// SPDX-License-Identifier: GPL-2.0/* * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com> * */#include <linux/sched/task_stack.h>#include <linux/stacktrace.h>#include <linux/kallsyms.h>#include <linux/seq_file.h>#include <linux/spinlock.h>#include <linux/uaccess.h>#include <linux/ftrace.h>#include <linux/module.h>#include <linux/sysctl.h>#include <linux/init.h> #include <asm/setup.h> #include "trace.h" #define STACK_TRACE_ENTRIES 500 static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES];static unsigned stack_trace_index[STACK_TRACE_ENTRIES]; static unsigned int stack_trace_nr_entries;static unsigned long stack_trace_max_size;static arch_spinlock_t stack_trace_max_lock =	(arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; DEFINE_PER_CPU(int, disable_stack_tracer);static DEFINE_MUTEX(stack_sysctl_mutex); int stack_tracer_enabled; static void print_max_stack(void){	long i;	int size; 	pr_emerg("        Depth    Size   Location    (%d entries)\n"			   "        -----    ----   --------\n",			   stack_trace_nr_entries); 	for (i = 0; i < stack_trace_nr_entries; i++) {		if (i + 1 == stack_trace_nr_entries)			size = stack_trace_index[i];		else			size = stack_trace_index[i] - stack_trace_index[i+1]; 		pr_emerg("%3ld) %8d   %5d   %pS\n", i, stack_trace_index[i],				size, (void *)stack_dump_trace[i]);	}} /* * The stack tracer looks for a maximum stack at each call from a function. It * registers a callback from ftrace, and in that callback it examines the stack * size. It determines the stack size from the variable passed in, which is the * address of a local variable in the stack_trace_call() callback function. * The stack size is calculated by the address of the local variable to the top * of the current stack. If that size is smaller than the currently saved max * stack size, nothing more is done. * * If the size of the stack is greater than the maximum recorded size, then the * following algorithm takes place. * * For architectures (like x86) that store the function's return address before * saving the function's local variables, the stack will look something like * this: * *   [ top of stack ] *    0: sys call entry frame *   10: return addr to entry code *   11: start of sys_foo frame *   20: return addr to sys_foo *   21: start of kernel_func_bar frame *   30: return addr to kernel_func_bar *   31: [ do trace stack here ] * * The save_stack_trace() is called returning all the functions it finds in the * current stack. Which would be (from the bottom of the stack to the top): * *   return addr to kernel_func_bar *   return addr to sys_foo *   return addr to entry code * * Now to figure out how much each of these functions' local variable size is, * a search of the stack is made to find these values. When a match is made, it * is added to the stack_dump_trace[] array. The offset into the stack is saved * in the stack_trace_index[] array. The above example would show: * *        stack_dump_trace[]        |   stack_trace_index[] *        ------------------        +   ------------------- *  return addr to kernel_func_bar  |          30 *  return addr to sys_foo          |          20 *  return addr to entry            |          10 * * The print_max_stack() function above, uses these values to print the size of * each function's portion of the stack. * *  for (i = 0; i < nr_entries; i++) { *     size = i == nr_entries - 1 ? stack_trace_index[i] : *                    stack_trace_index[i] - stack_trace_index[i+1] *     print "%d %d %d %s\n", i, stack_trace_index[i], size, stack_dump_trace[i]); *  } * * The above shows * *     depth size  location *     ----- ----  -------- *  0    30   10   kernel_func_bar *  1    20   10   sys_foo *  2    10   10   entry code * * Now for architectures that might save the return address after the functions * local variables (saving the link register before calling nested functions), * this will cause the stack to look a little different: * * [ top of stack ] *  0: sys call entry frame * 10: start of sys_foo_frame * 19: return addr to entry code << lr saved before calling kernel_func_bar * 20: start of kernel_func_bar frame * 29: return addr to sys_foo_frame << lr saved before calling next function * 30: [ do trace stack here ] * * Although the functions returned by save_stack_trace() may be the same, the * placement in the stack will be different. Using the same algorithm as above * would yield: * *        stack_dump_trace[]        |   stack_trace_index[] *        ------------------        +   ------------------- *  return addr to kernel_func_bar  |          30 *  return addr to sys_foo          |          29 *  return addr to entry            |          19 * * Where the mapping is off by one: * *   kernel_func_bar stack frame size is 29 - 19 not 30 - 29! * * To fix this, if the architecture sets ARCH_RET_ADDR_AFTER_LOCAL_VARS the * values in stack_trace_index[] are shifted by one to and the number of * stack trace entries is decremented by one. * *        stack_dump_trace[]        |   stack_trace_index[] *        ------------------        +   ------------------- *  return addr to kernel_func_bar  |          29 *  return addr to sys_foo          |          19 * * Although the entry function is not displayed, the first function (sys_foo) * will still include the stack size of it. */static void check_stack(unsigned long ip, unsigned long *stack){	unsigned long this_size, flags; unsigned long *p, *top, *start;	static int tracer_frame;	int frame_size = READ_ONCE(tracer_frame);	int i, x; 	this_size = ((unsigned long)stack) & (THREAD_SIZE-1);	this_size = THREAD_SIZE - this_size;	/* Remove the frame of the tracer */	this_size -= frame_size; 	if (this_size <= stack_trace_max_size)		return; 	/* we do not handle interrupt stacks yet */	if (!object_is_on_stack(stack))		return; 	/* Can't do this from NMI context (can cause deadlocks) */	if (in_nmi())		return; 	local_irq_save(flags);	arch_spin_lock(&stack_trace_max_lock); 	/* In case another CPU set the tracer_frame on us */	if (unlikely(!frame_size))		this_size -= tracer_frame; 	/* a race could have already updated it */	if (this_size <= stack_trace_max_size)		goto out; 	stack_trace_max_size = this_size; 	stack_trace_nr_entries = stack_trace_save(stack_dump_trace,					       ARRAY_SIZE(stack_dump_trace) - 1,					       0); 	/* Skip over the overhead of the stack tracer itself */	for (i = 0; i < stack_trace_nr_entries; i++) {		if (stack_dump_trace[i] == ip)			break;	} 	/*	 * Some archs may not have the passed in ip in the dump.	 * If that happens, we need to show everything.	 */	if (i == stack_trace_nr_entries)		i = 0; 	/*	 * Now find where in the stack these are.	 */	x = 0;	start = stack;	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 < stack_trace_nr_entries) {		int found = 0; 		stack_trace_index[x] = this_size;		p = start; 		for (; p < top && i < stack_trace_nr_entries; p++) {			/*			 * The READ_ONCE_NOCHECK is used to let KASAN know that			 * this is not a stack-out-of-bounds error.			 */			if ((READ_ONCE_NOCHECK(*p)) == stack_dump_trace[i]) {				stack_dump_trace[x] = stack_dump_trace[i++];				this_size = stack_trace_index[x++] =					(top - p) * sizeof(unsigned long);				found = 1;				/* Start the search from here */				start = p + 1;				/*				 * We do not want to show the overhead				 * of the stack tracer stack in the				 * max stack. If we haven't figured				 * out what that is, then figure it out				 * now.				 */				if (unlikely(!tracer_frame)) {					tracer_frame = (p - stack) *						sizeof(unsigned long);					stack_trace_max_size -= tracer_frame;				}			}		} 		if (!found)			i++;	} #ifdef ARCH_FTRACE_SHIFT_STACK_TRACER	/*	 * Some archs will store the link register before calling	 * nested functions. This means the saved return address	 * comes after the local storage, and we need to shift	 * for that.	 */	if (x > 1) {		memmove(&stack_trace_index[0], &stack_trace_index[1],			sizeof(stack_trace_index[0]) * (x - 1));		x--;	}#endif 	stack_trace_nr_entries = x; 	if (task_stack_end_corrupted(current)) {		print_max_stack();		BUG();	}  out:	arch_spin_unlock(&stack_trace_max_lock);	local_irq_restore(flags);} static voidstack_trace_call(unsigned long ip, unsigned long parent_ip,		 struct ftrace_ops *op, struct pt_regs *pt_regs){	unsigned long stack; 	preempt_disable_notrace(); 	/* no atomic needed, we only modify this variable by this cpu */	__this_cpu_inc(disable_stack_tracer);	if (__this_cpu_read(disable_stack_tracer) != 1)		goto out; 	/* If rcu is not watching, then save stack trace can fail */	if (!rcu_is_watching())		goto out; 	ip += MCOUNT_INSN_SIZE; 	check_stack(ip, &stack);  out:	__this_cpu_dec(disable_stack_tracer);	/* prevent recursion in schedule */	preempt_enable_notrace();} static struct ftrace_ops trace_ops __read_mostly ={	.func = stack_trace_call,	.flags = FTRACE_OPS_FL_RECURSION_SAFE,}; 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; 	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 disable_stack_tracer here.	 */	__this_cpu_inc(disable_stack_tracer); 	arch_spin_lock(&stack_trace_max_lock);	*ptr = val;	arch_spin_unlock(&stack_trace_max_lock); 	__this_cpu_dec(disable_stack_tracer);	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 >= stack_trace_nr_entries)		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){	local_irq_disable(); 	__this_cpu_inc(disable_stack_tracer); 	arch_spin_lock(&stack_trace_max_lock); 	if (*pos == 0)		return SEQ_START_TOKEN; 	return __next(m, pos);} static void t_stop(struct seq_file *m, void *p){	arch_spin_unlock(&stack_trace_max_lock); 	__this_cpu_dec(disable_stack_tracer); 	local_irq_enable();} static void trace_lookup_stack(struct seq_file *m, long i){	unsigned long addr = stack_dump_trace[i]; 	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",			   stack_trace_nr_entries); 		if (!stack_tracer_enabled && !stack_trace_max_size)			print_disabled(m); 		return 0;	} 	i = *(long *)v; 	if (i >= stack_trace_nr_entries)		return 0; 	if (i + 1 == stack_trace_nr_entries)		size = stack_trace_index[i];	else		size = stack_trace_index[i] - stack_trace_index[i+1]; 	seq_printf(m, "%3ld) %8d   %5d   ", i, stack_trace_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,}; #ifdef CONFIG_DYNAMIC_FTRACE static intstack_trace_filter_open(struct inode *inode, struct file *file){	struct ftrace_ops *ops = inode->i_private; 	return ftrace_regex_open(ops, FTRACE_ITER_FILTER,				 inode, file);} static const struct file_operations stack_trace_filter_fops = {	.open = stack_trace_filter_open,	.read = seq_read,	.write = ftrace_filter_write,	.llseek = tracing_lseek,	.release = ftrace_regex_release,};

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