/* * ring buffer based function tracer * * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com> * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com> * * Based on code from the latency_tracer, that is: * * Copyright (C) 2004-2006 Ingo Molnar * Copyright (C) 2004 Nadia Yvette Chambers */ #include <linux/ring_buffer.h> #include <linux/debugfs.h> #include <linux/uaccess.h> #include <linux/ftrace.h> #include <linux/slab.h> #include <linux/fs.h> #include "trace.h" static void tracing_start_function_trace(struct trace_array *tr); static void tracing_stop_function_trace(struct trace_array *tr); static void function_trace_call(unsigned long ip, unsigned long parent_ip, struct ftrace_ops *op, struct pt_regs *pt_regs); static void function_stack_trace_call(unsigned long ip, unsigned long parent_ip, struct ftrace_ops *op, struct pt_regs *pt_regs); static struct tracer_flags func_flags; /* Our option */ enum { TRACE_FUNC_OPT_STACK = 0x1, }; static int allocate_ftrace_ops(struct trace_array *tr) { struct ftrace_ops *ops; ops = kzalloc(sizeof(*ops), GFP_KERNEL); if (!ops) return -ENOMEM; /* Currently only the non stack verision is supported */ ops->func = function_trace_call; ops->flags = FTRACE_OPS_FL_RECURSION_SAFE | FTRACE_OPS_FL_PID; tr->ops = ops; ops->private = tr; return 0; } int ftrace_create_function_files(struct trace_array *tr, struct dentry *parent) { int ret; /* * The top level array uses the "global_ops", and the files are * created on boot up. */ if (tr->flags & TRACE_ARRAY_FL_GLOBAL) return 0; ret = allocate_ftrace_ops(tr); if (ret) return ret; ftrace_create_filter_files(tr->ops, parent); return 0; } void ftrace_destroy_function_files(struct trace_array *tr) { ftrace_destroy_filter_files(tr->ops); kfree(tr->ops); tr->ops = NULL; } static int function_trace_init(struct trace_array *tr) { ftrace_func_t func; /* * Instance trace_arrays get their ops allocated * at instance creation. Unless it failed * the allocation. */ if (!tr->ops) return -ENOMEM; /* Currently only the global instance can do stack tracing */ if (tr->flags & TRACE_ARRAY_FL_GLOBAL && func_flags.val & TRACE_FUNC_OPT_STACK) func = function_stack_trace_call; else func = function_trace_call; ftrace_init_array_ops(tr, func); tr->trace_buffer.cpu = get_cpu(); put_cpu(); tracing_start_cmdline_record(); tracing_start_function_trace(tr); return 0; } static void function_trace_reset(struct trace_array *tr) { tracing_stop_function_trace(tr); tracing_stop_cmdline_record(); ftrace_reset_array_ops(tr); } static void function_trace_start(struct trace_array *tr) { tracing_reset_online_cpus(&tr->trace_buffer); } static void function_trace_call(unsigned long ip, unsigned long parent_ip, struct ftrace_ops *op, struct pt_regs *pt_regs) { struct trace_array *tr = op->private; struct trace_array_cpu *data; unsigned long flags; int bit; int cpu; int pc; if (unlikely(!tr->function_enabled)) return; pc = preempt_count(); preempt_disable_notrace(); bit = trace_test_and_set_recursion(TRACE_FTRACE_START, TRACE_FTRACE_MAX); if (bit < 0) goto out; cpu = smp_processor_id(); data = per_cpu_ptr(tr->trace_buffer.data, cpu); if (!atomic_read(&data->disabled)) { local_save_flags(flags); trace_function(tr, ip, parent_ip, flags, pc); } trace_clear_recursion(bit); out: preempt_enable_notrace(); } static void function_stack_trace_call(unsigned long ip, unsigned long parent_ip, struct ftrace_ops *op, struct pt_regs *pt_regs) { struct trace_array *tr = op->private; struct trace_array_cpu *data; unsigned long flags; long disabled; int cpu; int pc; if (unlikely(!tr->function_enabled)) return; /* * Need to use raw, since this must be called before the * recursive protection is performed. */ local_irq_save(flags); cpu = raw_smp_processor_id(); data = per_cpu_ptr(tr->trace_buffer.data, cpu); disabled = atomic_inc_return(&data->disabled); if (likely(disabled == 1)) { pc = preempt_count(); trace_function(tr, ip, parent_ip, flags, pc); /* * skip over 5 funcs: * __ftrace_trace_stack, * __trace_stack, * function_stack_trace_call * ftrace_list_func * ftrace_call */ __trace_stack(tr, flags, 5, pc); } atomic_dec(&data->disabled); local_irq_restore(flags); } static struct tracer_opt func_opts[] = { #ifdef CONFIG_STACKTRACE { TRACER_OPT(func_stack_trace, TRACE_FUNC_OPT_STACK) }, #endif { } /* Always set a last empty entry */ }; static struct tracer_flags func_flags = { .val = 0, /* By default: all flags disabled */ .opts = func_opts }; static void tracing_start_function_trace(struct trace_array *tr) { tr->function_enabled = 0; register_ftrace_function(tr->ops); tr->function_enabled = 1; } static void tracing_stop_function_trace(struct trace_array *tr) { tr->function_enabled = 0; unregister_ftrace_function(tr->ops); } static struct tracer function_trace; static int func_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set) { switch (bit) { case TRACE_FUNC_OPT_STACK: /* do nothing if already set */ if (!!set == !!(func_flags.val & TRACE_FUNC_OPT_STACK)) break; /* We can change this flag when not running. */ if (tr->current_trace != &function_trace) break; unregister_ftrace_function(tr->ops); if (set) { tr->ops->func = function_stack_trace_call; register_ftrace_function(tr->ops); } else { tr->ops->func = function_trace_call; register_ftrace_function(tr->ops); } break; default: return -EINVAL; } return 0; } static struct tracer function_trace __tracer_data = { .name = "function", .init = function_trace_init, .reset = function_trace_reset, .start = function_trace_start, .flags = &func_flags, .set_flag = func_set_flag, .allow_instances = true, #ifdef CONFIG_FTRACE_SELFTEST .selftest = trace_selftest_startup_function, #endif }; #ifdef CONFIG_DYNAMIC_FTRACE static void update_traceon_count(void **data, bool on) { long *count = (long *)data; long old_count = *count; /* * Tracing gets disabled (or enabled) once per count. * This function can be called at the same time on multiple CPUs. * It is fine if both disable (or enable) tracing, as disabling * (or enabling) the second time doesn't do anything as the * state of the tracer is already disabled (or enabled). * What needs to be synchronized in this case is that the count * only gets decremented once, even if the tracer is disabled * (or enabled) twice, as the second one is really a nop. * * The memory barriers guarantee that we only decrement the * counter once. First the count is read to a local variable * and a read barrier is used to make sure that it is loaded * before checking if the tracer is in the state we want. * If the tracer is not in the state we want, then the count * is guaranteed to be the old count. * * Next the tracer is set to the state we want (disabled or enabled) * then a write memory barrier is used to make sure that * the new state is visible before changing the counter by * one minus the old counter. This guarantees that another CPU * executing this code will see the new state before seeing * the new counter value, and would not do anything if the new * counter is seen. * * Note, there is no synchronization between this and a user * setting the tracing_on file. But we currently don't care * about that. */ if (!old_count) return; /* Make sure we see count before checking tracing state */ smp_rmb(); if (on == !!tracing_is_on()) return; if (on) tracing_on(); else tracing_off(); /* unlimited? */ if (old_count == -1) return; /* Make sure tracing state is visible before updating count */ smp_wmb(); *count = old_count - 1; } static void ftrace_traceon_count(unsigned long ip, unsigned long parent_ip, void **data) { update_traceon_count(data, 1); } static void ftrace_traceoff_count(unsigned long ip, unsigned long parent_ip, void **data) { update_traceon_count(data, 0); } static void ftrace_traceon(unsigned long ip, unsigned long parent_ip, void **data) { if (tracing_is_on()) return; tracing_on(); } static void ftrace_traceoff(unsigned long ip, unsigned long parent_ip, void **data) { if (!tracing_is_on()) return; tracing_off(); } /* * Skip 4: * ftrace_stacktrace() * function_trace_probe_call() * ftrace_ops_list_func() * ftrace_call() */ #define STACK_SKIP 4 static void ftrace_stacktrace(unsigned long ip, unsigned long parent_ip, void **data) { trace_dump_stack(STACK_SKIP); } static void ftrace_stacktrace_count(unsigned long ip, unsigned long parent_ip, void **data) { long *count = (long *)data; long old_count; long new_count; /* * Stack traces should only execute the number of times the * user specified in the counter. */ do { if (!tracing_is_on()) return; old_count = *count; if (!old_count) return; /* unlimited? */ if (old_count == -1) { trace_dump_stack(STACK_SKIP); return; } new_count = old_count - 1; new_count = cmpxchg(count, old_count, new_count); if (new_count == old_count) trace_dump_stack(STACK_SKIP); } while (new_count != old_count); } static int update_count(void **data) { unsigned long *count = (long *)data; if (!*count) return 0; if (*count != -1) (*count)--; return 1; } static void ftrace_dump_probe(unsigned long ip, unsigned long parent_ip, void **data) { if (update_count(data)) ftrace_dump(DUMP_ALL); } /* Only dump the current CPU buffer. */ static void ftrace_cpudump_probe(unsigned long ip, unsigned long parent_ip, void **data) { if (update_count(data)) ftrace_dump(DUMP_ORIG); } static int ftrace_probe_print(const char *name, struct seq_file *m, unsigned long ip, void *data) { long count = (long)data; seq_printf(m, "%ps:%s", (void *)ip, name); if (count == -1) seq_puts(m, ":unlimited\n"); else seq_printf(m, ":count=%ld\n", count); return 0; } static int ftrace_traceon_print(struct seq_file *m, unsigned long ip, struct ftrace_probe_ops *ops, void *data) { return ftrace_probe_print("traceon", m, ip, data); } static int ftrace_traceoff_print(struct seq_file *m, unsigned long ip, struct ftrace_probe_ops *ops, void *data) { return ftrace_probe_print("traceoff", m, ip, data); } static int ftrace_stacktrace_print(struct seq_file *m, unsigned long ip, struct ftrace_probe_ops *ops, void *data) { return ftrace_probe_print("stacktrace", m, ip, data); } static int ftrace_dump_print(struct seq_file *m, unsigned long ip, struct ftrace_probe_ops *ops, void *data) { return ftrace_probe_print("dump", m, ip, data); } static int ftrace_cpudump_print(struct seq_file *m, unsigned long ip, struct ftrace_probe_ops *ops, void *data) { return ftrace_probe_print("cpudump", m, ip, data); } static struct ftrace_probe_ops traceon_count_probe_ops = { .func = ftrace_traceon_count, .print = ftrace_traceon_print, }; static struct ftrace_probe_ops traceoff_count_probe_ops = { .func = ftrace_traceoff_count, .print = ftrace_traceoff_print, }; static struct ftrace_probe_ops stacktrace_count_probe_ops = { .func = ftrace_stacktrace_count, .print = ftrace_stacktrace_print, }; static struct ftrace_probe_ops dump_probe_ops = { .func = ftrace_dump_probe, .print = ftrace_dump_print, }; static struct ftrace_probe_ops cpudump_probe_ops = { .func = ftrace_cpudump_probe, .print = ftrace_cpudump_print, }; static struct ftrace_probe_ops traceon_probe_ops = { .func = ftrace_traceon, .print = ftrace_traceon_print, }; static struct ftrace_probe_ops traceoff_probe_ops = { .func = ftrace_traceoff, .print = ftrace_traceoff_print, }; static struct ftrace_probe_ops stacktrace_probe_ops = { .func = ftrace_stacktrace, .print = ftrace_stacktrace_print, }; static int ftrace_trace_probe_callback(struct ftrace_probe_ops *ops, struct ftrace_hash *hash, char *glob, char *cmd, char *param, int enable) { void *count = (void *)-1; char *number; int ret; /* hash funcs only work with set_ftrace_filter */ if (!enable) return -EINVAL; if (glob[0] == '!') { unregister_ftrace_function_probe_func(glob+1, ops); return 0; } if (!param) goto out_reg; number = strsep(¶m, ":"); if (!strlen(number)) goto out_reg; /* * We use the callback data field (which is a pointer) * as our counter. */ ret = kstrtoul(number, 0, (unsigned long *)&count); if (ret) return ret; out_reg: ret = register_ftrace_function_probe(glob, ops, count); return ret < 0 ? ret : 0; } static int ftrace_trace_onoff_callback(struct ftrace_hash *hash, char *glob, char *cmd, char *param, int enable) { struct ftrace_probe_ops *ops; /* we register both traceon and traceoff to this callback */ if (strcmp(cmd, "traceon") == 0) ops = param ? &traceon_count_probe_ops : &traceon_probe_ops; else ops = param ? &traceoff_count_probe_ops : &traceoff_probe_ops; return ftrace_trace_probe_callback(ops, hash, glob, cmd, param, enable); } static int ftrace_stacktrace_callback(struct ftrace_hash *hash, char *glob, char *cmd, char *param, int enable) { struct ftrace_probe_ops *ops; ops = param ? &stacktrace_count_probe_ops : &stacktrace_probe_ops; return ftrace_trace_probe_callback(ops, hash, glob, cmd, param, enable); } static int ftrace_dump_callback(struct ftrace_hash *hash, char *glob, char *cmd, char *param, int enable) { struct ftrace_probe_ops *ops; ops = &dump_probe_ops; /* Only dump once. */ return ftrace_trace_probe_callback(ops, hash, glob, cmd, "1", enable); } static int ftrace_cpudump_callback(struct ftrace_hash *hash, char *glob, char *cmd, char *param, int enable) { struct ftrace_probe_ops *ops; ops = &cpudump_probe_ops; /* Only dump once. */ return ftrace_trace_probe_callback(ops, hash, glob, cmd, "1", enable); } static struct ftrace_func_command ftrace_traceon_cmd = { .name = "traceon", .func = ftrace_trace_onoff_callback, }; static struct ftrace_func_command ftrace_traceoff_cmd = { .name = "traceoff", .func = ftrace_trace_onoff_callback, }; static struct ftrace_func_command ftrace_stacktrace_cmd = { .name = "stacktrace", .func = ftrace_stacktrace_callback, }; static struct ftrace_func_command ftrace_dump_cmd = { .name = "dump", .func = ftrace_dump_callback, }; static struct ftrace_func_command ftrace_cpudump_cmd = { .name = "cpudump", .func = ftrace_cpudump_callback, }; static int __init init_func_cmd_traceon(void) { int ret; ret = register_ftrace_command(&ftrace_traceoff_cmd); if (ret) return ret; ret = register_ftrace_command(&ftrace_traceon_cmd); if (ret) goto out_free_traceoff; ret = register_ftrace_command(&ftrace_stacktrace_cmd); if (ret) goto out_free_traceon; ret = register_ftrace_command(&ftrace_dump_cmd); if (ret) goto out_free_stacktrace; ret = register_ftrace_command(&ftrace_cpudump_cmd); if (ret) goto out_free_dump; return 0; out_free_dump: unregister_ftrace_command(&ftrace_dump_cmd); out_free_stacktrace: unregister_ftrace_command(&ftrace_stacktrace_cmd); out_free_traceon: unregister_ftrace_command(&ftrace_traceon_cmd); out_free_traceoff: unregister_ftrace_command(&ftrace_traceoff_cmd); return ret; } #else static inline int init_func_cmd_traceon(void) { return 0; } #endif /* CONFIG_DYNAMIC_FTRACE */ static __init int init_function_trace(void) { init_func_cmd_traceon(); return register_tracer(&function_trace); } core_initcall(init_function_trace);