378 lines
9.9 KiB
C
378 lines
9.9 KiB
C
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/*
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* trace_seq.c
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*
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* Copyright (C) 2008-2014 Red Hat Inc, Steven Rostedt <srostedt@redhat.com>
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*
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* The trace_seq is a handy tool that allows you to pass a descriptor around
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* to a buffer that other functions can write to. It is similar to the
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* seq_file functionality but has some differences.
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*
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* To use it, the trace_seq must be initialized with trace_seq_init().
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* This will set up the counters within the descriptor. You can call
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* trace_seq_init() more than once to reset the trace_seq to start
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* from scratch.
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*
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* The buffer size is currently PAGE_SIZE, although it may become dynamic
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* in the future.
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*
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* A write to the buffer will either succed or fail. That is, unlike
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* sprintf() there will not be a partial write (well it may write into
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* the buffer but it wont update the pointers). This allows users to
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* try to write something into the trace_seq buffer and if it fails
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* they can flush it and try again.
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*
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*/
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#include <linux/uaccess.h>
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#include <linux/seq_file.h>
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#include <linux/trace_seq.h>
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/* How much buffer is left on the trace_seq? */
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#define TRACE_SEQ_BUF_LEFT(s) seq_buf_buffer_left(&(s)->seq)
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/* How much buffer is written? */
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#define TRACE_SEQ_BUF_USED(s) seq_buf_used(&(s)->seq)
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/*
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* trace_seq should work with being initialized with 0s.
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*/
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static inline void __trace_seq_init(struct trace_seq *s)
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{
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if (unlikely(!s->seq.size))
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trace_seq_init(s);
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}
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/**
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* trace_print_seq - move the contents of trace_seq into a seq_file
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* @m: the seq_file descriptor that is the destination
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* @s: the trace_seq descriptor that is the source.
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*
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* Returns 0 on success and non zero on error. If it succeeds to
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* write to the seq_file it will reset the trace_seq, otherwise
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* it does not modify the trace_seq to let the caller try again.
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*/
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int trace_print_seq(struct seq_file *m, struct trace_seq *s)
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{
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int ret;
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__trace_seq_init(s);
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ret = seq_buf_print_seq(m, &s->seq);
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/*
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* Only reset this buffer if we successfully wrote to the
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* seq_file buffer. This lets the caller try again or
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* do something else with the contents.
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*/
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if (!ret)
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trace_seq_init(s);
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return ret;
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}
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/**
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* trace_seq_printf - sequence printing of trace information
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* @s: trace sequence descriptor
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* @fmt: printf format string
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*
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* The tracer may use either sequence operations or its own
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* copy to user routines. To simplify formating of a trace
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* trace_seq_printf() is used to store strings into a special
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* buffer (@s). Then the output may be either used by
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* the sequencer or pulled into another buffer.
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*/
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void trace_seq_printf(struct trace_seq *s, const char *fmt, ...)
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{
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unsigned int save_len = s->seq.len;
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va_list ap;
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if (s->full)
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return;
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__trace_seq_init(s);
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va_start(ap, fmt);
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seq_buf_vprintf(&s->seq, fmt, ap);
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va_end(ap);
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/* If we can't write it all, don't bother writing anything */
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if (unlikely(seq_buf_has_overflowed(&s->seq))) {
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s->seq.len = save_len;
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s->full = 1;
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}
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}
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EXPORT_SYMBOL_GPL(trace_seq_printf);
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/**
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* trace_seq_bitmask - write a bitmask array in its ASCII representation
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* @s: trace sequence descriptor
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* @maskp: points to an array of unsigned longs that represent a bitmask
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* @nmaskbits: The number of bits that are valid in @maskp
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*
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* Writes a ASCII representation of a bitmask string into @s.
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*/
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void trace_seq_bitmask(struct trace_seq *s, const unsigned long *maskp,
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int nmaskbits)
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{
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unsigned int save_len = s->seq.len;
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if (s->full)
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return;
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__trace_seq_init(s);
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seq_buf_printf(&s->seq, "%*pb", nmaskbits, maskp);
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if (unlikely(seq_buf_has_overflowed(&s->seq))) {
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s->seq.len = save_len;
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s->full = 1;
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}
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}
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EXPORT_SYMBOL_GPL(trace_seq_bitmask);
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/**
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* trace_seq_vprintf - sequence printing of trace information
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* @s: trace sequence descriptor
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* @fmt: printf format string
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*
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* The tracer may use either sequence operations or its own
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* copy to user routines. To simplify formating of a trace
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* trace_seq_printf is used to store strings into a special
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* buffer (@s). Then the output may be either used by
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* the sequencer or pulled into another buffer.
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*/
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void trace_seq_vprintf(struct trace_seq *s, const char *fmt, va_list args)
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{
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unsigned int save_len = s->seq.len;
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if (s->full)
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return;
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__trace_seq_init(s);
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seq_buf_vprintf(&s->seq, fmt, args);
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/* If we can't write it all, don't bother writing anything */
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if (unlikely(seq_buf_has_overflowed(&s->seq))) {
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s->seq.len = save_len;
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s->full = 1;
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}
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}
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EXPORT_SYMBOL_GPL(trace_seq_vprintf);
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/**
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* trace_seq_bprintf - Write the printf string from binary arguments
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* @s: trace sequence descriptor
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* @fmt: The format string for the @binary arguments
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* @binary: The binary arguments for @fmt.
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*
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* When recording in a fast path, a printf may be recorded with just
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* saving the format and the arguments as they were passed to the
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* function, instead of wasting cycles converting the arguments into
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* ASCII characters. Instead, the arguments are saved in a 32 bit
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* word array that is defined by the format string constraints.
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*
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* This function will take the format and the binary array and finish
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* the conversion into the ASCII string within the buffer.
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*/
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void trace_seq_bprintf(struct trace_seq *s, const char *fmt, const u32 *binary)
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{
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unsigned int save_len = s->seq.len;
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if (s->full)
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return;
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__trace_seq_init(s);
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seq_buf_bprintf(&s->seq, fmt, binary);
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/* If we can't write it all, don't bother writing anything */
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if (unlikely(seq_buf_has_overflowed(&s->seq))) {
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s->seq.len = save_len;
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s->full = 1;
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return;
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}
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}
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EXPORT_SYMBOL_GPL(trace_seq_bprintf);
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/**
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* trace_seq_puts - trace sequence printing of simple string
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* @s: trace sequence descriptor
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* @str: simple string to record
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*
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* The tracer may use either the sequence operations or its own
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* copy to user routines. This function records a simple string
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* into a special buffer (@s) for later retrieval by a sequencer
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* or other mechanism.
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*/
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void trace_seq_puts(struct trace_seq *s, const char *str)
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{
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unsigned int len = strlen(str);
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if (s->full)
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return;
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__trace_seq_init(s);
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if (len > TRACE_SEQ_BUF_LEFT(s)) {
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s->full = 1;
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return;
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}
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seq_buf_putmem(&s->seq, str, len);
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}
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EXPORT_SYMBOL_GPL(trace_seq_puts);
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/**
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* trace_seq_putc - trace sequence printing of simple character
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* @s: trace sequence descriptor
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* @c: simple character to record
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*
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* The tracer may use either the sequence operations or its own
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* copy to user routines. This function records a simple charater
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* into a special buffer (@s) for later retrieval by a sequencer
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* or other mechanism.
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*/
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void trace_seq_putc(struct trace_seq *s, unsigned char c)
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{
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if (s->full)
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return;
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__trace_seq_init(s);
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if (TRACE_SEQ_BUF_LEFT(s) < 1) {
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s->full = 1;
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return;
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}
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seq_buf_putc(&s->seq, c);
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}
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EXPORT_SYMBOL_GPL(trace_seq_putc);
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/**
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* trace_seq_putmem - write raw data into the trace_seq buffer
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* @s: trace sequence descriptor
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* @mem: The raw memory to copy into the buffer
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* @len: The length of the raw memory to copy (in bytes)
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*
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* There may be cases where raw memory needs to be written into the
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* buffer and a strcpy() would not work. Using this function allows
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* for such cases.
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*/
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void trace_seq_putmem(struct trace_seq *s, const void *mem, unsigned int len)
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{
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if (s->full)
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return;
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__trace_seq_init(s);
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if (len > TRACE_SEQ_BUF_LEFT(s)) {
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s->full = 1;
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return;
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}
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seq_buf_putmem(&s->seq, mem, len);
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}
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EXPORT_SYMBOL_GPL(trace_seq_putmem);
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/**
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* trace_seq_putmem_hex - write raw memory into the buffer in ASCII hex
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* @s: trace sequence descriptor
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* @mem: The raw memory to write its hex ASCII representation of
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* @len: The length of the raw memory to copy (in bytes)
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*
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* This is similar to trace_seq_putmem() except instead of just copying the
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* raw memory into the buffer it writes its ASCII representation of it
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* in hex characters.
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*/
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void trace_seq_putmem_hex(struct trace_seq *s, const void *mem,
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unsigned int len)
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{
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unsigned int save_len = s->seq.len;
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if (s->full)
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return;
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__trace_seq_init(s);
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/* Each byte is represented by two chars */
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if (len * 2 > TRACE_SEQ_BUF_LEFT(s)) {
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s->full = 1;
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return;
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}
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/* The added spaces can still cause an overflow */
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seq_buf_putmem_hex(&s->seq, mem, len);
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if (unlikely(seq_buf_has_overflowed(&s->seq))) {
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s->seq.len = save_len;
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s->full = 1;
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return;
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}
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}
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EXPORT_SYMBOL_GPL(trace_seq_putmem_hex);
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/**
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* trace_seq_path - copy a path into the sequence buffer
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* @s: trace sequence descriptor
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* @path: path to write into the sequence buffer.
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*
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* Write a path name into the sequence buffer.
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*
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* Returns 1 if we successfully written all the contents to
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* the buffer.
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* Returns 0 if we the length to write is bigger than the
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* reserved buffer space. In this case, nothing gets written.
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*/
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int trace_seq_path(struct trace_seq *s, const struct path *path)
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{
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unsigned int save_len = s->seq.len;
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if (s->full)
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return 0;
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__trace_seq_init(s);
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if (TRACE_SEQ_BUF_LEFT(s) < 1) {
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s->full = 1;
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return 0;
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}
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seq_buf_path(&s->seq, path, "\n");
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if (unlikely(seq_buf_has_overflowed(&s->seq))) {
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s->seq.len = save_len;
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s->full = 1;
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return 0;
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}
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return 1;
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}
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EXPORT_SYMBOL_GPL(trace_seq_path);
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/**
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* trace_seq_to_user - copy the squence buffer to user space
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* @s: trace sequence descriptor
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* @ubuf: The userspace memory location to copy to
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* @cnt: The amount to copy
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*
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* Copies the sequence buffer into the userspace memory pointed to
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* by @ubuf. It starts from the last read position (@s->readpos)
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* and writes up to @cnt characters or till it reaches the end of
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* the content in the buffer (@s->len), which ever comes first.
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*
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* On success, it returns a positive number of the number of bytes
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* it copied.
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*
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* On failure it returns -EBUSY if all of the content in the
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* sequence has been already read, which includes nothing in the
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* sequenc (@s->len == @s->readpos).
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*
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* Returns -EFAULT if the copy to userspace fails.
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*/
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int trace_seq_to_user(struct trace_seq *s, char __user *ubuf, int cnt)
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{
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__trace_seq_init(s);
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return seq_buf_to_user(&s->seq, ubuf, cnt);
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}
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EXPORT_SYMBOL_GPL(trace_seq_to_user);
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