1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * kexec.c - kexec_load system call
4 * Copyright (C) 2002-2004 Eric Biederman  <ebiederm@xmission.com>
5 */
6
7#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
8
9#include <linux/capability.h>
10#include <linux/mm.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>
19
20#include "kexec_internal.h"
21
22static int kimage_alloc_init(struct kimage **rimage, unsigned long entry,
23			     unsigned long nr_segments,
24			     struct kexec_segment *segments,
25			     unsigned long flags)
26{
27	int ret;
28	struct kimage *image;
29	bool kexec_on_panic = flags & KEXEC_ON_CRASH;
30
31#ifdef CONFIG_CRASH_DUMP
32	if (kexec_on_panic) {
33		/* Verify we have a valid entry point */
34		if ((entry < phys_to_boot_phys(crashk_res.start)) ||
35		    (entry > phys_to_boot_phys(crashk_res.end)))
36			return -EADDRNOTAVAIL;
37	}
38#endif
39
40	/* Allocate and initialize a controlling structure */
41	image = do_kimage_alloc_init();
42	if (!image)
43		return -ENOMEM;
44
45	image->start = entry;
46	image->nr_segments = nr_segments;
47	memcpy(image->segment, segments, nr_segments * sizeof(*segments));
48
49#ifdef CONFIG_CRASH_DUMP
50	if (kexec_on_panic) {
51		/* Enable special crash kernel control page alloc policy. */
52		image->control_page = crashk_res.start;
53		image->type = KEXEC_TYPE_CRASH;
54	}
55#endif
56
57	ret = sanity_check_segment_list(image);
58	if (ret)
59		goto out_free_image;
60
61	/*
62	 * Find a location for the control code buffer, and add it
63	 * the vector of segments so that it's pages will also be
64	 * counted as destination pages.
65	 */
66	ret = -ENOMEM;
67	image->control_code_page = kimage_alloc_control_pages(image,
68					   get_order(KEXEC_CONTROL_PAGE_SIZE));
69	if (!image->control_code_page) {
70		pr_err("Could not allocate control_code_buffer\n");
71		goto out_free_image;
72	}
73
74	if (!kexec_on_panic) {
75		image->swap_page = kimage_alloc_control_pages(image, 0);
76		if (!image->swap_page) {
77			pr_err("Could not allocate swap buffer\n");
78			goto out_free_control_pages;
79		}
80	}
81
82	*rimage = image;
83	return 0;
84out_free_control_pages:
85	kimage_free_page_list(&image->control_pages);
86out_free_image:
87	kfree(image);
88	return ret;
89}
90
91static int do_kexec_load(unsigned long entry, unsigned long nr_segments,
92		struct kexec_segment *segments, unsigned long flags)
93{
94	struct kimage **dest_image, *image;
95	unsigned long i;
96	int ret;
97
98	/*
99	 * Because we write directly to the reserved memory region when loading
100	 * crash kernels we need a serialization here to prevent multiple crash
101	 * kernels from attempting to load simultaneously.
102	 */
103	if (!kexec_trylock())
104		return -EBUSY;
105
106#ifdef CONFIG_CRASH_DUMP
107	if (flags & KEXEC_ON_CRASH) {
108		dest_image = &kexec_crash_image;
109		if (kexec_crash_image)
110			arch_kexec_unprotect_crashkres();
111	} else
112#endif
113		dest_image = &kexec_image;
114
115	if (nr_segments == 0) {
116		/* Uninstall image */
117		kimage_free(xchg(dest_image, NULL));
118		ret = 0;
119		goto out_unlock;
120	}
121	if (flags & KEXEC_ON_CRASH) {
122		/*
123		 * Loading another kernel to switch to if this one
124		 * crashes.  Free any current crash dump kernel before
125		 * we corrupt it.
126		 */
127		kimage_free(xchg(&kexec_crash_image, NULL));
128	}
129
130	ret = kimage_alloc_init(&image, entry, nr_segments, segments, flags);
131	if (ret)
132		goto out_unlock;
133
134	if (flags & KEXEC_PRESERVE_CONTEXT)
135		image->preserve_context = 1;
136
137#ifdef CONFIG_CRASH_HOTPLUG
138	if (flags & KEXEC_UPDATE_ELFCOREHDR)
139		image->update_elfcorehdr = 1;
140#endif
141
142	ret = machine_kexec_prepare(image);
143	if (ret)
144		goto out;
145
146	/*
147	 * Some architecture(like S390) may touch the crash memory before
148	 * machine_kexec_prepare(), we must copy vmcoreinfo data after it.
149	 */
150	ret = kimage_crash_copy_vmcoreinfo(image);
151	if (ret)
152		goto out;
153
154	for (i = 0; i < nr_segments; i++) {
155		ret = kimage_load_segment(image, &image->segment[i]);
156		if (ret)
157			goto out;
158	}
159
160	kimage_terminate(image);
161
162	ret = machine_kexec_post_load(image);
163	if (ret)
164		goto out;
165
166	/* Install the new kernel and uninstall the old */
167	image = xchg(dest_image, image);
168
169out:
170#ifdef CONFIG_CRASH_DUMP
171	if ((flags & KEXEC_ON_CRASH) && kexec_crash_image)
172		arch_kexec_protect_crashkres();
173#endif
174
175	kimage_free(image);
176out_unlock:
177	kexec_unlock();
178	return ret;
179}
180
181/*
182 * Exec Kernel system call: for obvious reasons only root may call it.
183 *
184 * This call breaks up into three pieces.
185 * - A generic part which loads the new kernel from the current
186 *   address space, and very carefully places the data in the
187 *   allocated pages.
188 *
189 * - A generic part that interacts with the kernel and tells all of
190 *   the devices to shut down.  Preventing on-going dmas, and placing
191 *   the devices in a consistent state so a later kernel can
192 *   reinitialize them.
193 *
194 * - A machine specific part that includes the syscall number
195 *   and then copies the image to it's final destination.  And
196 *   jumps into the image at entry.
197 *
198 * kexec does not sync, or unmount filesystems so if you need
199 * that to happen you need to do that yourself.
200 */
201
202static inline int kexec_load_check(unsigned long nr_segments,
203				   unsigned long flags)
204{
205	int image_type = (flags & KEXEC_ON_CRASH) ?
206			 KEXEC_TYPE_CRASH : KEXEC_TYPE_DEFAULT;
207	int result;
208
209	/* We only trust the superuser with rebooting the system. */
210	if (!kexec_load_permitted(image_type))
211		return -EPERM;
212
213	/* Permit LSMs and IMA to fail the kexec */
214	result = security_kernel_load_data(LOADING_KEXEC_IMAGE, false);
215	if (result < 0)
216		return result;
217
218	/*
219	 * kexec can be used to circumvent module loading restrictions, so
220	 * prevent loading in that case
221	 */
222	result = security_locked_down(LOCKDOWN_KEXEC);
223	if (result)
224		return result;
225
226	/*
227	 * Verify we have a legal set of flags
228	 * This leaves us room for future extensions.
229	 */
230	if ((flags & KEXEC_FLAGS) != (flags & ~KEXEC_ARCH_MASK))
231		return -EINVAL;
232
233	/* Put an artificial cap on the number
234	 * of segments passed to kexec_load.
235	 */
236	if (nr_segments > KEXEC_SEGMENT_MAX)
237		return -EINVAL;
238
239	return 0;
240}
241
242SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
243		struct kexec_segment __user *, segments, unsigned long, flags)
244{
245	struct kexec_segment *ksegments;
246	unsigned long result;
247
248	result = kexec_load_check(nr_segments, flags);
249	if (result)
250		return result;
251
252	/* Verify we are on the appropriate architecture */
253	if (((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH) &&
254		((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH_DEFAULT))
255		return -EINVAL;
256
257	ksegments = memdup_array_user(segments, nr_segments, sizeof(ksegments[0]));
258	if (IS_ERR(ksegments))
259		return PTR_ERR(ksegments);
260
261	result = do_kexec_load(entry, nr_segments, ksegments, flags);
262	kfree(ksegments);
263
264	return result;
265}
266
267#ifdef CONFIG_COMPAT
268COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry,
269		       compat_ulong_t, nr_segments,
270		       struct compat_kexec_segment __user *, segments,
271		       compat_ulong_t, flags)
272{
273	struct compat_kexec_segment in;
274	struct kexec_segment *ksegments;
275	unsigned long i, result;
276
277	result = kexec_load_check(nr_segments, flags);
278	if (result)
279		return result;
280
281	/* Don't allow clients that don't understand the native
282	 * architecture to do anything.
283	 */
284	if ((flags & KEXEC_ARCH_MASK) == KEXEC_ARCH_DEFAULT)
285		return -EINVAL;
286
287	ksegments = kmalloc_array(nr_segments, sizeof(ksegments[0]),
288			GFP_KERNEL);
289	if (!ksegments)
290		return -ENOMEM;
291
292	for (i = 0; i < nr_segments; i++) {
293		result = copy_from_user(&in, &segments[i], sizeof(in));
294		if (result)
295			goto fail;
296
297		ksegments[i].buf   = compat_ptr(in.buf);
298		ksegments[i].bufsz = in.bufsz;
299		ksegments[i].mem   = in.mem;
300		ksegments[i].memsz = in.memsz;
301	}
302
303	result = do_kexec_load(entry, nr_segments, ksegments, flags);
304
305fail:
306	kfree(ksegments);
307	return result;
308}
309#endif
310