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 15 struct real_mode_header *real_mode_header; 16 u32 *trampoline_cr4_features; 17 18 /* Hold the pgd entry used on booting additional CPUs */ 19 pgd_t trampoline_pgd_entry; 20 21 void 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(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 47 void __init reserve_real_mode(void) 48 { 49 phys_addr_t mem, limit = x86_init.resources.realmode_limit; 50 size_t size = real_mode_size_needed(); 51 52 if (!size) 53 return; 54 55 WARN_ON(slab_is_available()); 56 57 mem = memblock_phys_alloc_range(size, PAGE_SIZE, 0, limit); 58 if (!mem) 59 pr_info("No memory below %pa for the real-mode trampoline\n", &limit); 60 else 61 set_real_mode_mem(mem); 62 63 /* 64 * Unconditionally reserve the entire first 1M, see comment in 65 * setup_arch(). 66 */ 67 memblock_reserve(0, SZ_1M); 68 69 memblock_clear_kho_scratch(0, SZ_1M); 70 } 71 72 static void __init sme_sev_setup_real_mode(struct trampoline_header *th) 73 { 74 #ifdef CONFIG_AMD_MEM_ENCRYPT 75 if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT)) 76 th->flags |= TH_FLAGS_SME_ACTIVE; 77 78 if (cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT)) { 79 /* 80 * Skip the call to verify_cpu() in secondary_startup_64 as it 81 * will cause #VC exceptions when the AP can't handle them yet. 82 */ 83 th->start = (u64) secondary_startup_64_no_verify; 84 85 if (sev_es_setup_ap_jump_table(real_mode_header)) 86 panic("Failed to get/update SEV-ES AP Jump Table"); 87 } 88 #endif 89 } 90 91 static void __init setup_real_mode(void) 92 { 93 u16 real_mode_seg; 94 const u32 *rel; 95 u32 count; 96 unsigned char *base; 97 unsigned long phys_base; 98 struct trampoline_header *trampoline_header; 99 size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob); 100 #ifdef CONFIG_X86_64 101 u64 *trampoline_pgd; 102 u64 efer; 103 int i; 104 #endif 105 106 base = (unsigned char *)real_mode_header; 107 108 /* 109 * If SME is active, the trampoline area will need to be in 110 * decrypted memory in order to bring up other processors 111 * successfully. This is not needed for SEV. 112 */ 113 if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT)) 114 set_memory_decrypted((unsigned long)base, size >> PAGE_SHIFT); 115 116 memcpy(base, real_mode_blob, size); 117 118 phys_base = __pa(base); 119 real_mode_seg = phys_base >> 4; 120 121 rel = (u32 *) real_mode_relocs; 122 123 /* 16-bit segment relocations. */ 124 count = *rel++; 125 while (count--) { 126 u16 *seg = (u16 *) (base + *rel++); 127 *seg = real_mode_seg; 128 } 129 130 /* 32-bit linear relocations. */ 131 count = *rel++; 132 while (count--) { 133 u32 *ptr = (u32 *) (base + *rel++); 134 *ptr += phys_base; 135 } 136 137 /* Must be performed *after* relocation. */ 138 trampoline_header = (struct trampoline_header *) 139 __va(real_mode_header->trampoline_header); 140 141 #ifdef CONFIG_X86_32 142 trampoline_header->start = __pa_symbol(startup_32_smp); 143 trampoline_header->gdt_limit = __BOOT_DS + 7; 144 trampoline_header->gdt_base = __pa_symbol(boot_gdt); 145 #else 146 /* 147 * Some AMD processors will #GP(0) if EFER.LMA is set in WRMSR 148 * so we need to mask it out. 149 */ 150 rdmsrq(MSR_EFER, efer); 151 trampoline_header->efer = efer & ~EFER_LMA; 152 153 trampoline_header->start = (u64) secondary_startup_64; 154 trampoline_cr4_features = &trampoline_header->cr4; 155 *trampoline_cr4_features = mmu_cr4_features; 156 157 trampoline_header->flags = 0; 158 159 trampoline_lock = &trampoline_header->lock; 160 *trampoline_lock = 0; 161 162 trampoline_pgd = (u64 *) __va(real_mode_header->trampoline_pgd); 163 164 /* Map the real mode stub as virtual == physical */ 165 trampoline_pgd[0] = trampoline_pgd_entry.pgd; 166 167 /* 168 * Include the entirety of the kernel mapping into the trampoline 169 * PGD. This way, all mappings present in the normal kernel page 170 * tables are usable while running on trampoline_pgd. 171 */ 172 for (i = pgd_index(__PAGE_OFFSET); i < PTRS_PER_PGD; i++) 173 trampoline_pgd[i] = init_top_pgt[i].pgd; 174 #endif 175 176 sme_sev_setup_real_mode(trampoline_header); 177 } 178 179 /* 180 * reserve_real_mode() gets called very early, to guarantee the 181 * availability of low memory. This is before the proper kernel page 182 * tables are set up, so we cannot set page permissions in that 183 * function. Also trampoline code will be executed by APs so we 184 * need to mark it executable at do_pre_smp_initcalls() at least, 185 * thus run it as a early_initcall(). 186 */ 187 static void __init set_real_mode_permissions(void) 188 { 189 unsigned char *base = (unsigned char *) real_mode_header; 190 size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob); 191 192 size_t ro_size = 193 PAGE_ALIGN(real_mode_header->ro_end) - 194 __pa(base); 195 196 size_t text_size = 197 PAGE_ALIGN(real_mode_header->ro_end) - 198 real_mode_header->text_start; 199 200 unsigned long text_start = 201 (unsigned long) __va(real_mode_header->text_start); 202 203 set_memory_nx((unsigned long) base, size >> PAGE_SHIFT); 204 set_memory_ro((unsigned long) base, ro_size >> PAGE_SHIFT); 205 set_memory_x((unsigned long) text_start, text_size >> PAGE_SHIFT); 206 } 207 208 void __init init_real_mode(void) 209 { 210 if (!real_mode_header) 211 panic("Real mode trampoline was not allocated"); 212 213 setup_real_mode(); 214 set_real_mode_permissions(); 215 } 216 217 static int __init do_init_real_mode(void) 218 { 219 x86_platform.realmode_init(); 220 return 0; 221 } 222 early_initcall(do_init_real_mode); 223