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tracing: Clean up trace_seq.c

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For using trace_seq_*() functions in NMI context, I posted a patch to move
it to the lib/ directory. This caused Andrew Morton to take a look at the code.
He went through and gave a lot of comments about missing kernel doc,
inconsistent types for the save variable, mix match of EXPORT_SYMBOL_GPL()
and EXPORT_SYMBOL() as well as missing EXPORT_SYMBOL*()s. There were
a few comments about the way variables were being compared (int vs uint).

All these were good review comments and should be implemented regardless of
if trace_seq.c should be moved to lib/ or not.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (Red Hat) 2014-06-20 17:38:01 -04:00 committed by Steven Rostedt
parent 12306276fa
commit 36aabfff50
2 changed files with 185 additions and 42 deletions
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20
include/linux/trace_seq.h
View File

@ -38,14 +38,14 @@ int trace_seq_vprintf(struct trace_seq *s, const char *fmt, va_list args);
extern int
trace_seq_bprintf(struct trace_seq *s, const char *fmt, const u32 *binary);
extern int trace_print_seq(struct seq_file *m, struct trace_seq *s);
extern ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf,
size_t cnt);
extern int trace_seq_to_user(struct trace_seq *s, char __user *ubuf,
int cnt);
extern int trace_seq_puts(struct trace_seq *s, const char *str);
extern int trace_seq_putc(struct trace_seq *s, unsigned char c);
extern int trace_seq_putmem(struct trace_seq *s, const void *mem, size_t len);
extern int trace_seq_putmem(struct trace_seq *s, const void *mem, unsigned int len);
extern int trace_seq_putmem_hex(struct trace_seq *s, const void *mem,
size_t len);
extern void *trace_seq_reserve(struct trace_seq *s, size_t len);
unsigned int len);
extern void *trace_seq_reserve(struct trace_seq *s, unsigned int len);
extern int trace_seq_path(struct trace_seq *s, const struct path *path);
extern int trace_seq_bitmask(struct trace_seq *s, const unsigned long *maskp,
@ -73,8 +73,8 @@ static inline int trace_print_seq(struct seq_file *m, struct trace_seq *s)
{
return 0;
}
static inline ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf,
size_t cnt)
static inline int trace_seq_to_user(struct trace_seq *s, char __user *ubuf,
int cnt)
{
return 0;
}
@ -87,16 +87,16 @@ static inline int trace_seq_putc(struct trace_seq *s, unsigned char c)
return 0;
}
static inline int
trace_seq_putmem(struct trace_seq *s, const void *mem, size_t len)
trace_seq_putmem(struct trace_seq *s, const void *mem, unsigned int len)
{
return 0;
}
static inline int trace_seq_putmem_hex(struct trace_seq *s, const void *mem,
size_t len)
unsigned int len)
{
return 0;
}
static inline void *trace_seq_reserve(struct trace_seq *s, size_t len)
static inline void *trace_seq_reserve(struct trace_seq *s, unsigned int len)
{
return NULL;
}

207
kernel/trace/trace_seq.c
View File

@ -3,21 +3,55 @@
*
* 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)
{
int len = s->len >= PAGE_SIZE ? PAGE_SIZE - 1 : s->len;
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.
* seq_file buffer. This lets the caller try again or
* do something else with the contents.
*/
if (!ret)
trace_seq_init(s);
@ -30,19 +64,20 @@ int trace_print_seq(struct seq_file *m, struct trace_seq *s)
* @s: trace sequence descriptor
* @fmt: printf format string
*
* It returns 0 if the trace oversizes the buffer's free
* space, 1 otherwise.
*
* 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
* 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, ...)
int trace_seq_printf(struct trace_seq *s, const char *fmt, ...)
{
int len = (PAGE_SIZE - 1) - s->len;
unsigned int len = TRACE_SEQ_BUF_LEFT(s);
va_list ap;
int ret;
@ -66,21 +101,22 @@ trace_seq_printf(struct trace_seq *s, const char *fmt, ...)
EXPORT_SYMBOL_GPL(trace_seq_printf);
/**
* trace_seq_bitmask - put a list of longs as a bitmask print output
* 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
*
* It returns 0 if the trace oversizes the buffer's free
* space, 1 otherwise.
*
* 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)
int trace_seq_bitmask(struct trace_seq *s, const unsigned long *maskp,
int nmaskbits)
{
int len = (PAGE_SIZE - 1) - s->len;
unsigned int len = TRACE_SEQ_BUF_LEFT(s);
int ret;
if (s->full || !len)
@ -103,11 +139,12 @@ EXPORT_SYMBOL_GPL(trace_seq_bitmask);
* 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)
int trace_seq_vprintf(struct trace_seq *s, const char *fmt, va_list args)
{
int len = (PAGE_SIZE - 1) - s->len;
unsigned int len = TRACE_SEQ_BUF_LEFT(s);
int ret;
if (s->full || !len)
@ -127,9 +164,26 @@ trace_seq_vprintf(struct trace_seq *s, const char *fmt, va_list args)
}
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)
{
int len = (PAGE_SIZE - 1) - s->len;
unsigned int len = TRACE_SEQ_BUF_LEFT(s);
int ret;
if (s->full || !len)
@ -147,6 +201,7 @@ int trace_seq_bprintf(struct trace_seq *s, const char *fmt, const u32 *binary)
return len;
}
EXPORT_SYMBOL_GPL(trace_seq_bprintf);
/**
* trace_seq_puts - trace sequence printing of simple string
@ -157,15 +212,17 @@ int trace_seq_bprintf(struct trace_seq *s, const char *fmt, const u32 *binary)
* 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)
{
int len = strlen(str);
unsigned int len = strlen(str);
if (s->full)
return 0;
if (len > ((PAGE_SIZE - 1) - s->len)) {
if (len > TRACE_SEQ_BUF_LEFT(s)) {
s->full = 1;
return 0;
}
@ -175,13 +232,26 @@ int trace_seq_puts(struct trace_seq *s, const char *str)
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 (s->len >= (PAGE_SIZE - 1)) {
if (TRACE_SEQ_BUF_LEFT(s) < 1) {
s->full = 1;
return 0;
}
@ -190,14 +260,26 @@ int trace_seq_putc(struct trace_seq *s, unsigned char c)
return 1;
}
EXPORT_SYMBOL(trace_seq_putc);
EXPORT_SYMBOL_GPL(trace_seq_putc);
int trace_seq_putmem(struct trace_seq *s, const void *mem, size_t len)
/**
* 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 > ((PAGE_SIZE - 1) - s->len)) {
if (len > TRACE_SEQ_BUF_LEFT(s)) {
s->full = 1;
return 0;
}
@ -207,10 +289,24 @@ int trace_seq_putmem(struct trace_seq *s, const void *mem, size_t len)
return len;
}
EXPORT_SYMBOL_GPL(trace_seq_putmem);
#define HEX_CHARS (MAX_MEMHEX_BYTES*2 + 1)
int trace_seq_putmem_hex(struct trace_seq *s, const void *mem, size_t len)
/**
* 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;
@ -231,15 +327,27 @@ int trace_seq_putmem_hex(struct trace_seq *s, const void *mem, size_t len)
return trace_seq_putmem(s, hex, j);
}
EXPORT_SYMBOL_GPL(trace_seq_putmem_hex);
void *trace_seq_reserve(struct trace_seq *s, size_t len)
/**
* trace_seq_reserve - reserve space on the sequence buffer
* @s: trace sequence descriptor
* @len: The amount to reserver.
*
* If for some reason there is a need to save some space on the
* buffer to fill in later, this function is used for that purpose.
* The given length will be reserved and the pointer to that
* location on the buffer is returned, unless there is not enough
* buffer left to hold the given length then NULL is returned.
*/
void *trace_seq_reserve(struct trace_seq *s, unsigned int len)
{
void *ret;
if (s->full)
return NULL;
if (len > ((PAGE_SIZE - 1) - s->len)) {
if (len > TRACE_SEQ_BUF_LEFT(s)) {
s->full = 1;
return NULL;
}
@ -249,7 +357,20 @@ void *trace_seq_reserve(struct trace_seq *s, size_t len)
return ret;
}
EXPORT_SYMBOL_GPL(trace_seq_reserve);
/**
* 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;
@ -257,7 +378,7 @@ int trace_seq_path(struct trace_seq *s, const struct path *path)
if (s->full)
return 0;
if (s->len >= (PAGE_SIZE - 1)) {
if (TRACE_SEQ_BUF_LEFT(s) < 1) {
s->full = 1;
return 0;
}
@ -277,8 +398,29 @@ int trace_seq_path(struct trace_seq *s, const struct path *path)
s->full = 1;
return 0;
}
EXPORT_SYMBOL_GPL(trace_seq_path);
ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf, size_t cnt)
/**
* 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;
@ -301,3 +443,4 @@ ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf, size_t cnt)
s->readpos += cnt;
return cnt;
}
EXPORT_SYMBOL_GPL(trace_seq_to_user);