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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_TRACE_PRINTK_H
#define _LINUX_TRACE_PRINTK_H
#include <linux/compiler_attributes.h>
#include <linux/instruction_pointer.h>
#include <linux/stddef.h>
#include <linux/stringify.h>
/*
* General tracing related utility functions - trace_printk(),
* tracing_on/tracing_off and tracing_start()/tracing_stop
*
* Use tracing_on/tracing_off when you want to quickly turn on or off
* tracing. It simply enables or disables the recording of the trace events.
* This also corresponds to the user space /sys/kernel/tracing/tracing_on
* file, which gives a means for the kernel and userspace to interact.
* Place a tracing_off() in the kernel where you want tracing to end.
* From user space, examine the trace, and then echo 1 > tracing_on
* to continue tracing.
*
* tracing_stop/tracing_start has slightly more overhead. It is used
* by things like suspend to ram where disabling the recording of the
* trace is not enough, but tracing must actually stop because things
* like calling smp_processor_id() may crash the system.
*
* Most likely, you want to use tracing_on/tracing_off.
*/
enum ftrace_dump_mode {
DUMP_NONE,
DUMP_ALL,
DUMP_ORIG,
DUMP_PARAM,
};
#ifdef CONFIG_TRACING
void tracing_on(void);
void tracing_off(void);
int tracing_is_on(void);
void tracing_snapshot(void);
void tracing_snapshot_alloc(void);
extern void tracing_start(void);
extern void tracing_stop(void);
static inline __printf(1, 2)
void ____trace_printk_check_format(const char *fmt, ...)
{
}
#define __trace_printk_check_format(fmt, args...) \
do { \
if (0) \
____trace_printk_check_format(fmt, ##args); \
} while (0)
/**
* trace_printk - printf formatting in the ftrace buffer
* @fmt: the printf format for printing
*
* Note: __trace_printk is an internal function for trace_printk() and
* the @ip is passed in via the trace_printk() macro.
*
* This function allows a kernel developer to debug fast path sections
* that printk is not appropriate for. By scattering in various
* printk like tracing in the code, a developer can quickly see
* where problems are occurring.
*
* This is intended as a debugging tool for the developer only.
* Please refrain from leaving trace_printks scattered around in
* your code. (Extra memory is used for special buffers that are
* allocated when trace_printk() is used.)
*
* A little optimization trick is done here. If there's only one
* argument, there's no need to scan the string for printf formats.
* The trace_puts() will suffice. But how can we take advantage of
* using trace_puts() when trace_printk() has only one argument?
* By stringifying the args and checking the size we can tell
* whether or not there are args. __stringify((__VA_ARGS__)) will
* turn into "()\0" with a size of 3 when there are no args, anything
* else will be bigger. All we need to do is define a string to this,
* and then take its size and compare to 3. If it's bigger, use
* do_trace_printk() otherwise, optimize it to trace_puts(). Then just
* let gcc optimize the rest.
*/
#define trace_printk(fmt, ...) \
do { \
char _______STR[] = __stringify((__VA_ARGS__)); \
if (sizeof(_______STR) > 3) \
do_trace_printk(fmt, ##__VA_ARGS__); \
else \
trace_puts(fmt); \
} while (0)
#define do_trace_printk(fmt, args...) \
do { \
static const char *trace_printk_fmt __used \
__section("__trace_printk_fmt") = \
__builtin_constant_p(fmt) ? fmt : NULL; \
\
__trace_printk_check_format(fmt, ##args); \
\
if (__builtin_constant_p(fmt)) \
__trace_bprintk(_THIS_IP_, trace_printk_fmt, ##args); \
else \
__trace_printk(_THIS_IP_, fmt, ##args); \
} while (0)
extern __printf(2, 3)
int __trace_bprintk(unsigned long ip, const char *fmt, ...);
extern __printf(2, 3)
int __trace_printk(unsigned long ip, const char *fmt, ...);
/**
* trace_puts - write a string into the ftrace buffer
* @str: the string to record
*
* Note: __trace_bputs is an internal function for trace_puts and
* the @ip is passed in via the trace_puts macro.
*
* This is similar to trace_printk() but is made for those really fast
* paths that a developer wants the least amount of "Heisenbug" effects,
* where the processing of the print format is still too much.
*
* This function allows a kernel developer to debug fast path sections
* that printk is not appropriate for. By scattering in various
* printk like tracing in the code, a developer can quickly see
* where problems are occurring.
*
* This is intended as a debugging tool for the developer only.
* Please refrain from leaving trace_puts scattered around in
* your code. (Extra memory is used for special buffers that are
* allocated when trace_puts() is used.)
*
* Returns: 0 if nothing was written, positive # if string was.
* (1 when __trace_bputs is used, strlen(str) when __trace_puts is used)
*/
#define trace_puts(str) ({ \
static const char *trace_printk_fmt __used \
__section("__trace_printk_fmt") = \
__builtin_constant_p(str) ? str : NULL; \
\
if (__builtin_constant_p(str)) \
__trace_bputs(_THIS_IP_, trace_printk_fmt); \
else \
__trace_puts(_THIS_IP_, str); \
})
extern int __trace_bputs(unsigned long ip, const char *str);
extern int __trace_puts(unsigned long ip, const char *str);
extern void trace_dump_stack(int skip);
/*
* The double __builtin_constant_p is because gcc will give us an error
* if we try to allocate the static variable to fmt if it is not a
* constant. Even with the outer if statement.
*/
#define ftrace_vprintk(fmt, vargs) \
do { \
if (__builtin_constant_p(fmt)) { \
static const char *trace_printk_fmt __used \
__section("__trace_printk_fmt") = \
__builtin_constant_p(fmt) ? fmt : NULL; \
\
__ftrace_vbprintk(_THIS_IP_, trace_printk_fmt, vargs); \
} else \
__ftrace_vprintk(_THIS_IP_, fmt, vargs); \
} while (0)
extern __printf(2, 0) int
__ftrace_vbprintk(unsigned long ip, const char *fmt, va_list ap);
extern __printf(2, 0) int
__ftrace_vprintk(unsigned long ip, const char *fmt, va_list ap);
extern void ftrace_dump(enum ftrace_dump_mode oops_dump_mode);
#else
static inline void tracing_start(void) { }
static inline void tracing_stop(void) { }
static inline void trace_dump_stack(int skip) { }
static inline void tracing_on(void) { }
static inline void tracing_off(void) { }
static inline int tracing_is_on(void) { return 0; }
static inline void tracing_snapshot(void) { }
static inline void tracing_snapshot_alloc(void) { }
static inline __printf(1, 2)
int trace_printk(const char *fmt, ...)
{
return 0;
}
static __printf(1, 0) inline int
ftrace_vprintk(const char *fmt, va_list ap)
{
return 0;
}
static inline void ftrace_dump(enum ftrace_dump_mode oops_dump_mode) { }
#endif /* CONFIG_TRACING */
#endif
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