// 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 kimage_alloc_init(struct kimage **rimage, unsigned long entry,

unsigned long nr_segments,

struct kexec_segment *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;

image->nr_segments = nr_segments;

memcpy(image->segment, segments, nr_segments * sizeof(*segments));

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 *segments, unsigned long flags)

{

struct kimage **dest_image, *image;

unsigned long i;

int ret;

/*

* 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;

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));

ret = 0;

goto out_unlock;

}

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)

goto out_unlock;

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);

out_unlock:

mutex_unlock(&kexec_mutex);

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)

{

struct kexec_segment *ksegments;

unsigned long 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;

ksegments = memdup_user(segments, nr_segments * sizeof(ksegments[0]));

if (IS_ERR(ksegments))

return PTR_ERR(ksegments);

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

kfree(ksegments);

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 *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 = kmalloc_array(nr_segments, sizeof(ksegments[0]),

GFP_KERNEL);

if (!ksegments)

return -ENOMEM;

for (i = 0; i < nr_segments; i++) {

result = copy_from_user(&in, &segments[i], sizeof(in));

if (result)

goto fail;

ksegments[i].buf = compat_ptr(in.buf);

ksegments[i].bufsz = in.bufsz;

ksegments[i].mem = in.mem;

ksegments[i].memsz = in.memsz;

}

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

fail:

kfree(ksegments);

return result;

}

#endif