+		/* The select will wait until an RTC interrupt happens. */
+		rc = select(self->fd + 1, &readfds, NULL, NULL, &tv);
+		ASSERT_NE(-1, rc);
+		ASSERT_NE(0, rc);
+
+		/* This read won't block */
+		rc = read(self->fd, &data, sizeof(unsigned long));
+		ASSERT_NE(-1, rc);
+		irq++;
+	}
+
+	EXPECT_EQ(NUM_UIE, irq);
+
+	rc = ioctl(self->fd, RTC_UIE_OFF, 0);
+	ASSERT_NE(-1, rc);
+}
+
+TEST_F(rtc, alarm_alm_set) {
+	struct timeval tv = { .tv_sec = ALARM_DELTA + 2 };
+	unsigned long data;
+	struct rtc_time tm;
+	fd_set readfds;
+	time_t secs, new;
+	int rc;
+	enum rtc_alarm_state alarm_state = RTC_ALARM_UNKNOWN;
+
+	if (self->fd == -1 && errno == ENOENT)
+		SKIP(return, "Skipping test since %s does not exist", rtc_file);
+	ASSERT_NE(-1, self->fd);
+
+	alarm_state = get_rtc_alarm_state(self->fd, 1);
+	if (alarm_state == RTC_ALARM_DISABLED)
+		SKIP(return, "Skipping test since alarms are not supported.");
+	if (alarm_state == RTC_ALARM_RES_MINUTE)
+		SKIP(return, "Skipping test since alarms has only minute granularity.");
+
+	rc = ioctl(self->fd, RTC_RD_TIME, &tm);
+	ASSERT_NE(-1, rc);
+
+	secs = timegm((struct tm *)&tm) + ALARM_DELTA;
+	gmtime_r(&secs, (struct tm *)&tm);
+
+	rc = ioctl(self->fd, RTC_ALM_SET, &tm);
+	if (rc == -1) {
+		/*
+		 * Report error if rtc alarm was enabled. Fallback to check ioctl
+		 * error number if rtc alarm state is unknown.
+		 */
+		ASSERT_EQ(RTC_ALARM_UNKNOWN, alarm_state);
+		ASSERT_EQ(EINVAL, errno);
+		TH_LOG("skip alarms are not supported.");
+		return;
+	}
+
+	rc = ioctl(self->fd, RTC_ALM_READ, &tm);
+	ASSERT_NE(-1, rc);
+
+	TH_LOG("Alarm time now set to %02d:%02d:%02d.",
+	       tm.tm_hour, tm.tm_min, tm.tm_sec);
+
+	/* Enable alarm interrupts */
+	rc = ioctl(self->fd, RTC_AIE_ON, 0);
+	ASSERT_NE(-1, rc);
+
+	FD_ZERO(&readfds);
+	FD_SET(self->fd, &readfds);
+
+	rc = select(self->fd + 1, &readfds, NULL, NULL, &tv);
+	ASSERT_NE(-1, rc);
+	ASSERT_NE(0, rc);
+
+	/* Disable alarm interrupts */
+	rc = ioctl(self->fd, RTC_AIE_OFF, 0);
+	ASSERT_NE(-1, rc);
+
+	rc = read(self->fd, &data, sizeof(unsigned long));
+	ASSERT_NE(-1, rc);
+	TH_LOG("data: %lx", data);
+
+	rc = ioctl(self->fd, RTC_RD_TIME, &tm);
+	ASSERT_NE(-1, rc);
+
+	new = timegm((struct tm *)&tm);
+	ASSERT_EQ(new, secs);
+}
+
+TEST_F(rtc, alarm_wkalm_set) {
+	struct timeval tv = { .tv_sec = ALARM_DELTA + 2 };
+	struct rtc_wkalrm alarm = { 0 };
+	struct rtc_time tm;
+	unsigned long data;
+	fd_set readfds;
+	time_t secs, new;
+	int rc;
+	enum rtc_alarm_state alarm_state = RTC_ALARM_UNKNOWN;
+
+	if (self->fd == -1 && errno == ENOENT)
+		SKIP(return, "Skipping test since %s does not exist", rtc_file);
+	ASSERT_NE(-1, self->fd);
+
+	alarm_state = get_rtc_alarm_state(self->fd, 1);
+	if (alarm_state == RTC_ALARM_DISABLED)
+		SKIP(return, "Skipping test since alarms are not supported.");
+	if (alarm_state == RTC_ALARM_RES_MINUTE)
+		SKIP(return, "Skipping test since alarms has only minute granularity.");
+
+	rc = ioctl(self->fd, RTC_RD_TIME, &alarm.time);
+	ASSERT_NE(-1, rc);
+
+	secs = timegm((struct tm *)&alarm.time) + ALARM_DELTA;
+	gmtime_r(&secs, (struct tm *)&alarm.time);
+
+	alarm.enabled = 1;
+
+	rc = ioctl(self->fd, RTC_WKALM_SET, &alarm);
+	if (rc == -1) {
+		/*
+		 * Report error if rtc alarm was enabled. Fallback to check ioctl
+		 * error number if rtc alarm state is unknown.
+		 */
+		ASSERT_EQ(RTC_ALARM_UNKNOWN, alarm_state);
+		ASSERT_EQ(EINVAL, errno);
+		TH_LOG("skip alarms are not supported.");
+		return;
+	}
+
+	rc = ioctl(self->fd, RTC_WKALM_RD, &alarm);
+	ASSERT_NE(-1, rc);
+
+	TH_LOG("Alarm time now set to %02d/%02d/%02d %02d:%02d:%02d.",
+	       alarm.time.tm_mday, alarm.time.tm_mon + 1,
+	       alarm.time.tm_year + 1900, alarm.time.tm_hour,
+	       alarm.time.tm_min, alarm.time.tm_sec);
+
+	FD_ZERO(&readfds);
+	FD_SET(self->fd, &readfds);
+
+	rc = select(self->fd + 1, &readfds, NULL, NULL, &tv);
+	ASSERT_NE(-1, rc);
+	ASSERT_NE(0, rc);
+
+	rc = read(self->fd, &data, sizeof(unsigned long));
+	ASSERT_NE(-1, rc);
+
+	rc = ioctl(self->fd, RTC_RD_TIME, &tm);
+	ASSERT_NE(-1, rc);
+
+	new = timegm((struct tm *)&tm);
+	ASSERT_EQ(new, secs);
+}
+
+TEST_F_TIMEOUT(rtc, alarm_alm_set_minute, 65) {
+	struct timeval tv = { .tv_sec = 62 };
+	unsigned long data;
+	struct rtc_time tm;
+	fd_set readfds;
+	time_t secs, new;
+	int rc;
+	enum rtc_alarm_state alarm_state = RTC_ALARM_UNKNOWN;
+
+	if (self->fd == -1 && errno == ENOENT)
+		SKIP(return, "Skipping test since %s does not exist", rtc_file);
+	ASSERT_NE(-1, self->fd);
+
+	alarm_state = get_rtc_alarm_state(self->fd, 0);
+	if (alarm_state == RTC_ALARM_DISABLED)
+		SKIP(return, "Skipping test since alarms are not supported.");
+
+	rc = ioctl(self->fd, RTC_RD_TIME, &tm);
+	ASSERT_NE(-1, rc);
+
+	secs = timegm((struct tm *)&tm) + 60 - tm.tm_sec;
+	gmtime_r(&secs, (struct tm *)&tm);
+
+	rc = ioctl(self->fd, RTC_ALM_SET, &tm);
+	if (rc == -1) {
+		/*
+		 * Report error if rtc alarm was enabled. Fallback to check ioctl
+		 * error number if rtc alarm state is unknown.
+		 */
+		ASSERT_EQ(RTC_ALARM_UNKNOWN, alarm_state);
+		ASSERT_EQ(EINVAL, errno);
+		TH_LOG("skip alarms are not supported.");
+		return;
+	}
+
+	rc = ioctl(self->fd, RTC_ALM_READ, &tm);
+	ASSERT_NE(-1, rc);
+
+	TH_LOG("Alarm time now set to %02d:%02d:%02d.",
+	       tm.tm_hour, tm.tm_min, tm.tm_sec);
+
+	/* Enable alarm interrupts */
+	rc = ioctl(self->fd, RTC_AIE_ON, 0);
+	ASSERT_NE(-1, rc);
+
+	FD_ZERO(&readfds);
+	FD_SET(self->fd, &readfds);
+
+	rc = select(self->fd + 1, &readfds, NULL, NULL, &tv);
+	ASSERT_NE(-1, rc);
+	ASSERT_NE(0, rc);
+
+	/* Disable alarm interrupts */
+	rc = ioctl(self->fd, RTC_AIE_OFF, 0);
+	ASSERT_NE(-1, rc);
+
+	rc = read(self->fd, &data, sizeof(unsigned long));
+	ASSERT_NE(-1, rc);
+	TH_LOG("data: %lx", data);
+
+	rc = ioctl(self->fd, RTC_RD_TIME, &tm);
+	ASSERT_NE(-1, rc);
+
+	new = timegm((struct tm *)&tm);
+	ASSERT_EQ(new, secs);
+}
+
+TEST_F_TIMEOUT(rtc, alarm_wkalm_set_minute, 65) {
+	struct timeval tv = { .tv_sec = 62 };
+	struct rtc_wkalrm alarm = { 0 };
+	struct rtc_time tm;
+	unsigned long data;
+	fd_set readfds;
+	time_t secs, new;
+	int rc;
+	enum rtc_alarm_state alarm_state = RTC_ALARM_UNKNOWN;
+
+	if (self->fd == -1 && errno == ENOENT)
+		SKIP(return, "Skipping test since %s does not exist", rtc_file);
+	ASSERT_NE(-1, self->fd);
+
+	alarm_state = get_rtc_alarm_state(self->fd, 0);
+	if (alarm_state == RTC_ALARM_DISABLED)
+		SKIP(return, "Skipping test since alarms are not supported.");
+
+	rc = ioctl(self->fd, RTC_RD_TIME, &alarm.time);
+	ASSERT_NE(-1, rc);
+
+	secs = timegm((struct tm *)&alarm.time) + 60 - alarm.time.tm_sec;
+	gmtime_r(&secs, (struct tm *)&alarm.time);
+
+	alarm.enabled = 1;
+
+	rc = ioctl(self->fd, RTC_WKALM_SET, &alarm);
+	if (rc == -1) {
+		/*
+		 * Report error if rtc alarm was enabled. Fallback to check ioctl
+		 * error number if rtc alarm state is unknown.
+		 */
+		ASSERT_EQ(RTC_ALARM_UNKNOWN, alarm_state);
+		ASSERT_EQ(EINVAL, errno);
+		TH_LOG("skip alarms are not supported.");
+		return;
+	}
+
+	rc = ioctl(self->fd, RTC_WKALM_RD, &alarm);
+	ASSERT_NE(-1, rc);
+
+	TH_LOG("Alarm time now set to %02d/%02d/%02d %02d:%02d:%02d.",
+	       alarm.time.tm_mday, alarm.time.tm_mon + 1,
+	       alarm.time.tm_year + 1900, alarm.time.tm_hour,
+	       alarm.time.tm_min, alarm.time.tm_sec);
+
+	FD_ZERO(&readfds);
+	FD_SET(self->fd, &readfds);
+
+	rc = select(self->fd + 1, &readfds, NULL, NULL, &tv);
+	ASSERT_NE(-1, rc);
+	ASSERT_NE(0, rc);
+
+	rc = read(self->fd, &data, sizeof(unsigned long));
+	ASSERT_NE(-1, rc);
+
+	rc = ioctl(self->fd, RTC_RD_TIME, &tm);
+	ASSERT_NE(-1, rc);
+
+	new = timegm((struct tm *)&tm);
+	ASSERT_EQ(new, secs);
+}
+
+int main(int argc, char **argv)
+{
+	int ret = -1;
+
+	switch (argc) {
+	case 2:
+		rtc_file = argv[1];
+		/* FALLTHROUGH */
+	case 1:
+		break;
+	default:
+		fprintf(stderr, "usage: %s [rtcdev]\n", argv[0]);
+		return 1;
+	}
+
+	/* Run the test if rtc_file is accessible */
+	if (access(rtc_file, R_OK) == 0)
+		ret = test_harness_run(argc, argv);
+	else
+		ksft_exit_skip("[SKIP]: Cannot access rtc file %s - Exiting\n",
+						rtc_file);
+
+	return ret;
+}
diff --git a/tools/testing/selftests/rtc/settings b/tools/testing/selftests/rtc/settings
new file mode 100644
index 000000000..0c1a2075d
--- /dev/null
+++ b/tools/testing/selftests/rtc/settings
@@ -0,0 +1 @@
+timeout=210