1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * PPC64 code to handle Linux booting another kernel.
4  *
5  * Copyright (C) 2004-2005, IBM Corp.
6  *
7  * Created by: Milton D Miller II
8  */
9 
10 
11 #include <linux/kexec.h>
12 #include <linux/smp.h>
13 #include <linux/thread_info.h>
14 #include <linux/init_task.h>
15 #include <linux/errno.h>
16 #include <linux/kernel.h>
17 #include <linux/cpu.h>
18 #include <linux/hardirq.h>
19 #include <linux/of.h>
20 
21 #include <asm/page.h>
22 #include <asm/current.h>
23 #include <asm/machdep.h>
24 #include <asm/cacheflush.h>
25 #include <asm/firmware.h>
26 #include <asm/paca.h>
27 #include <asm/mmu.h>
28 #include <asm/sections.h>	/* _end */
29 #include <asm/smp.h>
30 #include <asm/hw_breakpoint.h>
31 #include <asm/svm.h>
32 #include <asm/ultravisor.h>
33 
machine_kexec_prepare(struct kimage * image)34 int machine_kexec_prepare(struct kimage *image)
35 {
36 	int i;
37 	unsigned long begin, end;	/* limits of segment */
38 	unsigned long low, high;	/* limits of blocked memory range */
39 	struct device_node *node;
40 	const unsigned long *basep;
41 	const unsigned int *sizep;
42 
43 	/*
44 	 * Since we use the kernel fault handlers and paging code to
45 	 * handle the virtual mode, we must make sure no destination
46 	 * overlaps kernel static data or bss.
47 	 */
48 	for (i = 0; i < image->nr_segments; i++)
49 		if (image->segment[i].mem < __pa(_end))
50 			return -ETXTBSY;
51 
52 	/* We also should not overwrite the tce tables */
53 	for_each_node_by_type(node, "pci") {
54 		basep = of_get_property(node, "linux,tce-base", NULL);
55 		sizep = of_get_property(node, "linux,tce-size", NULL);
56 		if (basep == NULL || sizep == NULL)
57 			continue;
58 
59 		low = *basep;
60 		high = low + (*sizep);
61 
62 		for (i = 0; i < image->nr_segments; i++) {
63 			begin = image->segment[i].mem;
64 			end = begin + image->segment[i].memsz;
65 
66 			if ((begin < high) && (end > low)) {
67 				of_node_put(node);
68 				return -ETXTBSY;
69 			}
70 		}
71 	}
72 
73 	return 0;
74 }
75 
76 /* Called during kexec sequence with MMU off */
copy_segments(unsigned long ind)77 static notrace void copy_segments(unsigned long ind)
78 {
79 	unsigned long entry;
80 	unsigned long *ptr;
81 	void *dest;
82 	void *addr;
83 
84 	/*
85 	 * We rely on kexec_load to create a lists that properly
86 	 * initializes these pointers before they are used.
87 	 * We will still crash if the list is wrong, but at least
88 	 * the compiler will be quiet.
89 	 */
90 	ptr = NULL;
91 	dest = NULL;
92 
93 	for (entry = ind; !(entry & IND_DONE); entry = *ptr++) {
94 		addr = __va(entry & PAGE_MASK);
95 
96 		switch (entry & IND_FLAGS) {
97 		case IND_DESTINATION:
98 			dest = addr;
99 			break;
100 		case IND_INDIRECTION:
101 			ptr = addr;
102 			break;
103 		case IND_SOURCE:
104 			copy_page(dest, addr);
105 			dest += PAGE_SIZE;
106 		}
107 	}
108 }
109 
110 /* Called during kexec sequence with MMU off */
kexec_copy_flush(struct kimage * image)111 notrace void kexec_copy_flush(struct kimage *image)
112 {
113 	long i, nr_segments = image->nr_segments;
114 	struct  kexec_segment ranges[KEXEC_SEGMENT_MAX];
115 
116 	/* save the ranges on the stack to efficiently flush the icache */
117 	memcpy(ranges, image->segment, sizeof(ranges));
118 
119 	/*
120 	 * After this call we may not use anything allocated in dynamic
121 	 * memory, including *image.
122 	 *
123 	 * Only globals and the stack are allowed.
124 	 */
125 	copy_segments(image->head);
126 
127 	/*
128 	 * we need to clear the icache for all dest pages sometime,
129 	 * including ones that were in place on the original copy
130 	 */
131 	for (i = 0; i < nr_segments; i++)
132 		flush_icache_range((unsigned long)__va(ranges[i].mem),
133 			(unsigned long)__va(ranges[i].mem + ranges[i].memsz));
134 }
135 
136 #ifdef CONFIG_SMP
137 
138 static int kexec_all_irq_disabled = 0;
139 
kexec_smp_down(void * arg)140 static void kexec_smp_down(void *arg)
141 {
142 	local_irq_disable();
143 	hard_irq_disable();
144 
145 	mb(); /* make sure our irqs are disabled before we say they are */
146 	get_paca()->kexec_state = KEXEC_STATE_IRQS_OFF;
147 	while(kexec_all_irq_disabled == 0)
148 		cpu_relax();
149 	mb(); /* make sure all irqs are disabled before this */
150 	hw_breakpoint_disable();
151 	/*
152 	 * Now every CPU has IRQs off, we can clear out any pending
153 	 * IPIs and be sure that no more will come in after this.
154 	 */
155 	if (ppc_md.kexec_cpu_down)
156 		ppc_md.kexec_cpu_down(0, 1);
157 
158 	reset_sprs();
159 
160 	kexec_smp_wait();
161 	/* NOTREACHED */
162 }
163 
kexec_prepare_cpus_wait(int wait_state)164 static void kexec_prepare_cpus_wait(int wait_state)
165 {
166 	int my_cpu, i, notified=-1;
167 
168 	hw_breakpoint_disable();
169 	my_cpu = get_cpu();
170 	/* Make sure each CPU has at least made it to the state we need.
171 	 *
172 	 * FIXME: There is a (slim) chance of a problem if not all of the CPUs
173 	 * are correctly onlined.  If somehow we start a CPU on boot with RTAS
174 	 * start-cpu, but somehow that CPU doesn't write callin_cpu_map[] in
175 	 * time, the boot CPU will timeout.  If it does eventually execute
176 	 * stuff, the secondary will start up (paca_ptrs[]->cpu_start was
177 	 * written) and get into a peculiar state.
178 	 * If the platform supports smp_ops->take_timebase(), the secondary CPU
179 	 * will probably be spinning in there.  If not (i.e. pseries), the
180 	 * secondary will continue on and try to online itself/idle/etc. If it
181 	 * survives that, we need to find these
182 	 * possible-but-not-online-but-should-be CPUs and chaperone them into
183 	 * kexec_smp_wait().
184 	 */
185 	for_each_online_cpu(i) {
186 		if (i == my_cpu)
187 			continue;
188 
189 		while (paca_ptrs[i]->kexec_state < wait_state) {
190 			barrier();
191 			if (i != notified) {
192 				printk(KERN_INFO "kexec: waiting for cpu %d "
193 				       "(physical %d) to enter %i state\n",
194 				       i, paca_ptrs[i]->hw_cpu_id, wait_state);
195 				notified = i;
196 			}
197 		}
198 	}
199 	mb();
200 }
201 
202 /*
203  * We need to make sure each present CPU is online.  The next kernel will scan
204  * the device tree and assume primary threads are online and query secondary
205  * threads via RTAS to online them if required.  If we don't online primary
206  * threads, they will be stuck.  However, we also online secondary threads as we
207  * may be using 'cede offline'.  In this case RTAS doesn't see the secondary
208  * threads as offline -- and again, these CPUs will be stuck.
209  *
210  * So, we online all CPUs that should be running, including secondary threads.
211  */
wake_offline_cpus(void)212 static void wake_offline_cpus(void)
213 {
214 	int cpu = 0;
215 
216 	for_each_present_cpu(cpu) {
217 		if (!cpu_online(cpu)) {
218 			printk(KERN_INFO "kexec: Waking offline cpu %d.\n",
219 			       cpu);
220 			WARN_ON(add_cpu(cpu));
221 		}
222 	}
223 }
224 
kexec_prepare_cpus(void)225 static void kexec_prepare_cpus(void)
226 {
227 	wake_offline_cpus();
228 	smp_call_function(kexec_smp_down, NULL, /* wait */0);
229 	local_irq_disable();
230 	hard_irq_disable();
231 
232 	mb(); /* make sure IRQs are disabled before we say they are */
233 	get_paca()->kexec_state = KEXEC_STATE_IRQS_OFF;
234 
235 	kexec_prepare_cpus_wait(KEXEC_STATE_IRQS_OFF);
236 	/* we are sure every CPU has IRQs off at this point */
237 	kexec_all_irq_disabled = 1;
238 
239 	/*
240 	 * Before removing MMU mappings make sure all CPUs have entered real
241 	 * mode:
242 	 */
243 	kexec_prepare_cpus_wait(KEXEC_STATE_REAL_MODE);
244 
245 	/* after we tell the others to go down */
246 	if (ppc_md.kexec_cpu_down)
247 		ppc_md.kexec_cpu_down(0, 0);
248 
249 	put_cpu();
250 }
251 
252 #else /* ! SMP */
253 
kexec_prepare_cpus(void)254 static void kexec_prepare_cpus(void)
255 {
256 	/*
257 	 * move the secondarys to us so that we can copy
258 	 * the new kernel 0-0x100 safely
259 	 *
260 	 * do this if kexec in setup.c ?
261 	 *
262 	 * We need to release the cpus if we are ever going from an
263 	 * UP to an SMP kernel.
264 	 */
265 	smp_release_cpus();
266 	if (ppc_md.kexec_cpu_down)
267 		ppc_md.kexec_cpu_down(0, 0);
268 	local_irq_disable();
269 	hard_irq_disable();
270 }
271 
272 #endif /* SMP */
273 
274 /*
275  * kexec thread structure and stack.
276  *
277  * We need to make sure that this is 16384-byte aligned due to the
278  * way process stacks are handled.  It also must be statically allocated
279  * or allocated as part of the kimage, because everything else may be
280  * overwritten when we copy the kexec image.  We piggyback on the
281  * "init_task" linker section here to statically allocate a stack.
282  *
283  * We could use a smaller stack if we don't care about anything using
284  * current, but that audit has not been performed.
285  */
286 static union thread_union kexec_stack __init_task_data =
287 	{ };
288 
289 /*
290  * For similar reasons to the stack above, the kexecing CPU needs to be on a
291  * static PACA; we switch to kexec_paca.
292  */
293 static struct paca_struct kexec_paca;
294 
295 /* Our assembly helper, in misc_64.S */
296 extern void kexec_sequence(void *newstack, unsigned long start,
297 			   void *image, void *control,
298 			   void (*clear_all)(void),
299 			   bool copy_with_mmu_off) __noreturn;
300 
301 /* too late to fail here */
default_machine_kexec(struct kimage * image)302 void default_machine_kexec(struct kimage *image)
303 {
304 	bool copy_with_mmu_off;
305 
306 	/* prepare control code if any */
307 
308 	/*
309         * If the kexec boot is the normal one, need to shutdown other cpus
310         * into our wait loop and quiesce interrupts.
311         * Otherwise, in the case of crashed mode (crashing_cpu >= 0),
312         * stopping other CPUs and collecting their pt_regs is done before
313         * using debugger IPI.
314         */
315 
316 	if (!kdump_in_progress())
317 		kexec_prepare_cpus();
318 
319 	printk("kexec: Starting switchover sequence.\n");
320 
321 	/* switch to a staticly allocated stack.  Based on irq stack code.
322 	 * We setup preempt_count to avoid using VMX in memcpy.
323 	 * XXX: the task struct will likely be invalid once we do the copy!
324 	 */
325 	current_thread_info()->flags = 0;
326 	current_thread_info()->preempt_count = HARDIRQ_OFFSET;
327 
328 	/* We need a static PACA, too; copy this CPU's PACA over and switch to
329 	 * it. Also poison per_cpu_offset and NULL lppaca to catch anyone using
330 	 * non-static data.
331 	 */
332 	memcpy(&kexec_paca, get_paca(), sizeof(struct paca_struct));
333 	kexec_paca.data_offset = 0xedeaddeadeeeeeeeUL;
334 #ifdef CONFIG_PPC_PSERIES
335 	kexec_paca.lppaca_ptr = NULL;
336 #endif
337 
338 	if (is_secure_guest() && !(image->preserve_context ||
339 				   image->type == KEXEC_TYPE_CRASH)) {
340 		uv_unshare_all_pages();
341 		printk("kexec: Unshared all shared pages.\n");
342 	}
343 
344 	paca_ptrs[kexec_paca.paca_index] = &kexec_paca;
345 
346 	setup_paca(&kexec_paca);
347 
348 	/*
349 	 * The lppaca should be unregistered at this point so the HV won't
350 	 * touch it. In the case of a crash, none of the lppacas are
351 	 * unregistered so there is not much we can do about it here.
352 	 */
353 
354 	/*
355 	 * On Book3S, the copy must happen with the MMU off if we are either
356 	 * using Radix page tables or we are not in an LPAR since we can
357 	 * overwrite the page tables while copying.
358 	 *
359 	 * In an LPAR, we keep the MMU on otherwise we can't access beyond
360 	 * the RMA. On BookE there is no real MMU off mode, so we have to
361 	 * keep it enabled as well (but then we have bolted TLB entries).
362 	 */
363 #ifdef CONFIG_PPC_BOOK3E_64
364 	copy_with_mmu_off = false;
365 #else
366 	copy_with_mmu_off = radix_enabled() ||
367 		!(firmware_has_feature(FW_FEATURE_LPAR) ||
368 		  firmware_has_feature(FW_FEATURE_PS3_LV1));
369 #endif
370 
371 	/* Some things are best done in assembly.  Finding globals with
372 	 * a toc is easier in C, so pass in what we can.
373 	 */
374 	kexec_sequence(&kexec_stack, image->start, image,
375 		       page_address(image->control_code_page),
376 		       mmu_cleanup_all, copy_with_mmu_off);
377 	/* NOTREACHED */
378 }
379 
380 #ifdef CONFIG_PPC_64S_HASH_MMU
381 /* Values we need to export to the second kernel via the device tree. */
382 static unsigned long htab_base;
383 static unsigned long htab_size;
384 
385 static struct property htab_base_prop = {
386 	.name = "linux,htab-base",
387 	.length = sizeof(unsigned long),
388 	.value = &htab_base,
389 };
390 
391 static struct property htab_size_prop = {
392 	.name = "linux,htab-size",
393 	.length = sizeof(unsigned long),
394 	.value = &htab_size,
395 };
396 
export_htab_values(void)397 static int __init export_htab_values(void)
398 {
399 	struct device_node *node;
400 
401 	/* On machines with no htab htab_address is NULL */
402 	if (!htab_address)
403 		return -ENODEV;
404 
405 	node = of_find_node_by_path("/chosen");
406 	if (!node)
407 		return -ENODEV;
408 
409 	/* remove any stale properties so ours can be found */
410 	of_remove_property(node, of_find_property(node, htab_base_prop.name, NULL));
411 	of_remove_property(node, of_find_property(node, htab_size_prop.name, NULL));
412 
413 	htab_base = cpu_to_be64(__pa(htab_address));
414 	of_add_property(node, &htab_base_prop);
415 	htab_size = cpu_to_be64(htab_size_bytes);
416 	of_add_property(node, &htab_size_prop);
417 
418 	of_node_put(node);
419 	return 0;
420 }
421 late_initcall(export_htab_values);
422 #endif /* CONFIG_PPC_64S_HASH_MMU */
423