kernel/trace/trace_seq.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * trace_seq.c
  *
  * Copyright (C) 2008-2014 Red Hat Inc, Steven Rostedt <srostedt@redhat.com>
  *
  * The trace_seq is a handy tool that allows you to pass a descriptor around
  * to a buffer that other functions can write to. It is similar to the
  * seq_file functionality but has some differences.
  *
  * To use it, the trace_seq must be initialized with trace_seq_init().
  * This will set up the counters within the descriptor. You can call
  * trace_seq_init() more than once to reset the trace_seq to start
  * from scratch.
  *
  * The buffer size is currently PAGE_SIZE, although it may become dynamic
  * in the future.
  *
  * A write to the buffer will either succeed or fail. That is, unlike
  * sprintf() there will not be a partial write (well it may write into
  * the buffer but it wont update the pointers). This allows users to
  * try to write something into the trace_seq buffer and if it fails
  * they can flush it and try again.
  *
  */
 #include <linux/uaccess.h>
 #include <linux/seq_file.h>
 #include <linux/trace_seq.h>

 /* How much buffer is left on the trace_seq? */
 #define TRACE_SEQ_BUF_LEFT(s) seq_buf_buffer_left(&(s)->seq)

 /*
  * trace_seq should work with being initialized with 0s.
  */
 static inline void __trace_seq_init(struct trace_seq *s)
 {
 	if (unlikely(!s->seq.size))
 		trace_seq_init(s);
 }

 /**
  * trace_print_seq - move the contents of trace_seq into a seq_file
  * @m: the seq_file descriptor that is the destination
  * @s: the trace_seq descriptor that is the source.
  *
  * Returns 0 on success and non zero on error. If it succeeds to
  * write to the seq_file it will reset the trace_seq, otherwise
  * it does not modify the trace_seq to let the caller try again.
  */
 int trace_print_seq(struct seq_file *m, struct trace_seq *s)
 {
 	int ret;

 	__trace_seq_init(s);

 	ret = seq_buf_print_seq(m, &s->seq);

 	/*
 	 * Only reset this buffer if we successfully wrote to the
 	 * seq_file buffer. This lets the caller try again or
 	 * do something else with the contents.
 	 */
 	if (!ret)
 		trace_seq_init(s);

 	return ret;
 }

 /**
  * trace_seq_printf - sequence printing of trace information
  * @s: trace sequence descriptor
  * @fmt: printf format string
  *
  * The tracer may use either sequence operations or its own
  * copy to user routines. To simplify formatting of a trace
  * trace_seq_printf() is used to store strings into a special
  * buffer (@s). Then the output may be either used by
  * the sequencer or pulled into another buffer.
  */
 void trace_seq_printf(struct trace_seq *s, const char *fmt, ...)
 {
 	unsigned int save_len = s->seq.len;
 	va_list ap;

 	if (s->full)
 		return;

 	__trace_seq_init(s);

 	va_start(ap, fmt);
 	seq_buf_vprintf(&s->seq, fmt, ap);
 	va_end(ap);

 	/* If we can't write it all, don't bother writing anything */
 	if (unlikely(seq_buf_has_overflowed(&s->seq))) {
 		s->seq.len = save_len;
 		s->full = 1;
 	}
 }
 EXPORT_SYMBOL_GPL(trace_seq_printf);

 /**
  * trace_seq_bitmask - write a bitmask array in its ASCII representation
  * @s:		trace sequence descriptor
  * @maskp:	points to an array of unsigned longs that represent a bitmask
  * @nmaskbits:	The number of bits that are valid in @maskp
  *
  * Writes a ASCII representation of a bitmask string into @s.
  */
 void trace_seq_bitmask(struct trace_seq *s, const unsigned long *maskp,
 		      int nmaskbits)
 {
 	unsigned int save_len = s->seq.len;

 	if (s->full)
 		return;

 	__trace_seq_init(s);

 	seq_buf_printf(&s->seq, "%*pb", nmaskbits, maskp);

 	if (unlikely(seq_buf_has_overflowed(&s->seq))) {
 		s->seq.len = save_len;
 		s->full = 1;
 	}
 }
 EXPORT_SYMBOL_GPL(trace_seq_bitmask);

 /**
  * trace_seq_vprintf - sequence printing of trace information
  * @s: trace sequence descriptor
  * @fmt: printf format string
  *
  * The tracer may use either sequence operations or its own
  * copy to user routines. To simplify formatting of a trace
  * trace_seq_printf is used to store strings into a special
  * buffer (@s). Then the output may be either used by
  * the sequencer or pulled into another buffer.
  */
 void trace_seq_vprintf(struct trace_seq *s, const char *fmt, va_list args)
 {
 	unsigned int save_len = s->seq.len;

 	if (s->full)
 		return;

 	__trace_seq_init(s);

 	seq_buf_vprintf(&s->seq, fmt, args);

 	/* If we can't write it all, don't bother writing anything */
 	if (unlikely(seq_buf_has_overflowed(&s->seq))) {
 		s->seq.len = save_len;
 		s->full = 1;
 	}
 }
 EXPORT_SYMBOL_GPL(trace_seq_vprintf);

 /**
  * trace_seq_bprintf - Write the printf string from binary arguments
  * @s: trace sequence descriptor
  * @fmt: The format string for the @binary arguments
  * @binary: The binary arguments for @fmt.
  *
  * When recording in a fast path, a printf may be recorded with just
  * saving the format and the arguments as they were passed to the
  * function, instead of wasting cycles converting the arguments into
  * ASCII characters. Instead, the arguments are saved in a 32 bit
  * word array that is defined by the format string constraints.
  *
  * This function will take the format and the binary array and finish
  * the conversion into the ASCII string within the buffer.
  */
 void trace_seq_bprintf(struct trace_seq *s, const char *fmt, const u32 *binary)
 {
 	unsigned int save_len = s->seq.len;

 	if (s->full)
 		return;

 	__trace_seq_init(s);

 	seq_buf_bprintf(&s->seq, fmt, binary);

 	/* If we can't write it all, don't bother writing anything */
 	if (unlikely(seq_buf_has_overflowed(&s->seq))) {
 		s->seq.len = save_len;
 		s->full = 1;
 		return;
 	}
 }
 EXPORT_SYMBOL_GPL(trace_seq_bprintf);

 /**
  * trace_seq_puts - trace sequence printing of simple string
  * @s: trace sequence descriptor
  * @str: simple string to record
  *
  * The tracer may use either the sequence operations or its own
  * copy to user routines. This function records a simple string
  * into a special buffer (@s) for later retrieval by a sequencer
  * or other mechanism.
  */
 void trace_seq_puts(struct trace_seq *s, const char *str)
 {
 	unsigned int len = strlen(str);

 	if (s->full)
 		return;

 	__trace_seq_init(s);

 	if (len > TRACE_SEQ_BUF_LEFT(s)) {
 		s->full = 1;
 		return;
 	}

 	seq_buf_putmem(&s->seq, str, len);
 }
 EXPORT_SYMBOL_GPL(trace_seq_puts);

 /**
  * trace_seq_putc - trace sequence printing of simple character
  * @s: trace sequence descriptor
  * @c: simple character to record
  *
  * The tracer may use either the sequence operations or its own
  * copy to user routines. This function records a simple character
  * into a special buffer (@s) for later retrieval by a sequencer
  * or other mechanism.
  */
 void trace_seq_putc(struct trace_seq *s, unsigned char c)
 {
 	if (s->full)
 		return;

 	__trace_seq_init(s);

 	if (TRACE_SEQ_BUF_LEFT(s) < 1) {
 		s->full = 1;
 		return;
 	}

 	seq_buf_putc(&s->seq, c);
 }
 EXPORT_SYMBOL_GPL(trace_seq_putc);

 /**
  * trace_seq_putmem - write raw data into the trace_seq buffer
  * @s: trace sequence descriptor
  * @mem: The raw memory to copy into the buffer
  * @len: The length of the raw memory to copy (in bytes)
  *
  * There may be cases where raw memory needs to be written into the
  * buffer and a strcpy() would not work. Using this function allows
  * for such cases.
  */
 void trace_seq_putmem(struct trace_seq *s, const void *mem, unsigned int len)
 {
 	if (s->full)
 		return;

 	__trace_seq_init(s);

 	if (len > TRACE_SEQ_BUF_LEFT(s)) {
 		s->full = 1;
 		return;
 	}

 	seq_buf_putmem(&s->seq, mem, len);
 }
 EXPORT_SYMBOL_GPL(trace_seq_putmem);

 /**
  * trace_seq_putmem_hex - write raw memory into the buffer in ASCII hex
  * @s: trace sequence descriptor
  * @mem: The raw memory to write its hex ASCII representation of
  * @len: The length of the raw memory to copy (in bytes)
  *
  * This is similar to trace_seq_putmem() except instead of just copying the
  * raw memory into the buffer it writes its ASCII representation of it
  * in hex characters.
  */
 void trace_seq_putmem_hex(struct trace_seq *s, const void *mem,
 			 unsigned int len)
 {
 	unsigned int save_len = s->seq.len;

 	if (s->full)
 		return;

 	__trace_seq_init(s);

 	/* Each byte is represented by two chars */
 	if (len * 2 > TRACE_SEQ_BUF_LEFT(s)) {
 		s->full = 1;
 		return;
 	}

 	/* The added spaces can still cause an overflow */
 	seq_buf_putmem_hex(&s->seq, mem, len);

 	if (unlikely(seq_buf_has_overflowed(&s->seq))) {
 		s->seq.len = save_len;
 		s->full = 1;
 		return;
 	}
 }
 EXPORT_SYMBOL_GPL(trace_seq_putmem_hex);

 /**
  * trace_seq_path - copy a path into the sequence buffer
  * @s: trace sequence descriptor
  * @path: path to write into the sequence buffer.
  *
  * Write a path name into the sequence buffer.
  *
  * Returns 1 if we successfully written all the contents to
  *   the buffer.
  * Returns 0 if we the length to write is bigger than the
  *   reserved buffer space. In this case, nothing gets written.
  */
 int trace_seq_path(struct trace_seq *s, const struct path *path)
 {
 	unsigned int save_len = s->seq.len;

 	if (s->full)
 		return 0;

 	__trace_seq_init(s);

 	if (TRACE_SEQ_BUF_LEFT(s) < 1) {
 		s->full = 1;
 		return 0;
 	}

 	seq_buf_path(&s->seq, path, "\n");

 	if (unlikely(seq_buf_has_overflowed(&s->seq))) {
 		s->seq.len = save_len;
 		s->full = 1;
 		return 0;
 	}

 	return 1;
 }
 EXPORT_SYMBOL_GPL(trace_seq_path);

 /**
  * trace_seq_to_user - copy the sequence buffer to user space
  * @s: trace sequence descriptor
  * @ubuf: The userspace memory location to copy to
  * @cnt: The amount to copy
  *
  * Copies the sequence buffer into the userspace memory pointed to
  * by @ubuf. It starts from the last read position (@s->readpos)
  * and writes up to @cnt characters or till it reaches the end of
  * the content in the buffer (@s->len), which ever comes first.
  *
  * On success, it returns a positive number of the number of bytes
  * it copied.
  *
  * On failure it returns -EBUSY if all of the content in the
  * sequence has been already read, which includes nothing in the
  * sequence (@s->len == @s->readpos).
  *
  * Returns -EFAULT if the copy to userspace fails.
  */
 int trace_seq_to_user(struct trace_seq *s, char __user *ubuf, int cnt)
 {
 	__trace_seq_init(s);
 	return seq_buf_to_user(&s->seq, ubuf, cnt);
 }
 EXPORT_SYMBOL_GPL(trace_seq_to_user);

 int trace_seq_hex_dump(struct trace_seq *s, const char *prefix_str,
 		       int prefix_type, int rowsize, int groupsize,
 		       const void *buf, size_t len, bool ascii)
 {
 	unsigned int save_len = s->seq.len;

 	if (s->full)
 		return 0;

 	__trace_seq_init(s);

 	if (TRACE_SEQ_BUF_LEFT(s) < 1) {
 		s->full = 1;
 		return 0;
 	}

 	seq_buf_hex_dump(&(s->seq), prefix_str,
 		   prefix_type, rowsize, groupsize,
 		   buf, len, ascii);

 	if (unlikely(seq_buf_has_overflowed(&s->seq))) {
 		s->seq.len = save_len;
 		s->full = 1;
 		return 0;
 	}

 	return 1;
 }
 EXPORT_SYMBOL(trace_seq_hex_dump);

 /*
  * trace_seq_acquire - acquire seq buffer with size len
  * @s: trace sequence descriptor
  * @len: size of buffer to be acquired
  *
  * acquire buffer with size of @len from trace_seq for output usage,
  * user can fill string into that buffer.
  *
  * Returns start address of acquired buffer.
  *
  * it allow multiple usage in one trace output function call.
  */
 char *trace_seq_acquire(struct trace_seq *s, unsigned int len)
 {
 	char *ret = trace_seq_buffer_ptr(s);

 	if (!WARN_ON_ONCE(seq_buf_buffer_left(&s->seq) < len))
 		seq_buf_commit(&s->seq, len);

 	return ret;
 }
 EXPORT_SYMBOL(trace_seq_acquire);
	// SPDX-License-Identifier: GPL-2.0
	/*
	* trace_seq.c
	*
	* Copyright (C) 2008-2014 Red Hat Inc, Steven Rostedt <srostedt@redhat.com>
	*
	* The trace_seq is a handy tool that allows you to pass a descriptor around
	* to a buffer that other functions can write to. It is similar to the
	* seq_file functionality but has some differences.
	*
	* To use it, the trace_seq must be initialized with trace_seq_init().
	* This will set up the counters within the descriptor. You can call
	* trace_seq_init() more than once to reset the trace_seq to start
	* from scratch.
	*
	* The buffer size is currently PAGE_SIZE, although it may become dynamic
	* in the future.
	*
	* A write to the buffer will either succeed or fail. That is, unlike
	* sprintf() there will not be a partial write (well it may write into
	* the buffer but it wont update the pointers). This allows users to
	* try to write something into the trace_seq buffer and if it fails
	* they can flush it and try again.
	*
	*/
	#include <linux/uaccess.h>
	#include <linux/seq_file.h>
	#include <linux/trace_seq.h>

	/* How much buffer is left on the trace_seq? */
	#define TRACE_SEQ_BUF_LEFT(s) seq_buf_buffer_left(&(s)->seq)

	/*
	* trace_seq should work with being initialized with 0s.
	*/
	static inline void __trace_seq_init(struct trace_seq *s)
	{
	if (unlikely(!s->seq.size))
	trace_seq_init(s);
	}

	/**
	* trace_print_seq - move the contents of trace_seq into a seq_file
	* @m: the seq_file descriptor that is the destination
	* @s: the trace_seq descriptor that is the source.
	*
	* Returns 0 on success and non zero on error. If it succeeds to
	* write to the seq_file it will reset the trace_seq, otherwise
	* it does not modify the trace_seq to let the caller try again.
	*/
	int trace_print_seq(struct seq_file m, struct trace_seq s)
	{
	int ret;

	__trace_seq_init(s);

	ret = seq_buf_print_seq(m, &s->seq);

	/*
	* Only reset this buffer if we successfully wrote to the
	* seq_file buffer. This lets the caller try again or
	* do something else with the contents.
	*/
	if (!ret)
	trace_seq_init(s);

	return ret;
	}

	/**
	* trace_seq_printf - sequence printing of trace information
	* @s: trace sequence descriptor
	* @fmt: printf format string
	*
	* The tracer may use either sequence operations or its own
	* copy to user routines. To simplify formatting of a trace
	* trace_seq_printf() is used to store strings into a special
	* buffer (@s). Then the output may be either used by
	* the sequencer or pulled into another buffer.
	*/
	void trace_seq_printf(struct trace_seq s, const char fmt, ...)
	{
	unsigned int save_len = s->seq.len;
	va_list ap;

	if (s->full)
	return;

	__trace_seq_init(s);

	va_start(ap, fmt);
	seq_buf_vprintf(&s->seq, fmt, ap);
	va_end(ap);

	/* If we can't write it all, don't bother writing anything */
	if (unlikely(seq_buf_has_overflowed(&s->seq))) {
	s->seq.len = save_len;
	s->full = 1;
	}
	}
	EXPORT_SYMBOL_GPL(trace_seq_printf);

	/**
	* trace_seq_bitmask - write a bitmask array in its ASCII representation
	* @s: trace sequence descriptor
	* @maskp: points to an array of unsigned longs that represent a bitmask
	* @nmaskbits: The number of bits that are valid in @maskp
	*
	* Writes a ASCII representation of a bitmask string into @s.
	*/
	void trace_seq_bitmask(struct trace_seq s, const unsigned long maskp,
	int nmaskbits)
	{
	unsigned int save_len = s->seq.len;

	if (s->full)
	return;

	__trace_seq_init(s);

	seq_buf_printf(&s->seq, "%*pb", nmaskbits, maskp);

	if (unlikely(seq_buf_has_overflowed(&s->seq))) {
	s->seq.len = save_len;
	s->full = 1;
	}
	}
	EXPORT_SYMBOL_GPL(trace_seq_bitmask);

	/**
	* trace_seq_vprintf - sequence printing of trace information
	* @s: trace sequence descriptor
	* @fmt: printf format string
	*
	* The tracer may use either sequence operations or its own
	* copy to user routines. To simplify formatting of a trace
	* trace_seq_printf is used to store strings into a special
	* buffer (@s). Then the output may be either used by
	* the sequencer or pulled into another buffer.
	*/
	void trace_seq_vprintf(struct trace_seq s, const char fmt, va_list args)
	{
	unsigned int save_len = s->seq.len;

	if (s->full)
	return;

	__trace_seq_init(s);

	seq_buf_vprintf(&s->seq, fmt, args);

	/* If we can't write it all, don't bother writing anything */
	if (unlikely(seq_buf_has_overflowed(&s->seq))) {
	s->seq.len = save_len;
	s->full = 1;
	}
	}
	EXPORT_SYMBOL_GPL(trace_seq_vprintf);

	/**
	* trace_seq_bprintf - Write the printf string from binary arguments
	* @s: trace sequence descriptor
	* @fmt: The format string for the @binary arguments
	* @binary: The binary arguments for @fmt.
	*
	* When recording in a fast path, a printf may be recorded with just
	* saving the format and the arguments as they were passed to the
	* function, instead of wasting cycles converting the arguments into
	* ASCII characters. Instead, the arguments are saved in a 32 bit
	* word array that is defined by the format string constraints.
	*
	* This function will take the format and the binary array and finish
	* the conversion into the ASCII string within the buffer.
	*/
	void trace_seq_bprintf(struct trace_seq s, const char fmt, const u32 *binary)
	{
	unsigned int save_len = s->seq.len;

	if (s->full)
	return;

	__trace_seq_init(s);

	seq_buf_bprintf(&s->seq, fmt, binary);

	/* If we can't write it all, don't bother writing anything */
	if (unlikely(seq_buf_has_overflowed(&s->seq))) {
	s->seq.len = save_len;
	s->full = 1;
	return;
	}
	}
	EXPORT_SYMBOL_GPL(trace_seq_bprintf);

	/**
	* trace_seq_puts - trace sequence printing of simple string
	* @s: trace sequence descriptor
	* @str: simple string to record
	*
	* The tracer may use either the sequence operations or its own
	* copy to user routines. This function records a simple string
	* into a special buffer (@s) for later retrieval by a sequencer
	* or other mechanism.
	*/
	void trace_seq_puts(struct trace_seq s, const char str)
	{
	unsigned int len = strlen(str);

	if (s->full)
	return;

	__trace_seq_init(s);

	if (len > TRACE_SEQ_BUF_LEFT(s)) {
	s->full = 1;
	return;
	}

	seq_buf_putmem(&s->seq, str, len);
	}
	EXPORT_SYMBOL_GPL(trace_seq_puts);

	/**
	* trace_seq_putc - trace sequence printing of simple character
	* @s: trace sequence descriptor
	* @c: simple character to record
	*
	* The tracer may use either the sequence operations or its own
	* copy to user routines. This function records a simple character
	* into a special buffer (@s) for later retrieval by a sequencer
	* or other mechanism.
	*/
	void trace_seq_putc(struct trace_seq *s, unsigned char c)
	{
	if (s->full)
	return;

	__trace_seq_init(s);

	if (TRACE_SEQ_BUF_LEFT(s) < 1) {
	s->full = 1;
	return;
	}

	seq_buf_putc(&s->seq, c);
	}
	EXPORT_SYMBOL_GPL(trace_seq_putc);

	/**
	* trace_seq_putmem - write raw data into the trace_seq buffer
	* @s: trace sequence descriptor
	* @mem: The raw memory to copy into the buffer
	* @len: The length of the raw memory to copy (in bytes)
	*
	* There may be cases where raw memory needs to be written into the
	* buffer and a strcpy() would not work. Using this function allows
	* for such cases.
	*/
	void trace_seq_putmem(struct trace_seq s, const void mem, unsigned int len)
	{
	if (s->full)
	return;

	__trace_seq_init(s);

	if (len > TRACE_SEQ_BUF_LEFT(s)) {
	s->full = 1;
	return;
	}

	seq_buf_putmem(&s->seq, mem, len);
	}
	EXPORT_SYMBOL_GPL(trace_seq_putmem);

	/**
	* trace_seq_putmem_hex - write raw memory into the buffer in ASCII hex
	* @s: trace sequence descriptor
	* @mem: The raw memory to write its hex ASCII representation of
	* @len: The length of the raw memory to copy (in bytes)
	*
	* This is similar to trace_seq_putmem() except instead of just copying the
	* raw memory into the buffer it writes its ASCII representation of it
	* in hex characters.
	*/
	void trace_seq_putmem_hex(struct trace_seq s, const void mem,
	unsigned int len)
	{
	unsigned int save_len = s->seq.len;

	if (s->full)
	return;

	__trace_seq_init(s);

	/* Each byte is represented by two chars */
	if (len * 2 > TRACE_SEQ_BUF_LEFT(s)) {
	s->full = 1;
	return;
	}

	/* The added spaces can still cause an overflow */
	seq_buf_putmem_hex(&s->seq, mem, len);

	if (unlikely(seq_buf_has_overflowed(&s->seq))) {
	s->seq.len = save_len;
	s->full = 1;
	return;
	}
	}
	EXPORT_SYMBOL_GPL(trace_seq_putmem_hex);

	/**
	* trace_seq_path - copy a path into the sequence buffer
	* @s: trace sequence descriptor
	* @path: path to write into the sequence buffer.
	*
	* Write a path name into the sequence buffer.
	*
	* Returns 1 if we successfully written all the contents to
	* the buffer.
	* Returns 0 if we the length to write is bigger than the
	* reserved buffer space. In this case, nothing gets written.
	*/
	int trace_seq_path(struct trace_seq s, const struct path path)
	{
	unsigned int save_len = s->seq.len;

	if (s->full)
	return 0;

	__trace_seq_init(s);

	if (TRACE_SEQ_BUF_LEFT(s) < 1) {
	s->full = 1;
	return 0;
	}

	seq_buf_path(&s->seq, path, "\n");

	if (unlikely(seq_buf_has_overflowed(&s->seq))) {
	s->seq.len = save_len;
	s->full = 1;
	return 0;
	}

	return 1;
	}
	EXPORT_SYMBOL_GPL(trace_seq_path);

	/**
	* trace_seq_to_user - copy the sequence buffer to user space
	* @s: trace sequence descriptor
	* @ubuf: The userspace memory location to copy to
	* @cnt: The amount to copy
	*
	* Copies the sequence buffer into the userspace memory pointed to
	* by @ubuf. It starts from the last read position (@s->readpos)
	* and writes up to @cnt characters or till it reaches the end of
	* the content in the buffer (@s->len), which ever comes first.
	*
	* On success, it returns a positive number of the number of bytes
	* it copied.
	*
	* On failure it returns -EBUSY if all of the content in the
	* sequence has been already read, which includes nothing in the
	* sequence (@s->len == @s->readpos).
	*
	* Returns -EFAULT if the copy to userspace fails.
	*/
	int trace_seq_to_user(struct trace_seq s, char __user ubuf, int cnt)
	{
	__trace_seq_init(s);
	return seq_buf_to_user(&s->seq, ubuf, cnt);
	}
	EXPORT_SYMBOL_GPL(trace_seq_to_user);

	int trace_seq_hex_dump(struct trace_seq s, const char prefix_str,
	int prefix_type, int rowsize, int groupsize,
	const void *buf, size_t len, bool ascii)
	{
	unsigned int save_len = s->seq.len;

	if (s->full)
	return 0;

	__trace_seq_init(s);

	if (TRACE_SEQ_BUF_LEFT(s) < 1) {
	s->full = 1;
	return 0;
	}

	seq_buf_hex_dump(&(s->seq), prefix_str,
	prefix_type, rowsize, groupsize,
	buf, len, ascii);

	if (unlikely(seq_buf_has_overflowed(&s->seq))) {
	s->seq.len = save_len;
	s->full = 1;
	return 0;
	}

	return 1;
	}
	EXPORT_SYMBOL(trace_seq_hex_dump);

	/*
	* trace_seq_acquire - acquire seq buffer with size len
	* @s: trace sequence descriptor
	* @len: size of buffer to be acquired
	*
	* acquire buffer with size of @len from trace_seq for output usage,
	* user can fill string into that buffer.
	*
	* Returns start address of acquired buffer.
	*
	* it allow multiple usage in one trace output function call.
	*/
	char trace_seq_acquire(struct trace_seq s, unsigned int len)
	{
	char *ret = trace_seq_buffer_ptr(s);

	if (!WARN_ON_ONCE(seq_buf_buffer_left(&s->seq) < len))
	seq_buf_commit(&s->seq, len);

	return ret;
	}
	EXPORT_SYMBOL(trace_seq_acquire);