// SPDX-License-Identifier: GPL-2.0-only
/*
 * kexec.c - kexec_load system call
 * Copyright (C) 2002-2004 Eric Biederman  <ebiederm@xmission.com>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/capability.h>
#include <linux/mm.h>
#include <linux/file.h>
#include <linux/security.h>
#include <linux/kexec.h>
#include <linux/mutex.h>
#include <linux/list.h>
#include <linux/syscalls.h>
#include <linux/vmalloc.h>
#include <linux/slab.h>

#include "kexec_internal.h"

static int copy_user_segment_list(struct kimage *image,
                                  unsigned long nr_segments,
                                  struct kexec_segment __user *segments)
{
        int ret;
        size_t segment_bytes;

        /* Read in the segments */
        image->nr_segments = nr_segments;
        segment_bytes = nr_segments * sizeof(*segments);
        ret = copy_from_user(image->segment, segments, segment_bytes);
        if (ret)
                ret = -EFAULT;

        return ret;
}

static int kimage_alloc_init(struct kimage **rimage, unsigned long entry,
                             unsigned long nr_segments,
                             struct kexec_segment __user *segments,
                             unsigned long flags)
{
        int ret;
        struct kimage *image;
        bool kexec_on_panic = flags & KEXEC_ON_CRASH;

        if (kexec_on_panic) {
                /* Verify we have a valid entry point */
                if ((entry < phys_to_boot_phys(crashk_res.start)) ||
                    (entry > phys_to_boot_phys(crashk_res.end)))
                        return -EADDRNOTAVAIL;
        }

        /* Allocate and initialize a controlling structure */
        image = do_kimage_alloc_init();
        if (!image)
                return -ENOMEM;

        image->start = entry;

        ret = copy_user_segment_list(image, nr_segments, segments);
        if (ret)
                goto out_free_image;

        if (kexec_on_panic) {
                /* Enable special crash kernel control page alloc policy. */
                image->control_page = crashk_res.start;
                image->type = KEXEC_TYPE_CRASH;
        }

        ret = sanity_check_segment_list(image);
        if (ret)
                goto out_free_image;

        /*
         * Find a location for the control code buffer, and add it
         * the vector of segments so that it's pages will also be
         * counted as destination pages.
         */
        ret = -ENOMEM;
        image->control_code_page = kimage_alloc_control_pages(image,
                                           get_order(KEXEC_CONTROL_PAGE_SIZE));
        if (!image->control_code_page) {
                pr_err("Could not allocate control_code_buffer\n");
                goto out_free_image;
        }

        if (!kexec_on_panic) {
                image->swap_page = kimage_alloc_control_pages(image, 0);
                if (!image->swap_page) {
                        pr_err("Could not allocate swap buffer\n");
                        goto out_free_control_pages;
                }
        }

        *rimage = image;
        return 0;
out_free_control_pages:
        kimage_free_page_list(&image->control_pages);
out_free_image:
        kfree(image);
        return ret;
}

static int do_kexec_load(unsigned long entry, unsigned long nr_segments,
                struct kexec_segment __user *segments, unsigned long flags)
{
        struct kimage **dest_image, *image;
        unsigned long i;
        int ret;

        if (flags & KEXEC_ON_CRASH) {
                dest_image = &kexec_crash_image;
                if (kexec_crash_image)
                        arch_kexec_unprotect_crashkres();
        } else {
                dest_image = &kexec_image;
        }

        if (nr_segments == 0) {
                /* Uninstall image */
                kimage_free(xchg(dest_image, NULL));
                return 0;
        }
        if (flags & KEXEC_ON_CRASH) {
                /*
                 * Loading another kernel to switch to if this one
                 * crashes.  Free any current crash dump kernel before
                 * we corrupt it.
                 */
                kimage_free(xchg(&kexec_crash_image, NULL));
        }

        ret = kimage_alloc_init(&image, entry, nr_segments, segments, flags);
        if (ret)
                return ret;

        if (flags & KEXEC_PRESERVE_CONTEXT)
                image->preserve_context = 1;

        ret = machine_kexec_prepare(image);
        if (ret)
                goto out;

        /*
         * Some architecture(like S390) may touch the crash memory before
         * machine_kexec_prepare(), we must copy vmcoreinfo data after it.
         */
        ret = kimage_crash_copy_vmcoreinfo(image);
        if (ret)
                goto out;

        for (i = 0; i < nr_segments; i++) {
                ret = kimage_load_segment(image, &image->segment[i]);
                if (ret)
                        goto out;
        }

        kimage_terminate(image);

        ret = machine_kexec_post_load(image);
        if (ret)
                goto out;

        /* Install the new kernel and uninstall the old */
        image = xchg(dest_image, image);

out:
        if ((flags & KEXEC_ON_CRASH) && kexec_crash_image)
                arch_kexec_protect_crashkres();

        kimage_free(image);
        return ret;
}

/*
 * Exec Kernel system call: for obvious reasons only root may call it.
 *
 * This call breaks up into three pieces.
 * - A generic part which loads the new kernel from the current
 *   address space, and very carefully places the data in the
 *   allocated pages.
 *
 * - A generic part that interacts with the kernel and tells all of
 *   the devices to shut down.  Preventing on-going dmas, and placing
 *   the devices in a consistent state so a later kernel can
 *   reinitialize them.
 *
 * - A machine specific part that includes the syscall number
 *   and then copies the image to it's final destination.  And
 *   jumps into the image at entry.
 *
 * kexec does not sync, or unmount filesystems so if you need
 * that to happen you need to do that yourself.
 */

static inline int kexec_load_check(unsigned long nr_segments,
                                   unsigned long flags)
{
        int result;

        /* We only trust the superuser with rebooting the system. */
        if (!capable(CAP_SYS_BOOT) || kexec_load_disabled)
                return -EPERM;

        /* Permit LSMs and IMA to fail the kexec */
        result = security_kernel_load_data(LOADING_KEXEC_IMAGE, false);
        if (result < 0)
                return result;

        /*
         * kexec can be used to circumvent module loading restrictions, so
         * prevent loading in that case
         */
        result = security_locked_down(LOCKDOWN_KEXEC);
        if (result)
                return result;

        /*
         * Verify we have a legal set of flags
         * This leaves us room for future extensions.
         */
        if ((flags & KEXEC_FLAGS) != (flags & ~KEXEC_ARCH_MASK))
                return -EINVAL;

        /* Put an artificial cap on the number
         * of segments passed to kexec_load.
         */
        if (nr_segments > KEXEC_SEGMENT_MAX)
                return -EINVAL;

        return 0;
}

SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
                struct kexec_segment __user *, segments, unsigned long, flags)
{
        int result;

        result = kexec_load_check(nr_segments, flags);
        if (result)
                return result;

        /* Verify we are on the appropriate architecture */
        if (((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH) &&
                ((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH_DEFAULT))
                return -EINVAL;

        /* Because we write directly to the reserved memory
         * region when loading crash kernels we need a mutex here to
         * prevent multiple crash  kernels from attempting to load
         * simultaneously, and to prevent a crash kernel from loading
         * over the top of a in use crash kernel.
         *
         * KISS: always take the mutex.
         */
        if (!mutex_trylock(&kexec_mutex))
                return -EBUSY;

        result = do_kexec_load(entry, nr_segments, segments, flags);

        mutex_unlock(&kexec_mutex);

        return result;
}

#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry,
                       compat_ulong_t, nr_segments,
                       struct compat_kexec_segment __user *, segments,
                       compat_ulong_t, flags)
{
        struct compat_kexec_segment in;
        struct kexec_segment out, __user *ksegments;
        unsigned long i, result;

        result = kexec_load_check(nr_segments, flags);
        if (result)
                return result;

        /* Don't allow clients that don't understand the native
         * architecture to do anything.
         */
        if ((flags & KEXEC_ARCH_MASK) == KEXEC_ARCH_DEFAULT)
                return -EINVAL;

        ksegments = compat_alloc_user_space(nr_segments * sizeof(out));
        for (i = 0; i < nr_segments; i++) {
                result = copy_from_user(&in, &segments[i], sizeof(in));
                if (result)
                        return -EFAULT;

                out.buf   = compat_ptr(in.buf);
                out.bufsz = in.bufsz;
                out.mem   = in.mem;
                out.memsz = in.memsz;

                result = copy_to_user(&ksegments[i], &out, sizeof(out));
                if (result)
                        return -EFAULT;
        }

        /* Because we write directly to the reserved memory
         * region when loading crash kernels we need a mutex here to
         * prevent multiple crash  kernels from attempting to load
         * simultaneously, and to prevent a crash kernel from loading
         * over the top of a in use crash kernel.
         *
         * KISS: always take the mutex.
         */
        if (!mutex_trylock(&kexec_mutex))
                return -EBUSY;

        result = do_kexec_load(entry, nr_segments, ksegments, flags);

        mutex_unlock(&kexec_mutex);

        return result;
}
#endif