// SPDX-License-Identifier: GPL-2.0-only
/*
 * kernel/stacktrace.c
 *
 * Stack trace management functions
 *
 *  Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 */
#include <linux/sched/task_stack.h>
#include <linux/sched/debug.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/kallsyms.h>
#include <linux/stacktrace.h>

/**
 * stack_trace_print - Print the entries in the stack trace
 * @entries:    Pointer to storage array
 * @nr_entries: Number of entries in the storage array
 * @spaces:     Number of leading spaces to print
 */
void stack_trace_print(const unsigned long *entries, unsigned int nr_entries,
                       int spaces)
{
        unsigned int i;

        if (WARN_ON(!entries))
                return;

        for (i = 0; i < nr_entries; i++)
                printk("%*c%pS\n", 1 + spaces, ' ', (void *)entries[i]);
}
EXPORT_SYMBOL_GPL(stack_trace_print);

/**
 * stack_trace_snprint - Print the entries in the stack trace into a buffer
 * @buf:        Pointer to the print buffer
 * @size:       Size of the print buffer
 * @entries:    Pointer to storage array
 * @nr_entries: Number of entries in the storage array
 * @spaces:     Number of leading spaces to print
 *
 * Return: Number of bytes printed.
 */
int stack_trace_snprint(char *buf, size_t size, const unsigned long *entries,
                        unsigned int nr_entries, int spaces)
{
        unsigned int generated, i, total = 0;

        if (WARN_ON(!entries))
                return 0;

        for (i = 0; i < nr_entries && size; i++) {
                generated = snprintf(buf, size, "%*c%pS\n", 1 + spaces, ' ',
                                     (void *)entries[i]);

                total += generated;
                if (generated >= size) {
                        buf += size;
                        size = 0;
                } else {
                        buf += generated;
                        size -= generated;
                }
        }

        return total;
}
EXPORT_SYMBOL_GPL(stack_trace_snprint);

#ifdef CONFIG_ARCH_STACKWALK

struct stacktrace_cookie {
        unsigned long   *store;
        unsigned int    size;
        unsigned int    skip;
        unsigned int    len;
};

static bool stack_trace_consume_entry(void *cookie, unsigned long addr)
{
        struct stacktrace_cookie *c = cookie;

        if (c->len >= c->size)
                return false;

        if (c->skip > 0) {
                c->skip--;
                return true;
        }
        c->store[c->len++] = addr;
        return c->len < c->size;
}

static bool stack_trace_consume_entry_nosched(void *cookie, unsigned long addr)
{
        if (in_sched_functions(addr))
                return true;
        return stack_trace_consume_entry(cookie, addr);
}

/**
 * stack_trace_save - Save a stack trace into a storage array
 * @store:      Pointer to storage array
 * @size:       Size of the storage array
 * @skipnr:     Number of entries to skip at the start of the stack trace
 *
 * Return: Number of trace entries stored.
 */
unsigned int stack_trace_save(unsigned long *store, unsigned int size,
                              unsigned int skipnr)
{
        stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
        struct stacktrace_cookie c = {
                .store  = store,
                .size   = size,
                .skip   = skipnr + 1,
        };

        arch_stack_walk(consume_entry, &c, current, NULL);
        return c.len;
}
EXPORT_SYMBOL_GPL(stack_trace_save);

/**
 * stack_trace_save_tsk - Save a task stack trace into a storage array
 * @task:       The task to examine
 * @store:      Pointer to storage array
 * @size:       Size of the storage array
 * @skipnr:     Number of entries to skip at the start of the stack trace
 *
 * Return: Number of trace entries stored.
 */
unsigned int stack_trace_save_tsk(struct task_struct *tsk, unsigned long *store,
                                  unsigned int size, unsigned int skipnr)
{
        stack_trace_consume_fn consume_entry = stack_trace_consume_entry_nosched;
        struct stacktrace_cookie c = {
                .store  = store,
                .size   = size,
                /* skip this function if they are tracing us */
                .skip   = skipnr + (current == tsk),
        };

        if (!try_get_task_stack(tsk))
                return 0;

        arch_stack_walk(consume_entry, &c, tsk, NULL);
        put_task_stack(tsk);
        return c.len;
}

/**
 * stack_trace_save_regs - Save a stack trace based on pt_regs into a storage array
 * @regs:       Pointer to pt_regs to examine
 * @store:      Pointer to storage array
 * @size:       Size of the storage array
 * @skipnr:     Number of entries to skip at the start of the stack trace
 *
 * Return: Number of trace entries stored.
 */
unsigned int stack_trace_save_regs(struct pt_regs *regs, unsigned long *store,
                                   unsigned int size, unsigned int skipnr)
{
        stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
        struct stacktrace_cookie c = {
                .store  = store,
                .size   = size,
                .skip   = skipnr,
        };

        arch_stack_walk(consume_entry, &c, current, regs);
        return c.len;
}

#ifdef CONFIG_HAVE_RELIABLE_STACKTRACE
/**
 * stack_trace_save_tsk_reliable - Save task stack with verification
 * @tsk:        Pointer to the task to examine
 * @store:      Pointer to storage array
 * @size:       Size of the storage array
 *
 * Return:      An error if it detects any unreliable features of the
 *              stack. Otherwise it guarantees that the stack trace is
 *              reliable and returns the number of entries stored.
 *
 * If the task is not 'current', the caller *must* ensure the task is inactive.
 */
int stack_trace_save_tsk_reliable(struct task_struct *tsk, unsigned long *store,
                                  unsigned int size)
{
        stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
        struct stacktrace_cookie c = {
                .store  = store,
                .size   = size,
        };
        int ret;

        /*
         * If the task doesn't have a stack (e.g., a zombie), the stack is
         * "reliably" empty.
         */
        if (!try_get_task_stack(tsk))
                return 0;

        ret = arch_stack_walk_reliable(consume_entry, &c, tsk);
        put_task_stack(tsk);
        return ret ? ret : c.len;
}
#endif

#ifdef CONFIG_USER_STACKTRACE_SUPPORT
/**
 * stack_trace_save_user - Save a user space stack trace into a storage array
 * @store:      Pointer to storage array
 * @size:       Size of the storage array
 *
 * Return: Number of trace entries stored.
 */
unsigned int stack_trace_save_user(unsigned long *store, unsigned int size)
{
        stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
        struct stacktrace_cookie c = {
                .store  = store,
                .size   = size,
        };
        mm_segment_t fs;

        /* Trace user stack if not a kernel thread */
        if (current->flags & PF_KTHREAD)
                return 0;

        fs = force_uaccess_begin();
        arch_stack_walk_user(consume_entry, &c, task_pt_regs(current));
        force_uaccess_end(fs);

        return c.len;
}
#endif

#else /* CONFIG_ARCH_STACKWALK */

/*
 * Architectures that do not implement save_stack_trace_*()
 * get these weak aliases and once-per-bootup warnings
 * (whenever this facility is utilized - for example by procfs):
 */
__weak void
save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
{
        WARN_ONCE(1, KERN_INFO "save_stack_trace_tsk() not implemented yet.\n");
}

__weak void
save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
{
        WARN_ONCE(1, KERN_INFO "save_stack_trace_regs() not implemented yet.\n");
}

/**
 * stack_trace_save - Save a stack trace into a storage array
 * @store:      Pointer to storage array
 * @size:       Size of the storage array
 * @skipnr:     Number of entries to skip at the start of the stack trace
 *
 * Return: Number of trace entries stored
 */
unsigned int stack_trace_save(unsigned long *store, unsigned int size,
                              unsigned int skipnr)
{
        struct stack_trace trace = {
                .entries        = store,
                .max_entries    = size,
                .skip           = skipnr + 1,
        };

        save_stack_trace(&trace);
        return trace.nr_entries;
}
EXPORT_SYMBOL_GPL(stack_trace_save);

/**
 * stack_trace_save_tsk - Save a task stack trace into a storage array
 * @task:       The task to examine
 * @store:      Pointer to storage array
 * @size:       Size of the storage array
 * @skipnr:     Number of entries to skip at the start of the stack trace
 *
 * Return: Number of trace entries stored
 */
unsigned int stack_trace_save_tsk(struct task_struct *task,
                                  unsigned long *store, unsigned int size,
                                  unsigned int skipnr)
{
        struct stack_trace trace = {
                .entries        = store,
                .max_entries    = size,
                /* skip this function if they are tracing us */
                .skip   = skipnr + (current == task),
        };

        save_stack_trace_tsk(task, &trace);
        return trace.nr_entries;
}

/**
 * stack_trace_save_regs - Save a stack trace based on pt_regs into a storage array
 * @regs:       Pointer to pt_regs to examine
 * @store:      Pointer to storage array
 * @size:       Size of the storage array
 * @skipnr:     Number of entries to skip at the start of the stack trace
 *
 * Return: Number of trace entries stored
 */
unsigned int stack_trace_save_regs(struct pt_regs *regs, unsigned long *store,
                                   unsigned int size, unsigned int skipnr)
{
        struct stack_trace trace = {
                .entries        = store,
                .max_entries    = size,
                .skip           = skipnr,
        };

        save_stack_trace_regs(regs, &trace);
        return trace.nr_entries;
}

#ifdef CONFIG_HAVE_RELIABLE_STACKTRACE
/**
 * stack_trace_save_tsk_reliable - Save task stack with verification
 * @tsk:        Pointer to the task to examine
 * @store:      Pointer to storage array
 * @size:       Size of the storage array
 *
 * Return:      An error if it detects any unreliable features of the
 *              stack. Otherwise it guarantees that the stack trace is
 *              reliable and returns the number of entries stored.
 *
 * If the task is not 'current', the caller *must* ensure the task is inactive.
 */
int stack_trace_save_tsk_reliable(struct task_struct *tsk, unsigned long *store,
                                  unsigned int size)
{
        struct stack_trace trace = {
                .entries        = store,
                .max_entries    = size,
        };
        int ret = save_stack_trace_tsk_reliable(tsk, &trace);

        return ret ? ret : trace.nr_entries;
}
#endif

#ifdef CONFIG_USER_STACKTRACE_SUPPORT
/**
 * stack_trace_save_user - Save a user space stack trace into a storage array
 * @store:      Pointer to storage array
 * @size:       Size of the storage array
 *
 * Return: Number of trace entries stored
 */
unsigned int stack_trace_save_user(unsigned long *store, unsigned int size)
{
        struct stack_trace trace = {
                .entries        = store,
                .max_entries    = size,
        };

        save_stack_trace_user(&trace);
        return trace.nr_entries;
}
#endif /* CONFIG_USER_STACKTRACE_SUPPORT */

#endif /* !CONFIG_ARCH_STACKWALK */