Version:  2.0.40 2.2.26 2.4.37 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2 4.3 4.4 4.5 4.6

Linux/include/linux/kernel.h

  1 #ifndef _LINUX_KERNEL_H
  2 #define _LINUX_KERNEL_H
  3 
  4 
  5 #include <stdarg.h>
  6 #include <linux/linkage.h>
  7 #include <linux/stddef.h>
  8 #include <linux/types.h>
  9 #include <linux/compiler.h>
 10 #include <linux/bitops.h>
 11 #include <linux/log2.h>
 12 #include <linux/typecheck.h>
 13 #include <linux/printk.h>
 14 #include <linux/dynamic_debug.h>
 15 #include <asm/byteorder.h>
 16 #include <uapi/linux/kernel.h>
 17 
 18 #define USHRT_MAX       ((u16)(~0U))
 19 #define SHRT_MAX        ((s16)(USHRT_MAX>>1))
 20 #define SHRT_MIN        ((s16)(-SHRT_MAX - 1))
 21 #define INT_MAX         ((int)(~0U>>1))
 22 #define INT_MIN         (-INT_MAX - 1)
 23 #define UINT_MAX        (~0U)
 24 #define LONG_MAX        ((long)(~0UL>>1))
 25 #define LONG_MIN        (-LONG_MAX - 1)
 26 #define ULONG_MAX       (~0UL)
 27 #define LLONG_MAX       ((long long)(~0ULL>>1))
 28 #define LLONG_MIN       (-LLONG_MAX - 1)
 29 #define ULLONG_MAX      (~0ULL)
 30 #define SIZE_MAX        (~(size_t)0)
 31 
 32 #define U8_MAX          ((u8)~0U)
 33 #define S8_MAX          ((s8)(U8_MAX>>1))
 34 #define S8_MIN          ((s8)(-S8_MAX - 1))
 35 #define U16_MAX         ((u16)~0U)
 36 #define S16_MAX         ((s16)(U16_MAX>>1))
 37 #define S16_MIN         ((s16)(-S16_MAX - 1))
 38 #define U32_MAX         ((u32)~0U)
 39 #define S32_MAX         ((s32)(U32_MAX>>1))
 40 #define S32_MIN         ((s32)(-S32_MAX - 1))
 41 #define U64_MAX         ((u64)~0ULL)
 42 #define S64_MAX         ((s64)(U64_MAX>>1))
 43 #define S64_MIN         ((s64)(-S64_MAX - 1))
 44 
 45 #define STACK_MAGIC     0xdeadbeef
 46 
 47 #define REPEAT_BYTE(x)  ((~0ul / 0xff) * (x))
 48 
 49 #define ALIGN(x, a)             __ALIGN_KERNEL((x), (a))
 50 #define __ALIGN_MASK(x, mask)   __ALIGN_KERNEL_MASK((x), (mask))
 51 #define PTR_ALIGN(p, a)         ((typeof(p))ALIGN((unsigned long)(p), (a)))
 52 #define IS_ALIGNED(x, a)                (((x) & ((typeof(x))(a) - 1)) == 0)
 53 
 54 #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]) + __must_be_array(arr))
 55 
 56 /*
 57  * This looks more complex than it should be. But we need to
 58  * get the type for the ~ right in round_down (it needs to be
 59  * as wide as the result!), and we want to evaluate the macro
 60  * arguments just once each.
 61  */
 62 #define __round_mask(x, y) ((__typeof__(x))((y)-1))
 63 #define round_up(x, y) ((((x)-1) | __round_mask(x, y))+1)
 64 #define round_down(x, y) ((x) & ~__round_mask(x, y))
 65 
 66 #define FIELD_SIZEOF(t, f) (sizeof(((t*)0)->f))
 67 #define DIV_ROUND_UP __KERNEL_DIV_ROUND_UP
 68 #define DIV_ROUND_UP_ULL(ll,d) \
 69         ({ unsigned long long _tmp = (ll)+(d)-1; do_div(_tmp, d); _tmp; })
 70 
 71 #if BITS_PER_LONG == 32
 72 # define DIV_ROUND_UP_SECTOR_T(ll,d) DIV_ROUND_UP_ULL(ll, d)
 73 #else
 74 # define DIV_ROUND_UP_SECTOR_T(ll,d) DIV_ROUND_UP(ll,d)
 75 #endif
 76 
 77 /* The `const' in roundup() prevents gcc-3.3 from calling __divdi3 */
 78 #define roundup(x, y) (                                 \
 79 {                                                       \
 80         const typeof(y) __y = y;                        \
 81         (((x) + (__y - 1)) / __y) * __y;                \
 82 }                                                       \
 83 )
 84 #define rounddown(x, y) (                               \
 85 {                                                       \
 86         typeof(x) __x = (x);                            \
 87         __x - (__x % (y));                              \
 88 }                                                       \
 89 )
 90 
 91 /*
 92  * Divide positive or negative dividend by positive divisor and round
 93  * to closest integer. Result is undefined for negative divisors and
 94  * for negative dividends if the divisor variable type is unsigned.
 95  */
 96 #define DIV_ROUND_CLOSEST(x, divisor)(                  \
 97 {                                                       \
 98         typeof(x) __x = x;                              \
 99         typeof(divisor) __d = divisor;                  \
100         (((typeof(x))-1) > 0 ||                         \
101          ((typeof(divisor))-1) > 0 || (__x) > 0) ?      \
102                 (((__x) + ((__d) / 2)) / (__d)) :       \
103                 (((__x) - ((__d) / 2)) / (__d));        \
104 }                                                       \
105 )
106 /*
107  * Same as above but for u64 dividends. divisor must be a 32-bit
108  * number.
109  */
110 #define DIV_ROUND_CLOSEST_ULL(x, divisor)(              \
111 {                                                       \
112         typeof(divisor) __d = divisor;                  \
113         unsigned long long _tmp = (x) + (__d) / 2;      \
114         do_div(_tmp, __d);                              \
115         _tmp;                                           \
116 }                                                       \
117 )
118 
119 /*
120  * Multiplies an integer by a fraction, while avoiding unnecessary
121  * overflow or loss of precision.
122  */
123 #define mult_frac(x, numer, denom)(                     \
124 {                                                       \
125         typeof(x) quot = (x) / (denom);                 \
126         typeof(x) rem  = (x) % (denom);                 \
127         (quot * (numer)) + ((rem * (numer)) / (denom)); \
128 }                                                       \
129 )
130 
131 
132 #define _RET_IP_                (unsigned long)__builtin_return_address(0)
133 #define _THIS_IP_  ({ __label__ __here; __here: (unsigned long)&&__here; })
134 
135 #ifdef CONFIG_LBDAF
136 # include <asm/div64.h>
137 # define sector_div(a, b) do_div(a, b)
138 #else
139 # define sector_div(n, b)( \
140 { \
141         int _res; \
142         _res = (n) % (b); \
143         (n) /= (b); \
144         _res; \
145 } \
146 )
147 #endif
148 
149 /**
150  * upper_32_bits - return bits 32-63 of a number
151  * @n: the number we're accessing
152  *
153  * A basic shift-right of a 64- or 32-bit quantity.  Use this to suppress
154  * the "right shift count >= width of type" warning when that quantity is
155  * 32-bits.
156  */
157 #define upper_32_bits(n) ((u32)(((n) >> 16) >> 16))
158 
159 /**
160  * lower_32_bits - return bits 0-31 of a number
161  * @n: the number we're accessing
162  */
163 #define lower_32_bits(n) ((u32)(n))
164 
165 struct completion;
166 struct pt_regs;
167 struct user;
168 
169 #ifdef CONFIG_PREEMPT_VOLUNTARY
170 extern int _cond_resched(void);
171 # define might_resched() _cond_resched()
172 #else
173 # define might_resched() do { } while (0)
174 #endif
175 
176 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
177   void ___might_sleep(const char *file, int line, int preempt_offset);
178   void __might_sleep(const char *file, int line, int preempt_offset);
179 /**
180  * might_sleep - annotation for functions that can sleep
181  *
182  * this macro will print a stack trace if it is executed in an atomic
183  * context (spinlock, irq-handler, ...).
184  *
185  * This is a useful debugging help to be able to catch problems early and not
186  * be bitten later when the calling function happens to sleep when it is not
187  * supposed to.
188  */
189 # define might_sleep() \
190         do { __might_sleep(__FILE__, __LINE__, 0); might_resched(); } while (0)
191 # define sched_annotate_sleep() (current->task_state_change = 0)
192 #else
193   static inline void ___might_sleep(const char *file, int line,
194                                    int preempt_offset) { }
195   static inline void __might_sleep(const char *file, int line,
196                                    int preempt_offset) { }
197 # define might_sleep() do { might_resched(); } while (0)
198 # define sched_annotate_sleep() do { } while (0)
199 #endif
200 
201 #define might_sleep_if(cond) do { if (cond) might_sleep(); } while (0)
202 
203 /**
204  * abs - return absolute value of an argument
205  * @x: the value.  If it is unsigned type, it is converted to signed type first.
206  *     char is treated as if it was signed (regardless of whether it really is)
207  *     but the macro's return type is preserved as char.
208  *
209  * Return: an absolute value of x.
210  */
211 #define abs(x)  __abs_choose_expr(x, long long,                         \
212                 __abs_choose_expr(x, long,                              \
213                 __abs_choose_expr(x, int,                               \
214                 __abs_choose_expr(x, short,                             \
215                 __abs_choose_expr(x, char,                              \
216                 __builtin_choose_expr(                                  \
217                         __builtin_types_compatible_p(typeof(x), char),  \
218                         (char)({ signed char __x = (x); __x<0?-__x:__x; }), \
219                         ((void)0)))))))
220 
221 #define __abs_choose_expr(x, type, other) __builtin_choose_expr(        \
222         __builtin_types_compatible_p(typeof(x),   signed type) ||       \
223         __builtin_types_compatible_p(typeof(x), unsigned type),         \
224         ({ signed type __x = (x); __x < 0 ? -__x : __x; }), other)
225 
226 /**
227  * reciprocal_scale - "scale" a value into range [0, ep_ro)
228  * @val: value
229  * @ep_ro: right open interval endpoint
230  *
231  * Perform a "reciprocal multiplication" in order to "scale" a value into
232  * range [0, ep_ro), where the upper interval endpoint is right-open.
233  * This is useful, e.g. for accessing a index of an array containing
234  * ep_ro elements, for example. Think of it as sort of modulus, only that
235  * the result isn't that of modulo. ;) Note that if initial input is a
236  * small value, then result will return 0.
237  *
238  * Return: a result based on val in interval [0, ep_ro).
239  */
240 static inline u32 reciprocal_scale(u32 val, u32 ep_ro)
241 {
242         return (u32)(((u64) val * ep_ro) >> 32);
243 }
244 
245 #if defined(CONFIG_MMU) && \
246         (defined(CONFIG_PROVE_LOCKING) || defined(CONFIG_DEBUG_ATOMIC_SLEEP))
247 #define might_fault() __might_fault(__FILE__, __LINE__)
248 void __might_fault(const char *file, int line);
249 #else
250 static inline void might_fault(void) { }
251 #endif
252 
253 extern struct atomic_notifier_head panic_notifier_list;
254 extern long (*panic_blink)(int state);
255 __printf(1, 2)
256 void panic(const char *fmt, ...)
257         __noreturn __cold;
258 void nmi_panic(struct pt_regs *regs, const char *msg);
259 extern void oops_enter(void);
260 extern void oops_exit(void);
261 void print_oops_end_marker(void);
262 extern int oops_may_print(void);
263 void do_exit(long error_code)
264         __noreturn;
265 void complete_and_exit(struct completion *, long)
266         __noreturn;
267 
268 /* Internal, do not use. */
269 int __must_check _kstrtoul(const char *s, unsigned int base, unsigned long *res);
270 int __must_check _kstrtol(const char *s, unsigned int base, long *res);
271 
272 int __must_check kstrtoull(const char *s, unsigned int base, unsigned long long *res);
273 int __must_check kstrtoll(const char *s, unsigned int base, long long *res);
274 
275 /**
276  * kstrtoul - convert a string to an unsigned long
277  * @s: The start of the string. The string must be null-terminated, and may also
278  *  include a single newline before its terminating null. The first character
279  *  may also be a plus sign, but not a minus sign.
280  * @base: The number base to use. The maximum supported base is 16. If base is
281  *  given as 0, then the base of the string is automatically detected with the
282  *  conventional semantics - If it begins with 0x the number will be parsed as a
283  *  hexadecimal (case insensitive), if it otherwise begins with 0, it will be
284  *  parsed as an octal number. Otherwise it will be parsed as a decimal.
285  * @res: Where to write the result of the conversion on success.
286  *
287  * Returns 0 on success, -ERANGE on overflow and -EINVAL on parsing error.
288  * Used as a replacement for the obsolete simple_strtoull. Return code must
289  * be checked.
290 */
291 static inline int __must_check kstrtoul(const char *s, unsigned int base, unsigned long *res)
292 {
293         /*
294          * We want to shortcut function call, but
295          * __builtin_types_compatible_p(unsigned long, unsigned long long) = 0.
296          */
297         if (sizeof(unsigned long) == sizeof(unsigned long long) &&
298             __alignof__(unsigned long) == __alignof__(unsigned long long))
299                 return kstrtoull(s, base, (unsigned long long *)res);
300         else
301                 return _kstrtoul(s, base, res);
302 }
303 
304 /**
305  * kstrtol - convert a string to a long
306  * @s: The start of the string. The string must be null-terminated, and may also
307  *  include a single newline before its terminating null. The first character
308  *  may also be a plus sign or a minus sign.
309  * @base: The number base to use. The maximum supported base is 16. If base is
310  *  given as 0, then the base of the string is automatically detected with the
311  *  conventional semantics - If it begins with 0x the number will be parsed as a
312  *  hexadecimal (case insensitive), if it otherwise begins with 0, it will be
313  *  parsed as an octal number. Otherwise it will be parsed as a decimal.
314  * @res: Where to write the result of the conversion on success.
315  *
316  * Returns 0 on success, -ERANGE on overflow and -EINVAL on parsing error.
317  * Used as a replacement for the obsolete simple_strtoull. Return code must
318  * be checked.
319  */
320 static inline int __must_check kstrtol(const char *s, unsigned int base, long *res)
321 {
322         /*
323          * We want to shortcut function call, but
324          * __builtin_types_compatible_p(long, long long) = 0.
325          */
326         if (sizeof(long) == sizeof(long long) &&
327             __alignof__(long) == __alignof__(long long))
328                 return kstrtoll(s, base, (long long *)res);
329         else
330                 return _kstrtol(s, base, res);
331 }
332 
333 int __must_check kstrtouint(const char *s, unsigned int base, unsigned int *res);
334 int __must_check kstrtoint(const char *s, unsigned int base, int *res);
335 
336 static inline int __must_check kstrtou64(const char *s, unsigned int base, u64 *res)
337 {
338         return kstrtoull(s, base, res);
339 }
340 
341 static inline int __must_check kstrtos64(const char *s, unsigned int base, s64 *res)
342 {
343         return kstrtoll(s, base, res);
344 }
345 
346 static inline int __must_check kstrtou32(const char *s, unsigned int base, u32 *res)
347 {
348         return kstrtouint(s, base, res);
349 }
350 
351 static inline int __must_check kstrtos32(const char *s, unsigned int base, s32 *res)
352 {
353         return kstrtoint(s, base, res);
354 }
355 
356 int __must_check kstrtou16(const char *s, unsigned int base, u16 *res);
357 int __must_check kstrtos16(const char *s, unsigned int base, s16 *res);
358 int __must_check kstrtou8(const char *s, unsigned int base, u8 *res);
359 int __must_check kstrtos8(const char *s, unsigned int base, s8 *res);
360 int __must_check kstrtobool(const char *s, bool *res);
361 
362 int __must_check kstrtoull_from_user(const char __user *s, size_t count, unsigned int base, unsigned long long *res);
363 int __must_check kstrtoll_from_user(const char __user *s, size_t count, unsigned int base, long long *res);
364 int __must_check kstrtoul_from_user(const char __user *s, size_t count, unsigned int base, unsigned long *res);
365 int __must_check kstrtol_from_user(const char __user *s, size_t count, unsigned int base, long *res);
366 int __must_check kstrtouint_from_user(const char __user *s, size_t count, unsigned int base, unsigned int *res);
367 int __must_check kstrtoint_from_user(const char __user *s, size_t count, unsigned int base, int *res);
368 int __must_check kstrtou16_from_user(const char __user *s, size_t count, unsigned int base, u16 *res);
369 int __must_check kstrtos16_from_user(const char __user *s, size_t count, unsigned int base, s16 *res);
370 int __must_check kstrtou8_from_user(const char __user *s, size_t count, unsigned int base, u8 *res);
371 int __must_check kstrtos8_from_user(const char __user *s, size_t count, unsigned int base, s8 *res);
372 int __must_check kstrtobool_from_user(const char __user *s, size_t count, bool *res);
373 
374 static inline int __must_check kstrtou64_from_user(const char __user *s, size_t count, unsigned int base, u64 *res)
375 {
376         return kstrtoull_from_user(s, count, base, res);
377 }
378 
379 static inline int __must_check kstrtos64_from_user(const char __user *s, size_t count, unsigned int base, s64 *res)
380 {
381         return kstrtoll_from_user(s, count, base, res);
382 }
383 
384 static inline int __must_check kstrtou32_from_user(const char __user *s, size_t count, unsigned int base, u32 *res)
385 {
386         return kstrtouint_from_user(s, count, base, res);
387 }
388 
389 static inline int __must_check kstrtos32_from_user(const char __user *s, size_t count, unsigned int base, s32 *res)
390 {
391         return kstrtoint_from_user(s, count, base, res);
392 }
393 
394 /* Obsolete, do not use.  Use kstrto<foo> instead */
395 
396 extern unsigned long simple_strtoul(const char *,char **,unsigned int);
397 extern long simple_strtol(const char *,char **,unsigned int);
398 extern unsigned long long simple_strtoull(const char *,char **,unsigned int);
399 extern long long simple_strtoll(const char *,char **,unsigned int);
400 
401 extern int num_to_str(char *buf, int size, unsigned long long num);
402 
403 /* lib/printf utilities */
404 
405 extern __printf(2, 3) int sprintf(char *buf, const char * fmt, ...);
406 extern __printf(2, 0) int vsprintf(char *buf, const char *, va_list);
407 extern __printf(3, 4)
408 int snprintf(char *buf, size_t size, const char *fmt, ...);
409 extern __printf(3, 0)
410 int vsnprintf(char *buf, size_t size, const char *fmt, va_list args);
411 extern __printf(3, 4)
412 int scnprintf(char *buf, size_t size, const char *fmt, ...);
413 extern __printf(3, 0)
414 int vscnprintf(char *buf, size_t size, const char *fmt, va_list args);
415 extern __printf(2, 3)
416 char *kasprintf(gfp_t gfp, const char *fmt, ...);
417 extern __printf(2, 0)
418 char *kvasprintf(gfp_t gfp, const char *fmt, va_list args);
419 extern __printf(2, 0)
420 const char *kvasprintf_const(gfp_t gfp, const char *fmt, va_list args);
421 
422 extern __scanf(2, 3)
423 int sscanf(const char *, const char *, ...);
424 extern __scanf(2, 0)
425 int vsscanf(const char *, const char *, va_list);
426 
427 extern int get_option(char **str, int *pint);
428 extern char *get_options(const char *str, int nints, int *ints);
429 extern unsigned long long memparse(const char *ptr, char **retptr);
430 extern bool parse_option_str(const char *str, const char *option);
431 
432 extern int core_kernel_text(unsigned long addr);
433 extern int core_kernel_data(unsigned long addr);
434 extern int __kernel_text_address(unsigned long addr);
435 extern int kernel_text_address(unsigned long addr);
436 extern int func_ptr_is_kernel_text(void *ptr);
437 
438 unsigned long int_sqrt(unsigned long);
439 
440 extern void bust_spinlocks(int yes);
441 extern int oops_in_progress;            /* If set, an oops, panic(), BUG() or die() is in progress */
442 extern int panic_timeout;
443 extern int panic_on_oops;
444 extern int panic_on_unrecovered_nmi;
445 extern int panic_on_io_nmi;
446 extern int panic_on_warn;
447 extern int sysctl_panic_on_stackoverflow;
448 
449 extern bool crash_kexec_post_notifiers;
450 
451 /*
452  * panic_cpu is used for synchronizing panic() and crash_kexec() execution. It
453  * holds a CPU number which is executing panic() currently. A value of
454  * PANIC_CPU_INVALID means no CPU has entered panic() or crash_kexec().
455  */
456 extern atomic_t panic_cpu;
457 #define PANIC_CPU_INVALID       -1
458 
459 /*
460  * Only to be used by arch init code. If the user over-wrote the default
461  * CONFIG_PANIC_TIMEOUT, honor it.
462  */
463 static inline void set_arch_panic_timeout(int timeout, int arch_default_timeout)
464 {
465         if (panic_timeout == arch_default_timeout)
466                 panic_timeout = timeout;
467 }
468 extern const char *print_tainted(void);
469 enum lockdep_ok {
470         LOCKDEP_STILL_OK,
471         LOCKDEP_NOW_UNRELIABLE
472 };
473 extern void add_taint(unsigned flag, enum lockdep_ok);
474 extern int test_taint(unsigned flag);
475 extern unsigned long get_taint(void);
476 extern int root_mountflags;
477 
478 extern bool early_boot_irqs_disabled;
479 
480 /* Values used for system_state */
481 extern enum system_states {
482         SYSTEM_BOOTING,
483         SYSTEM_RUNNING,
484         SYSTEM_HALT,
485         SYSTEM_POWER_OFF,
486         SYSTEM_RESTART,
487 } system_state;
488 
489 #define TAINT_PROPRIETARY_MODULE        0
490 #define TAINT_FORCED_MODULE             1
491 #define TAINT_CPU_OUT_OF_SPEC           2
492 #define TAINT_FORCED_RMMOD              3
493 #define TAINT_MACHINE_CHECK             4
494 #define TAINT_BAD_PAGE                  5
495 #define TAINT_USER                      6
496 #define TAINT_DIE                       7
497 #define TAINT_OVERRIDDEN_ACPI_TABLE     8
498 #define TAINT_WARN                      9
499 #define TAINT_CRAP                      10
500 #define TAINT_FIRMWARE_WORKAROUND       11
501 #define TAINT_OOT_MODULE                12
502 #define TAINT_UNSIGNED_MODULE           13
503 #define TAINT_SOFTLOCKUP                14
504 #define TAINT_LIVEPATCH                 15
505 
506 extern const char hex_asc[];
507 #define hex_asc_lo(x)   hex_asc[((x) & 0x0f)]
508 #define hex_asc_hi(x)   hex_asc[((x) & 0xf0) >> 4]
509 
510 static inline char *hex_byte_pack(char *buf, u8 byte)
511 {
512         *buf++ = hex_asc_hi(byte);
513         *buf++ = hex_asc_lo(byte);
514         return buf;
515 }
516 
517 extern const char hex_asc_upper[];
518 #define hex_asc_upper_lo(x)     hex_asc_upper[((x) & 0x0f)]
519 #define hex_asc_upper_hi(x)     hex_asc_upper[((x) & 0xf0) >> 4]
520 
521 static inline char *hex_byte_pack_upper(char *buf, u8 byte)
522 {
523         *buf++ = hex_asc_upper_hi(byte);
524         *buf++ = hex_asc_upper_lo(byte);
525         return buf;
526 }
527 
528 extern int hex_to_bin(char ch);
529 extern int __must_check hex2bin(u8 *dst, const char *src, size_t count);
530 extern char *bin2hex(char *dst, const void *src, size_t count);
531 
532 bool mac_pton(const char *s, u8 *mac);
533 
534 /*
535  * General tracing related utility functions - trace_printk(),
536  * tracing_on/tracing_off and tracing_start()/tracing_stop
537  *
538  * Use tracing_on/tracing_off when you want to quickly turn on or off
539  * tracing. It simply enables or disables the recording of the trace events.
540  * This also corresponds to the user space /sys/kernel/debug/tracing/tracing_on
541  * file, which gives a means for the kernel and userspace to interact.
542  * Place a tracing_off() in the kernel where you want tracing to end.
543  * From user space, examine the trace, and then echo 1 > tracing_on
544  * to continue tracing.
545  *
546  * tracing_stop/tracing_start has slightly more overhead. It is used
547  * by things like suspend to ram where disabling the recording of the
548  * trace is not enough, but tracing must actually stop because things
549  * like calling smp_processor_id() may crash the system.
550  *
551  * Most likely, you want to use tracing_on/tracing_off.
552  */
553 
554 enum ftrace_dump_mode {
555         DUMP_NONE,
556         DUMP_ALL,
557         DUMP_ORIG,
558 };
559 
560 #ifdef CONFIG_TRACING
561 void tracing_on(void);
562 void tracing_off(void);
563 int tracing_is_on(void);
564 void tracing_snapshot(void);
565 void tracing_snapshot_alloc(void);
566 
567 extern void tracing_start(void);
568 extern void tracing_stop(void);
569 
570 static inline __printf(1, 2)
571 void ____trace_printk_check_format(const char *fmt, ...)
572 {
573 }
574 #define __trace_printk_check_format(fmt, args...)                       \
575 do {                                                                    \
576         if (0)                                                          \
577                 ____trace_printk_check_format(fmt, ##args);             \
578 } while (0)
579 
580 /**
581  * trace_printk - printf formatting in the ftrace buffer
582  * @fmt: the printf format for printing
583  *
584  * Note: __trace_printk is an internal function for trace_printk and
585  *       the @ip is passed in via the trace_printk macro.
586  *
587  * This function allows a kernel developer to debug fast path sections
588  * that printk is not appropriate for. By scattering in various
589  * printk like tracing in the code, a developer can quickly see
590  * where problems are occurring.
591  *
592  * This is intended as a debugging tool for the developer only.
593  * Please refrain from leaving trace_printks scattered around in
594  * your code. (Extra memory is used for special buffers that are
595  * allocated when trace_printk() is used)
596  *
597  * A little optization trick is done here. If there's only one
598  * argument, there's no need to scan the string for printf formats.
599  * The trace_puts() will suffice. But how can we take advantage of
600  * using trace_puts() when trace_printk() has only one argument?
601  * By stringifying the args and checking the size we can tell
602  * whether or not there are args. __stringify((__VA_ARGS__)) will
603  * turn into "()\0" with a size of 3 when there are no args, anything
604  * else will be bigger. All we need to do is define a string to this,
605  * and then take its size and compare to 3. If it's bigger, use
606  * do_trace_printk() otherwise, optimize it to trace_puts(). Then just
607  * let gcc optimize the rest.
608  */
609 
610 #define trace_printk(fmt, ...)                          \
611 do {                                                    \
612         char _______STR[] = __stringify((__VA_ARGS__)); \
613         if (sizeof(_______STR) > 3)                     \
614                 do_trace_printk(fmt, ##__VA_ARGS__);    \
615         else                                            \
616                 trace_puts(fmt);                        \
617 } while (0)
618 
619 #define do_trace_printk(fmt, args...)                                   \
620 do {                                                                    \
621         static const char *trace_printk_fmt __used                      \
622                 __attribute__((section("__trace_printk_fmt"))) =        \
623                 __builtin_constant_p(fmt) ? fmt : NULL;                 \
624                                                                         \
625         __trace_printk_check_format(fmt, ##args);                       \
626                                                                         \
627         if (__builtin_constant_p(fmt))                                  \
628                 __trace_bprintk(_THIS_IP_, trace_printk_fmt, ##args);   \
629         else                                                            \
630                 __trace_printk(_THIS_IP_, fmt, ##args);                 \
631 } while (0)
632 
633 extern __printf(2, 3)
634 int __trace_bprintk(unsigned long ip, const char *fmt, ...);
635 
636 extern __printf(2, 3)
637 int __trace_printk(unsigned long ip, const char *fmt, ...);
638 
639 /**
640  * trace_puts - write a string into the ftrace buffer
641  * @str: the string to record
642  *
643  * Note: __trace_bputs is an internal function for trace_puts and
644  *       the @ip is passed in via the trace_puts macro.
645  *
646  * This is similar to trace_printk() but is made for those really fast
647  * paths that a developer wants the least amount of "Heisenbug" affects,
648  * where the processing of the print format is still too much.
649  *
650  * This function allows a kernel developer to debug fast path sections
651  * that printk is not appropriate for. By scattering in various
652  * printk like tracing in the code, a developer can quickly see
653  * where problems are occurring.
654  *
655  * This is intended as a debugging tool for the developer only.
656  * Please refrain from leaving trace_puts scattered around in
657  * your code. (Extra memory is used for special buffers that are
658  * allocated when trace_puts() is used)
659  *
660  * Returns: 0 if nothing was written, positive # if string was.
661  *  (1 when __trace_bputs is used, strlen(str) when __trace_puts is used)
662  */
663 
664 #define trace_puts(str) ({                                              \
665         static const char *trace_printk_fmt __used                      \
666                 __attribute__((section("__trace_printk_fmt"))) =        \
667                 __builtin_constant_p(str) ? str : NULL;                 \
668                                                                         \
669         if (__builtin_constant_p(str))                                  \
670                 __trace_bputs(_THIS_IP_, trace_printk_fmt);             \
671         else                                                            \
672                 __trace_puts(_THIS_IP_, str, strlen(str));              \
673 })
674 extern int __trace_bputs(unsigned long ip, const char *str);
675 extern int __trace_puts(unsigned long ip, const char *str, int size);
676 
677 extern void trace_dump_stack(int skip);
678 
679 /*
680  * The double __builtin_constant_p is because gcc will give us an error
681  * if we try to allocate the static variable to fmt if it is not a
682  * constant. Even with the outer if statement.
683  */
684 #define ftrace_vprintk(fmt, vargs)                                      \
685 do {                                                                    \
686         if (__builtin_constant_p(fmt)) {                                \
687                 static const char *trace_printk_fmt __used              \
688                   __attribute__((section("__trace_printk_fmt"))) =      \
689                         __builtin_constant_p(fmt) ? fmt : NULL;         \
690                                                                         \
691                 __ftrace_vbprintk(_THIS_IP_, trace_printk_fmt, vargs);  \
692         } else                                                          \
693                 __ftrace_vprintk(_THIS_IP_, fmt, vargs);                \
694 } while (0)
695 
696 extern __printf(2, 0) int
697 __ftrace_vbprintk(unsigned long ip, const char *fmt, va_list ap);
698 
699 extern __printf(2, 0) int
700 __ftrace_vprintk(unsigned long ip, const char *fmt, va_list ap);
701 
702 extern void ftrace_dump(enum ftrace_dump_mode oops_dump_mode);
703 #else
704 static inline void tracing_start(void) { }
705 static inline void tracing_stop(void) { }
706 static inline void trace_dump_stack(int skip) { }
707 
708 static inline void tracing_on(void) { }
709 static inline void tracing_off(void) { }
710 static inline int tracing_is_on(void) { return 0; }
711 static inline void tracing_snapshot(void) { }
712 static inline void tracing_snapshot_alloc(void) { }
713 
714 static inline __printf(1, 2)
715 int trace_printk(const char *fmt, ...)
716 {
717         return 0;
718 }
719 static __printf(1, 0) inline int
720 ftrace_vprintk(const char *fmt, va_list ap)
721 {
722         return 0;
723 }
724 static inline void ftrace_dump(enum ftrace_dump_mode oops_dump_mode) { }
725 #endif /* CONFIG_TRACING */
726 
727 /*
728  * min()/max()/clamp() macros that also do
729  * strict type-checking.. See the
730  * "unnecessary" pointer comparison.
731  */
732 #define min(x, y) ({                            \
733         typeof(x) _min1 = (x);                  \
734         typeof(y) _min2 = (y);                  \
735         (void) (&_min1 == &_min2);              \
736         _min1 < _min2 ? _min1 : _min2; })
737 
738 #define max(x, y) ({                            \
739         typeof(x) _max1 = (x);                  \
740         typeof(y) _max2 = (y);                  \
741         (void) (&_max1 == &_max2);              \
742         _max1 > _max2 ? _max1 : _max2; })
743 
744 #define min3(x, y, z) min((typeof(x))min(x, y), z)
745 #define max3(x, y, z) max((typeof(x))max(x, y), z)
746 
747 /**
748  * min_not_zero - return the minimum that is _not_ zero, unless both are zero
749  * @x: value1
750  * @y: value2
751  */
752 #define min_not_zero(x, y) ({                   \
753         typeof(x) __x = (x);                    \
754         typeof(y) __y = (y);                    \
755         __x == 0 ? __y : ((__y == 0) ? __x : min(__x, __y)); })
756 
757 /**
758  * clamp - return a value clamped to a given range with strict typechecking
759  * @val: current value
760  * @lo: lowest allowable value
761  * @hi: highest allowable value
762  *
763  * This macro does strict typechecking of lo/hi to make sure they are of the
764  * same type as val.  See the unnecessary pointer comparisons.
765  */
766 #define clamp(val, lo, hi) min((typeof(val))max(val, lo), hi)
767 
768 /*
769  * ..and if you can't take the strict
770  * types, you can specify one yourself.
771  *
772  * Or not use min/max/clamp at all, of course.
773  */
774 #define min_t(type, x, y) ({                    \
775         type __min1 = (x);                      \
776         type __min2 = (y);                      \
777         __min1 < __min2 ? __min1: __min2; })
778 
779 #define max_t(type, x, y) ({                    \
780         type __max1 = (x);                      \
781         type __max2 = (y);                      \
782         __max1 > __max2 ? __max1: __max2; })
783 
784 /**
785  * clamp_t - return a value clamped to a given range using a given type
786  * @type: the type of variable to use
787  * @val: current value
788  * @lo: minimum allowable value
789  * @hi: maximum allowable value
790  *
791  * This macro does no typechecking and uses temporary variables of type
792  * 'type' to make all the comparisons.
793  */
794 #define clamp_t(type, val, lo, hi) min_t(type, max_t(type, val, lo), hi)
795 
796 /**
797  * clamp_val - return a value clamped to a given range using val's type
798  * @val: current value
799  * @lo: minimum allowable value
800  * @hi: maximum allowable value
801  *
802  * This macro does no typechecking and uses temporary variables of whatever
803  * type the input argument 'val' is.  This is useful when val is an unsigned
804  * type and min and max are literals that will otherwise be assigned a signed
805  * integer type.
806  */
807 #define clamp_val(val, lo, hi) clamp_t(typeof(val), val, lo, hi)
808 
809 
810 /*
811  * swap - swap value of @a and @b
812  */
813 #define swap(a, b) \
814         do { typeof(a) __tmp = (a); (a) = (b); (b) = __tmp; } while (0)
815 
816 /**
817  * container_of - cast a member of a structure out to the containing structure
818  * @ptr:        the pointer to the member.
819  * @type:       the type of the container struct this is embedded in.
820  * @member:     the name of the member within the struct.
821  *
822  */
823 #define container_of(ptr, type, member) ({                      \
824         const typeof( ((type *)0)->member ) *__mptr = (ptr);    \
825         (type *)( (char *)__mptr - offsetof(type,member) );})
826 
827 /* Rebuild everything on CONFIG_FTRACE_MCOUNT_RECORD */
828 #ifdef CONFIG_FTRACE_MCOUNT_RECORD
829 # define REBUILD_DUE_TO_FTRACE_MCOUNT_RECORD
830 #endif
831 
832 /* Permissions on a sysfs file: you didn't miss the 0 prefix did you? */
833 #define VERIFY_OCTAL_PERMISSIONS(perms)                                         \
834         (BUILD_BUG_ON_ZERO((perms) < 0) +                                       \
835          BUILD_BUG_ON_ZERO((perms) > 0777) +                                    \
836          /* USER_READABLE >= GROUP_READABLE >= OTHER_READABLE */                \
837          BUILD_BUG_ON_ZERO((((perms) >> 6) & 4) < (((perms) >> 3) & 4)) +       \
838          BUILD_BUG_ON_ZERO((((perms) >> 3) & 4) < ((perms) & 4)) +              \
839          /* USER_WRITABLE >= GROUP_WRITABLE */                                  \
840          BUILD_BUG_ON_ZERO((((perms) >> 6) & 2) < (((perms) >> 3) & 2)) +       \
841          /* OTHER_WRITABLE?  Generally considered a bad idea. */                \
842          BUILD_BUG_ON_ZERO((perms) & 2) +                                       \
843          (perms))
844 #endif
845 

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