1 // SPDX-License-Identifier: GPL-2.0-only
3 * kexec.c - kexec_load system call
4 * Copyright (C) 2002-2004 Eric Biederman <ebiederm@xmission.com>
7 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
9 #include <linux/capability.h>
11 #include <linux/file.h>
12 #include <linux/security.h>
13 #include <linux/kexec.h>
14 #include <linux/mutex.h>
15 #include <linux/list.h>
16 #include <linux/syscalls.h>
17 #include <linux/vmalloc.h>
18 #include <linux/slab.h>
20 #include "kexec_internal.h"
22 static int copy_user_segment_list(struct kimage *image,
23 unsigned long nr_segments,
24 struct kexec_segment __user *segments)
29 /* Read in the segments */
30 image->nr_segments = nr_segments;
31 segment_bytes = nr_segments * sizeof(*segments);
32 ret = copy_from_user(image->segment, segments, segment_bytes);
39 static int kimage_alloc_init(struct kimage **rimage, unsigned long entry,
40 unsigned long nr_segments,
41 struct kexec_segment __user *segments,
46 bool kexec_on_panic = flags & KEXEC_ON_CRASH;
49 /* Verify we have a valid entry point */
50 if ((entry < phys_to_boot_phys(crashk_res.start)) ||
51 (entry > phys_to_boot_phys(crashk_res.end)))
52 return -EADDRNOTAVAIL;
55 /* Allocate and initialize a controlling structure */
56 image = do_kimage_alloc_init();
62 ret = copy_user_segment_list(image, nr_segments, segments);
67 /* Enable special crash kernel control page alloc policy. */
68 image->control_page = crashk_res.start;
69 image->type = KEXEC_TYPE_CRASH;
72 ret = sanity_check_segment_list(image);
77 * Find a location for the control code buffer, and add it
78 * the vector of segments so that it's pages will also be
79 * counted as destination pages.
82 image->control_code_page = kimage_alloc_control_pages(image,
83 get_order(KEXEC_CONTROL_PAGE_SIZE));
84 if (!image->control_code_page) {
85 pr_err("Could not allocate control_code_buffer\n");
89 if (!kexec_on_panic) {
90 image->swap_page = kimage_alloc_control_pages(image, 0);
91 if (!image->swap_page) {
92 pr_err("Could not allocate swap buffer\n");
93 goto out_free_control_pages;
99 out_free_control_pages:
100 kimage_free_page_list(&image->control_pages);
106 static int do_kexec_load(unsigned long entry, unsigned long nr_segments,
107 struct kexec_segment __user *segments, unsigned long flags)
109 struct kimage **dest_image, *image;
114 * Because we write directly to the reserved memory region when loading
115 * crash kernels we need a mutex here to prevent multiple crash kernels
116 * from attempting to load simultaneously, and to prevent a crash kernel
117 * from loading over the top of a in use crash kernel.
119 * KISS: always take the mutex.
121 if (!mutex_trylock(&kexec_mutex))
124 if (flags & KEXEC_ON_CRASH) {
125 dest_image = &kexec_crash_image;
126 if (kexec_crash_image)
127 arch_kexec_unprotect_crashkres();
129 dest_image = &kexec_image;
132 if (nr_segments == 0) {
133 /* Uninstall image */
134 kimage_free(xchg(dest_image, NULL));
138 if (flags & KEXEC_ON_CRASH) {
140 * Loading another kernel to switch to if this one
141 * crashes. Free any current crash dump kernel before
144 kimage_free(xchg(&kexec_crash_image, NULL));
147 ret = kimage_alloc_init(&image, entry, nr_segments, segments, flags);
151 if (flags & KEXEC_PRESERVE_CONTEXT)
152 image->preserve_context = 1;
154 ret = machine_kexec_prepare(image);
159 * Some architecture(like S390) may touch the crash memory before
160 * machine_kexec_prepare(), we must copy vmcoreinfo data after it.
162 ret = kimage_crash_copy_vmcoreinfo(image);
166 for (i = 0; i < nr_segments; i++) {
167 ret = kimage_load_segment(image, &image->segment[i]);
172 kimage_terminate(image);
174 ret = machine_kexec_post_load(image);
178 /* Install the new kernel and uninstall the old */
179 image = xchg(dest_image, image);
182 if ((flags & KEXEC_ON_CRASH) && kexec_crash_image)
183 arch_kexec_protect_crashkres();
187 mutex_unlock(&kexec_mutex);
192 * Exec Kernel system call: for obvious reasons only root may call it.
194 * This call breaks up into three pieces.
195 * - A generic part which loads the new kernel from the current
196 * address space, and very carefully places the data in the
199 * - A generic part that interacts with the kernel and tells all of
200 * the devices to shut down. Preventing on-going dmas, and placing
201 * the devices in a consistent state so a later kernel can
204 * - A machine specific part that includes the syscall number
205 * and then copies the image to it's final destination. And
206 * jumps into the image at entry.
208 * kexec does not sync, or unmount filesystems so if you need
209 * that to happen you need to do that yourself.
212 static inline int kexec_load_check(unsigned long nr_segments,
217 /* We only trust the superuser with rebooting the system. */
218 if (!capable(CAP_SYS_BOOT) || kexec_load_disabled)
221 /* Permit LSMs and IMA to fail the kexec */
222 result = security_kernel_load_data(LOADING_KEXEC_IMAGE, false);
227 * kexec can be used to circumvent module loading restrictions, so
228 * prevent loading in that case
230 result = security_locked_down(LOCKDOWN_KEXEC);
235 * Verify we have a legal set of flags
236 * This leaves us room for future extensions.
238 if ((flags & KEXEC_FLAGS) != (flags & ~KEXEC_ARCH_MASK))
241 /* Put an artificial cap on the number
242 * of segments passed to kexec_load.
244 if (nr_segments > KEXEC_SEGMENT_MAX)
250 SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
251 struct kexec_segment __user *, segments, unsigned long, flags)
255 result = kexec_load_check(nr_segments, flags);
259 /* Verify we are on the appropriate architecture */
260 if (((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH) &&
261 ((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH_DEFAULT))
264 result = do_kexec_load(entry, nr_segments, segments, flags);
270 COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry,
271 compat_ulong_t, nr_segments,
272 struct compat_kexec_segment __user *, segments,
273 compat_ulong_t, flags)
275 struct compat_kexec_segment in;
276 struct kexec_segment out, __user *ksegments;
277 unsigned long i, result;
279 result = kexec_load_check(nr_segments, flags);
283 /* Don't allow clients that don't understand the native
284 * architecture to do anything.
286 if ((flags & KEXEC_ARCH_MASK) == KEXEC_ARCH_DEFAULT)
289 ksegments = compat_alloc_user_space(nr_segments * sizeof(out));
290 for (i = 0; i < nr_segments; i++) {
291 result = copy_from_user(&in, &segments[i], sizeof(in));
295 out.buf = compat_ptr(in.buf);
296 out.bufsz = in.bufsz;
298 out.memsz = in.memsz;
300 result = copy_to_user(&ksegments[i], &out, sizeof(out));
305 result = do_kexec_load(entry, nr_segments, ksegments, flags);