1 // SPDX-License-Identifier: GPL-2.0 2 3 #include <linux/spinlock.h> 4 #include <linux/percpu.h> 5 #include <linux/kallsyms.h> 6 #include <linux/kcore.h> 7 #include <linux/pgtable.h> 8 9 #include <asm/cpu_entry_area.h> 10 #include <asm/fixmap.h> 11 #include <asm/desc.h> 12 #include <asm/kasan.h> 13 #include <asm/setup.h> 14 15 static DEFINE_PER_CPU_PAGE_ALIGNED(struct entry_stack_page, entry_stack_storage); 16 17 #ifdef CONFIG_X86_64 18 static DEFINE_PER_CPU_PAGE_ALIGNED(struct exception_stacks, exception_stacks); 19 DEFINE_PER_CPU(struct cea_exception_stacks*, cea_exception_stacks); 20 21 static DEFINE_PER_CPU_READ_MOSTLY(unsigned long, _cea_offset); 22 23 static __always_inline unsigned int cea_offset(unsigned int cpu) 24 { 25 return per_cpu(_cea_offset, cpu); 26 } 27 28 static __init void init_cea_offsets(void) 29 { 30 unsigned int max_cea; 31 unsigned int i, j; 32 33 if (!kaslr_enabled()) { 34 for_each_possible_cpu(i) 35 per_cpu(_cea_offset, i) = i; 36 return; 37 } 38 39 max_cea = (CPU_ENTRY_AREA_MAP_SIZE - PAGE_SIZE) / CPU_ENTRY_AREA_SIZE; 40 41 /* O(sodding terrible) */ 42 for_each_possible_cpu(i) { 43 unsigned int cea; 44 45 again: 46 cea = get_random_u32_below(max_cea); 47 48 for_each_possible_cpu(j) { 49 if (cea_offset(j) == cea) 50 goto again; 51 52 if (i == j) 53 break; 54 } 55 56 per_cpu(_cea_offset, i) = cea; 57 } 58 } 59 #else /* !X86_64 */ 60 DECLARE_PER_CPU_PAGE_ALIGNED(struct doublefault_stack, doublefault_stack); 61 62 static __always_inline unsigned int cea_offset(unsigned int cpu) 63 { 64 return cpu; 65 } 66 static inline void init_cea_offsets(void) { } 67 #endif 68 69 /* Is called from entry code, so must be noinstr */ 70 noinstr struct cpu_entry_area *get_cpu_entry_area(int cpu) 71 { 72 unsigned long va = CPU_ENTRY_AREA_PER_CPU + cea_offset(cpu) * CPU_ENTRY_AREA_SIZE; 73 BUILD_BUG_ON(sizeof(struct cpu_entry_area) % PAGE_SIZE != 0); 74 75 return (struct cpu_entry_area *) va; 76 } 77 EXPORT_SYMBOL(get_cpu_entry_area); 78 79 void cea_set_pte(void *cea_vaddr, phys_addr_t pa, pgprot_t flags) 80 { 81 unsigned long va = (unsigned long) cea_vaddr; 82 pte_t pte = pfn_pte(pa >> PAGE_SHIFT, flags); 83 84 /* 85 * The cpu_entry_area is shared between the user and kernel 86 * page tables. All of its ptes can safely be global. 87 * _PAGE_GLOBAL gets reused to help indicate PROT_NONE for 88 * non-present PTEs, so be careful not to set it in that 89 * case to avoid confusion. 90 */ 91 if (boot_cpu_has(X86_FEATURE_PGE) && 92 (pgprot_val(flags) & _PAGE_PRESENT)) 93 pte = pte_set_flags(pte, _PAGE_GLOBAL); 94 95 set_pte_vaddr(va, pte); 96 } 97 98 static void __init 99 cea_map_percpu_pages(void *cea_vaddr, void *ptr, int pages, pgprot_t prot) 100 { 101 for ( ; pages; pages--, cea_vaddr+= PAGE_SIZE, ptr += PAGE_SIZE) 102 cea_set_pte(cea_vaddr, per_cpu_ptr_to_phys(ptr), prot); 103 } 104 105 static void __init percpu_setup_debug_store(unsigned int cpu) 106 { 107 #ifdef CONFIG_CPU_SUP_INTEL 108 unsigned int npages; 109 void *cea; 110 111 if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) 112 return; 113 114 cea = &get_cpu_entry_area(cpu)->cpu_debug_store; 115 npages = sizeof(struct debug_store) / PAGE_SIZE; 116 BUILD_BUG_ON(sizeof(struct debug_store) % PAGE_SIZE != 0); 117 cea_map_percpu_pages(cea, &per_cpu(cpu_debug_store, cpu), npages, 118 PAGE_KERNEL); 119 120 cea = &get_cpu_entry_area(cpu)->cpu_debug_buffers; 121 /* 122 * Force the population of PMDs for not yet allocated per cpu 123 * memory like debug store buffers. 124 */ 125 npages = sizeof(struct debug_store_buffers) / PAGE_SIZE; 126 for (; npages; npages--, cea += PAGE_SIZE) 127 cea_set_pte(cea, 0, PAGE_NONE); 128 #endif 129 } 130 131 #ifdef CONFIG_X86_64 132 133 #define cea_map_stack(name) do { \ 134 npages = sizeof(estacks->name## _stack) / PAGE_SIZE; \ 135 cea_map_percpu_pages(cea->estacks.name## _stack, \ 136 estacks->name## _stack, npages, PAGE_KERNEL); \ 137 } while (0) 138 139 static void __init percpu_setup_exception_stacks(unsigned int cpu) 140 { 141 struct exception_stacks *estacks = per_cpu_ptr(&exception_stacks, cpu); 142 struct cpu_entry_area *cea = get_cpu_entry_area(cpu); 143 unsigned int npages; 144 145 BUILD_BUG_ON(sizeof(exception_stacks) % PAGE_SIZE != 0); 146 147 per_cpu(cea_exception_stacks, cpu) = &cea->estacks; 148 149 /* 150 * The exceptions stack mappings in the per cpu area are protected 151 * by guard pages so each stack must be mapped separately. DB2 is 152 * not mapped; it just exists to catch triple nesting of #DB. 153 */ 154 cea_map_stack(DF); 155 cea_map_stack(NMI); 156 cea_map_stack(DB); 157 cea_map_stack(MCE); 158 159 if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT)) { 160 if (cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT)) { 161 cea_map_stack(VC); 162 cea_map_stack(VC2); 163 } 164 } 165 } 166 #else 167 static void __init percpu_setup_exception_stacks(unsigned int cpu) 168 { 169 struct cpu_entry_area *cea = get_cpu_entry_area(cpu); 170 171 cea_map_percpu_pages(&cea->doublefault_stack, 172 &per_cpu(doublefault_stack, cpu), 1, PAGE_KERNEL); 173 } 174 #endif 175 176 /* Setup the fixmap mappings only once per-processor */ 177 static void __init setup_cpu_entry_area(unsigned int cpu) 178 { 179 struct cpu_entry_area *cea = get_cpu_entry_area(cpu); 180 #ifdef CONFIG_X86_64 181 /* On 64-bit systems, we use a read-only fixmap GDT and TSS. */ 182 pgprot_t gdt_prot = PAGE_KERNEL_RO; 183 pgprot_t tss_prot = PAGE_KERNEL_RO; 184 #else 185 /* 186 * On 32-bit systems, the GDT cannot be read-only because 187 * our double fault handler uses a task gate, and entering through 188 * a task gate needs to change an available TSS to busy. If the 189 * GDT is read-only, that will triple fault. The TSS cannot be 190 * read-only because the CPU writes to it on task switches. 191 */ 192 pgprot_t gdt_prot = PAGE_KERNEL; 193 pgprot_t tss_prot = PAGE_KERNEL; 194 #endif 195 196 kasan_populate_shadow_for_vaddr(cea, CPU_ENTRY_AREA_SIZE, 197 early_cpu_to_node(cpu)); 198 199 cea_set_pte(&cea->gdt, get_cpu_gdt_paddr(cpu), gdt_prot); 200 201 cea_map_percpu_pages(&cea->entry_stack_page, 202 per_cpu_ptr(&entry_stack_storage, cpu), 1, 203 PAGE_KERNEL); 204 205 /* 206 * The Intel SDM says (Volume 3, 7.2.1): 207 * 208 * Avoid placing a page boundary in the part of the TSS that the 209 * processor reads during a task switch (the first 104 bytes). The 210 * processor may not correctly perform address translations if a 211 * boundary occurs in this area. During a task switch, the processor 212 * reads and writes into the first 104 bytes of each TSS (using 213 * contiguous physical addresses beginning with the physical address 214 * of the first byte of the TSS). So, after TSS access begins, if 215 * part of the 104 bytes is not physically contiguous, the processor 216 * will access incorrect information without generating a page-fault 217 * exception. 218 * 219 * There are also a lot of errata involving the TSS spanning a page 220 * boundary. Assert that we're not doing that. 221 */ 222 BUILD_BUG_ON((offsetof(struct tss_struct, x86_tss) ^ 223 offsetofend(struct tss_struct, x86_tss)) & PAGE_MASK); 224 BUILD_BUG_ON(sizeof(struct tss_struct) % PAGE_SIZE != 0); 225 /* 226 * VMX changes the host TR limit to 0x67 after a VM exit. This is 227 * okay, since 0x67 covers the size of struct x86_hw_tss. Make sure 228 * that this is correct. 229 */ 230 BUILD_BUG_ON(offsetof(struct tss_struct, x86_tss) != 0); 231 BUILD_BUG_ON(sizeof(struct x86_hw_tss) != 0x68); 232 233 cea_map_percpu_pages(&cea->tss, &per_cpu(cpu_tss_rw, cpu), 234 sizeof(struct tss_struct) / PAGE_SIZE, tss_prot); 235 236 #ifdef CONFIG_X86_32 237 per_cpu(cpu_entry_area, cpu) = cea; 238 #endif 239 240 percpu_setup_exception_stacks(cpu); 241 242 percpu_setup_debug_store(cpu); 243 } 244 245 static __init void setup_cpu_entry_area_ptes(void) 246 { 247 #ifdef CONFIG_X86_32 248 unsigned long start, end; 249 250 /* The +1 is for the readonly IDT: */ 251 BUILD_BUG_ON((CPU_ENTRY_AREA_PAGES+1)*PAGE_SIZE != CPU_ENTRY_AREA_MAP_SIZE); 252 BUG_ON(CPU_ENTRY_AREA_BASE & ~PMD_MASK); 253 254 start = CPU_ENTRY_AREA_BASE; 255 end = start + CPU_ENTRY_AREA_MAP_SIZE; 256 257 /* Careful here: start + PMD_SIZE might wrap around */ 258 for (; start < end && start >= CPU_ENTRY_AREA_BASE; start += PMD_SIZE) 259 populate_extra_pte(start); 260 #endif 261 } 262 263 void __init setup_cpu_entry_areas(void) 264 { 265 unsigned int cpu; 266 267 init_cea_offsets(); 268 269 setup_cpu_entry_area_ptes(); 270 271 for_each_possible_cpu(cpu) 272 setup_cpu_entry_area(cpu); 273 274 /* 275 * This is the last essential update to swapper_pgdir which needs 276 * to be synchronized to initial_page_table on 32bit. 277 */ 278 sync_initial_page_table(); 279 } 280