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