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/mem_encrypt.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-es.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_find_in_range(0, 1<<20, size, PAGE_SIZE);
58 if (!mem) {
59 pr_info("No sub-1M memory is available for the trampoline\n");
60 return;
61 }
62
63 memblock_reserve(mem, size);
64 set_real_mode_mem(mem);
65 crash_reserve_low_1M();
66 }
67
sme_sev_setup_real_mode(struct trampoline_header * th)68 static void sme_sev_setup_real_mode(struct trampoline_header *th)
69 {
70 #ifdef CONFIG_AMD_MEM_ENCRYPT
71 if (sme_active())
72 th->flags |= TH_FLAGS_SME_ACTIVE;
73
74 if (sev_es_active()) {
75 /*
76 * Skip the call to verify_cpu() in secondary_startup_64 as it
77 * will cause #VC exceptions when the AP can't handle them yet.
78 */
79 th->start = (u64) secondary_startup_64_no_verify;
80
81 if (sev_es_setup_ap_jump_table(real_mode_header))
82 panic("Failed to get/update SEV-ES AP Jump Table");
83 }
84 #endif
85 }
86
setup_real_mode(void)87 static void __init setup_real_mode(void)
88 {
89 u16 real_mode_seg;
90 const u32 *rel;
91 u32 count;
92 unsigned char *base;
93 unsigned long phys_base;
94 struct trampoline_header *trampoline_header;
95 size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
96 #ifdef CONFIG_X86_64
97 u64 *trampoline_pgd;
98 u64 efer;
99 int i;
100 #endif
101
102 base = (unsigned char *)real_mode_header;
103
104 /*
105 * If SME is active, the trampoline area will need to be in
106 * decrypted memory in order to bring up other processors
107 * successfully. This is not needed for SEV.
108 */
109 if (sme_active())
110 set_memory_decrypted((unsigned long)base, size >> PAGE_SHIFT);
111
112 memcpy(base, real_mode_blob, size);
113
114 phys_base = __pa(base);
115 real_mode_seg = phys_base >> 4;
116
117 rel = (u32 *) real_mode_relocs;
118
119 /* 16-bit segment relocations. */
120 count = *rel++;
121 while (count--) {
122 u16 *seg = (u16 *) (base + *rel++);
123 *seg = real_mode_seg;
124 }
125
126 /* 32-bit linear relocations. */
127 count = *rel++;
128 while (count--) {
129 u32 *ptr = (u32 *) (base + *rel++);
130 *ptr += phys_base;
131 }
132
133 /* Must be perfomed *after* relocation. */
134 trampoline_header = (struct trampoline_header *)
135 __va(real_mode_header->trampoline_header);
136
137 #ifdef CONFIG_X86_32
138 trampoline_header->start = __pa_symbol(startup_32_smp);
139 trampoline_header->gdt_limit = __BOOT_DS + 7;
140 trampoline_header->gdt_base = __pa_symbol(boot_gdt);
141 #else
142 /*
143 * Some AMD processors will #GP(0) if EFER.LMA is set in WRMSR
144 * so we need to mask it out.
145 */
146 rdmsrl(MSR_EFER, efer);
147 trampoline_header->efer = efer & ~EFER_LMA;
148
149 trampoline_header->start = (u64) secondary_startup_64;
150 trampoline_cr4_features = &trampoline_header->cr4;
151 *trampoline_cr4_features = mmu_cr4_features;
152
153 trampoline_header->flags = 0;
154
155 trampoline_pgd = (u64 *) __va(real_mode_header->trampoline_pgd);
156
157 /* Map the real mode stub as virtual == physical */
158 trampoline_pgd[0] = trampoline_pgd_entry.pgd;
159
160 /*
161 * Include the entirety of the kernel mapping into the trampoline
162 * PGD. This way, all mappings present in the normal kernel page
163 * tables are usable while running on trampoline_pgd.
164 */
165 for (i = pgd_index(__PAGE_OFFSET); i < PTRS_PER_PGD; i++)
166 trampoline_pgd[i] = init_top_pgt[i].pgd;
167 #endif
168
169 sme_sev_setup_real_mode(trampoline_header);
170 }
171
172 /*
173 * reserve_real_mode() gets called very early, to guarantee the
174 * availability of low memory. This is before the proper kernel page
175 * tables are set up, so we cannot set page permissions in that
176 * function. Also trampoline code will be executed by APs so we
177 * need to mark it executable at do_pre_smp_initcalls() at least,
178 * thus run it as a early_initcall().
179 */
set_real_mode_permissions(void)180 static void __init set_real_mode_permissions(void)
181 {
182 unsigned char *base = (unsigned char *) real_mode_header;
183 size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
184
185 size_t ro_size =
186 PAGE_ALIGN(real_mode_header->ro_end) -
187 __pa(base);
188
189 size_t text_size =
190 PAGE_ALIGN(real_mode_header->ro_end) -
191 real_mode_header->text_start;
192
193 unsigned long text_start =
194 (unsigned long) __va(real_mode_header->text_start);
195
196 set_memory_nx((unsigned long) base, size >> PAGE_SHIFT);
197 set_memory_ro((unsigned long) base, ro_size >> PAGE_SHIFT);
198 set_memory_x((unsigned long) text_start, text_size >> PAGE_SHIFT);
199 }
200
init_real_mode(void)201 static int __init init_real_mode(void)
202 {
203 if (!real_mode_header)
204 panic("Real mode trampoline was not allocated");
205
206 setup_real_mode();
207 set_real_mode_permissions();
208
209 return 0;
210 }
211 early_initcall(init_real_mode);
212