#ifndef _LINUX_KERNEL_TRACE_H #define _LINUX_KERNEL_TRACE_H #include #include #include #include #include #include #include #include #include #include enum trace_type { __TRACE_FIRST_TYPE = 0, TRACE_FN, TRACE_CTX, TRACE_WAKE, TRACE_STACK, TRACE_PRINT, TRACE_BPRINT, TRACE_SPECIAL, TRACE_MMIO_RW, TRACE_MMIO_MAP, TRACE_BRANCH, TRACE_BOOT_CALL, TRACE_BOOT_RET, TRACE_GRAPH_RET, TRACE_GRAPH_ENT, TRACE_USER_STACK, TRACE_HW_BRANCHES, TRACE_SYSCALL_ENTER, TRACE_SYSCALL_EXIT, TRACE_KMEM_ALLOC, TRACE_KMEM_FREE, TRACE_POWER, TRACE_BLK, __TRACE_LAST_TYPE, }; /* * The trace entry - the most basic unit of tracing. This is what * is printed in the end as a single line in the trace output, such as: * * bash-15816 [01] 235.197585: idle_cpu <- irq_enter */ struct trace_entry { unsigned char type; unsigned char flags; unsigned char preempt_count; int pid; int tgid; }; /* * Function trace entry - function address and parent function addres: */ struct ftrace_entry { struct trace_entry ent; unsigned long ip; unsigned long parent_ip; }; /* Function call entry */ struct ftrace_graph_ent_entry { struct trace_entry ent; struct ftrace_graph_ent graph_ent; }; /* Function return entry */ struct ftrace_graph_ret_entry { struct trace_entry ent; struct ftrace_graph_ret ret; }; extern struct tracer boot_tracer; /* * Context switch trace entry - which task (and prio) we switched from/to: */ struct ctx_switch_entry { struct trace_entry ent; unsigned int prev_pid; unsigned char prev_prio; unsigned char prev_state; unsigned int next_pid; unsigned char next_prio; unsigned char next_state; unsigned int next_cpu; }; /* * Special (free-form) trace entry: */ struct special_entry { struct trace_entry ent; unsigned long arg1; unsigned long arg2; unsigned long arg3; }; /* * Stack-trace entry: */ #define FTRACE_STACK_ENTRIES 8 struct stack_entry { struct trace_entry ent; unsigned long caller[FTRACE_STACK_ENTRIES]; }; struct userstack_entry { struct trace_entry ent; unsigned long caller[FTRACE_STACK_ENTRIES]; }; /* * trace_printk entry: */ struct bprint_entry { struct trace_entry ent; unsigned long ip; const char *fmt; u32 buf[]; }; struct print_entry { struct trace_entry ent; unsigned long ip; char buf[]; }; #define TRACE_OLD_SIZE 88 struct trace_field_cont { unsigned char type; /* Temporary till we get rid of this completely */ char buf[TRACE_OLD_SIZE - 1]; }; struct trace_mmiotrace_rw { struct trace_entry ent; struct mmiotrace_rw rw; }; struct trace_mmiotrace_map { struct trace_entry ent; struct mmiotrace_map map; }; struct trace_boot_call { struct trace_entry ent; struct boot_trace_call boot_call; }; struct trace_boot_ret { struct trace_entry ent; struct boot_trace_ret boot_ret; }; #define TRACE_FUNC_SIZE 30 #define TRACE_FILE_SIZE 20 struct trace_branch { struct trace_entry ent; unsigned line; char func[TRACE_FUNC_SIZE+1]; char file[TRACE_FILE_SIZE+1]; char correct; }; struct hw_branch_entry { struct trace_entry ent; u64 from; u64 to; }; struct trace_power { struct trace_entry ent; struct power_trace state_data; }; struct kmemtrace_alloc_entry { struct trace_entry ent; enum kmemtrace_type_id type_id; unsigned long call_site; const void *ptr; size_t bytes_req; size_t bytes_alloc; gfp_t gfp_flags; int node; }; struct kmemtrace_free_entry { struct trace_entry ent; enum kmemtrace_type_id type_id; unsigned long call_site; const void *ptr; }; struct syscall_trace_enter { struct trace_entry ent; int nr; unsigned long args[]; }; struct syscall_trace_exit { struct trace_entry ent; int nr; unsigned long ret; }; /* * trace_flag_type is an enumeration that holds different * states when a trace occurs. These are: * IRQS_OFF - interrupts were disabled * IRQS_NOSUPPORT - arch does not support irqs_disabled_flags * NEED_RESCED - reschedule is requested * HARDIRQ - inside an interrupt handler * SOFTIRQ - inside a softirq handler */ enum trace_flag_type { TRACE_FLAG_IRQS_OFF = 0x01, TRACE_FLAG_IRQS_NOSUPPORT = 0x02, TRACE_FLAG_NEED_RESCHED = 0x04, TRACE_FLAG_HARDIRQ = 0x08, TRACE_FLAG_SOFTIRQ = 0x10, }; #define TRACE_BUF_SIZE 1024 /* * The CPU trace array - it consists of thousands of trace entries * plus some other descriptor data: (for example which task started * the trace, etc.) */ struct trace_array_cpu { atomic_t disabled; void *buffer_page; /* ring buffer spare */ /* these fields get copied into max-trace: */ unsigned long trace_idx; unsigned long overrun; unsigned long saved_latency; unsigned long critical_start; unsigned long critical_end; unsigned long critical_sequence; unsigned long nice; unsigned long policy; unsigned long rt_priority; cycle_t preempt_timestamp; pid_t pid; uid_t uid; char comm[TASK_COMM_LEN]; }; struct trace_iterator; /* * The trace array - an array of per-CPU trace arrays. This is the * highest level data structure that individual tracers deal with. * They have on/off state as well: */ struct trace_array { struct ring_buffer *buffer; unsigned long entries; int cpu; cycle_t time_start; struct task_struct *waiter; struct trace_array_cpu *data[NR_CPUS]; }; #define FTRACE_CMP_TYPE(var, type) \ __builtin_types_compatible_p(typeof(var), type *) #undef IF_ASSIGN #define IF_ASSIGN(var, entry, etype, id) \ if (FTRACE_CMP_TYPE(var, etype)) { \ var = (typeof(var))(entry); \ WARN_ON(id && (entry)->type != id); \ break; \ } /* Will cause compile errors if type is not found. */ extern void __ftrace_bad_type(void); /* * The trace_assign_type is a verifier that the entry type is * the same as the type being assigned. To add new types simply * add a line with the following format: * * IF_ASSIGN(var, ent, type, id); * * Where "type" is the trace type that includes the trace_entry * as the "ent" item. And "id" is the trace identifier that is * used in the trace_type enum. * * If the type can have more than one id, then use zero. */ #define trace_assign_type(var, ent) \ do { \ IF_ASSIGN(var, ent, struct ftrace_entry, TRACE_FN); \ IF_ASSIGN(var, ent, struct ctx_switch_entry, 0); \ IF_ASSIGN(var, ent, struct stack_entry, TRACE_STACK); \ IF_ASSIGN(var, ent, struct userstack_entry, TRACE_USER_STACK);\ IF_ASSIGN(var, ent, struct print_entry, TRACE_PRINT); \ IF_ASSIGN(var, ent, struct bprint_entry, TRACE_BPRINT); \ IF_ASSIGN(var, ent, struct special_entry, 0); \ IF_ASSIGN(var, ent, struct trace_mmiotrace_rw, \ TRACE_MMIO_RW); \ IF_ASSIGN(var, ent, struct trace_mmiotrace_map, \ TRACE_MMIO_MAP); \ IF_ASSIGN(var, ent, struct trace_boot_call, TRACE_BOOT_CALL);\ IF_ASSIGN(var, ent, struct trace_boot_ret, TRACE_BOOT_RET);\ IF_ASSIGN(var, ent, struct trace_branch, TRACE_BRANCH); \ IF_ASSIGN(var, ent, struct ftrace_graph_ent_entry, \ TRACE_GRAPH_ENT); \ IF_ASSIGN(var, ent, struct ftrace_graph_ret_entry, \ TRACE_GRAPH_RET); \ IF_ASSIGN(var, ent, struct hw_branch_entry, TRACE_HW_BRANCHES);\ IF_ASSIGN(var, ent, struct trace_power, TRACE_POWER); \ IF_ASSIGN(var, ent, struct kmemtrace_alloc_entry, \ TRACE_KMEM_ALLOC); \ IF_ASSIGN(var, ent, struct kmemtrace_free_entry, \ TRACE_KMEM_FREE); \ IF_ASSIGN(var, ent, struct syscall_trace_enter, \ TRACE_SYSCALL_ENTER); \ IF_ASSIGN(var, ent, struct syscall_trace_exit, \ TRACE_SYSCALL_EXIT); \ __ftrace_bad_type(); \ } while (0) /* Return values for print_line callback */ enum print_line_t { TRACE_TYPE_PARTIAL_LINE = 0, /* Retry after flushing the seq */ TRACE_TYPE_HANDLED = 1, TRACE_TYPE_UNHANDLED = 2, /* Relay to other output functions */ TRACE_TYPE_NO_CONSUME = 3 /* Handled but ask to not consume */ }; /* * An option specific to a tracer. This is a boolean value. * The bit is the bit index that sets its value on the * flags value in struct tracer_flags. */ struct tracer_opt { const char *name; /* Will appear on the trace_options file */ u32 bit; /* Mask assigned in val field in tracer_flags */ }; /* * The set of specific options for a tracer. Your tracer * have to set the initial value of the flags val. */ struct tracer_flags { u32 val; struct tracer_opt *opts; }; /* Makes more easy to define a tracer opt */ #define TRACER_OPT(s, b) .name = #s, .bit = b /** * struct tracer - a specific tracer and its callbacks to interact with debugfs * @name: the name chosen to select it on the available_tracers file * @init: called when one switches to this tracer (echo name > current_tracer) * @reset: called when one switches to another tracer * @start: called when tracing is unpaused (echo 1 > tracing_enabled) * @stop: called when tracing is paused (echo 0 > tracing_enabled) * @open: called when the trace file is opened * @pipe_open: called when the trace_pipe file is opened * @wait_pipe: override how the user waits for traces on trace_pipe * @close: called when the trace file is released * @read: override the default read callback on trace_pipe * @splice_read: override the default splice_read callback on trace_pipe * @selftest: selftest to run on boot (see trace_selftest.c) * @print_headers: override the first lines that describe your columns * @print_line: callback that prints a trace * @set_flag: signals one of your private flags changed (trace_options file) * @flags: your private flags */ struct tracer { const char *name; int (*init)(struct trace_array *tr); void (*reset)(struct trace_array *tr); void (*start)(struct trace_array *tr); void (*stop)(struct trace_array *tr); void (*open)(struct trace_iterator *iter); void (*pipe_open)(struct trace_iterator *iter); void (*wait_pipe)(struct trace_iterator *iter); void (*close)(struct trace_iterator *iter); ssize_t (*read)(struct trace_iterator *iter, struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos); ssize_t (*splice_read)(struct trace_iterator *iter, struct file *filp, loff_t *ppos, struct pipe_inode_info *pipe, size_t len, unsigned int flags); #ifdef CONFIG_FTRACE_STARTUP_TEST int (*selftest)(struct tracer *trace, struct trace_array *tr); #endif void (*print_header)(struct seq_file *m); enum print_line_t (*print_line)(struct trace_iterator *iter); /* If you handled the flag setting, return 0 */ int (*set_flag)(u32 old_flags, u32 bit, int set); struct tracer *next; int print_max; struct tracer_flags *flags; struct tracer_stat *stats; }; struct trace_seq { unsigned char buffer[PAGE_SIZE]; unsigned int len; unsigned int readpos; }; static inline void trace_seq_init(struct trace_seq *s) { s->len = 0; s->readpos = 0; } #define TRACE_PIPE_ALL_CPU -1 /* * Trace iterator - used by printout routines who present trace * results to users and which routines might sleep, etc: */ struct trace_iterator { struct trace_array *tr; struct tracer *trace; void *private; int cpu_file; struct mutex mutex; struct ring_buffer_iter *buffer_iter[NR_CPUS]; /* The below is zeroed out in pipe_read */ struct trace_seq seq; struct trace_entry *ent; int cpu; u64 ts; unsigned long iter_flags; loff_t pos; long idx; cpumask_var_t started; }; int tracer_init(struct tracer *t, struct trace_array *tr); int tracing_is_enabled(void); void trace_wake_up(void); void tracing_reset(struct trace_array *tr, int cpu); void tracing_reset_online_cpus(struct trace_array *tr); int tracing_open_generic(struct inode *inode, struct file *filp); struct dentry *tracing_init_dentry(void); void init_tracer_sysprof_debugfs(struct dentry *d_tracer); struct ring_buffer_event; struct ring_buffer_event *trace_buffer_lock_reserve(struct trace_array *tr, unsigned char type, unsigned long len, unsigned long flags, int pc); void trace_buffer_unlock_commit(struct trace_array *tr, struct ring_buffer_event *event, unsigned long flags, int pc); struct ring_buffer_event * trace_current_buffer_lock_reserve(unsigned char type, unsigned long len, unsigned long flags, int pc); void trace_current_buffer_unlock_commit(struct ring_buffer_event *event, unsigned long flags, int pc); void trace_nowake_buffer_unlock_commit(struct ring_buffer_event *event, unsigned long flags, int pc); struct trace_entry *tracing_get_trace_entry(struct trace_array *tr, struct trace_array_cpu *data); struct trace_entry *trace_find_next_entry(struct trace_iterator *iter, int *ent_cpu, u64 *ent_ts); void tracing_generic_entry_update(struct trace_entry *entry, unsigned long flags, int pc); void default_wait_pipe(struct trace_iterator *iter); void poll_wait_pipe(struct trace_iterator *iter); void ftrace(struct trace_array *tr, struct trace_array_cpu *data, unsigned long ip, unsigned long parent_ip, unsigned long flags, int pc); void tracing_sched_switch_trace(struct trace_array *tr, struct task_struct *prev, struct task_struct *next, unsigned long flags, int pc); void tracing_record_cmdline(struct task_struct *tsk); void tracing_sched_wakeup_trace(struct trace_array *tr, struct task_struct *wakee, struct task_struct *cur, unsigned long flags, int pc); void trace_special(struct trace_array *tr, struct trace_array_cpu *data, unsigned long arg1, unsigned long arg2, unsigned long arg3, int pc); void trace_function(struct trace_array *tr, unsigned long ip, unsigned long parent_ip, unsigned long flags, int pc); void trace_graph_return(struct ftrace_graph_ret *trace); int trace_graph_entry(struct ftrace_graph_ent *trace); void tracing_start_cmdline_record(void); void tracing_stop_cmdline_record(void); void tracing_sched_switch_assign_trace(struct trace_array *tr); void tracing_stop_sched_switch_record(void); void tracing_start_sched_switch_record(void); int register_tracer(struct tracer *type); void unregister_tracer(struct tracer *type); extern unsigned long nsecs_to_usecs(unsigned long nsecs); extern unsigned long tracing_max_latency; extern unsigned long tracing_thresh; void update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu); void update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu); void __trace_stack(struct trace_array *tr, unsigned long flags, int skip, int pc); extern cycle_t ftrace_now(int cpu); #ifdef CONFIG_CONTEXT_SWITCH_TRACER typedef void (*tracer_switch_func_t)(void *private, void *__rq, struct task_struct *prev, struct task_struct *next); struct tracer_switch_ops { tracer_switch_func_t func; void *private; struct tracer_switch_ops *next; }; #endif /* CONFIG_CONTEXT_SWITCH_TRACER */ extern void trace_find_cmdline(int pid, char comm[]); #ifdef CONFIG_DYNAMIC_FTRACE extern unsigned long ftrace_update_tot_cnt; #define DYN_FTRACE_TEST_NAME trace_selftest_dynamic_test_func extern int DYN_FTRACE_TEST_NAME(void); #endif #ifdef CONFIG_FTRACE_STARTUP_TEST extern int trace_selftest_startup_function(struct tracer *trace, struct trace_array *tr); extern int trace_selftest_startup_function_graph(struct tracer *trace, struct trace_array *tr); extern int trace_selftest_startup_irqsoff(struct tracer *trace, struct trace_array *tr); extern int trace_selftest_startup_preemptoff(struct tracer *trace, struct trace_array *tr); extern int trace_selftest_startup_preemptirqsoff(struct tracer *trace, struct trace_array *tr); extern int trace_selftest_startup_wakeup(struct tracer *trace, struct trace_array *tr); extern int trace_selftest_startup_nop(struct tracer *trace, struct trace_array *tr); extern int trace_selftest_startup_sched_switch(struct tracer *trace, struct trace_array *tr); extern int trace_selftest_startup_sysprof(struct tracer *trace, struct trace_array *tr); extern int trace_selftest_startup_branch(struct tracer *trace, struct trace_array *tr); #endif /* CONFIG_FTRACE_STARTUP_TEST */ extern void *head_page(struct trace_array_cpu *data); extern long ns2usecs(cycle_t nsec); extern int trace_vbprintk(unsigned long ip, const char *fmt, va_list args); extern int trace_vprintk(unsigned long ip, const char *fmt, va_list args); extern unsigned long trace_flags; /* Standard output formatting function used for function return traces */ #ifdef CONFIG_FUNCTION_GRAPH_TRACER extern enum print_line_t print_graph_function(struct trace_iterator *iter); #ifdef CONFIG_DYNAMIC_FTRACE /* TODO: make this variable */ #define FTRACE_GRAPH_MAX_FUNCS 32 extern int ftrace_graph_count; extern unsigned long ftrace_graph_funcs[FTRACE_GRAPH_MAX_FUNCS]; static inline int ftrace_graph_addr(unsigned long addr) { int i; if (!ftrace_graph_count || test_tsk_trace_graph(current)) return 1; for (i = 0; i < ftrace_graph_count; i++) { if (addr == ftrace_graph_funcs[i]) return 1; } return 0; } #else static inline int ftrace_trace_addr(unsigned long addr) { return 1; } static inline int ftrace_graph_addr(unsigned long addr) { return 1; } #endif /* CONFIG_DYNAMIC_FTRACE */ #else /* CONFIG_FUNCTION_GRAPH_TRACER */ static inline enum print_line_t print_graph_function(struct trace_iterator *iter) { return TRACE_TYPE_UNHANDLED; } #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ extern struct pid *ftrace_pid_trace; static inline int ftrace_trace_task(struct task_struct *task) { if (!ftrace_pid_trace) return 1; return test_tsk_trace_trace(task); } /* * trace_iterator_flags is an enumeration that defines bit * positions into trace_flags that controls the output. * * NOTE: These bits must match the trace_options array in * trace.c. */ enum trace_iterator_flags { TRACE_ITER_PRINT_PARENT = 0x01, TRACE_ITER_SYM_OFFSET = 0x02, TRACE_ITER_SYM_ADDR = 0x04, TRACE_ITER_VERBOSE = 0x08, TRACE_ITER_RAW = 0x10, TRACE_ITER_HEX = 0x20, TRACE_ITER_BIN = 0x40, TRACE_ITER_BLOCK = 0x80, TRACE_ITER_STACKTRACE = 0x100, TRACE_ITER_SCHED_TREE = 0x200, TRACE_ITER_PRINTK = 0x400, TRACE_ITER_PREEMPTONLY = 0x800, TRACE_ITER_BRANCH = 0x1000, TRACE_ITER_ANNOTATE = 0x2000, TRACE_ITER_USERSTACKTRACE = 0x4000, TRACE_ITER_SYM_USEROBJ = 0x8000, TRACE_ITER_PRINTK_MSGONLY = 0x10000, TRACE_ITER_CONTEXT_INFO = 0x20000, /* Print pid/cpu/time */ TRACE_ITER_LATENCY_FMT = 0x40000, TRACE_ITER_GLOBAL_CLK = 0x80000, TRACE_ITER_SLEEP_TIME = 0x100000, }; /* * TRACE_ITER_SYM_MASK masks the options in trace_flags that * control the output of kernel symbols. */ #define TRACE_ITER_SYM_MASK \ (TRACE_ITER_PRINT_PARENT|TRACE_ITER_SYM_OFFSET|TRACE_ITER_SYM_ADDR) extern struct tracer nop_trace; /** * ftrace_preempt_disable - disable preemption scheduler safe * * When tracing can happen inside the scheduler, there exists * cases that the tracing might happen before the need_resched * flag is checked. If this happens and the tracer calls * preempt_enable (after a disable), a schedule might take place * causing an infinite recursion. * * To prevent this, we read the need_resched flag before * disabling preemption. When we want to enable preemption we * check the flag, if it is set, then we call preempt_enable_no_resched. * Otherwise, we call preempt_enable. * * The rational for doing the above is that if need_resched is set * and we have yet to reschedule, we are either in an atomic location * (where we do not need to check for scheduling) or we are inside * the scheduler and do not want to resched. */ static inline int ftrace_preempt_disable(void) { int resched; resched = need_resched(); preempt_disable_notrace(); return resched; } /** * ftrace_preempt_enable - enable preemption scheduler safe * @resched: the return value from ftrace_preempt_disable * * This is a scheduler safe way to enable preemption and not miss * any preemption checks. The disabled saved the state of preemption. * If resched is set, then we are either inside an atomic or * are inside the scheduler (we would have already scheduled * otherwise). In this case, we do not want to call normal * preempt_enable, but preempt_enable_no_resched instead. */ static inline void ftrace_preempt_enable(int resched) { if (resched) preempt_enable_no_resched_notrace(); else preempt_enable_notrace(); } #ifdef CONFIG_BRANCH_TRACER extern int enable_branch_tracing(struct trace_array *tr); extern void disable_branch_tracing(void); static inline int trace_branch_enable(struct trace_array *tr) { if (trace_flags & TRACE_ITER_BRANCH) return enable_branch_tracing(tr); return 0; } static inline void trace_branch_disable(void) { /* due to races, always disable */ disable_branch_tracing(); } #else static inline int trace_branch_enable(struct trace_array *tr) { return 0; } static inline void trace_branch_disable(void) { } #endif /* CONFIG_BRANCH_TRACER */ /* set ring buffers to default size if not already done so */ int tracing_update_buffers(void); /* trace event type bit fields, not numeric */ enum { TRACE_EVENT_TYPE_PRINTF = 1, TRACE_EVENT_TYPE_RAW = 2, }; struct ftrace_event_field { struct list_head link; char *name; char *type; int offset; int size; }; struct ftrace_event_call { char *name; char *system; struct dentry *dir; int enabled; int (*regfunc)(void); void (*unregfunc)(void); int id; int (*raw_init)(void); int (*show_format)(struct trace_seq *s); int (*define_fields)(void); struct list_head fields; struct filter_pred **preds; #ifdef CONFIG_EVENT_PROFILE atomic_t profile_count; int (*profile_enable)(struct ftrace_event_call *); void (*profile_disable)(struct ftrace_event_call *); #endif }; struct event_subsystem { struct list_head list; const char *name; struct dentry *entry; struct filter_pred **preds; }; #define events_for_each(event) \ for (event = __start_ftrace_events; \ (unsigned long)event < (unsigned long)__stop_ftrace_events; \ event++) #define MAX_FILTER_PRED 8 struct filter_pred; typedef int (*filter_pred_fn_t) (struct filter_pred *pred, void *event); struct filter_pred { filter_pred_fn_t fn; u64 val; char *str_val; int str_len; char *field_name; int offset; int not; int or; int compound; int clear; }; int trace_define_field(struct ftrace_event_call *call, char *type, char *name, int offset, int size); extern void filter_free_pred(struct filter_pred *pred); extern void filter_print_preds(struct filter_pred **preds, struct trace_seq *s); extern int filter_parse(char **pbuf, struct filter_pred *pred); extern int filter_add_pred(struct ftrace_event_call *call, struct filter_pred *pred); extern void filter_free_preds(struct ftrace_event_call *call); extern int filter_match_preds(struct ftrace_event_call *call, void *rec); extern void filter_free_subsystem_preds(struct event_subsystem *system); extern int filter_add_subsystem_pred(struct event_subsystem *system, struct filter_pred *pred); void event_trace_printk(unsigned long ip, const char *fmt, ...); extern struct ftrace_event_call __start_ftrace_events[]; extern struct ftrace_event_call __stop_ftrace_events[]; #define for_each_event(event) \ for (event = __start_ftrace_events; \ (unsigned long)event < (unsigned long)__stop_ftrace_events; \ event++) extern const char *__start___trace_bprintk_fmt[]; extern const char *__stop___trace_bprintk_fmt[]; /* * 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 optimizing out. */ #define event_trace_printk(ip, fmt, args...) \ do { \ __trace_printk_check_format(fmt, ##args); \ tracing_record_cmdline(current); \ if (__builtin_constant_p(fmt)) { \ static const char *trace_printk_fmt \ __attribute__((section("__trace_printk_fmt"))) = \ __builtin_constant_p(fmt) ? fmt : NULL; \ \ __trace_bprintk(ip, trace_printk_fmt, ##args); \ } else \ __trace_printk(ip, fmt, ##args); \ } while (0) #endif /* _LINUX_KERNEL_TRACE_H */