1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/io.h>
3 #include <linux/slab.h>
4 #include <linux/memblock.h>
5 #include <linux/cc_platform.h>
6 #include <linux/pgtable.h>
7 
8 #include <asm/set_memory.h>
9 #include <asm/realmode.h>
10 #include <asm/tlbflush.h>
11 #include <asm/crash.h>
12 #include <asm/sev.h>
13 
14 struct real_mode_header *real_mode_header;
15 u32 *trampoline_cr4_features;
16 
17 /* Hold the pgd entry used on booting additional CPUs */
18 pgd_t trampoline_pgd_entry;
19 
load_trampoline_pgtable(void)20 void load_trampoline_pgtable(void)
21 {
22 #ifdef CONFIG_X86_32
23 	load_cr3(initial_page_table);
24 #else
25 	/*
26 	 * This function is called before exiting to real-mode and that will
27 	 * fail with CR4.PCIDE still set.
28 	 */
29 	if (boot_cpu_has(X86_FEATURE_PCID))
30 		cr4_clear_bits(X86_CR4_PCIDE);
31 
32 	write_cr3(real_mode_header->trampoline_pgd);
33 #endif
34 
35 	/*
36 	 * The CR3 write above will not flush global TLB entries.
37 	 * Stale, global entries from previous page tables may still be
38 	 * present.  Flush those stale entries.
39 	 *
40 	 * This ensures that memory accessed while running with
41 	 * trampoline_pgd is *actually* mapped into trampoline_pgd.
42 	 */
43 	__flush_tlb_all();
44 }
45 
reserve_real_mode(void)46 void __init reserve_real_mode(void)
47 {
48 	phys_addr_t mem;
49 	size_t size = real_mode_size_needed();
50 
51 	if (!size)
52 		return;
53 
54 	WARN_ON(slab_is_available());
55 
56 	/* Has to be under 1M so we can execute real-mode AP code. */
57 	mem = memblock_phys_alloc_range(size, PAGE_SIZE, 0, 1<<20);
58 	if (!mem)
59 		pr_info("No sub-1M memory is available for the trampoline\n");
60 	else
61 		set_real_mode_mem(mem);
62 
63 	/*
64 	 * Unconditionally reserve the entire fisrt 1M, see comment in
65 	 * setup_arch().
66 	 */
67 	memblock_reserve(0, SZ_1M);
68 }
69 
sme_sev_setup_real_mode(struct trampoline_header * th)70 static void __init sme_sev_setup_real_mode(struct trampoline_header *th)
71 {
72 #ifdef CONFIG_AMD_MEM_ENCRYPT
73 	if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT))
74 		th->flags |= TH_FLAGS_SME_ACTIVE;
75 
76 	if (cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT)) {
77 		/*
78 		 * Skip the call to verify_cpu() in secondary_startup_64 as it
79 		 * will cause #VC exceptions when the AP can't handle them yet.
80 		 */
81 		th->start = (u64) secondary_startup_64_no_verify;
82 
83 		if (sev_es_setup_ap_jump_table(real_mode_header))
84 			panic("Failed to get/update SEV-ES AP Jump Table");
85 	}
86 #endif
87 }
88 
setup_real_mode(void)89 static void __init setup_real_mode(void)
90 {
91 	u16 real_mode_seg;
92 	const u32 *rel;
93 	u32 count;
94 	unsigned char *base;
95 	unsigned long phys_base;
96 	struct trampoline_header *trampoline_header;
97 	size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
98 #ifdef CONFIG_X86_64
99 	u64 *trampoline_pgd;
100 	u64 efer;
101 	int i;
102 #endif
103 
104 	base = (unsigned char *)real_mode_header;
105 
106 	/*
107 	 * If SME is active, the trampoline area will need to be in
108 	 * decrypted memory in order to bring up other processors
109 	 * successfully. This is not needed for SEV.
110 	 */
111 	if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT))
112 		set_memory_decrypted((unsigned long)base, size >> PAGE_SHIFT);
113 
114 	memcpy(base, real_mode_blob, size);
115 
116 	phys_base = __pa(base);
117 	real_mode_seg = phys_base >> 4;
118 
119 	rel = (u32 *) real_mode_relocs;
120 
121 	/* 16-bit segment relocations. */
122 	count = *rel++;
123 	while (count--) {
124 		u16 *seg = (u16 *) (base + *rel++);
125 		*seg = real_mode_seg;
126 	}
127 
128 	/* 32-bit linear relocations. */
129 	count = *rel++;
130 	while (count--) {
131 		u32 *ptr = (u32 *) (base + *rel++);
132 		*ptr += phys_base;
133 	}
134 
135 	/* Must be performed *after* relocation. */
136 	trampoline_header = (struct trampoline_header *)
137 		__va(real_mode_header->trampoline_header);
138 
139 #ifdef CONFIG_X86_32
140 	trampoline_header->start = __pa_symbol(startup_32_smp);
141 	trampoline_header->gdt_limit = __BOOT_DS + 7;
142 	trampoline_header->gdt_base = __pa_symbol(boot_gdt);
143 #else
144 	/*
145 	 * Some AMD processors will #GP(0) if EFER.LMA is set in WRMSR
146 	 * so we need to mask it out.
147 	 */
148 	rdmsrl(MSR_EFER, efer);
149 	trampoline_header->efer = efer & ~EFER_LMA;
150 
151 	trampoline_header->start = (u64) secondary_startup_64;
152 	trampoline_cr4_features = &trampoline_header->cr4;
153 	*trampoline_cr4_features = mmu_cr4_features;
154 
155 	trampoline_header->flags = 0;
156 
157 	trampoline_pgd = (u64 *) __va(real_mode_header->trampoline_pgd);
158 
159 	/* Map the real mode stub as virtual == physical */
160 	trampoline_pgd[0] = trampoline_pgd_entry.pgd;
161 
162 	/*
163 	 * Include the entirety of the kernel mapping into the trampoline
164 	 * PGD.  This way, all mappings present in the normal kernel page
165 	 * tables are usable while running on trampoline_pgd.
166 	 */
167 	for (i = pgd_index(__PAGE_OFFSET); i < PTRS_PER_PGD; i++)
168 		trampoline_pgd[i] = init_top_pgt[i].pgd;
169 #endif
170 
171 	sme_sev_setup_real_mode(trampoline_header);
172 }
173 
174 /*
175  * reserve_real_mode() gets called very early, to guarantee the
176  * availability of low memory. This is before the proper kernel page
177  * tables are set up, so we cannot set page permissions in that
178  * function. Also trampoline code will be executed by APs so we
179  * need to mark it executable at do_pre_smp_initcalls() at least,
180  * thus run it as a early_initcall().
181  */
set_real_mode_permissions(void)182 static void __init set_real_mode_permissions(void)
183 {
184 	unsigned char *base = (unsigned char *) real_mode_header;
185 	size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
186 
187 	size_t ro_size =
188 		PAGE_ALIGN(real_mode_header->ro_end) -
189 		__pa(base);
190 
191 	size_t text_size =
192 		PAGE_ALIGN(real_mode_header->ro_end) -
193 		real_mode_header->text_start;
194 
195 	unsigned long text_start =
196 		(unsigned long) __va(real_mode_header->text_start);
197 
198 	set_memory_nx((unsigned long) base, size >> PAGE_SHIFT);
199 	set_memory_ro((unsigned long) base, ro_size >> PAGE_SHIFT);
200 	set_memory_x((unsigned long) text_start, text_size >> PAGE_SHIFT);
201 }
202 
init_real_mode(void)203 static int __init init_real_mode(void)
204 {
205 	if (!real_mode_header)
206 		panic("Real mode trampoline was not allocated");
207 
208 	setup_real_mode();
209 	set_real_mode_permissions();
210 
211 	return 0;
212 }
213 early_initcall(init_real_mode);
214