- 根目录:
- kernel
- trace
- trace_seq.c
/*
* 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) seq_buf_buffer_left(&(s)->seq)
/* How much buffer is written? */
#define TRACE_SEQ_BUF_USED(s) seq_buf_used(&(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 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.
*/
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 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.
*/
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 charater
* 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 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)
{
__trace_seq_init(s);
return seq_buf_to_user(&s->seq, ubuf, cnt);
}
EXPORT_SYMBOL_GPL(trace_seq_to_user);