diff --git a/MAINTAINERS b/MAINTAINERS
index a61f4f3b78a91f13e25826d1b407e9ccbbb48cf8..a19a104e0cc4c0e4391a80506731d7e27df03e20 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14918,6 +14918,11 @@ S:	Maintained
 F:	include/linux/printk.h
 F:	kernel/printk/
 
+PRINTK INDEXING
+R:	Chris Down <chris@chrisdown.name>
+S:	Maintained
+F:	kernel/printk/index.c
+
 PRISM54 WIRELESS DRIVER
 M:	Luis Chamberlain <mcgrof@kernel.org>
 L:	linux-wireless@vger.kernel.org
diff --git a/arch/arm/kernel/entry-v7m.S b/arch/arm/kernel/entry-v7m.S
index d0e898608d3033ac72123e2caf9a61a3cf6a6a9b..7bde93c10962da9ffdf56965cf3c81b677808f06 100644
--- a/arch/arm/kernel/entry-v7m.S
+++ b/arch/arm/kernel/entry-v7m.S
@@ -23,7 +23,7 @@ __invalid_entry:
 	adr	r0, strerr
 	mrs	r1, ipsr
 	mov	r2, lr
-	bl	printk
+	bl	_printk
 #endif
 	mov	r0, sp
 	bl	show_regs
diff --git a/arch/arm/lib/backtrace-clang.S b/arch/arm/lib/backtrace-clang.S
index 6174c45f53a5dbfc8c0e2de3de8175b6e17a8d5e..5b2cdb1003e35806d0873880d741c70b1d41024d 100644
--- a/arch/arm/lib/backtrace-clang.S
+++ b/arch/arm/lib/backtrace-clang.S
@@ -202,7 +202,7 @@ finished_setup:
 1006:		adr	r0, .Lbad
 		mov	r1, loglvl
 		mov	r2, frame
-		bl	printk
+		bl	_printk
 no_frame:	ldmfd	sp!, {r4 - r9, fp, pc}
 ENDPROC(c_backtrace)
 		.pushsection __ex_table,"a"
diff --git a/arch/arm/lib/backtrace.S b/arch/arm/lib/backtrace.S
index 872f658638d99710710963266900701a3a69c2a7..e8408f22d4dc97af0b0be3532dbdaf7cba08988e 100644
--- a/arch/arm/lib/backtrace.S
+++ b/arch/arm/lib/backtrace.S
@@ -103,7 +103,7 @@ for_each_frame:	tst	frame, mask		@ Check for address exceptions
 1006:		adr	r0, .Lbad
 		mov	r1, loglvl
 		mov	r2, frame
-		bl	printk
+		bl	_printk
 no_frame:	ldmfd	sp!, {r4 - r9, pc}
 ENDPROC(c_backtrace)
 		
diff --git a/arch/arm/mach-rpc/io-acorn.S b/arch/arm/mach-rpc/io-acorn.S
index b9082a2a2a01436784ff3d34161dbc83bfefa750..aa9bf0d771c0a4e0d66921401345910676c523d3 100644
--- a/arch/arm/mach-rpc/io-acorn.S
+++ b/arch/arm/mach-rpc/io-acorn.S
@@ -25,4 +25,4 @@ ENTRY(insl)
 ENTRY(outsl)
 		adr	r0, .Liosl_warning
 		mov	r1, lr
-		b	printk
+		b	_printk
diff --git a/arch/arm/vfp/vfphw.S b/arch/arm/vfp/vfphw.S
index d5837bf05a9a53ed3ea9befc26e7efa9ceb017ea..6f7926c9c1790f6675bac00adc1a58f10b67002e 100644
--- a/arch/arm/vfp/vfphw.S
+++ b/arch/arm/vfp/vfphw.S
@@ -23,7 +23,7 @@
 #ifdef DEBUG
 	stmfd	sp!, {r0-r3, ip, lr}
 	ldr	r0, =1f
-	bl	printk
+	bl	_printk
 	ldmfd	sp!, {r0-r3, ip, lr}
 
 	.pushsection .rodata, "a"
@@ -38,7 +38,7 @@
 	stmfd	sp!, {r0-r3, ip, lr}
 	mov	r1, \arg
 	ldr	r0, =1f
-	bl	printk
+	bl	_printk
 	ldmfd	sp!, {r0-r3, ip, lr}
 
 	.pushsection .rodata, "a"
@@ -55,7 +55,7 @@
 	mov	r2, \arg2
 	mov	r1, \arg1
 	ldr	r0, =1f
-	bl	printk
+	bl	_printk
 	ldmfd	sp!, {r0-r3, ip, lr}
 
 	.pushsection .rodata, "a"
diff --git a/arch/ia64/include/uapi/asm/cmpxchg.h b/arch/ia64/include/uapi/asm/cmpxchg.h
index 926c6cb1e029783758178530dd44d7cbc6eae026..2c2f3cfeaa77b399ebca27cda689b0238727f85f 100644
--- a/arch/ia64/include/uapi/asm/cmpxchg.h
+++ b/arch/ia64/include/uapi/asm/cmpxchg.h
@@ -143,9 +143,9 @@ extern long ia64_cmpxchg_called_with_bad_pointer(void);
 do {									\
 	if (_cmpxchg_bugcheck_count-- <= 0) {				\
 		void *ip;						\
-		extern int printk(const char *fmt, ...);		\
+		extern int _printk(const char *fmt, ...);		\
 		ip = (void *) ia64_getreg(_IA64_REG_IP);		\
-		printk("CMPXCHG_BUGCHECK: stuck at %p on word %p\n", ip, (v));\
+		_printk("CMPXCHG_BUGCHECK: stuck at %p on word %p\n", ip, (v));\
 		break;							\
 	}								\
 } while (0)
diff --git a/arch/openrisc/kernel/entry.S b/arch/openrisc/kernel/entry.S
index bc657e55c15f8e1dfb2ef718d138a40998ffc7b4..947613f61d4ac1707f1ecd8948db1fb3acae7930 100644
--- a/arch/openrisc/kernel/entry.S
+++ b/arch/openrisc/kernel/entry.S
@@ -551,7 +551,7 @@ EXCEPTION_ENTRY(_external_irq_handler)
 	l.movhi r3,hi(42f)
 	l.ori	r3,r3,lo(42f)
 	l.sw    0x0(r1),r3
-	l.jal   printk
+	l.jal   _printk
 	l.sw    0x4(r1),r4
 	l.addi  r1,r1,0x8
 
@@ -681,8 +681,8 @@ _syscall_debug:
 	l.sw    -4(r1),r27
 	l.sw    -8(r1),r11
 	l.addi  r1,r1,-8
-	l.movhi r27,hi(printk)
-	l.ori   r27,r27,lo(printk)
+	l.movhi r27,hi(_printk)
+	l.ori   r27,r27,lo(_printk)
 	l.jalr  r27
 	 l.nop
 	l.addi  r1,r1,8
diff --git a/arch/powerpc/kernel/head_fsl_booke.S b/arch/powerpc/kernel/head_fsl_booke.S
index 0f9642f36b4900dee70507359451f93f57a7d4f2..9a2f4265e6d215e6ec3279cd86c75cbaef75b1ab 100644
--- a/arch/powerpc/kernel/head_fsl_booke.S
+++ b/arch/powerpc/kernel/head_fsl_booke.S
@@ -858,7 +858,7 @@ KernelSPE:
 	ori	r3,r3,87f@l
 	mr	r4,r2		/* current */
 	lwz	r5,_NIP(r1)
-	bl	printk
+	bl	_printk
 #endif
 	b	interrupt_return
 #ifdef CONFIG_PRINTK
diff --git a/arch/um/include/shared/user.h b/arch/um/include/shared/user.h
index e793e4212f0a5f80eca76d55dea6cb2f4b94809a..dd4badffdeb3d76a35551387108a3ccf0288b8e2 100644
--- a/arch/um/include/shared/user.h
+++ b/arch/um/include/shared/user.h
@@ -38,7 +38,8 @@ extern void panic(const char *fmt, ...)
 #define UM_KERN_CONT	KERN_CONT
 
 #ifdef UML_CONFIG_PRINTK
-extern int printk(const char *fmt, ...)
+#define printk(...) _printk(__VA_ARGS__)
+extern int _printk(const char *fmt, ...)
 	__attribute__ ((format (printf, 1, 2)));
 #else
 static inline int printk(const char *fmt, ...)
diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index 67f590425d90b783165b4e79fb2b4acc1b01db1d..d8c64dab0efe07cb03332d684a47e624a69526ad 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -432,7 +432,7 @@ SYM_FUNC_START(early_ignore_irq)
 	pushl 32(%esp)
 	pushl 40(%esp)
 	pushl $int_msg
-	call printk
+	call _printk
 
 	call dump_stack
 
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 17325416e2dee2e400dfb531e9bc5ffc64e13306..ddb2ff158321aa9d5e2f1b77449a1da8f296e812 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -483,6 +483,8 @@
 									\
 	TRACEDATA							\
 									\
+	PRINTK_INDEX							\
+									\
 	/* Kernel symbol table: Normal symbols */			\
 	__ksymtab         : AT(ADDR(__ksymtab) - LOAD_OFFSET) {		\
 		__start___ksymtab = .;					\
@@ -893,6 +895,17 @@
 #define TRACEDATA
 #endif
 
+#ifdef CONFIG_PRINTK_INDEX
+#define PRINTK_INDEX							\
+	.printk_index : AT(ADDR(.printk_index) - LOAD_OFFSET) {		\
+		__start_printk_index = .;				\
+		*(.printk_index)					\
+		__stop_printk_index = .;				\
+	}
+#else
+#define PRINTK_INDEX
+#endif
+
 #define NOTES								\
 	.notes : AT(ADDR(.notes) - LOAD_OFFSET) {			\
 		__start_notes = .;					\
diff --git a/include/linux/module.h b/include/linux/module.h
index 8a298d820dbce63195f0c7238f719e8744b7679c..c9f1200b23121a4199ca9fad1d97ce0d6a6c84ad 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -511,6 +511,11 @@ struct module {
 	struct klp_modinfo *klp_info;
 #endif
 
+#ifdef CONFIG_PRINTK_INDEX
+	unsigned int printk_index_size;
+	struct pi_entry **printk_index_start;
+#endif
+
 #ifdef CONFIG_MODULE_UNLOAD
 	/* What modules depend on me? */
 	struct list_head source_list;
diff --git a/include/linux/printk.h b/include/linux/printk.h
index e834d78f047884bab2bec5fd0fbc5d75ace977dc..2651b82ed35299bab55c69c0cba5aa7362929090 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -174,12 +174,12 @@ asmlinkage __printf(1, 0)
 int vprintk(const char *fmt, va_list args);
 
 asmlinkage __printf(1, 2) __cold
-int printk(const char *fmt, ...);
+int _printk(const char *fmt, ...);
 
 /*
  * Special printk facility for scheduler/timekeeping use only, _DO_NOT_USE_ !
  */
-__printf(1, 2) __cold int printk_deferred(const char *fmt, ...);
+__printf(1, 2) __cold int _printk_deferred(const char *fmt, ...);
 
 /*
  * Please don't use printk_ratelimit(), because it shares ratelimiting state
@@ -218,12 +218,12 @@ int vprintk(const char *s, va_list args)
 	return 0;
 }
 static inline __printf(1, 2) __cold
-int printk(const char *s, ...)
+int _printk(const char *s, ...)
 {
 	return 0;
 }
 static inline __printf(1, 2) __cold
-int printk_deferred(const char *s, ...)
+int _printk_deferred(const char *s, ...)
 {
 	return 0;
 }
@@ -348,6 +348,93 @@ extern int kptr_restrict;
 #define pr_fmt(fmt) fmt
 #endif
 
+struct module;
+
+#ifdef CONFIG_PRINTK_INDEX
+struct pi_entry {
+	const char *fmt;
+	const char *func;
+	const char *file;
+	unsigned int line;
+
+	/*
+	 * While printk and pr_* have the level stored in the string at compile
+	 * time, some subsystems dynamically add it at runtime through the
+	 * format string. For these dynamic cases, we allow the subsystem to
+	 * tell us the level at compile time.
+	 *
+	 * NULL indicates that the level, if any, is stored in fmt.
+	 */
+	const char *level;
+
+	/*
+	 * The format string used by various subsystem specific printk()
+	 * wrappers to prefix the message.
+	 *
+	 * Note that the static prefix defined by the pr_fmt() macro is stored
+	 * directly in the message format (@fmt), not here.
+	 */
+	const char *subsys_fmt_prefix;
+} __packed;
+
+#define __printk_index_emit(_fmt, _level, _subsys_fmt_prefix)		\
+	do {								\
+		if (__builtin_constant_p(_fmt) && __builtin_constant_p(_level)) { \
+			/*
+			 * We check __builtin_constant_p multiple times here
+			 * for the same input because GCC will produce an error
+			 * if we try to assign a static variable to fmt if it
+			 * is not a constant, even with the outer if statement.
+			 */						\
+			static const struct pi_entry _entry		\
+			__used = {					\
+				.fmt = __builtin_constant_p(_fmt) ? (_fmt) : NULL, \
+				.func = __func__,			\
+				.file = __FILE__,			\
+				.line = __LINE__,			\
+				.level = __builtin_constant_p(_level) ? (_level) : NULL, \
+				.subsys_fmt_prefix = _subsys_fmt_prefix,\
+			};						\
+			static const struct pi_entry *_entry_ptr	\
+			__used __section(".printk_index") = &_entry;	\
+		}							\
+	} while (0)
+
+#else /* !CONFIG_PRINTK_INDEX */
+#define __printk_index_emit(...) do {} while (0)
+#endif /* CONFIG_PRINTK_INDEX */
+
+/*
+ * Some subsystems have their own custom printk that applies a va_format to a
+ * generic format, for example, to include a device number or other metadata
+ * alongside the format supplied by the caller.
+ *
+ * In order to store these in the way they would be emitted by the printk
+ * infrastructure, the subsystem provides us with the start, fixed string, and
+ * any subsequent text in the format string.
+ *
+ * We take a variable argument list as pr_fmt/dev_fmt/etc are sometimes passed
+ * as multiple arguments (eg: `"%s: ", "blah"`), and we must only take the
+ * first one.
+ *
+ * subsys_fmt_prefix must be known at compile time, or compilation will fail
+ * (since this is a mistake). If fmt or level is not known at compile time, no
+ * index entry will be made (since this can legitimately happen).
+ */
+#define printk_index_subsys_emit(subsys_fmt_prefix, level, fmt, ...) \
+	__printk_index_emit(fmt, level, subsys_fmt_prefix)
+
+#define printk_index_wrap(_p_func, _fmt, ...)				\
+	({								\
+		__printk_index_emit(_fmt, NULL, NULL);			\
+		_p_func(_fmt, ##__VA_ARGS__);				\
+	})
+
+
+#define printk(fmt, ...) printk_index_wrap(_printk, fmt, ##__VA_ARGS__)
+#define printk_deferred(fmt, ...)					\
+	printk_index_wrap(_printk_deferred, fmt, ##__VA_ARGS__)
+
 /**
  * pr_emerg - Print an emergency-level message
  * @fmt: format string
diff --git a/init/Kconfig b/init/Kconfig
index bb0d6e6262b152099ce42488f74640388e3dbdcb..ccffa7ae5ccc0f0b882d7a7e21f2c9f66b211813 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -775,6 +775,20 @@ config PRINTK_SAFE_LOG_BUF_SHIFT
 		     13 =>   8 KB for each CPU
 		     12 =>   4 KB for each CPU
 
+config PRINTK_INDEX
+	bool "Printk indexing debugfs interface"
+	depends on PRINTK && DEBUG_FS
+	help
+	  Add support for indexing of all printk formats known at compile time
+	  at <debugfs>/printk/index/<module>.
+
+	  This can be used as part of maintaining daemons which monitor
+	  /dev/kmsg, as it permits auditing the printk formats present in a
+	  kernel, allowing detection of cases where monitored printks are
+	  changed or no longer present.
+
+	  There is no additional runtime cost to printk with this enabled.
+
 #
 # Architectures with an unreliable sched_clock() should select this:
 #
diff --git a/kernel/module.c b/kernel/module.c
index ed13917ea5f39e1cfcee909084691d67476b1cf7..40ec9a030eecf41d5597e6c910746aab385b1da0 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -3355,6 +3355,11 @@ static int find_module_sections(struct module *mod, struct load_info *info)
 						sizeof(unsigned long),
 						&mod->num_kprobe_blacklist);
 #endif
+#ifdef CONFIG_PRINTK_INDEX
+	mod->printk_index_start = section_objs(info, ".printk_index",
+					       sizeof(*mod->printk_index_start),
+					       &mod->printk_index_size);
+#endif
 #ifdef CONFIG_HAVE_STATIC_CALL_INLINE
 	mod->static_call_sites = section_objs(info, ".static_call_sites",
 					      sizeof(*mod->static_call_sites),
diff --git a/kernel/printk/Makefile b/kernel/printk/Makefile
index eee3dc9b60a9aaaa6a62a0d18141163b380224be..d118739874c0da81e59fca3845c5ad14264d2261 100644
--- a/kernel/printk/Makefile
+++ b/kernel/printk/Makefile
@@ -3,3 +3,4 @@ obj-y	= printk.o
 obj-$(CONFIG_PRINTK)	+= printk_safe.o
 obj-$(CONFIG_A11Y_BRAILLE_CONSOLE)	+= braille.o
 obj-$(CONFIG_PRINTK)	+= printk_ringbuffer.o
+obj-$(CONFIG_PRINTK_INDEX)	+= index.o
diff --git a/kernel/printk/index.c b/kernel/printk/index.c
new file mode 100644
index 0000000000000000000000000000000000000000..ca062f5e177946014e48e59fb6906076cc313ccf
--- /dev/null
+++ b/kernel/printk/index.c
@@ -0,0 +1,195 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Userspace indexing of printk formats
+ */
+
+#include <linux/debugfs.h>
+#include <linux/module.h>
+#include <linux/printk.h>
+#include <linux/slab.h>
+#include <linux/string_helpers.h>
+
+#include "internal.h"
+
+extern struct pi_entry *__start_printk_index[];
+extern struct pi_entry *__stop_printk_index[];
+
+/* The base dir for module formats, typically debugfs/printk/index/ */
+static struct dentry *dfs_index;
+
+static struct pi_entry *pi_get_entry(const struct module *mod, loff_t pos)
+{
+	struct pi_entry **entries;
+	unsigned int nr_entries;
+
+#ifdef CONFIG_MODULES
+	if (mod) {
+		entries = mod->printk_index_start;
+		nr_entries = mod->printk_index_size;
+	}
+#endif
+
+	if (!mod) {
+		/* vmlinux, comes from linker symbols */
+		entries = __start_printk_index;
+		nr_entries = __stop_printk_index - __start_printk_index;
+	}
+
+	if (pos >= nr_entries)
+		return NULL;
+
+	return entries[pos];
+}
+
+static void *pi_next(struct seq_file *s, void *v, loff_t *pos)
+{
+	const struct module *mod = s->file->f_inode->i_private;
+	struct pi_entry *entry = pi_get_entry(mod, *pos);
+
+	(*pos)++;
+
+	return entry;
+}
+
+static void *pi_start(struct seq_file *s, loff_t *pos)
+{
+	/*
+	 * Make show() print the header line. Do not update *pos because
+	 * pi_next() still has to return the entry at index 0 later.
+	 */
+	if (*pos == 0)
+		return SEQ_START_TOKEN;
+
+	return pi_next(s, NULL, pos);
+}
+
+/*
+ * We need both ESCAPE_ANY and explicit characters from ESCAPE_SPECIAL in @only
+ * because otherwise ESCAPE_NAP will cause double quotes and backslashes to be
+ * ignored for quoting.
+ */
+#define seq_escape_printf_format(s, src) \
+	seq_escape_str(s, src, ESCAPE_ANY | ESCAPE_NAP | ESCAPE_APPEND, "\"\\")
+
+static int pi_show(struct seq_file *s, void *v)
+{
+	const struct pi_entry *entry = v;
+	int level = LOGLEVEL_DEFAULT;
+	enum printk_info_flags flags = 0;
+	u16 prefix_len = 0;
+
+	if (v == SEQ_START_TOKEN) {
+		seq_puts(s, "# <level/flags> filename:line function \"format\"\n");
+		return 0;
+	}
+
+	if (!entry->fmt)
+		return 0;
+
+	if (entry->level)
+		printk_parse_prefix(entry->level, &level, &flags);
+	else
+		prefix_len = printk_parse_prefix(entry->fmt, &level, &flags);
+
+
+	if (flags & LOG_CONT) {
+		/*
+		 * LOGLEVEL_DEFAULT here means "use the same level as the
+		 * message we're continuing from", not the default message
+		 * loglevel, so don't display it as such.
+		 */
+		if (level == LOGLEVEL_DEFAULT)
+			seq_puts(s, "<c>");
+		else
+			seq_printf(s, "<%d,c>", level);
+	} else
+		seq_printf(s, "<%d>", level);
+
+	seq_printf(s, " %s:%d %s \"", entry->file, entry->line, entry->func);
+	if (entry->subsys_fmt_prefix)
+		seq_escape_printf_format(s, entry->subsys_fmt_prefix);
+	seq_escape_printf_format(s, entry->fmt + prefix_len);
+	seq_puts(s, "\"\n");
+
+	return 0;
+}
+
+static void pi_stop(struct seq_file *p, void *v) { }
+
+static const struct seq_operations dfs_index_sops = {
+	.start = pi_start,
+	.next  = pi_next,
+	.show  = pi_show,
+	.stop  = pi_stop,
+};
+
+DEFINE_SEQ_ATTRIBUTE(dfs_index);
+
+#ifdef CONFIG_MODULES
+static const char *pi_get_module_name(struct module *mod)
+{
+	return mod ? mod->name : "vmlinux";
+}
+#else
+static const char *pi_get_module_name(struct module *mod)
+{
+	return "vmlinux";
+}
+#endif
+
+void pi_create_file(struct module *mod)
+{
+	debugfs_create_file(pi_get_module_name(mod), 0444, dfs_index,
+				       mod, &dfs_index_fops);
+}
+
+void pi_remove_file(struct module *mod)
+{
+	debugfs_remove(debugfs_lookup(pi_get_module_name(mod), dfs_index));
+}
+
+#ifdef CONFIG_MODULES
+static int pi_module_notify(struct notifier_block *nb, unsigned long op,
+			    void *data)
+{
+	struct module *mod = data;
+
+	switch (op) {
+	case MODULE_STATE_COMING:
+		pi_create_file(mod);
+		break;
+	case MODULE_STATE_GOING:
+		pi_remove_file(mod);
+		break;
+	default: /* we don't care about other module states */
+		break;
+	}
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block module_printk_fmts_nb = {
+	.notifier_call = pi_module_notify,
+};
+
+static void __init pi_setup_module_notifier(void)
+{
+	register_module_notifier(&module_printk_fmts_nb);
+}
+#else
+static inline void __init pi_setup_module_notifier(void) { }
+#endif
+
+static int __init pi_init(void)
+{
+	struct dentry *dfs_root = debugfs_create_dir("printk", NULL);
+
+	dfs_index = debugfs_create_dir("index", dfs_root);
+	pi_setup_module_notifier();
+	pi_create_file(NULL);
+
+	return 0;
+}
+
+/* debugfs comes up on core and must be initialised first */
+postcore_initcall(pi_init);
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 03956c3eb7456bdaadaf8a2d2d0b17e271a32c16..765f7af6ce56bcb6405de53288e117501c1a3dcf 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2184,10 +2184,13 @@ int vprintk_default(const char *fmt, va_list args)
 EXPORT_SYMBOL_GPL(vprintk_default);
 
 /**
- * printk - print a kernel message
+ * _printk - print a kernel message
  * @fmt: format string
  *
- * This is printk(). It can be called from any context. We want it to work.
+ * This is _printk(). It can be called from any context. We want it to work.
+ *
+ * If printk indexing is enabled, _printk() is called from printk_index_wrap.
+ * Otherwise, printk is simply #defined to _printk.
  *
  * We try to grab the console_lock. If we succeed, it's easy - we log the
  * output and call the console drivers.  If we fail to get the semaphore, we
@@ -2204,7 +2207,7 @@ EXPORT_SYMBOL_GPL(vprintk_default);
  *
  * See the vsnprintf() documentation for format string extensions over C99.
  */
-asmlinkage __visible int printk(const char *fmt, ...)
+asmlinkage __visible int _printk(const char *fmt, ...)
 {
 	va_list args;
 	int r;
@@ -2215,7 +2218,7 @@ asmlinkage __visible int printk(const char *fmt, ...)
 
 	return r;
 }
-EXPORT_SYMBOL(printk);
+EXPORT_SYMBOL(_printk);
 
 #else /* CONFIG_PRINTK */
 
@@ -3200,7 +3203,7 @@ int vprintk_deferred(const char *fmt, va_list args)
 	return r;
 }
 
-int printk_deferred(const char *fmt, ...)
+int _printk_deferred(const char *fmt, ...)
 {
 	va_list args;
 	int r;