/*
 * Stack trace management functions
 *
 *  Copyright (C) 2006-2009 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 */
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/sched/task_stack.h>
#include <linux/stacktrace.h>
#include <linux/export.h>
#include <linux/uaccess.h>
#include <asm/stacktrace.h>
#include <asm/unwind.h>

void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
                     struct task_struct *task, struct pt_regs *regs)
{
        struct unwind_state state;
        unsigned long addr;

        if (regs && !consume_entry(cookie, regs->ip))
                return;

        for (unwind_start(&state, task, regs, NULL); !unwind_done(&state);
             unwind_next_frame(&state)) {
                addr = unwind_get_return_address(&state);
                if (!addr || !consume_entry(cookie, addr))
                        break;
        }
}

int arch_stack_walk_reliable(stack_trace_consume_fn consume_entry,
                             void *cookie, struct task_struct *task)
{
        struct unwind_state state;
        struct pt_regs *regs;
        unsigned long addr;

        for (unwind_start(&state, task, NULL, NULL);
             !unwind_done(&state) && !unwind_error(&state);
             unwind_next_frame(&state)) {

                regs = unwind_get_entry_regs(&state, NULL);
                if (regs) {
                        /* Success path for user tasks */
                        if (user_mode(regs))
                                return 0;

                        /*
                         * Kernel mode registers on the stack indicate an
                         * in-kernel interrupt or exception (e.g., preemption
                         * or a page fault), which can make frame pointers
                         * unreliable.
                         */
                        if (IS_ENABLED(CONFIG_FRAME_POINTER))
                                return -EINVAL;
                }

                addr = unwind_get_return_address(&state);

                /*
                 * A NULL or invalid return address probably means there's some
                 * generated code which __kernel_text_address() doesn't know
                 * about.
                 */
                if (!addr)
                        return -EINVAL;

                if (!consume_entry(cookie, addr))
                        return -EINVAL;
        }

        /* Check for stack corruption */
        if (unwind_error(&state))
                return -EINVAL;

        return 0;
}

/* Userspace stacktrace - based on kernel/trace/trace_sysprof.c */

struct stack_frame_user {
        const void __user       *next_fp;
        unsigned long           ret_addr;
};

static int
copy_stack_frame(const struct stack_frame_user __user *fp,
                 struct stack_frame_user *frame)
{
        int ret;

        if (!__access_ok(fp, sizeof(*frame)))
                return 0;

        ret = 1;
        pagefault_disable();
        if (__get_user(frame->next_fp, &fp->next_fp) ||
            __get_user(frame->ret_addr, &fp->ret_addr))
                ret = 0;
        pagefault_enable();

        return ret;
}

void arch_stack_walk_user(stack_trace_consume_fn consume_entry, void *cookie,
                          const struct pt_regs *regs)
{
        const void __user *fp = (const void __user *)regs->bp;

        if (!consume_entry(cookie, regs->ip))
                return;

        while (1) {
                struct stack_frame_user frame;

                frame.next_fp = NULL;
                frame.ret_addr = 0;
                if (!copy_stack_frame(fp, &frame))
                        break;
                if ((unsigned long)fp < regs->sp)
                        break;
                if (!frame.ret_addr)
                        break;
                if (!consume_entry(cookie, frame.ret_addr))
                        break;
                fp = frame.next_fp;
        }
}