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/msr.h>
13#include <asm/sev.h>
14
15struct real_mode_header *real_mode_header;
16u32 *trampoline_cr4_features;
17
18/* Hold the pgd entry used on booting additional CPUs */
19pgd_t trampoline_pgd_entry;
20
21void load_trampoline_pgtable(void)
22{
23#ifdef CONFIG_X86_32
24 load_cr3(initial_page_table);
25#else
26 /*
27 * This function is called before exiting to real-mode and that will
28 * fail with CR4.PCIDE still set.
29 */
30 if (boot_cpu_has(X86_FEATURE_PCID))
31 cr4_clear_bits(X86_CR4_PCIDE);
32
33 write_cr3(x: real_mode_header->trampoline_pgd);
34#endif
35
36 /*
37 * The CR3 write above will not flush global TLB entries.
38 * Stale, global entries from previous page tables may still be
39 * present. Flush those stale entries.
40 *
41 * This ensures that memory accessed while running with
42 * trampoline_pgd is *actually* mapped into trampoline_pgd.
43 */
44 __flush_tlb_all();
45}
46
47void __init reserve_real_mode(void)
48{
49 phys_addr_t mem;
50 size_t size = real_mode_size_needed();
51
52 if (!size)
53 return;
54
55 WARN_ON(slab_is_available());
56
57 /* Has to be under 1M so we can execute real-mode AP code. */
58 mem = memblock_phys_alloc_range(size, PAGE_SIZE, start: 0, end: 1<<20);
59 if (!mem)
60 pr_info("No sub-1M memory is available for the trampoline\n");
61 else
62 set_real_mode_mem(mem);
63
64 /*
65 * Unconditionally reserve the entire first 1M, see comment in
66 * setup_arch().
67 */
68 memblock_reserve(base: 0, SZ_1M);
69
70 memblock_clear_kho_scratch(base: 0, SZ_1M);
71}
72
73static void __init sme_sev_setup_real_mode(struct trampoline_header *th)
74{
75#ifdef CONFIG_AMD_MEM_ENCRYPT
76 if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT))
77 th->flags |= TH_FLAGS_SME_ACTIVE;
78
79 if (cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT)) {
80 /*
81 * Skip the call to verify_cpu() in secondary_startup_64 as it
82 * will cause #VC exceptions when the AP can't handle them yet.
83 */
84 th->start = (u64) secondary_startup_64_no_verify;
85
86 if (sev_es_setup_ap_jump_table(real_mode_header))
87 panic("Failed to get/update SEV-ES AP Jump Table");
88 }
89#endif
90}
91
92static void __init setup_real_mode(void)
93{
94 u16 real_mode_seg;
95 const u32 *rel;
96 u32 count;
97 unsigned char *base;
98 unsigned long phys_base;
99 struct trampoline_header *trampoline_header;
100 size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
101#ifdef CONFIG_X86_64
102 u64 *trampoline_pgd;
103 u64 efer;
104 int i;
105#endif
106
107 base = (unsigned char *)real_mode_header;
108
109 /*
110 * If SME is active, the trampoline area will need to be in
111 * decrypted memory in order to bring up other processors
112 * successfully. This is not needed for SEV.
113 */
114 if (cc_platform_has(attr: CC_ATTR_HOST_MEM_ENCRYPT))
115 set_memory_decrypted(addr: (unsigned long)base, numpages: size >> PAGE_SHIFT);
116
117 memcpy(to: base, from: real_mode_blob, len: size);
118
119 phys_base = __pa(base);
120 real_mode_seg = phys_base >> 4;
121
122 rel = (u32 *) real_mode_relocs;
123
124 /* 16-bit segment relocations. */
125 count = *rel++;
126 while (count--) {
127 u16 *seg = (u16 *) (base + *rel++);
128 *seg = real_mode_seg;
129 }
130
131 /* 32-bit linear relocations. */
132 count = *rel++;
133 while (count--) {
134 u32 *ptr = (u32 *) (base + *rel++);
135 *ptr += phys_base;
136 }
137
138 /* Must be performed *after* relocation. */
139 trampoline_header = (struct trampoline_header *)
140 __va(real_mode_header->trampoline_header);
141
142#ifdef CONFIG_X86_32
143 trampoline_header->start = __pa_symbol(startup_32_smp);
144 trampoline_header->gdt_limit = __BOOT_DS + 7;
145 trampoline_header->gdt_base = __pa_symbol(boot_gdt);
146#else
147 /*
148 * Some AMD processors will #GP(0) if EFER.LMA is set in WRMSR
149 * so we need to mask it out.
150 */
151 rdmsrq(MSR_EFER, efer);
152 trampoline_header->efer = efer & ~EFER_LMA;
153
154 trampoline_header->start = (u64) secondary_startup_64;
155 trampoline_cr4_features = &trampoline_header->cr4;
156 *trampoline_cr4_features = mmu_cr4_features;
157
158 trampoline_header->flags = 0;
159
160 trampoline_lock = &trampoline_header->lock;
161 *trampoline_lock = 0;
162
163 trampoline_pgd = (u64 *) __va(real_mode_header->trampoline_pgd);
164
165 /* Map the real mode stub as virtual == physical */
166 trampoline_pgd[0] = trampoline_pgd_entry.pgd;
167
168 /*
169 * Include the entirety of the kernel mapping into the trampoline
170 * PGD. This way, all mappings present in the normal kernel page
171 * tables are usable while running on trampoline_pgd.
172 */
173 for (i = pgd_index(__PAGE_OFFSET); i < PTRS_PER_PGD; i++)
174 trampoline_pgd[i] = init_top_pgt[i].pgd;
175#endif
176
177 sme_sev_setup_real_mode(th: trampoline_header);
178}
179
180/*
181 * reserve_real_mode() gets called very early, to guarantee the
182 * availability of low memory. This is before the proper kernel page
183 * tables are set up, so we cannot set page permissions in that
184 * function. Also trampoline code will be executed by APs so we
185 * need to mark it executable at do_pre_smp_initcalls() at least,
186 * thus run it as a early_initcall().
187 */
188static void __init set_real_mode_permissions(void)
189{
190 unsigned char *base = (unsigned char *) real_mode_header;
191 size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
192
193 size_t ro_size =
194 PAGE_ALIGN(real_mode_header->ro_end) -
195 __pa(base);
196
197 size_t text_size =
198 PAGE_ALIGN(real_mode_header->ro_end) -
199 real_mode_header->text_start;
200
201 unsigned long text_start =
202 (unsigned long) __va(real_mode_header->text_start);
203
204 set_memory_nx(addr: (unsigned long) base, numpages: size >> PAGE_SHIFT);
205 set_memory_ro(addr: (unsigned long) base, numpages: ro_size >> PAGE_SHIFT);
206 set_memory_x(addr: (unsigned long) text_start, numpages: text_size >> PAGE_SHIFT);
207}
208
209void __init init_real_mode(void)
210{
211 if (!real_mode_header)
212 panic(fmt: "Real mode trampoline was not allocated");
213
214 setup_real_mode();
215 set_real_mode_permissions();
216}
217
218static int __init do_init_real_mode(void)
219{
220 x86_platform.realmode_init();
221 return 0;
222}
223early_initcall(do_init_real_mode);
224