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
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_find_in_range(0, 1<<20, size, PAGE_SIZE);
32 if (!mem) {
33 pr_info("No sub-1M memory is available for the trampoline\n");
34 return;
35 }
36
37 memblock_reserve(mem, size);
38 set_real_mode_mem(mem);
39 crash_reserve_low_1M();
40 }
41
sme_sev_setup_real_mode(struct trampoline_header * th)42 static void sme_sev_setup_real_mode(struct trampoline_header *th)
43 {
44 #ifdef CONFIG_AMD_MEM_ENCRYPT
45 if (sme_active())
46 th->flags |= TH_FLAGS_SME_ACTIVE;
47
48 if (sev_es_active()) {
49 /*
50 * Skip the call to verify_cpu() in secondary_startup_64 as it
51 * will cause #VC exceptions when the AP can't handle them yet.
52 */
53 th->start = (u64) secondary_startup_64_no_verify;
54
55 if (sev_es_setup_ap_jump_table(real_mode_header))
56 panic("Failed to get/update SEV-ES AP Jump Table");
57 }
58 #endif
59 }
60
setup_real_mode(void)61 static void __init setup_real_mode(void)
62 {
63 u16 real_mode_seg;
64 const u32 *rel;
65 u32 count;
66 unsigned char *base;
67 unsigned long phys_base;
68 struct trampoline_header *trampoline_header;
69 size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
70 #ifdef CONFIG_X86_64
71 u64 *trampoline_pgd;
72 u64 efer;
73 #endif
74
75 base = (unsigned char *)real_mode_header;
76
77 /*
78 * If SME is active, the trampoline area will need to be in
79 * decrypted memory in order to bring up other processors
80 * successfully. This is not needed for SEV.
81 */
82 if (sme_active())
83 set_memory_decrypted((unsigned long)base, size >> PAGE_SHIFT);
84
85 memcpy(base, real_mode_blob, size);
86
87 phys_base = __pa(base);
88 real_mode_seg = phys_base >> 4;
89
90 rel = (u32 *) real_mode_relocs;
91
92 /* 16-bit segment relocations. */
93 count = *rel++;
94 while (count--) {
95 u16 *seg = (u16 *) (base + *rel++);
96 *seg = real_mode_seg;
97 }
98
99 /* 32-bit linear relocations. */
100 count = *rel++;
101 while (count--) {
102 u32 *ptr = (u32 *) (base + *rel++);
103 *ptr += phys_base;
104 }
105
106 /* Must be perfomed *after* relocation. */
107 trampoline_header = (struct trampoline_header *)
108 __va(real_mode_header->trampoline_header);
109
110 #ifdef CONFIG_X86_32
111 trampoline_header->start = __pa_symbol(startup_32_smp);
112 trampoline_header->gdt_limit = __BOOT_DS + 7;
113 trampoline_header->gdt_base = __pa_symbol(boot_gdt);
114 #else
115 /*
116 * Some AMD processors will #GP(0) if EFER.LMA is set in WRMSR
117 * so we need to mask it out.
118 */
119 rdmsrl(MSR_EFER, efer);
120 trampoline_header->efer = efer & ~EFER_LMA;
121
122 trampoline_header->start = (u64) secondary_startup_64;
123 trampoline_cr4_features = &trampoline_header->cr4;
124 *trampoline_cr4_features = mmu_cr4_features;
125
126 trampoline_header->flags = 0;
127
128 trampoline_pgd = (u64 *) __va(real_mode_header->trampoline_pgd);
129 trampoline_pgd[0] = trampoline_pgd_entry.pgd;
130 trampoline_pgd[511] = init_top_pgt[511].pgd;
131 #endif
132
133 sme_sev_setup_real_mode(trampoline_header);
134 }
135
136 /*
137 * reserve_real_mode() gets called very early, to guarantee the
138 * availability of low memory. This is before the proper kernel page
139 * tables are set up, so we cannot set page permissions in that
140 * function. Also trampoline code will be executed by APs so we
141 * need to mark it executable at do_pre_smp_initcalls() at least,
142 * thus run it as a early_initcall().
143 */
set_real_mode_permissions(void)144 static void __init set_real_mode_permissions(void)
145 {
146 unsigned char *base = (unsigned char *) real_mode_header;
147 size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
148
149 size_t ro_size =
150 PAGE_ALIGN(real_mode_header->ro_end) -
151 __pa(base);
152
153 size_t text_size =
154 PAGE_ALIGN(real_mode_header->ro_end) -
155 real_mode_header->text_start;
156
157 unsigned long text_start =
158 (unsigned long) __va(real_mode_header->text_start);
159
160 set_memory_nx((unsigned long) base, size >> PAGE_SHIFT);
161 set_memory_ro((unsigned long) base, ro_size >> PAGE_SHIFT);
162 set_memory_x((unsigned long) text_start, text_size >> PAGE_SHIFT);
163 }
164
init_real_mode(void)165 static int __init init_real_mode(void)
166 {
167 if (!real_mode_header)
168 panic("Real mode trampoline was not allocated");
169
170 setup_real_mode();
171 set_real_mode_permissions();
172
173 return 0;
174 }
175 early_initcall(init_real_mode);
176
