Merge tag 'printk-for-5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux

Pull printk updates from Petr Mladek:

 - Add %pt[RT]s modifier to vsprintf(). It overrides ISO 8601 separator
   by using ' ' (space). It produces "YYYY-mm-dd HH:MM:SS" instead of
   "YYYY-mm-ddTHH:MM:SS".

 - Correctly parse long row of numbers by sscanf() when using the field
   width. Add extensive sscanf() selftest.

 - Generalize re-entrant CPU lock that has already been used to
   serialize dump_stack() output. It is part of the ongoing printk
   rework. It will allow to remove the obsoleted printk_safe buffers and
   introduce atomic consoles.

 - Some code clean up and sparse warning fixes.

* tag 'printk-for-5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
  printk: fix cpu lock ordering
  lib/dump_stack: move cpu lock to printk.c
  printk: Remove trailing semicolon in macros
  random32: Fix implicit truncation warning in prandom_seed_state()
  lib: test_scanf: Remove pointless use of type_min() with unsigned types
  selftests: lib: Add wrapper script for test_scanf
  lib: test_scanf: Add tests for sscanf number conversion
  lib: vsprintf: Fix handling of number field widths in vsscanf
  lib: vsprintf: scanf: Negative number must have field width > 1
  usb: host: xhci-tegra: Switch to use %ptTs
  nilfs2: Switch to use %ptTs
  kdb: Switch to use %ptTs
  lib/vsprintf: Allow to override ISO 8601 date and time separator

Documentation/core-api/printk-formats.rst

@@ -513,9 +513,10 @@ Time and date
 ::
 
 	%pt[RT]			YYYY-mm-ddTHH:MM:SS
+	%pt[RT]s		YYYY-mm-dd HH:MM:SS
 	%pt[RT]d		YYYY-mm-dd
 	%pt[RT]t		HH:MM:SS
-	%pt[RT][dt][r]
+	%pt[RT][dt][r][s]
 
 For printing date and time as represented by::
 
@@ -527,6 +528,10 @@ in human readable format.
 By default year will be incremented by 1900 and month by 1.
 Use %pt[RT]r (raw) to suppress this behaviour.
 
+The %pt[RT]s (space) will override ISO 8601 separator by using ' ' (space)
+instead of 'T' (Capital T) between date and time. It won't have any effect
+when date or time is omitted.
+
 Passed by reference.
 
 struct clk

MAINTAINERS

@@ -19629,6 +19629,7 @@ S:	Maintained
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk.git
 F:	Documentation/core-api/printk-formats.rst
 F:	lib/test_printf.c
+F:	lib/test_scanf.c
 F:	lib/vsprintf.c
 
 VT1211 HARDWARE MONITOR DRIVER

drivers/usb/host/xhci-tegra.c

@@ -917,7 +917,6 @@ static int tegra_xusb_load_firmware(struct tegra_xusb *tegra)
 	struct xhci_op_regs __iomem *op;
 	unsigned long timeout;
 	time64_t timestamp;
-	struct tm time;
 	u64 address;
 	u32 value;
 	int err;
@@ -1014,11 +1013,8 @@ static int tegra_xusb_load_firmware(struct tegra_xusb *tegra)
 	}
 
 	timestamp = le32_to_cpu(header->fwimg_created_time);
-	time64_to_tm(timestamp, 0, &time);
 
-	dev_info(dev, "Firmware timestamp: %ld-%02d-%02d %02d:%02d:%02d UTC\n",
-		 time.tm_year + 1900, time.tm_mon + 1, time.tm_mday,
-		 time.tm_hour, time.tm_min, time.tm_sec);
+	dev_info(dev, "Firmware timestamp: %ptTs UTC\n", &timestamp);
 
 	return 0;
 }

fs/nilfs2/sysfs.c

@@ -19,19 +19,6 @@
 /* /sys/fs/<nilfs>/ */
 static struct kset *nilfs_kset;
 
-#define NILFS_SHOW_TIME(time_t_val, buf) ({ \
-		struct tm res; \
-		int count = 0; \
-		time64_to_tm(time_t_val, 0, &res); \
-		res.tm_year += 1900; \
-		res.tm_mon += 1; \
-		count = scnprintf(buf, PAGE_SIZE, \
-				    "%ld-%.2d-%.2d %.2d:%.2d:%.2d\n", \
-				    res.tm_year, res.tm_mon, res.tm_mday, \
-				    res.tm_hour, res.tm_min, res.tm_sec);\
-		count; \
-})
-
 #define NILFS_DEV_INT_GROUP_OPS(name, parent_name) \
 static ssize_t nilfs_##name##_attr_show(struct kobject *kobj, \
 					struct attribute *attr, char *buf) \
@@ -576,7 +563,7 @@ nilfs_segctor_last_seg_write_time_show(struct nilfs_segctor_attr *attr,
 	ctime = nilfs->ns_ctime;
 	up_read(&nilfs->ns_segctor_sem);
 
-	return NILFS_SHOW_TIME(ctime, buf);
+	return sysfs_emit(buf, "%ptTs\n", &ctime);
 }
 
 static ssize_t
@@ -604,7 +591,7 @@ nilfs_segctor_last_nongc_write_time_show(struct nilfs_segctor_attr *attr,
 	nongc_ctime = nilfs->ns_nongc_ctime;
 	up_read(&nilfs->ns_segctor_sem);
 
-	return NILFS_SHOW_TIME(nongc_ctime, buf);
+	return sysfs_emit(buf, "%ptTs\n", &nongc_ctime);
 }
 
 static ssize_t
@@ -724,7 +711,7 @@ nilfs_superblock_sb_write_time_show(struct nilfs_superblock_attr *attr,
 	sbwtime = nilfs->ns_sbwtime;
 	up_read(&nilfs->ns_sem);
 
-	return NILFS_SHOW_TIME(sbwtime, buf);
+	return sysfs_emit(buf, "%ptTs\n", &sbwtime);
 }
 
 static ssize_t

include/linux/dev_printk.h

@@ -236,7 +236,7 @@ do {									\
  * using WARN/WARN_ONCE to include file/line information and a backtrace.
  */
 #define dev_WARN(dev, format, arg...) \
-	WARN(1, "%s %s: " format, dev_driver_string(dev), dev_name(dev), ## arg);
+	WARN(1, "%s %s: " format, dev_driver_string(dev), dev_name(dev), ## arg)
 
 #define dev_WARN_ONCE(dev, condition, format, arg...) \
 	WARN_ONCE(condition, "%s %s: " format, \

include/linux/prandom.h

@@ -111,7 +111,7 @@ static inline u32 __seed(u32 x, u32 m)
  */
 static inline void prandom_seed_state(struct rnd_state *state, u64 seed)
 {
-	u32 i = (seed >> 32) ^ (seed << 10) ^ seed;
+	u32 i = ((seed >> 32) ^ (seed << 10) ^ seed) & 0xffffffffUL;
 
 	state->s1 = __seed(i,   2U);
 	state->s2 = __seed(i,   8U);

include/linux/printk.h

@@ -282,6 +282,47 @@ static inline void printk_safe_flush_on_panic(void)
 }
 #endif
 
+#ifdef CONFIG_SMP
+extern int __printk_cpu_trylock(void);
+extern void __printk_wait_on_cpu_lock(void);
+extern void __printk_cpu_unlock(void);
+
+/**
+ * printk_cpu_lock_irqsave() - Acquire the printk cpu-reentrant spinning
+ *                             lock and disable interrupts.
+ * @flags: Stack-allocated storage for saving local interrupt state,
+ *         to be passed to printk_cpu_unlock_irqrestore().
+ *
+ * If the lock is owned by another CPU, spin until it becomes available.
+ * Interrupts are restored while spinning.
+ */
+#define printk_cpu_lock_irqsave(flags)		\
+	for (;;) {				\
+		local_irq_save(flags);		\
+		if (__printk_cpu_trylock())	\
+			break;			\
+		local_irq_restore(flags);	\
+		__printk_wait_on_cpu_lock();	\
+	}
+
+/**
+ * printk_cpu_unlock_irqrestore() - Release the printk cpu-reentrant spinning
+ *                                  lock and restore interrupts.
+ * @flags: Caller's saved interrupt state, from printk_cpu_lock_irqsave().
+ */
+#define printk_cpu_unlock_irqrestore(flags)	\
+	do {					\
+		__printk_cpu_unlock();		\
+		local_irq_restore(flags);	\
+	} while (0)				\
+
+#else
+
+#define printk_cpu_lock_irqsave(flags) ((void)flags)
+#define printk_cpu_unlock_irqrestore(flags) ((void)flags)
+
+#endif /* CONFIG_SMP */
+
 extern int kptr_restrict;
 
 /**

kernel/debug/kdb/kdb_main.c

@@ -2488,7 +2488,6 @@ static void kdb_sysinfo(struct sysinfo *val)
 static int kdb_summary(int argc, const char **argv)
 {
 	time64_t now;
-	struct tm tm;
 	struct sysinfo val;
 
 	if (argc)
@@ -2502,13 +2501,7 @@ static int kdb_summary(int argc, const char **argv)
 	kdb_printf("domainname %s\n", init_uts_ns.name.domainname);
 
 	now = __ktime_get_real_seconds();
-	time64_to_tm(now, 0, &tm);
-	kdb_printf("date       %04ld-%02d-%02d %02d:%02d:%02d "
-		   "tz_minuteswest %d\n",
-		1900+tm.tm_year, tm.tm_mon+1, tm.tm_mday,
-		tm.tm_hour, tm.tm_min, tm.tm_sec,
-		sys_tz.tz_minuteswest);
-
+	kdb_printf("date       %ptTs tz_minuteswest %d\n", &now, sys_tz.tz_minuteswest);
 	kdb_sysinfo(&val);
 	kdb_printf("uptime     ");
 	if (val.uptime > (24*60*60)) {

kernel/printk/printk.c

@@ -3531,3 +3531,119 @@ void kmsg_dump_rewind(struct kmsg_dump_iter *iter)
 EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
 
 #endif
+
+#ifdef CONFIG_SMP
+static atomic_t printk_cpulock_owner = ATOMIC_INIT(-1);
+static atomic_t printk_cpulock_nested = ATOMIC_INIT(0);
+
+/**
+ * __printk_wait_on_cpu_lock() - Busy wait until the printk cpu-reentrant
+ *                               spinning lock is not owned by any CPU.
+ *
+ * Context: Any context.
+ */
+void __printk_wait_on_cpu_lock(void)
+{
+	do {
+		cpu_relax();
+	} while (atomic_read(&printk_cpulock_owner) != -1);
+}
+EXPORT_SYMBOL(__printk_wait_on_cpu_lock);
+
+/**
+ * __printk_cpu_trylock() - Try to acquire the printk cpu-reentrant
+ *                          spinning lock.
+ *
+ * If no processor has the lock, the calling processor takes the lock and
+ * becomes the owner. If the calling processor is already the owner of the
+ * lock, this function succeeds immediately.
+ *
+ * Context: Any context. Expects interrupts to be disabled.
+ * Return: 1 on success, otherwise 0.
+ */
+int __printk_cpu_trylock(void)
+{
+	int cpu;
+	int old;
+
+	cpu = smp_processor_id();
+
+	/*
+	 * Guarantee loads and stores from this CPU when it is the lock owner
+	 * are _not_ visible to the previous lock owner. This pairs with
+	 * __printk_cpu_unlock:B.
+	 *
+	 * Memory barrier involvement:
+	 *
+	 * If __printk_cpu_trylock:A reads from __printk_cpu_unlock:B, then
+	 * __printk_cpu_unlock:A can never read from __printk_cpu_trylock:B.
+	 *
+	 * Relies on:
+	 *
+	 * RELEASE from __printk_cpu_unlock:A to __printk_cpu_unlock:B
+	 * of the previous CPU
+	 *    matching
+	 * ACQUIRE from __printk_cpu_trylock:A to __printk_cpu_trylock:B
+	 * of this CPU
+	 */
+	old = atomic_cmpxchg_acquire(&printk_cpulock_owner, -1,
+				     cpu); /* LMM(__printk_cpu_trylock:A) */
+	if (old == -1) {
+		/*
+		 * This CPU is now the owner and begins loading/storing
+		 * data: LMM(__printk_cpu_trylock:B)
+		 */
+		return 1;
+
+	} else if (old == cpu) {
+		/* This CPU is already the owner. */
+		atomic_inc(&printk_cpulock_nested);
+		return 1;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(__printk_cpu_trylock);
+
+/**
+ * __printk_cpu_unlock() - Release the printk cpu-reentrant spinning lock.
+ *
+ * The calling processor must be the owner of the lock.
+ *
+ * Context: Any context. Expects interrupts to be disabled.
+ */
+void __printk_cpu_unlock(void)
+{
+	if (atomic_read(&printk_cpulock_nested)) {
+		atomic_dec(&printk_cpulock_nested);
+		return;
+	}
+
+	/*
+	 * This CPU is finished loading/storing data:
+	 * LMM(__printk_cpu_unlock:A)
+	 */
+
+	/*
+	 * Guarantee loads and stores from this CPU when it was the
+	 * lock owner are visible to the next lock owner. This pairs
+	 * with __printk_cpu_trylock:A.
+	 *
+	 * Memory barrier involvement:
+	 *
+	 * If __printk_cpu_trylock:A reads from __printk_cpu_unlock:B,
+	 * then __printk_cpu_trylock:B reads from __printk_cpu_unlock:A.
+	 *
+	 * Relies on:
+	 *
+	 * RELEASE from __printk_cpu_unlock:A to __printk_cpu_unlock:B
+	 * of this CPU
+	 *    matching
+	 * ACQUIRE from __printk_cpu_trylock:A to __printk_cpu_trylock:B
+	 * of the next CPU
+	 */
+	atomic_set_release(&printk_cpulock_owner,
+			   -1); /* LMM(__printk_cpu_unlock:B) */
+}
+EXPORT_SYMBOL(__printk_cpu_unlock);
+#endif /* CONFIG_SMP */

lib/Kconfig.debug

@@ -2180,6 +2180,9 @@ config TEST_KSTRTOX
 config TEST_PRINTF
 	tristate "Test printf() family of functions at runtime"
 
+config TEST_SCANF
+	tristate "Test scanf() family of functions at runtime"
+
 config TEST_BITMAP
 	tristate "Test bitmap_*() family of functions at runtime"
 	help

lib/Makefile

@@ -83,6 +83,7 @@ obj-$(CONFIG_TEST_USER_COPY) += test_user_copy.o
 obj-$(CONFIG_TEST_STATIC_KEYS) += test_static_keys.o
 obj-$(CONFIG_TEST_STATIC_KEYS) += test_static_key_base.o
 obj-$(CONFIG_TEST_PRINTF) += test_printf.o
+obj-$(CONFIG_TEST_SCANF) += test_scanf.o
 obj-$(CONFIG_TEST_BITMAP) += test_bitmap.o
 obj-$(CONFIG_TEST_STRSCPY) += test_strscpy.o
 obj-$(CONFIG_TEST_UUID) += test_uuid.o

lib/dump_stack.c

@@ -84,50 +84,16 @@ static void __dump_stack(void)
  *
  * Architectures can override this implementation by implementing its own.
  */
-#ifdef CONFIG_SMP
-static atomic_t dump_lock = ATOMIC_INIT(-1);
-
 asmlinkage __visible void dump_stack(void)
 {
 	unsigned long flags;
-	int was_locked;
-	int old;
-	int cpu;
 
 	/*
 	 * Permit this cpu to perform nested stack dumps while serialising
 	 * against other CPUs
 	 */
-retry:
-	local_irq_save(flags);
-	cpu = smp_processor_id();
-	old = atomic_cmpxchg(&dump_lock, -1, cpu);
-	if (old == -1) {
-		was_locked = 0;
-	} else if (old == cpu) {
-		was_locked = 1;
-	} else {
-		local_irq_restore(flags);
-		/*
-		 * Wait for the lock to release before jumping to
-		 * atomic_cmpxchg() in order to mitigate the thundering herd
-		 * problem.
-		 */
-		do { cpu_relax(); } while (atomic_read(&dump_lock) != -1);
-		goto retry;
-	}
-
-	__dump_stack();
-
-	if (!was_locked)
-		atomic_set(&dump_lock, -1);
-
-	local_irq_restore(flags);
-}
-#else
-asmlinkage __visible void dump_stack(void)
-{
+	printk_cpu_lock_irqsave(flags);
 	__dump_stack();
+	printk_cpu_unlock_irqrestore(flags);
 }
-#endif
 EXPORT_SYMBOL(dump_stack);

lib/kstrtox.c

@@ -39,20 +39,22 @@ const char *_parse_integer_fixup_radix(const char *s, unsigned int *base)
 
 /*
  * Convert non-negative integer string representation in explicitly given radix
- * to an integer.
+ * to an integer. A maximum of max_chars characters will be converted.
+ *
  * Return number of characters consumed maybe or-ed with overflow bit.
  * If overflow occurs, result integer (incorrect) is still returned.
  *
  * Don't you dare use this function.
  */
-unsigned int _parse_integer(const char *s, unsigned int base, unsigned long long *p)
+unsigned int _parse_integer_limit(const char *s, unsigned int base, unsigned long long *p,
+				  size_t max_chars)
 {
 	unsigned long long res;
 	unsigned int rv;
 
 	res = 0;
 	rv = 0;
-	while (1) {
+	while (max_chars--) {
 		unsigned int c = *s;
 		unsigned int lc = c | 0x20; /* don't tolower() this line */
 		unsigned int val;
@@ -82,6 +84,11 @@ unsigned int _parse_integer(const char *s, unsigned int base, unsigned long long
 	return rv;
 }
 
+unsigned int _parse_integer(const char *s, unsigned int base, unsigned long long *p)
+{
+	return _parse_integer_limit(s, base, p, INT_MAX);
+}
+
 static int _kstrtoull(const char *s, unsigned int base, unsigned long long *res)
 {
 	unsigned long long _res;

lib/kstrtox.h

@@ -4,6 +4,8 @@
 
 #define KSTRTOX_OVERFLOW	(1U << 31)
 const char *_parse_integer_fixup_radix(const char *s, unsigned int *base);
+unsigned int _parse_integer_limit(const char *s, unsigned int base, unsigned long long *res,
+				  size_t max_chars);
 unsigned int _parse_integer(const char *s, unsigned int base, unsigned long long *res);
 
 #endif

lib/test_printf.c

@@ -528,6 +528,11 @@ time_and_date(void)
 	test("0119-00-04T15:32:23", "%ptTr", &t);
 	test("15:32:23|2019-01-04", "%ptTt|%ptTd", &t, &t);
 	test("15:32:23|0119-00-04", "%ptTtr|%ptTdr", &t, &t);
+
+	test("2019-01-04 15:32:23", "%ptTs", &t);
+	test("0119-00-04 15:32:23", "%ptTsr", &t);
+	test("15:32:23|2019-01-04", "%ptTts|%ptTds", &t, &t);
+	test("15:32:23|0119-00-04", "%ptTtrs|%ptTdrs", &t, &t);
 }
 
 static void __init

lib/vsprintf.c

@@ -53,29 +53,43 @@
 #include <linux/string_helpers.h>
 #include "kstrtox.h"
 
-/**
- * simple_strtoull - convert a string to an unsigned long long
- * @cp: The start of the string
- * @endp: A pointer to the end of the parsed string will be placed here
- * @base: The number base to use
- *
- * This function has caveats. Please use kstrtoull instead.
- */
-unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int base)
+static unsigned long long simple_strntoull(const char *startp, size_t max_chars,
+					   char **endp, unsigned int base)
 {
-	unsigned long long result;
+	const char *cp;
+	unsigned long long result = 0ULL;
+	size_t prefix_chars;
 	unsigned int rv;
 
-	cp = _parse_integer_fixup_radix(cp, &base);
-	rv = _parse_integer(cp, base, &result);
+	cp = _parse_integer_fixup_radix(startp, &base);
+	prefix_chars = cp - startp;
+	if (prefix_chars < max_chars) {
+		rv = _parse_integer_limit(cp, base, &result, max_chars - prefix_chars);
 		/* FIXME */
 		cp += (rv & ~KSTRTOX_OVERFLOW);
+	} else {
+		/* Field too short for prefix + digit, skip over without converting */
+		cp = startp + max_chars;
+	}
 
 	if (endp)
 		*endp = (char *)cp;
 
 	return result;
 }
+
+/**
+ * simple_strtoull - convert a string to an unsigned long long
+ * @cp: The start of the string
+ * @endp: A pointer to the end of the parsed string will be placed here
+ * @base: The number base to use
+ *
+ * This function has caveats. Please use kstrtoull instead.
+ */
+unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int base)
+{
+	return simple_strntoull(cp, INT_MAX, endp, base);
+}
 EXPORT_SYMBOL(simple_strtoull);
 
 /**
@@ -109,6 +123,21 @@ long simple_strtol(const char *cp, char **endp, unsigned int base)
 }
 EXPORT_SYMBOL(simple_strtol);
 
+static long long simple_strntoll(const char *cp, size_t max_chars, char **endp,
+				 unsigned int base)
+{
+	/*
+	 * simple_strntoull() safely handles receiving max_chars==0 in the
+	 * case cp[0] == '-' && max_chars == 1.
+	 * If max_chars == 0 we can drop through and pass it to simple_strntoull()
+	 * and the content of *cp is irrelevant.
+	 */
+	if (*cp == '-' && max_chars > 0)
+		return -simple_strntoull(cp + 1, max_chars - 1, endp, base);
+
+	return simple_strntoull(cp, max_chars, endp, base);
+}
+
 /**
  * simple_strtoll - convert a string to a signed long long
  * @cp: The start of the string
@@ -119,10 +148,7 @@ EXPORT_SYMBOL(simple_strtol);
  */
 long long simple_strtoll(const char *cp, char **endp, unsigned int base)
 {
-	if (*cp == '-')
-		return -simple_strtoull(cp + 1, endp, base);
-
-	return simple_strtoull(cp, endp, base);
+	return simple_strntoll(cp, INT_MAX, endp, base);
 }
 EXPORT_SYMBOL(simple_strtoll);
 
@@ -1834,7 +1860,8 @@ char *rtc_str(char *buf, char *end, const struct rtc_time *tm,
 	      struct printf_spec spec, const char *fmt)
 {
 	bool have_t = true, have_d = true;
-	bool raw = false;
+	bool raw = false, iso8601_separator = true;
+	bool found = true;
 	int count = 2;
 
 	if (check_pointer(&buf, end, tm, spec))
@@ -1851,14 +1878,25 @@ char *rtc_str(char *buf, char *end, const struct rtc_time *tm,
 		break;
 	}
 
-	raw = fmt[count] == 'r';
+	do {
+		switch (fmt[count++]) {
+		case 'r':
+			raw = true;
+			break;
+		case 's':
+			iso8601_separator = false;
+			break;
+		default:
+			found = false;
+			break;
+		}
+	} while (found);
 
 	if (have_d)
 		buf = date_str(buf, end, tm, raw);
 	if (have_d && have_t) {
-		/* Respect ISO 8601 */
 		if (buf < end)
-			*buf = 'T';
+			*buf = iso8601_separator ? 'T' : ' ';
 		buf++;
 	}
 	if (have_t)
@@ -2298,7 +2336,7 @@ early_param("no_hash_pointers", no_hash_pointers_enable);
  * - 'd[234]' For a dentry name (optionally 2-4 last components)
  * - 'D[234]' Same as 'd' but for a struct file
  * - 'g' For block_device name (gendisk + partition number)
- * - 't[RT][dt][r]' For time and date as represented by:
+ * - 't[RT][dt][r][s]' For time and date as represented by:
  *      R    struct rtc_time
  *      T    time64_t
  * - 'C' For a clock, it prints the name (Common Clock Framework) or address
@@ -3565,8 +3603,12 @@ int vsscanf(const char *buf, const char *fmt, va_list args)
 		str = skip_spaces(str);
 
 		digit = *str;
-		if (is_sign && digit == '-')
+		if (is_sign && digit == '-') {
+			if (field_width == 1)
+				break;
+
 			digit = *(str + 1);
+		}
 
 		if (!digit
 		    || (base == 16 && !isxdigit(digit))
@@ -3576,25 +3618,13 @@ int vsscanf(const char *buf, const char *fmt, va_list args)
 			break;
 
 		if (is_sign)
-			val.s = qualifier != 'L' ?
-				simple_strtol(str, &next, base) :
-				simple_strtoll(str, &next, base);
-		else
-			val.u = qualifier != 'L' ?
-				simple_strtoul(str, &next, base) :
-				simple_strtoull(str, &next, base);
-
-		if (field_width > 0 && next - str > field_width) {
-			if (base == 0)
-				_parse_integer_fixup_radix(str, &base);
-			while (next - str > field_width) {
-				if (is_sign)
-					val.s = div_s64(val.s, base);
+			val.s = simple_strntoll(str,
+						field_width >= 0 ? field_width : INT_MAX,
+						&next, base);
 		else
-					val.u = div_u64(val.u, base);
-				--next;
-			}
-		}
+			val.u = simple_strntoull(str,
+						 field_width >= 0 ? field_width : INT_MAX,
+						 &next, base);
 
 		switch (qualifier) {
 		case 'H':	/* that's 'hh' in format */

tools/testing/selftests/lib/Makefile

@@ -4,6 +4,6 @@
 # No binaries, but make sure arg-less "make" doesn't trigger "run_tests"
 all:
 
-TEST_PROGS := printf.sh bitmap.sh prime_numbers.sh strscpy.sh
+TEST_PROGS := printf.sh bitmap.sh prime_numbers.sh scanf.sh strscpy.sh
 
 include ../lib.mk

tools/testing/selftests/lib/config

 CONFIG_TEST_PRINTF=m
+CONFIG_TEST_SCANF=m
 CONFIG_TEST_BITMAP=m
 CONFIG_PRIME_NUMBERS=m
 CONFIG_TEST_STRSCPY=m

tools/testing/selftests/lib/scanf.sh

+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# Tests the scanf infrastructure using test_scanf kernel module.
+$(dirname $0)/../kselftest/module.sh "scanf" test_scanf