/* * trace_seq.c * * Copyright (C) 2008-2014 Red Hat Inc, Steven Rostedt * * 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 #include #include /* 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) min((s)->seq.len, (unsigned int)(PAGE_SIZE - 1)) /* * 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_bitmask(&s->seq, maskp, nmaskbits); 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);