1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * handle transition of Linux booting another kernel
4  * Copyright (C) 2002-2005 Eric Biederman  <ebiederm@xmission.com>
5  */
6 
7 #include <linux/mm.h>
8 #include <linux/kexec.h>
9 #include <linux/delay.h>
10 #include <linux/numa.h>
11 #include <linux/ftrace.h>
12 #include <linux/suspend.h>
13 #include <linux/gfp.h>
14 #include <linux/io.h>
15 
16 #include <asm/pgalloc.h>
17 #include <asm/tlbflush.h>
18 #include <asm/mmu_context.h>
19 #include <asm/apic.h>
20 #include <asm/io_apic.h>
21 #include <asm/cpufeature.h>
22 #include <asm/desc.h>
23 #include <asm/set_memory.h>
24 #include <asm/debugreg.h>
25 
26 static void load_segments(void)
27 {
28 #define __STR(X) #X
29 #define STR(X) __STR(X)
30 
31 	__asm__ __volatile__ (
32 		"\tljmp $"STR(__KERNEL_CS)",$1f\n"
33 		"\t1:\n"
34 		"\tmovl $"STR(__KERNEL_DS)",%%eax\n"
35 		"\tmovl %%eax,%%ds\n"
36 		"\tmovl %%eax,%%es\n"
37 		"\tmovl %%eax,%%ss\n"
38 		: : : "eax", "memory");
39 #undef STR
40 #undef __STR
41 }
42 
43 static void machine_kexec_free_page_tables(struct kimage *image)
44 {
45 	free_pages((unsigned long)image->arch.pgd, PGD_ALLOCATION_ORDER);
46 	image->arch.pgd = NULL;
47 #ifdef CONFIG_X86_PAE
48 	free_page((unsigned long)image->arch.pmd0);
49 	image->arch.pmd0 = NULL;
50 	free_page((unsigned long)image->arch.pmd1);
51 	image->arch.pmd1 = NULL;
52 #endif
53 	free_page((unsigned long)image->arch.pte0);
54 	image->arch.pte0 = NULL;
55 	free_page((unsigned long)image->arch.pte1);
56 	image->arch.pte1 = NULL;
57 }
58 
59 static int machine_kexec_alloc_page_tables(struct kimage *image)
60 {
61 	image->arch.pgd = (pgd_t *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
62 						    PGD_ALLOCATION_ORDER);
63 #ifdef CONFIG_X86_PAE
64 	image->arch.pmd0 = (pmd_t *)get_zeroed_page(GFP_KERNEL);
65 	image->arch.pmd1 = (pmd_t *)get_zeroed_page(GFP_KERNEL);
66 #endif
67 	image->arch.pte0 = (pte_t *)get_zeroed_page(GFP_KERNEL);
68 	image->arch.pte1 = (pte_t *)get_zeroed_page(GFP_KERNEL);
69 	if (!image->arch.pgd ||
70 #ifdef CONFIG_X86_PAE
71 	    !image->arch.pmd0 || !image->arch.pmd1 ||
72 #endif
73 	    !image->arch.pte0 || !image->arch.pte1) {
74 		return -ENOMEM;
75 	}
76 	return 0;
77 }
78 
79 static void machine_kexec_page_table_set_one(
80 	pgd_t *pgd, pmd_t *pmd, pte_t *pte,
81 	unsigned long vaddr, unsigned long paddr)
82 {
83 	p4d_t *p4d;
84 	pud_t *pud;
85 
86 	pgd += pgd_index(vaddr);
87 #ifdef CONFIG_X86_PAE
88 	if (!(pgd_val(*pgd) & _PAGE_PRESENT))
89 		set_pgd(pgd, __pgd(__pa(pmd) | _PAGE_PRESENT));
90 #endif
91 	p4d = p4d_offset(pgd, vaddr);
92 	pud = pud_offset(p4d, vaddr);
93 	pmd = pmd_offset(pud, vaddr);
94 	if (!(pmd_val(*pmd) & _PAGE_PRESENT))
95 		set_pmd(pmd, __pmd(__pa(pte) | _PAGE_TABLE));
96 	pte = pte_offset_kernel(pmd, vaddr);
97 	set_pte(pte, pfn_pte(paddr >> PAGE_SHIFT, PAGE_KERNEL_EXEC));
98 }
99 
100 static void machine_kexec_prepare_page_tables(struct kimage *image)
101 {
102 	void *control_page;
103 	pmd_t *pmd = NULL;
104 
105 	control_page = page_address(image->control_code_page);
106 #ifdef CONFIG_X86_PAE
107 	pmd = image->arch.pmd0;
108 #endif
109 	machine_kexec_page_table_set_one(
110 		image->arch.pgd, pmd, image->arch.pte0,
111 		(unsigned long)control_page, __pa(control_page));
112 #ifdef CONFIG_X86_PAE
113 	pmd = image->arch.pmd1;
114 #endif
115 	machine_kexec_page_table_set_one(
116 		image->arch.pgd, pmd, image->arch.pte1,
117 		__pa(control_page), __pa(control_page));
118 }
119 
120 /*
121  * A architecture hook called to validate the
122  * proposed image and prepare the control pages
123  * as needed.  The pages for KEXEC_CONTROL_PAGE_SIZE
124  * have been allocated, but the segments have yet
125  * been copied into the kernel.
126  *
127  * Do what every setup is needed on image and the
128  * reboot code buffer to allow us to avoid allocations
129  * later.
130  *
131  * - Make control page executable.
132  * - Allocate page tables
133  * - Setup page tables
134  */
135 int machine_kexec_prepare(struct kimage *image)
136 {
137 	int error;
138 
139 	set_memory_x((unsigned long)page_address(image->control_code_page), 1);
140 	error = machine_kexec_alloc_page_tables(image);
141 	if (error)
142 		return error;
143 	machine_kexec_prepare_page_tables(image);
144 	return 0;
145 }
146 
147 /*
148  * Undo anything leftover by machine_kexec_prepare
149  * when an image is freed.
150  */
151 void machine_kexec_cleanup(struct kimage *image)
152 {
153 	set_memory_nx((unsigned long)page_address(image->control_code_page), 1);
154 	machine_kexec_free_page_tables(image);
155 }
156 
157 /*
158  * Do not allocate memory (or fail in any way) in machine_kexec().
159  * We are past the point of no return, committed to rebooting now.
160  */
161 void machine_kexec(struct kimage *image)
162 {
163 	unsigned long page_list[PAGES_NR];
164 	void *control_page;
165 	int save_ftrace_enabled;
166 	asmlinkage unsigned long
167 		(*relocate_kernel_ptr)(unsigned long indirection_page,
168 				       unsigned long control_page,
169 				       unsigned long start_address,
170 				       unsigned int has_pae,
171 				       unsigned int preserve_context);
172 
173 #ifdef CONFIG_KEXEC_JUMP
174 	if (image->preserve_context)
175 		save_processor_state();
176 #endif
177 
178 	save_ftrace_enabled = __ftrace_enabled_save();
179 
180 	/* Interrupts aren't acceptable while we reboot */
181 	local_irq_disable();
182 	hw_breakpoint_disable();
183 
184 	if (image->preserve_context) {
185 #ifdef CONFIG_X86_IO_APIC
186 		/*
187 		 * We need to put APICs in legacy mode so that we can
188 		 * get timer interrupts in second kernel. kexec/kdump
189 		 * paths already have calls to restore_boot_irq_mode()
190 		 * in one form or other. kexec jump path also need one.
191 		 */
192 		clear_IO_APIC();
193 		restore_boot_irq_mode();
194 #endif
195 	}
196 
197 	control_page = page_address(image->control_code_page);
198 	memcpy(control_page, relocate_kernel, KEXEC_CONTROL_CODE_MAX_SIZE);
199 
200 	relocate_kernel_ptr = control_page;
201 	page_list[PA_CONTROL_PAGE] = __pa(control_page);
202 	page_list[VA_CONTROL_PAGE] = (unsigned long)control_page;
203 	page_list[PA_PGD] = __pa(image->arch.pgd);
204 
205 	if (image->type == KEXEC_TYPE_DEFAULT)
206 		page_list[PA_SWAP_PAGE] = (page_to_pfn(image->swap_page)
207 						<< PAGE_SHIFT);
208 
209 	/*
210 	 * The segment registers are funny things, they have both a
211 	 * visible and an invisible part.  Whenever the visible part is
212 	 * set to a specific selector, the invisible part is loaded
213 	 * with from a table in memory.  At no other time is the
214 	 * descriptor table in memory accessed.
215 	 *
216 	 * I take advantage of this here by force loading the
217 	 * segments, before I zap the gdt with an invalid value.
218 	 */
219 	load_segments();
220 	/*
221 	 * The gdt & idt are now invalid.
222 	 * If you want to load them you must set up your own idt & gdt.
223 	 */
224 	native_idt_invalidate();
225 	native_gdt_invalidate();
226 
227 	/* now call it */
228 	image->start = relocate_kernel_ptr((unsigned long)image->head,
229 					   (unsigned long)page_list,
230 					   image->start,
231 					   boot_cpu_has(X86_FEATURE_PAE),
232 					   image->preserve_context);
233 
234 #ifdef CONFIG_KEXEC_JUMP
235 	if (image->preserve_context)
236 		restore_processor_state();
237 #endif
238 
239 	__ftrace_enabled_restore(save_ftrace_enabled);
240 }
241