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
7 #include <asm/set_memory.h>
8 #include <asm/pgtable.h>
9 #include <asm/realmode.h>
10 #include <asm/tlbflush.h>
11
12 struct real_mode_header *real_mode_header;
13 u32 *trampoline_cr4_features;
14
15 /* Hold the pgd entry used on booting additional CPUs */
16 pgd_t trampoline_pgd_entry;
17
set_real_mode_mem(phys_addr_t mem,size_t size)18 void __init set_real_mode_mem(phys_addr_t mem, size_t size)
19 {
20 void *base = __va(mem);
21
22 real_mode_header = (struct real_mode_header *) base;
23 printk(KERN_DEBUG "Base memory trampoline at [%p] %llx size %zu\n",
24 base, (unsigned long long)mem, size);
25 }
26
reserve_real_mode(void)27 void __init reserve_real_mode(void)
28 {
29 phys_addr_t mem;
30 size_t size = real_mode_size_needed();
31
32 if (!size)
33 return;
34
35 WARN_ON(slab_is_available());
36
37 /* Has to be under 1M so we can execute real-mode AP code. */
38 mem = memblock_find_in_range(0, 1<<20, size, PAGE_SIZE);
39 if (!mem) {
40 pr_info("No sub-1M memory is available for the trampoline\n");
41 return;
42 }
43
44 memblock_reserve(mem, size);
45 set_real_mode_mem(mem, size);
46 }
47
setup_real_mode(void)48 static void __init setup_real_mode(void)
49 {
50 u16 real_mode_seg;
51 const u32 *rel;
52 u32 count;
53 unsigned char *base;
54 unsigned long phys_base;
55 struct trampoline_header *trampoline_header;
56 size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
57 #ifdef CONFIG_X86_64
58 u64 *trampoline_pgd;
59 u64 efer;
60 #endif
61
62 base = (unsigned char *)real_mode_header;
63
64 /*
65 * If SME is active, the trampoline area will need to be in
66 * decrypted memory in order to bring up other processors
67 * successfully. This is not needed for SEV.
68 */
69 if (sme_active())
70 set_memory_decrypted((unsigned long)base, size >> PAGE_SHIFT);
71
72 memcpy(base, real_mode_blob, size);
73
74 phys_base = __pa(base);
75 real_mode_seg = phys_base >> 4;
76
77 rel = (u32 *) real_mode_relocs;
78
79 /* 16-bit segment relocations. */
80 count = *rel++;
81 while (count--) {
82 u16 *seg = (u16 *) (base + *rel++);
83 *seg = real_mode_seg;
84 }
85
86 /* 32-bit linear relocations. */
87 count = *rel++;
88 while (count--) {
89 u32 *ptr = (u32 *) (base + *rel++);
90 *ptr += phys_base;
91 }
92
93 /* Must be perfomed *after* relocation. */
94 trampoline_header = (struct trampoline_header *)
95 __va(real_mode_header->trampoline_header);
96
97 #ifdef CONFIG_X86_32
98 trampoline_header->start = __pa_symbol(startup_32_smp);
99 trampoline_header->gdt_limit = __BOOT_DS + 7;
100 trampoline_header->gdt_base = __pa_symbol(boot_gdt);
101 #else
102 /*
103 * Some AMD processors will #GP(0) if EFER.LMA is set in WRMSR
104 * so we need to mask it out.
105 */
106 rdmsrl(MSR_EFER, efer);
107 trampoline_header->efer = efer & ~EFER_LMA;
108
109 trampoline_header->start = (u64) secondary_startup_64;
110 trampoline_cr4_features = &trampoline_header->cr4;
111 *trampoline_cr4_features = mmu_cr4_features;
112
113 trampoline_header->flags = 0;
114 if (sme_active())
115 trampoline_header->flags |= TH_FLAGS_SME_ACTIVE;
116
117 trampoline_pgd = (u64 *) __va(real_mode_header->trampoline_pgd);
118 trampoline_pgd[0] = trampoline_pgd_entry.pgd;
119 trampoline_pgd[511] = init_top_pgt[511].pgd;
120 #endif
121 }
122
123 /*
124 * reserve_real_mode() gets called very early, to guarantee the
125 * availability of low memory. This is before the proper kernel page
126 * tables are set up, so we cannot set page permissions in that
127 * function. Also trampoline code will be executed by APs so we
128 * need to mark it executable at do_pre_smp_initcalls() at least,
129 * thus run it as a early_initcall().
130 */
set_real_mode_permissions(void)131 static void __init set_real_mode_permissions(void)
132 {
133 unsigned char *base = (unsigned char *) real_mode_header;
134 size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
135
136 size_t ro_size =
137 PAGE_ALIGN(real_mode_header->ro_end) -
138 __pa(base);
139
140 size_t text_size =
141 PAGE_ALIGN(real_mode_header->ro_end) -
142 real_mode_header->text_start;
143
144 unsigned long text_start =
145 (unsigned long) __va(real_mode_header->text_start);
146
147 set_memory_nx((unsigned long) base, size >> PAGE_SHIFT);
148 set_memory_ro((unsigned long) base, ro_size >> PAGE_SHIFT);
149 set_memory_x((unsigned long) text_start, text_size >> PAGE_SHIFT);
150 }
151
init_real_mode(void)152 static int __init init_real_mode(void)
153 {
154 if (!real_mode_header)
155 panic("Real mode trampoline was not allocated");
156
157 setup_real_mode();
158 set_real_mode_permissions();
159
160 return 0;
161 }
162 early_initcall(init_real_mode);
163
