/* * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com> * */#include <linux/stacktrace.h>#include <linux/kallsyms.h>#include <linux/seq_file.h>#include <linux/spinlock.h>#include <linux/uaccess.h>#include <linux/debugfs.h>#include <linux/ftrace.h>#include <linux/module.h>#include <linux/sysctl.h>#include <linux/init.h>#include <linux/fs.h>#include "trace.h" #define STACK_TRACE_ENTRIES 500 static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] =	 { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX };static unsigned stack_dump_index[STACK_TRACE_ENTRIES]; static struct stack_trace max_stack_trace = {	.max_entries		= STACK_TRACE_ENTRIES,	.entries		= stack_dump_trace,}; static unsigned long max_stack_size;static arch_spinlock_t max_stack_lock =	(arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; static int stack_trace_disabled __read_mostly;static DEFINE_PER_CPU(int, trace_active);static DEFINE_MUTEX(stack_sysctl_mutex); int stack_tracer_enabled;static int last_stack_tracer_enabled; static inline void check_stack(void){	unsigned long this_size, flags;	unsigned long *p, *top, *start;	int i; 	this_size = ((unsigned long)&this_size) & (THREAD_SIZE-1);	this_size = THREAD_SIZE - this_size; 	if (this_size <= max_stack_size)		return; 	/* we do not handle interrupt stacks yet */	if (!object_is_on_stack(&this_size))		return; 	local_irq_save(flags);	arch_spin_lock(&max_stack_lock); 	/* a race could have already updated it */	if (this_size <= max_stack_size)		goto out; 	max_stack_size = this_size; 	max_stack_trace.nr_entries	= 0;	max_stack_trace.skip		= 3; 	save_stack_trace(&max_stack_trace); 	/*	 * Now find where in the stack these are.	 */	i = 0;	start = &this_size;	top = (unsigned long *)		(((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE); 	/*	 * Loop through all the entries. One of the entries may	 * for some reason be missed on the stack, so we may	 * have to account for them. If they are all there, this	 * loop will only happen once. This code only takes place	 * on a new max, so it is far from a fast path.	 */	while (i < max_stack_trace.nr_entries) {		int found = 0; 		stack_dump_index[i] = this_size;		p = start; 		for (; p < top && i < max_stack_trace.nr_entries; p++) {			if (*p == stack_dump_trace[i]) {				this_size = stack_dump_index[i++] =					(top - p) * sizeof(unsigned long);				found = 1;				/* Start the search from here */				start = p + 1;			}		} 		if (!found)			i++;	}  out:	arch_spin_unlock(&max_stack_lock);	local_irq_restore(flags);} static voidstack_trace_call(unsigned long ip, unsigned long parent_ip){	int cpu; 	if (unlikely(!ftrace_enabled || stack_trace_disabled))		return; 	preempt_disable_notrace(); 	cpu = raw_smp_processor_id();	/* no atomic needed, we only modify this variable by this cpu */	if (per_cpu(trace_active, cpu)++ != 0)		goto out; 	check_stack();  out:	per_cpu(trace_active, cpu)--;	/* prevent recursion in schedule */	preempt_enable_notrace();} static struct ftrace_ops trace_ops __read_mostly ={	.func = stack_trace_call,	.flags = FTRACE_OPS_FL_GLOBAL,}; static ssize_tstack_max_size_read(struct file *filp, char __user *ubuf,		    size_t count, loff_t *ppos){	unsigned long *ptr = filp->private_data;	char buf[64];	int r; 	r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);	if (r > sizeof(buf))		r = sizeof(buf);	return simple_read_from_buffer(ubuf, count, ppos, buf, r);} static ssize_tstack_max_size_write(struct file *filp, const char __user *ubuf,		     size_t count, loff_t *ppos){	long *ptr = filp->private_data;	unsigned long val, flags;	int ret;	int cpu; 	ret = kstrtoul_from_user(ubuf, count, 10, &val);	if (ret)		return ret; 	local_irq_save(flags); 	/*	 * In case we trace inside arch_spin_lock() or after (NMI),	 * we will cause circular lock, so we also need to increase	 * the percpu trace_active here.	 */	cpu = smp_processor_id();	per_cpu(trace_active, cpu)++; 	arch_spin_lock(&max_stack_lock);	*ptr = val;	arch_spin_unlock(&max_stack_lock); 	per_cpu(trace_active, cpu)--;	local_irq_restore(flags); 	return count;} static const struct file_operations stack_max_size_fops = {	.open		= tracing_open_generic,	.read		= stack_max_size_read,	.write		= stack_max_size_write,	.llseek		= default_llseek,}; static void *__next(struct seq_file *m, loff_t *pos){	long n = *pos - 1; 	if (n >= max_stack_trace.nr_entries || stack_dump_trace[n] == ULONG_MAX)		return NULL; 	m->private = (void *)n;	return &m->private;} static void *t_next(struct seq_file *m, void *v, loff_t *pos){	(*pos)++;	return __next(m, pos);} static void *t_start(struct seq_file *m, loff_t *pos){	int cpu; 	local_irq_disable(); 	cpu = smp_processor_id();	per_cpu(trace_active, cpu)++; 	arch_spin_lock(&max_stack_lock); 	if (*pos == 0)		return SEQ_START_TOKEN; 	return __next(m, pos);} static void t_stop(struct seq_file *m, void *p){	int cpu; 	arch_spin_unlock(&max_stack_lock); 	cpu = smp_processor_id();	per_cpu(trace_active, cpu)--; 	local_irq_enable();} static int trace_lookup_stack(struct seq_file *m, long i){	unsigned long addr = stack_dump_trace[i]; 	return seq_printf(m, "%pS\n", (void *)addr);} static void print_disabled(struct seq_file *m){	seq_puts(m, "#\n"		 "#  Stack tracer disabled\n"		 "#\n"		 "# To enable the stack tracer, either add 'stacktrace' to the\n"		 "# kernel command line\n"		 "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n"		 "#\n");} static int t_show(struct seq_file *m, void *v){	long i;	int size; 	if (v == SEQ_START_TOKEN) {		seq_printf(m, "        Depth    Size   Location"			   "    (%d entries)\n"			   "        -----    ----   --------\n",			   max_stack_trace.nr_entries - 1); 		if (!stack_tracer_enabled && !max_stack_size)			print_disabled(m); 		return 0;	} 	i = *(long *)v; 	if (i >= max_stack_trace.nr_entries ||	    stack_dump_trace[i] == ULONG_MAX)		return 0; 	if (i+1 == max_stack_trace.nr_entries ||	    stack_dump_trace[i+1] == ULONG_MAX)		size = stack_dump_index[i];	else		size = stack_dump_index[i] - stack_dump_index[i+1]; 	seq_printf(m, "%3ld) %8d   %5d   ", i, stack_dump_index[i], size); 	trace_lookup_stack(m, i); 	return 0;} static const struct seq_operations stack_trace_seq_ops = {	.start		= t_start,	.next		= t_next,	.stop		= t_stop,	.show		= t_show,}; static int stack_trace_open(struct inode *inode, struct file *file){	return seq_open(file, &stack_trace_seq_ops);} static const struct file_operations stack_trace_fops = {	.open		= stack_trace_open,	.read		= seq_read,	.llseek		= seq_lseek,	.release	= seq_release,}; intstack_trace_sysctl(struct ctl_table *table, int write,		   void __user *buffer, size_t *lenp,		   loff_t *ppos){	int ret; 	mutex_lock(&stack_sysctl_mutex); 	ret = proc_dointvec(table, write, buffer, lenp, ppos); 	if (ret || !write ||	    (last_stack_tracer_enabled == !!stack_tracer_enabled))		goto out; 	last_stack_tracer_enabled = !!stack_tracer_enabled; 	if (stack_tracer_enabled)		register_ftrace_function(&trace_ops);	else		unregister_ftrace_function(&trace_ops);  out:	mutex_unlock(&stack_sysctl_mutex);	return ret;} static __init int enable_stacktrace(char *str){	stack_tracer_enabled = 1;	last_stack_tracer_enabled = 1;	return 1;}__setup("stacktrace", enable_stacktrace); static __init int stack_trace_init(void){	struct dentry *d_tracer; 	d_tracer = tracing_init_dentry(); 	trace_create_file("stack_max_size", 0644, d_tracer,			&max_stack_size, &stack_max_size_fops); 	trace_create_file("stack_trace", 0444, d_tracer,			NULL, &stack_trace_fops); 	if (stack_tracer_enabled)		register_ftrace_function(&trace_ops); 	return 0;} device_initcall(stack_trace_init);