/* * 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 succed 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) ((PAGE_SIZE - 1) - (s)->len) /* How much buffer is written? */#define TRACE_SEQ_BUF_USED(s) min((s)->len, (unsigned int)(PAGE_SIZE - 1)) /** * 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){	unsigned int len = TRACE_SEQ_BUF_USED(s);	int ret; 	ret = seq_write(m, s->buffer, len); 	/*	 * 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 formating 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. * * 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_printf(struct trace_seq *s, const char *fmt, ...){	unsigned int len = TRACE_SEQ_BUF_LEFT(s);	va_list ap;	int ret; 	if (s->full || !len)		return 0; 	va_start(ap, fmt);	ret = vsnprintf(s->buffer + s->len, len, fmt, ap);	va_end(ap); 	/* If we can't write it all, don't bother writing anything */	if (ret >= len) {		s->full = 1;		return 0;	} 	s->len += ret; 	return 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. * * 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_bitmask(struct trace_seq *s, const unsigned long *maskp,		      int nmaskbits){	unsigned int len = TRACE_SEQ_BUF_LEFT(s);	int ret; 	if (s->full || !len)		return 0; 	ret = bitmap_scnprintf(s->buffer, len, maskp, nmaskbits);	s->len += ret; 	return 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 formating 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. * * Returns how much it wrote to the buffer. */int trace_seq_vprintf(struct trace_seq *s, const char *fmt, va_list args){	unsigned int len = TRACE_SEQ_BUF_LEFT(s);	int ret; 	if (s->full || !len)		return 0; 	ret = vsnprintf(s->buffer + s->len, len, fmt, args); 	/* If we can't write it all, don't bother writing anything */	if (ret >= len) {		s->full = 1;		return 0;	} 	s->len += ret; 	return len;}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. * * Returns how much it wrote to the buffer. */int trace_seq_bprintf(struct trace_seq *s, const char *fmt, const u32 *binary){	unsigned int len = TRACE_SEQ_BUF_LEFT(s);	int ret; 	if (s->full || !len)		return 0; 	ret = bstr_printf(s->buffer + s->len, len, fmt, binary); 	/* If we can't write it all, don't bother writing anything */	if (ret >= len) {		s->full = 1;		return 0;	} 	s->len += ret; 	return len;}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. * * Returns how much it wrote to the buffer. */int trace_seq_puts(struct trace_seq *s, const char *str){	unsigned int len = strlen(str); 	if (s->full)		return 0; 	if (len > TRACE_SEQ_BUF_LEFT(s)) {		s->full = 1;		return 0;	} 	memcpy(s->buffer + s->len, str, len);	s->len += len; 	return 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 charater * into a special buffer (@s) for later retrieval by a sequencer * or other mechanism. * * Returns how much it wrote to the buffer. */int trace_seq_putc(struct trace_seq *s, unsigned char c){	if (s->full)		return 0; 	if (TRACE_SEQ_BUF_LEFT(s) < 1) {		s->full = 1;		return 0;	} 	s->buffer[s->len++] = c; 	return 1;}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. * * Returns how much it wrote to the buffer. */int trace_seq_putmem(struct trace_seq *s, const void *mem, unsigned int len){	if (s->full)		return 0; 	if (len > TRACE_SEQ_BUF_LEFT(s)) {		s->full = 1;		return 0;	} 	memcpy(s->buffer + s->len, mem, len);	s->len += len; 	return len;}EXPORT_SYMBOL_GPL(trace_seq_putmem); #define MAX_MEMHEX_BYTES	8U#define HEX_CHARS		(MAX_MEMHEX_BYTES*2 + 1) /** * 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. * * Returns how much it wrote to the buffer. */int trace_seq_putmem_hex(struct trace_seq *s, const void *mem,			 unsigned int len){	unsigned char hex[HEX_CHARS];	const unsigned char *data = mem;	unsigned int start_len;	int i, j;	int cnt = 0; 	if (s->full)		return 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++] = ' '; 		cnt += trace_seq_putmem(s, hex, j);	}	return cnt;}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 char *p; 	if (s->full)		return 0; 	if (TRACE_SEQ_BUF_LEFT(s) < 1) {		s->full = 1;		return 0;	} 	p = d_path(path, s->buffer + s->len, PAGE_SIZE - s->len);	if (!IS_ERR(p)) {		p = mangle_path(s->buffer + s->len, p, "\n");		if (p) {			s->len = p - s->buffer;			return 1;		}	} else {		s->buffer[s->len++] = '?';		return 1;	} 	s->full = 1;	return 0;}EXPORT_SYMBOL_GPL(trace_seq_path); /** * trace_seq_to_user - copy the squence 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 * sequenc (@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){	int len;	int ret; 	if (!cnt)		return 0; 	if (s->len <= s->readpos)		return -EBUSY; 	len = s->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;}EXPORT_SYMBOL_GPL(trace_seq_to_user);