lib/seq_buf.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * seq_buf.c
  *
  * Copyright (C) 2014 Red Hat Inc, Steven Rostedt <srostedt@redhat.com>
  *
  * The seq_buf 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 seq_buf must be initialized with seq_buf_init().
  * This will set up the counters within the descriptor. You can call
  * seq_buf_init() more than once to reset the seq_buf to start
  * from scratch.
  */
 #include <linux/uaccess.h>
 #include <linux/seq_file.h>
 #include <linux/seq_buf.h>

 /**
  * seq_buf_can_fit - can the new data fit in the current buffer?
  * @s: the seq_buf descriptor
  * @len: The length to see if it can fit in the current buffer
  *
  * Returns true if there's enough unused space in the seq_buf buffer
  * to fit the amount of new data according to @len.
  */
 static bool seq_buf_can_fit(struct seq_buf *s, size_t len)
 {
 	return s->len + len <= s->size;
 }

 /**
  * seq_buf_print_seq - move the contents of seq_buf into a seq_file
  * @m: the seq_file descriptor that is the destination
  * @s: the seq_buf descriptor that is the source.
  *
  * Returns zero on success, non zero otherwise
  */
 int seq_buf_print_seq(struct seq_file *m, struct seq_buf *s)
 {
 	unsigned int len = seq_buf_used(s);

 	return seq_write(m, s->buffer, len);
 }

 /**
  * seq_buf_vprintf - sequence printing of information.
  * @s: seq_buf descriptor
  * @fmt: printf format string
  * @args: va_list of arguments from a printf() type function
  *
  * Writes a vnprintf() format into the sequencce buffer.
  *
  * Returns zero on success, -1 on overflow.
  */
 int seq_buf_vprintf(struct seq_buf *s, const char *fmt, va_list args)
 {
 	int len;

 	WARN_ON(s->size == 0);

 	if (s->len < s->size) {
 		len = vsnprintf(s->buffer + s->len, s->size - s->len, fmt, args);
 		if (s->len + len < s->size) {
 			s->len += len;
 			return 0;
 		}
 	}
 	seq_buf_set_overflow(s);
 	return -1;
 }

 /**
  * seq_buf_printf - sequence printing of information
  * @s: seq_buf descriptor
  * @fmt: printf format string
  *
  * Writes a printf() format into the sequence buffer.
  *
  * Returns zero on success, -1 on overflow.
  */
 int seq_buf_printf(struct seq_buf *s, const char *fmt, ...)
 {
 	va_list ap;
 	int ret;

 	va_start(ap, fmt);
 	ret = seq_buf_vprintf(s, fmt, ap);
 	va_end(ap);

 	return ret;
 }

 #ifdef CONFIG_BINARY_PRINTF
 /**
  * seq_buf_bprintf - Write the printf string from binary arguments
  * @s: seq_buf 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.
  *
  * Returns zero on success, -1 on overflow.
  */
 int seq_buf_bprintf(struct seq_buf *s, const char *fmt, const u32 *binary)
 {
 	unsigned int len = seq_buf_buffer_left(s);
 	int ret;

 	WARN_ON(s->size == 0);

 	if (s->len < s->size) {
 		ret = bstr_printf(s->buffer + s->len, len, fmt, binary);
 		if (s->len + ret < s->size) {
 			s->len += ret;
 			return 0;
 		}
 	}
 	seq_buf_set_overflow(s);
 	return -1;
 }
 #endif /* CONFIG_BINARY_PRINTF */

 /**
  * seq_buf_puts - sequence printing of simple string
  * @s: seq_buf descriptor
  * @str: simple string to record
  *
  * Copy a simple string into the sequence buffer.
  *
  * Returns zero on success, -1 on overflow
  */
 int seq_buf_puts(struct seq_buf *s, const char *str)
 {
 	size_t len = strlen(str);

 	WARN_ON(s->size == 0);

 	/* Add 1 to len for the trailing null byte which must be there */
 	len += 1;

 	if (seq_buf_can_fit(s, len)) {
 		memcpy(s->buffer + s->len, str, len);
 		/* Don't count the trailing null byte against the capacity */
 		s->len += len - 1;
 		return 0;
 	}
 	seq_buf_set_overflow(s);
 	return -1;
 }

 /**
  * seq_buf_putc - sequence printing of simple character
  * @s: seq_buf descriptor
  * @c: simple character to record
  *
  * Copy a single character into the sequence buffer.
  *
  * Returns zero on success, -1 on overflow
  */
 int seq_buf_putc(struct seq_buf *s, unsigned char c)
 {
 	WARN_ON(s->size == 0);

 	if (seq_buf_can_fit(s, 1)) {
 		s->buffer[s->len++] = c;
 		return 0;
 	}
 	seq_buf_set_overflow(s);
 	return -1;
 }

 /**
  * seq_buf_putmem - write raw data into the sequenc buffer
  * @s: seq_buf 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.
  *
  * Returns zero on success, -1 on overflow
  */
 int seq_buf_putmem(struct seq_buf *s, const void *mem, unsigned int len)
 {
 	WARN_ON(s->size == 0);

 	if (seq_buf_can_fit(s, len)) {
 		memcpy(s->buffer + s->len, mem, len);
 		s->len += len;
 		return 0;
 	}
 	seq_buf_set_overflow(s);
 	return -1;
 }

 #define MAX_MEMHEX_BYTES	8U
 #define HEX_CHARS		(MAX_MEMHEX_BYTES*2 + 1)

 /**
  * seq_buf_putmem_hex - write raw memory into the buffer in ASCII hex
  * @s: seq_buf 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 seq_buf_putmem() except instead of just copying the
  * raw memory into the buffer it writes its ASCII representation of it
  * in hex characters.
  *
  * Returns zero on success, -1 on overflow
  */
 int seq_buf_putmem_hex(struct seq_buf *s, const void *mem,
 		       unsigned int len)
 {
 	unsigned char hex[HEX_CHARS];
 	const unsigned char *data = mem;
 	unsigned int start_len;
 	int i, j;

 	WARN_ON(s->size == 0);

 	while (len) {
 		start_len = min(len, HEX_CHARS - 1);
 #ifdef __BIG_ENDIAN
 		for (i = 0, j = 0; i < start_len; i++) {
 #else
 		for (i = start_len-1, j = 0; i >= 0; i--) {
 #endif
 			hex[j++] = hex_asc_hi(data[i]);
 			hex[j++] = hex_asc_lo(data[i]);
 		}
 		if (WARN_ON_ONCE(j == 0 || j/2 > len))
 			break;

 		/* j increments twice per loop */
 		len -= j / 2;
 		hex[j++] = ' ';

 		seq_buf_putmem(s, hex, j);
 		if (seq_buf_has_overflowed(s))
 			return -1;
 	}
 	return 0;
 }

 /**
  * seq_buf_path - copy a path into the sequence buffer
  * @s: seq_buf descriptor
  * @path: path to write into the sequence buffer.
  * @esc: set of characters to escape in the output
  *
  * Write a path name into the sequence buffer.
  *
  * Returns the number of written bytes on success, -1 on overflow
  */
 int seq_buf_path(struct seq_buf *s, const struct path *path, const char *esc)
 {
 	char *buf;
 	size_t size = seq_buf_get_buf(s, &buf);
 	int res = -1;

 	WARN_ON(s->size == 0);

 	if (size) {
 		char *p = d_path(path, buf, size);
 		if (!IS_ERR(p)) {
 			char *end = mangle_path(buf, p, esc);
 			if (end)
 				res = end - buf;
 		}
 	}
 	seq_buf_commit(s, res);

 	return res;
 }

 /**
  * seq_buf_to_user - copy the squence buffer to user space
  * @s: seq_buf 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 seq_buf_to_user(struct seq_buf *s, char __user *ubuf, int cnt)
 {
 	int len;
 	int ret;

 	if (!cnt)
 		return 0;

 	len = seq_buf_used(s);

 	if (len <= s->readpos)
 		return -EBUSY;

 	len -= s->readpos;
 	if (cnt > len)
 		cnt = len;
 	ret = copy_to_user(ubuf, s->buffer + s->readpos, cnt);
 	if (ret == cnt)
 		return -EFAULT;

 	cnt -= ret;

 	s->readpos += cnt;
 	return cnt;
 }
	// SPDX-License-Identifier: GPL-2.0
	/*
	* seq_buf.c
	*
	* Copyright (C) 2014 Red Hat Inc, Steven Rostedt <srostedt@redhat.com>
	*
	* The seq_buf 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 seq_buf must be initialized with seq_buf_init().
	* This will set up the counters within the descriptor. You can call
	* seq_buf_init() more than once to reset the seq_buf to start
	* from scratch.
	*/
	#include <linux/uaccess.h>
	#include <linux/seq_file.h>
	#include <linux/seq_buf.h>

	/**
	* seq_buf_can_fit - can the new data fit in the current buffer?
	* @s: the seq_buf descriptor
	* @len: The length to see if it can fit in the current buffer
	*
	* Returns true if there's enough unused space in the seq_buf buffer
	* to fit the amount of new data according to @len.
	*/
	static bool seq_buf_can_fit(struct seq_buf *s, size_t len)
	{
	return s->len + len <= s->size;
	}

	/**
	* seq_buf_print_seq - move the contents of seq_buf into a seq_file
	* @m: the seq_file descriptor that is the destination
	* @s: the seq_buf descriptor that is the source.
	*
	* Returns zero on success, non zero otherwise
	*/
	int seq_buf_print_seq(struct seq_file m, struct seq_buf s)
	{
	unsigned int len = seq_buf_used(s);

	return seq_write(m, s->buffer, len);
	}

	/**
	* seq_buf_vprintf - sequence printing of information.
	* @s: seq_buf descriptor
	* @fmt: printf format string
	* @args: va_list of arguments from a printf() type function
	*
	* Writes a vnprintf() format into the sequencce buffer.
	*
	* Returns zero on success, -1 on overflow.
	*/
	int seq_buf_vprintf(struct seq_buf s, const char fmt, va_list args)
	{
	int len;

	WARN_ON(s->size == 0);

	if (s->len < s->size) {
	len = vsnprintf(s->buffer + s->len, s->size - s->len, fmt, args);
	if (s->len + len < s->size) {
	s->len += len;
	return 0;
	}
	}
	seq_buf_set_overflow(s);
	return -1;
	}

	/**
	* seq_buf_printf - sequence printing of information
	* @s: seq_buf descriptor
	* @fmt: printf format string
	*
	* Writes a printf() format into the sequence buffer.
	*
	* Returns zero on success, -1 on overflow.
	*/
	int seq_buf_printf(struct seq_buf s, const char fmt, ...)
	{
	va_list ap;
	int ret;

	va_start(ap, fmt);
	ret = seq_buf_vprintf(s, fmt, ap);
	va_end(ap);

	return ret;
	}

	#ifdef CONFIG_BINARY_PRINTF
	/**
	* seq_buf_bprintf - Write the printf string from binary arguments
	* @s: seq_buf 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.
	*
	* Returns zero on success, -1 on overflow.
	*/
	int seq_buf_bprintf(struct seq_buf s, const char fmt, const u32 *binary)
	{
	unsigned int len = seq_buf_buffer_left(s);
	int ret;

	WARN_ON(s->size == 0);

	if (s->len < s->size) {
	ret = bstr_printf(s->buffer + s->len, len, fmt, binary);
	if (s->len + ret < s->size) {
	s->len += ret;
	return 0;
	}
	}
	seq_buf_set_overflow(s);
	return -1;
	}
	#endif /* CONFIG_BINARY_PRINTF */

	/**
	* seq_buf_puts - sequence printing of simple string
	* @s: seq_buf descriptor
	* @str: simple string to record
	*
	* Copy a simple string into the sequence buffer.
	*
	* Returns zero on success, -1 on overflow
	*/
	int seq_buf_puts(struct seq_buf s, const char str)
	{
	size_t len = strlen(str);

	WARN_ON(s->size == 0);

	/* Add 1 to len for the trailing null byte which must be there */
	len += 1;

	if (seq_buf_can_fit(s, len)) {
	memcpy(s->buffer + s->len, str, len);
	/* Don't count the trailing null byte against the capacity */
	s->len += len - 1;
	return 0;
	}
	seq_buf_set_overflow(s);
	return -1;
	}

	/**
	* seq_buf_putc - sequence printing of simple character
	* @s: seq_buf descriptor
	* @c: simple character to record
	*
	* Copy a single character into the sequence buffer.
	*
	* Returns zero on success, -1 on overflow
	*/
	int seq_buf_putc(struct seq_buf *s, unsigned char c)
	{
	WARN_ON(s->size == 0);

	if (seq_buf_can_fit(s, 1)) {
	s->buffer[s->len++] = c;
	return 0;
	}
	seq_buf_set_overflow(s);
	return -1;
	}

	/**
	* seq_buf_putmem - write raw data into the sequenc buffer
	* @s: seq_buf 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.
	*
	* Returns zero on success, -1 on overflow
	*/
	int seq_buf_putmem(struct seq_buf s, const void mem, unsigned int len)
	{
	WARN_ON(s->size == 0);

	if (seq_buf_can_fit(s, len)) {
	memcpy(s->buffer + s->len, mem, len);
	s->len += len;
	return 0;
	}
	seq_buf_set_overflow(s);
	return -1;
	}

	#define MAX_MEMHEX_BYTES 8U
	#define HEX_CHARS (MAX_MEMHEX_BYTES*2 + 1)

	/**
	* seq_buf_putmem_hex - write raw memory into the buffer in ASCII hex
	* @s: seq_buf 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 seq_buf_putmem() except instead of just copying the
	* raw memory into the buffer it writes its ASCII representation of it
	* in hex characters.
	*
	* Returns zero on success, -1 on overflow
	*/
	int seq_buf_putmem_hex(struct seq_buf s, const void mem,
	unsigned int len)
	{
	unsigned char hex[HEX_CHARS];
	const unsigned char *data = mem;
	unsigned int start_len;
	int i, j;

	WARN_ON(s->size == 0);

	while (len) {
	start_len = min(len, HEX_CHARS - 1);
	#ifdef __BIG_ENDIAN
	for (i = 0, j = 0; i < start_len; i++) {
	#else
	for (i = start_len-1, j = 0; i >= 0; i--) {
	#endif
	hex[j++] = hex_asc_hi(data[i]);
	hex[j++] = hex_asc_lo(data[i]);
	}
	if (WARN_ON_ONCE(j == 0 \|\| j/2 > len))
	break;

	/* j increments twice per loop */
	len -= j / 2;
	hex[j++] = ' ';

	seq_buf_putmem(s, hex, j);
	if (seq_buf_has_overflowed(s))
	return -1;
	}
	return 0;
	}

	/**
	* seq_buf_path - copy a path into the sequence buffer
	* @s: seq_buf descriptor
	* @path: path to write into the sequence buffer.
	* @esc: set of characters to escape in the output
	*
	* Write a path name into the sequence buffer.
	*
	* Returns the number of written bytes on success, -1 on overflow
	*/
	int seq_buf_path(struct seq_buf s, const struct path path, const char *esc)
	{
	char *buf;
	size_t size = seq_buf_get_buf(s, &buf);
	int res = -1;

	WARN_ON(s->size == 0);

	if (size) {
	char *p = d_path(path, buf, size);
	if (!IS_ERR(p)) {
	char *end = mangle_path(buf, p, esc);
	if (end)
	res = end - buf;
	}
	}
	seq_buf_commit(s, res);

	return res;
	}

	/**
	* seq_buf_to_user - copy the squence buffer to user space
	* @s: seq_buf 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 seq_buf_to_user(struct seq_buf s, char __user ubuf, int cnt)
	{
	int len;
	int ret;

	if (!cnt)
	return 0;

	len = seq_buf_used(s);

	if (len <= s->readpos)
	return -EBUSY;

	len -= s->readpos;
	if (cnt > len)
	cnt = len;
	ret = copy_to_user(ubuf, s->buffer + s->readpos, cnt);
	if (ret == cnt)
	return -EFAULT;

	cnt -= ret;

	s->readpos += cnt;
	return cnt;
	}