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