1 /*
2  * handle transition of Linux booting another kernel
3  * Copyright (C) 2002-2005 Eric Biederman  <ebiederm@xmission.com>
4  *
5  * This source code is licensed under the GNU General Public License,
6  * Version 2.  See the file COPYING for more details.
7  */
8 
9 #define pr_fmt(fmt)	"kexec: " fmt
10 
11 #include <linux/mm.h>
12 #include <linux/kexec.h>
13 #include <linux/string.h>
14 #include <linux/gfp.h>
15 #include <linux/reboot.h>
16 #include <linux/numa.h>
17 #include <linux/ftrace.h>
18 #include <linux/io.h>
19 #include <linux/suspend.h>
20 
21 #include <asm/init.h>
22 #include <asm/pgtable.h>
23 #include <asm/tlbflush.h>
24 #include <asm/mmu_context.h>
25 #include <asm/debugreg.h>
26 #include <asm/kexec-bzimage64.h>
27 
28 #ifdef CONFIG_KEXEC_FILE
29 static struct kexec_file_ops *kexec_file_loaders[] = {
30 		&kexec_bzImage64_ops,
31 };
32 #endif
33 
34 static void free_transition_pgtable(struct kimage *image)
35 {
36 	free_page((unsigned long)image->arch.pud);
37 	free_page((unsigned long)image->arch.pmd);
38 	free_page((unsigned long)image->arch.pte);
39 }
40 
41 static int init_transition_pgtable(struct kimage *image, pgd_t *pgd)
42 {
43 	pud_t *pud;
44 	pmd_t *pmd;
45 	pte_t *pte;
46 	unsigned long vaddr, paddr;
47 	int result = -ENOMEM;
48 
49 	vaddr = (unsigned long)relocate_kernel;
50 	paddr = __pa(page_address(image->control_code_page)+PAGE_SIZE);
51 	pgd += pgd_index(vaddr);
52 	if (!pgd_present(*pgd)) {
53 		pud = (pud_t *)get_zeroed_page(GFP_KERNEL);
54 		if (!pud)
55 			goto err;
56 		image->arch.pud = pud;
57 		set_pgd(pgd, __pgd(__pa(pud) | _KERNPG_TABLE));
58 	}
59 	pud = pud_offset(pgd, vaddr);
60 	if (!pud_present(*pud)) {
61 		pmd = (pmd_t *)get_zeroed_page(GFP_KERNEL);
62 		if (!pmd)
63 			goto err;
64 		image->arch.pmd = pmd;
65 		set_pud(pud, __pud(__pa(pmd) | _KERNPG_TABLE));
66 	}
67 	pmd = pmd_offset(pud, vaddr);
68 	if (!pmd_present(*pmd)) {
69 		pte = (pte_t *)get_zeroed_page(GFP_KERNEL);
70 		if (!pte)
71 			goto err;
72 		image->arch.pte = pte;
73 		set_pmd(pmd, __pmd(__pa(pte) | _KERNPG_TABLE));
74 	}
75 	pte = pte_offset_kernel(pmd, vaddr);
76 	set_pte(pte, pfn_pte(paddr >> PAGE_SHIFT, PAGE_KERNEL_EXEC));
77 	return 0;
78 err:
79 	free_transition_pgtable(image);
80 	return result;
81 }
82 
83 static void *alloc_pgt_page(void *data)
84 {
85 	struct kimage *image = (struct kimage *)data;
86 	struct page *page;
87 	void *p = NULL;
88 
89 	page = kimage_alloc_control_pages(image, 0);
90 	if (page) {
91 		p = page_address(page);
92 		clear_page(p);
93 	}
94 
95 	return p;
96 }
97 
98 static int init_pgtable(struct kimage *image, unsigned long start_pgtable)
99 {
100 	struct x86_mapping_info info = {
101 		.alloc_pgt_page	= alloc_pgt_page,
102 		.context	= image,
103 		.pmd_flag	= __PAGE_KERNEL_LARGE_EXEC,
104 	};
105 	unsigned long mstart, mend;
106 	pgd_t *level4p;
107 	int result;
108 	int i;
109 
110 	level4p = (pgd_t *)__va(start_pgtable);
111 	clear_page(level4p);
112 	for (i = 0; i < nr_pfn_mapped; i++) {
113 		mstart = pfn_mapped[i].start << PAGE_SHIFT;
114 		mend   = pfn_mapped[i].end << PAGE_SHIFT;
115 
116 		result = kernel_ident_mapping_init(&info,
117 						 level4p, mstart, mend);
118 		if (result)
119 			return result;
120 	}
121 
122 	/*
123 	 * segments's mem ranges could be outside 0 ~ max_pfn,
124 	 * for example when jump back to original kernel from kexeced kernel.
125 	 * or first kernel is booted with user mem map, and second kernel
126 	 * could be loaded out of that range.
127 	 */
128 	for (i = 0; i < image->nr_segments; i++) {
129 		mstart = image->segment[i].mem;
130 		mend   = mstart + image->segment[i].memsz;
131 
132 		result = kernel_ident_mapping_init(&info,
133 						 level4p, mstart, mend);
134 
135 		if (result)
136 			return result;
137 	}
138 
139 	return init_transition_pgtable(image, level4p);
140 }
141 
142 static void set_idt(void *newidt, u16 limit)
143 {
144 	struct desc_ptr curidt;
145 
146 	/* x86-64 supports unaliged loads & stores */
147 	curidt.size    = limit;
148 	curidt.address = (unsigned long)newidt;
149 
150 	__asm__ __volatile__ (
151 		"lidtq %0\n"
152 		: : "m" (curidt)
153 		);
154 };
155 
156 
157 static void set_gdt(void *newgdt, u16 limit)
158 {
159 	struct desc_ptr curgdt;
160 
161 	/* x86-64 supports unaligned loads & stores */
162 	curgdt.size    = limit;
163 	curgdt.address = (unsigned long)newgdt;
164 
165 	__asm__ __volatile__ (
166 		"lgdtq %0\n"
167 		: : "m" (curgdt)
168 		);
169 };
170 
171 static void load_segments(void)
172 {
173 	__asm__ __volatile__ (
174 		"\tmovl %0,%%ds\n"
175 		"\tmovl %0,%%es\n"
176 		"\tmovl %0,%%ss\n"
177 		"\tmovl %0,%%fs\n"
178 		"\tmovl %0,%%gs\n"
179 		: : "a" (__KERNEL_DS) : "memory"
180 		);
181 }
182 
183 #ifdef CONFIG_KEXEC_FILE
184 /* Update purgatory as needed after various image segments have been prepared */
185 static int arch_update_purgatory(struct kimage *image)
186 {
187 	int ret = 0;
188 
189 	if (!image->file_mode)
190 		return 0;
191 
192 	/* Setup copying of backup region */
193 	if (image->type == KEXEC_TYPE_CRASH) {
194 		ret = kexec_purgatory_get_set_symbol(image, "backup_dest",
195 				&image->arch.backup_load_addr,
196 				sizeof(image->arch.backup_load_addr), 0);
197 		if (ret)
198 			return ret;
199 
200 		ret = kexec_purgatory_get_set_symbol(image, "backup_src",
201 				&image->arch.backup_src_start,
202 				sizeof(image->arch.backup_src_start), 0);
203 		if (ret)
204 			return ret;
205 
206 		ret = kexec_purgatory_get_set_symbol(image, "backup_sz",
207 				&image->arch.backup_src_sz,
208 				sizeof(image->arch.backup_src_sz), 0);
209 		if (ret)
210 			return ret;
211 	}
212 
213 	return ret;
214 }
215 #else /* !CONFIG_KEXEC_FILE */
216 static inline int arch_update_purgatory(struct kimage *image)
217 {
218 	return 0;
219 }
220 #endif /* CONFIG_KEXEC_FILE */
221 
222 int machine_kexec_prepare(struct kimage *image)
223 {
224 	unsigned long start_pgtable;
225 	int result;
226 
227 	/* Calculate the offsets */
228 	start_pgtable = page_to_pfn(image->control_code_page) << PAGE_SHIFT;
229 
230 	/* Setup the identity mapped 64bit page table */
231 	result = init_pgtable(image, start_pgtable);
232 	if (result)
233 		return result;
234 
235 	/* update purgatory as needed */
236 	result = arch_update_purgatory(image);
237 	if (result)
238 		return result;
239 
240 	return 0;
241 }
242 
243 void machine_kexec_cleanup(struct kimage *image)
244 {
245 	free_transition_pgtable(image);
246 }
247 
248 /*
249  * Do not allocate memory (or fail in any way) in machine_kexec().
250  * We are past the point of no return, committed to rebooting now.
251  */
252 void machine_kexec(struct kimage *image)
253 {
254 	unsigned long page_list[PAGES_NR];
255 	void *control_page;
256 	int save_ftrace_enabled;
257 
258 #ifdef CONFIG_KEXEC_JUMP
259 	if (image->preserve_context)
260 		save_processor_state();
261 #endif
262 
263 	save_ftrace_enabled = __ftrace_enabled_save();
264 
265 	/* Interrupts aren't acceptable while we reboot */
266 	local_irq_disable();
267 	hw_breakpoint_disable();
268 
269 	if (image->preserve_context) {
270 #ifdef CONFIG_X86_IO_APIC
271 		/*
272 		 * We need to put APICs in legacy mode so that we can
273 		 * get timer interrupts in second kernel. kexec/kdump
274 		 * paths already have calls to disable_IO_APIC() in
275 		 * one form or other. kexec jump path also need
276 		 * one.
277 		 */
278 		disable_IO_APIC();
279 #endif
280 	}
281 
282 	control_page = page_address(image->control_code_page) + PAGE_SIZE;
283 	memcpy(control_page, relocate_kernel, KEXEC_CONTROL_CODE_MAX_SIZE);
284 
285 	page_list[PA_CONTROL_PAGE] = virt_to_phys(control_page);
286 	page_list[VA_CONTROL_PAGE] = (unsigned long)control_page;
287 	page_list[PA_TABLE_PAGE] =
288 	  (unsigned long)__pa(page_address(image->control_code_page));
289 
290 	if (image->type == KEXEC_TYPE_DEFAULT)
291 		page_list[PA_SWAP_PAGE] = (page_to_pfn(image->swap_page)
292 						<< PAGE_SHIFT);
293 
294 	/*
295 	 * The segment registers are funny things, they have both a
296 	 * visible and an invisible part.  Whenever the visible part is
297 	 * set to a specific selector, the invisible part is loaded
298 	 * with from a table in memory.  At no other time is the
299 	 * descriptor table in memory accessed.
300 	 *
301 	 * I take advantage of this here by force loading the
302 	 * segments, before I zap the gdt with an invalid value.
303 	 */
304 	load_segments();
305 	/*
306 	 * The gdt & idt are now invalid.
307 	 * If you want to load them you must set up your own idt & gdt.
308 	 */
309 	set_gdt(phys_to_virt(0), 0);
310 	set_idt(phys_to_virt(0), 0);
311 
312 	/* now call it */
313 	image->start = relocate_kernel((unsigned long)image->head,
314 				       (unsigned long)page_list,
315 				       image->start,
316 				       image->preserve_context);
317 
318 #ifdef CONFIG_KEXEC_JUMP
319 	if (image->preserve_context)
320 		restore_processor_state();
321 #endif
322 
323 	__ftrace_enabled_restore(save_ftrace_enabled);
324 }
325 
326 void arch_crash_save_vmcoreinfo(void)
327 {
328 	VMCOREINFO_SYMBOL(phys_base);
329 	VMCOREINFO_SYMBOL(init_level4_pgt);
330 
331 #ifdef CONFIG_NUMA
332 	VMCOREINFO_SYMBOL(node_data);
333 	VMCOREINFO_LENGTH(node_data, MAX_NUMNODES);
334 #endif
335 	vmcoreinfo_append_str("KERNELOFFSET=%lx\n",
336 			      (unsigned long)&_text - __START_KERNEL);
337 }
338 
339 /* arch-dependent functionality related to kexec file-based syscall */
340 
341 #ifdef CONFIG_KEXEC_FILE
342 int arch_kexec_kernel_image_probe(struct kimage *image, void *buf,
343 				  unsigned long buf_len)
344 {
345 	int i, ret = -ENOEXEC;
346 	struct kexec_file_ops *fops;
347 
348 	for (i = 0; i < ARRAY_SIZE(kexec_file_loaders); i++) {
349 		fops = kexec_file_loaders[i];
350 		if (!fops || !fops->probe)
351 			continue;
352 
353 		ret = fops->probe(buf, buf_len);
354 		if (!ret) {
355 			image->fops = fops;
356 			return ret;
357 		}
358 	}
359 
360 	return ret;
361 }
362 
363 void *arch_kexec_kernel_image_load(struct kimage *image)
364 {
365 	vfree(image->arch.elf_headers);
366 	image->arch.elf_headers = NULL;
367 
368 	if (!image->fops || !image->fops->load)
369 		return ERR_PTR(-ENOEXEC);
370 
371 	return image->fops->load(image, image->kernel_buf,
372 				 image->kernel_buf_len, image->initrd_buf,
373 				 image->initrd_buf_len, image->cmdline_buf,
374 				 image->cmdline_buf_len);
375 }
376 
377 int arch_kimage_file_post_load_cleanup(struct kimage *image)
378 {
379 	if (!image->fops || !image->fops->cleanup)
380 		return 0;
381 
382 	return image->fops->cleanup(image->image_loader_data);
383 }
384 
385 int arch_kexec_kernel_verify_sig(struct kimage *image, void *kernel,
386 				 unsigned long kernel_len)
387 {
388 	if (!image->fops || !image->fops->verify_sig) {
389 		pr_debug("kernel loader does not support signature verification.");
390 		return -EKEYREJECTED;
391 	}
392 
393 	return image->fops->verify_sig(kernel, kernel_len);
394 }
395 
396 /*
397  * Apply purgatory relocations.
398  *
399  * ehdr: Pointer to elf headers
400  * sechdrs: Pointer to section headers.
401  * relsec: section index of SHT_RELA section.
402  *
403  * TODO: Some of the code belongs to generic code. Move that in kexec.c.
404  */
405 int arch_kexec_apply_relocations_add(const Elf64_Ehdr *ehdr,
406 				     Elf64_Shdr *sechdrs, unsigned int relsec)
407 {
408 	unsigned int i;
409 	Elf64_Rela *rel;
410 	Elf64_Sym *sym;
411 	void *location;
412 	Elf64_Shdr *section, *symtabsec;
413 	unsigned long address, sec_base, value;
414 	const char *strtab, *name, *shstrtab;
415 
416 	/*
417 	 * ->sh_offset has been modified to keep the pointer to section
418 	 * contents in memory
419 	 */
420 	rel = (void *)sechdrs[relsec].sh_offset;
421 
422 	/* Section to which relocations apply */
423 	section = &sechdrs[sechdrs[relsec].sh_info];
424 
425 	pr_debug("Applying relocate section %u to %u\n", relsec,
426 		 sechdrs[relsec].sh_info);
427 
428 	/* Associated symbol table */
429 	symtabsec = &sechdrs[sechdrs[relsec].sh_link];
430 
431 	/* String table */
432 	if (symtabsec->sh_link >= ehdr->e_shnum) {
433 		/* Invalid strtab section number */
434 		pr_err("Invalid string table section index %d\n",
435 		       symtabsec->sh_link);
436 		return -ENOEXEC;
437 	}
438 
439 	strtab = (char *)sechdrs[symtabsec->sh_link].sh_offset;
440 
441 	/* section header string table */
442 	shstrtab = (char *)sechdrs[ehdr->e_shstrndx].sh_offset;
443 
444 	for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
445 
446 		/*
447 		 * rel[i].r_offset contains byte offset from beginning
448 		 * of section to the storage unit affected.
449 		 *
450 		 * This is location to update (->sh_offset). This is temporary
451 		 * buffer where section is currently loaded. This will finally
452 		 * be loaded to a different address later, pointed to by
453 		 * ->sh_addr. kexec takes care of moving it
454 		 *  (kexec_load_segment()).
455 		 */
456 		location = (void *)(section->sh_offset + rel[i].r_offset);
457 
458 		/* Final address of the location */
459 		address = section->sh_addr + rel[i].r_offset;
460 
461 		/*
462 		 * rel[i].r_info contains information about symbol table index
463 		 * w.r.t which relocation must be made and type of relocation
464 		 * to apply. ELF64_R_SYM() and ELF64_R_TYPE() macros get
465 		 * these respectively.
466 		 */
467 		sym = (Elf64_Sym *)symtabsec->sh_offset +
468 				ELF64_R_SYM(rel[i].r_info);
469 
470 		if (sym->st_name)
471 			name = strtab + sym->st_name;
472 		else
473 			name = shstrtab + sechdrs[sym->st_shndx].sh_name;
474 
475 		pr_debug("Symbol: %s info: %02x shndx: %02x value=%llx size: %llx\n",
476 			 name, sym->st_info, sym->st_shndx, sym->st_value,
477 			 sym->st_size);
478 
479 		if (sym->st_shndx == SHN_UNDEF) {
480 			pr_err("Undefined symbol: %s\n", name);
481 			return -ENOEXEC;
482 		}
483 
484 		if (sym->st_shndx == SHN_COMMON) {
485 			pr_err("symbol '%s' in common section\n", name);
486 			return -ENOEXEC;
487 		}
488 
489 		if (sym->st_shndx == SHN_ABS)
490 			sec_base = 0;
491 		else if (sym->st_shndx >= ehdr->e_shnum) {
492 			pr_err("Invalid section %d for symbol %s\n",
493 			       sym->st_shndx, name);
494 			return -ENOEXEC;
495 		} else
496 			sec_base = sechdrs[sym->st_shndx].sh_addr;
497 
498 		value = sym->st_value;
499 		value += sec_base;
500 		value += rel[i].r_addend;
501 
502 		switch (ELF64_R_TYPE(rel[i].r_info)) {
503 		case R_X86_64_NONE:
504 			break;
505 		case R_X86_64_64:
506 			*(u64 *)location = value;
507 			break;
508 		case R_X86_64_32:
509 			*(u32 *)location = value;
510 			if (value != *(u32 *)location)
511 				goto overflow;
512 			break;
513 		case R_X86_64_32S:
514 			*(s32 *)location = value;
515 			if ((s64)value != *(s32 *)location)
516 				goto overflow;
517 			break;
518 		case R_X86_64_PC32:
519 			value -= (u64)address;
520 			*(u32 *)location = value;
521 			break;
522 		default:
523 			pr_err("Unknown rela relocation: %llu\n",
524 			       ELF64_R_TYPE(rel[i].r_info));
525 			return -ENOEXEC;
526 		}
527 	}
528 	return 0;
529 
530 overflow:
531 	pr_err("Overflow in relocation type %d value 0x%lx\n",
532 	       (int)ELF64_R_TYPE(rel[i].r_info), value);
533 	return -ENOEXEC;
534 }
535 #endif /* CONFIG_KEXEC_FILE */
536