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ad90c0e3ce
In dynamic ftrace, the mcount function starts off pointing to a stub function that just returns. On start up, the call to the stub is modified to point to a "record_ip" function. The job of the record_ip function is to add the function to a pre-allocated hash list. If the function is already there, it simply is ignored, otherwise it is added to the list. Later, a ftraced daemon wakes up and calls kstop_machine if any functions have been recorded, and changes the calls to the recorded functions to a simple nop. If no functions were recorded, the daemon goes back to sleep. The daemon wakes up once a second to see if it needs to update any newly recorded functions into nops. Usually it does not, but if a lot of code has been executed for the first time in the kernel, the ftraced daemon will call kstop_machine to update those into nops. The problem currently is that there's no way to stop the daemon from doing this, and it can cause unneeded latencies (800us which for some is bothersome). This patch adds a new file /debugfs/tracing/ftraced_enabled. If the daemon is active, reading this will return "enabled\n" and "disabled\n" when the daemon is not running. To disable the daemon, the user can echo "0" or "disable" into this file, and "1" or "enable" to re-enable the daemon. Since the daemon is used to convert the functions into nops to increase the performance of the system, I also added that anytime something is written into the ftraced_enabled file, kstop_machine will run if there are new functions that have been detected that need to be converted. This way the user can disable the daemon but still be able to control the conversion of the mcount calls to nops by simply, "echo 0 > /debugfs/tracing/ftraced_enabled" when they need to do more conversions. To see the number of converted functions: "cat /debugfs/tracing/dyn_ftrace_total_info" Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
139 lines
4.2 KiB
C
139 lines
4.2 KiB
C
#ifndef _LINUX_FTRACE_H
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#define _LINUX_FTRACE_H
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#ifdef CONFIG_FTRACE
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#include <linux/linkage.h>
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#include <linux/fs.h>
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extern int ftrace_enabled;
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extern int
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ftrace_enable_sysctl(struct ctl_table *table, int write,
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struct file *filp, void __user *buffer, size_t *lenp,
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loff_t *ppos);
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typedef void (*ftrace_func_t)(unsigned long ip, unsigned long parent_ip);
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struct ftrace_ops {
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ftrace_func_t func;
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struct ftrace_ops *next;
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};
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/*
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* The ftrace_ops must be a static and should also
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* be read_mostly. These functions do modify read_mostly variables
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* so use them sparely. Never free an ftrace_op or modify the
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* next pointer after it has been registered. Even after unregistering
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* it, the next pointer may still be used internally.
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*/
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int register_ftrace_function(struct ftrace_ops *ops);
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int unregister_ftrace_function(struct ftrace_ops *ops);
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void clear_ftrace_function(void);
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extern void ftrace_stub(unsigned long a0, unsigned long a1);
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extern void mcount(void);
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#else /* !CONFIG_FTRACE */
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# define register_ftrace_function(ops) do { } while (0)
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# define unregister_ftrace_function(ops) do { } while (0)
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# define clear_ftrace_function(ops) do { } while (0)
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#endif /* CONFIG_FTRACE */
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#ifdef CONFIG_DYNAMIC_FTRACE
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# define FTRACE_HASHBITS 10
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# define FTRACE_HASHSIZE (1<<FTRACE_HASHBITS)
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enum {
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FTRACE_FL_FREE = (1 << 0),
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FTRACE_FL_FAILED = (1 << 1),
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FTRACE_FL_FILTER = (1 << 2),
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FTRACE_FL_ENABLED = (1 << 3),
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FTRACE_FL_NOTRACE = (1 << 4),
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};
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struct dyn_ftrace {
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struct hlist_node node;
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unsigned long ip;
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unsigned long flags;
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};
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int ftrace_force_update(void);
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void ftrace_set_filter(unsigned char *buf, int len, int reset);
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/* defined in arch */
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extern int ftrace_ip_converted(unsigned long ip);
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extern unsigned char *ftrace_nop_replace(void);
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extern unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr);
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extern int ftrace_dyn_arch_init(void *data);
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extern int ftrace_mcount_set(unsigned long *data);
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extern int ftrace_modify_code(unsigned long ip, unsigned char *old_code,
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unsigned char *new_code);
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extern int ftrace_update_ftrace_func(ftrace_func_t func);
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extern void ftrace_caller(void);
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extern void ftrace_call(void);
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extern void mcount_call(void);
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void ftrace_disable_daemon(void);
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void ftrace_enable_daemon(void);
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#else
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# define ftrace_force_update() ({ 0; })
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# define ftrace_set_filter(buf, len, reset) do { } while (0)
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# define ftrace_disable_daemon() do { } while (0)
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# define ftrace_enable_daemon() do { } while (0)
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#endif
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/* totally disable ftrace - can not re-enable after this */
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void ftrace_kill(void);
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static inline void tracer_disable(void)
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{
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#ifdef CONFIG_FTRACE
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ftrace_enabled = 0;
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#endif
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}
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#ifdef CONFIG_FRAME_POINTER
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/* TODO: need to fix this for ARM */
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# define CALLER_ADDR0 ((unsigned long)__builtin_return_address(0))
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# define CALLER_ADDR1 ((unsigned long)__builtin_return_address(1))
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# define CALLER_ADDR2 ((unsigned long)__builtin_return_address(2))
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# define CALLER_ADDR3 ((unsigned long)__builtin_return_address(3))
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# define CALLER_ADDR4 ((unsigned long)__builtin_return_address(4))
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# define CALLER_ADDR5 ((unsigned long)__builtin_return_address(5))
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# define CALLER_ADDR6 ((unsigned long)__builtin_return_address(6))
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#else
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# define CALLER_ADDR0 ((unsigned long)__builtin_return_address(0))
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# define CALLER_ADDR1 0UL
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# define CALLER_ADDR2 0UL
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# define CALLER_ADDR3 0UL
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# define CALLER_ADDR4 0UL
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# define CALLER_ADDR5 0UL
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# define CALLER_ADDR6 0UL
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#endif
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#ifdef CONFIG_IRQSOFF_TRACER
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extern void time_hardirqs_on(unsigned long a0, unsigned long a1);
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extern void time_hardirqs_off(unsigned long a0, unsigned long a1);
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#else
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# define time_hardirqs_on(a0, a1) do { } while (0)
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# define time_hardirqs_off(a0, a1) do { } while (0)
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#endif
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#ifdef CONFIG_PREEMPT_TRACER
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extern void trace_preempt_on(unsigned long a0, unsigned long a1);
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extern void trace_preempt_off(unsigned long a0, unsigned long a1);
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#else
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# define trace_preempt_on(a0, a1) do { } while (0)
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# define trace_preempt_off(a0, a1) do { } while (0)
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#endif
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#ifdef CONFIG_TRACING
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extern void
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ftrace_special(unsigned long arg1, unsigned long arg2, unsigned long arg3);
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#else
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static inline void
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ftrace_special(unsigned long arg1, unsigned long arg2, unsigned long arg3) { }
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#endif
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#endif /* _LINUX_FTRACE_H */
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