1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef _ASM_X86_SEGMENT_H 3 #define _ASM_X86_SEGMENT_H 4 5 #include <linux/const.h> 6 #include <asm/alternative.h> 7 #include <asm/ibt.h> 8 9 /* 10 * Constructor for a conventional segment GDT (or LDT) entry. 11 * This is a macro so it can be used in initializers. 12 */ 13 #define GDT_ENTRY(flags, base, limit) \ 14 ((((base) & _AC(0xff000000,ULL)) << (56-24)) | \ 15 (((flags) & _AC(0x0000f0ff,ULL)) << 40) | \ 16 (((limit) & _AC(0x000f0000,ULL)) << (48-16)) | \ 17 (((base) & _AC(0x00ffffff,ULL)) << 16) | \ 18 (((limit) & _AC(0x0000ffff,ULL)))) 19 20 /* Simple and small GDT entries for booting only: */ 21 22 #define GDT_ENTRY_BOOT_CS 2 23 #define GDT_ENTRY_BOOT_DS 3 24 #define GDT_ENTRY_BOOT_TSS 4 25 #define __BOOT_CS (GDT_ENTRY_BOOT_CS*8) 26 #define __BOOT_DS (GDT_ENTRY_BOOT_DS*8) 27 #define __BOOT_TSS (GDT_ENTRY_BOOT_TSS*8) 28 29 /* 30 * Bottom two bits of selector give the ring 31 * privilege level 32 */ 33 #define SEGMENT_RPL_MASK 0x3 34 35 /* 36 * When running on Xen PV, the actual privilege level of the kernel is 1, 37 * not 0. Testing the Requested Privilege Level in a segment selector to 38 * determine whether the context is user mode or kernel mode with 39 * SEGMENT_RPL_MASK is wrong because the PV kernel's privilege level 40 * matches the 0x3 mask. 41 * 42 * Testing with USER_SEGMENT_RPL_MASK is valid for both native and Xen PV 43 * kernels because privilege level 2 is never used. 44 */ 45 #define USER_SEGMENT_RPL_MASK 0x2 46 47 /* User mode is privilege level 3: */ 48 #define USER_RPL 0x3 49 50 /* Bit 2 is Table Indicator (TI): selects between LDT or GDT */ 51 #define SEGMENT_TI_MASK 0x4 52 /* LDT segment has TI set ... */ 53 #define SEGMENT_LDT 0x4 54 /* ... GDT has it cleared */ 55 #define SEGMENT_GDT 0x0 56 57 #define GDT_ENTRY_INVALID_SEG 0 58 59 #ifdef CONFIG_X86_32 60 /* 61 * The layout of the per-CPU GDT under Linux: 62 * 63 * 0 - null <=== cacheline #1 64 * 1 - reserved 65 * 2 - reserved 66 * 3 - reserved 67 * 68 * 4 - unused <=== cacheline #2 69 * 5 - unused 70 * 71 * ------- start of TLS (Thread-Local Storage) segments: 72 * 73 * 6 - TLS segment #1 [ glibc's TLS segment ] 74 * 7 - TLS segment #2 [ Wine's %fs Win32 segment ] 75 * 8 - TLS segment #3 <=== cacheline #3 76 * 9 - reserved 77 * 10 - reserved 78 * 11 - reserved 79 * 80 * ------- start of kernel segments: 81 * 82 * 12 - kernel code segment <=== cacheline #4 83 * 13 - kernel data segment 84 * 14 - default user CS 85 * 15 - default user DS 86 * 16 - TSS <=== cacheline #5 87 * 17 - LDT 88 * 18 - PNPBIOS support (16->32 gate) 89 * 19 - PNPBIOS support 90 * 20 - PNPBIOS support <=== cacheline #6 91 * 21 - PNPBIOS support 92 * 22 - PNPBIOS support 93 * 23 - APM BIOS support 94 * 24 - APM BIOS support <=== cacheline #7 95 * 25 - APM BIOS support 96 * 97 * 26 - ESPFIX small SS 98 * 27 - per-cpu [ offset to per-cpu data area ] 99 * 28 - VDSO getcpu 100 * 29 - unused 101 * 30 - unused 102 * 31 - TSS for double fault handler 103 */ 104 #define GDT_ENTRY_TLS_MIN 6 105 #define GDT_ENTRY_TLS_MAX (GDT_ENTRY_TLS_MIN + GDT_ENTRY_TLS_ENTRIES - 1) 106 107 #define GDT_ENTRY_KERNEL_CS 12 108 #define GDT_ENTRY_KERNEL_DS 13 109 #define GDT_ENTRY_DEFAULT_USER_CS 14 110 #define GDT_ENTRY_DEFAULT_USER_DS 15 111 #define GDT_ENTRY_TSS 16 112 #define GDT_ENTRY_LDT 17 113 #define GDT_ENTRY_PNPBIOS_CS32 18 114 #define GDT_ENTRY_PNPBIOS_CS16 19 115 #define GDT_ENTRY_PNPBIOS_DS 20 116 #define GDT_ENTRY_PNPBIOS_TS1 21 117 #define GDT_ENTRY_PNPBIOS_TS2 22 118 #define GDT_ENTRY_APMBIOS_BASE 23 119 120 #define GDT_ENTRY_ESPFIX_SS 26 121 #define GDT_ENTRY_PERCPU 27 122 #define GDT_ENTRY_CPUNODE 28 123 124 #define GDT_ENTRY_DOUBLEFAULT_TSS 31 125 126 /* 127 * Number of entries in the GDT table: 128 */ 129 #define GDT_ENTRIES 32 130 131 /* 132 * Segment selector values corresponding to the above entries: 133 */ 134 135 #define __KERNEL_CS (GDT_ENTRY_KERNEL_CS*8) 136 #define __KERNEL_DS (GDT_ENTRY_KERNEL_DS*8) 137 #define __USER_DS (GDT_ENTRY_DEFAULT_USER_DS*8 + 3) 138 #define __USER_CS (GDT_ENTRY_DEFAULT_USER_CS*8 + 3) 139 #define __USER32_CS __USER_CS 140 #define __ESPFIX_SS (GDT_ENTRY_ESPFIX_SS*8) 141 142 /* segment for calling fn: */ 143 #define PNP_CS32 (GDT_ENTRY_PNPBIOS_CS32*8) 144 /* code segment for BIOS: */ 145 #define PNP_CS16 (GDT_ENTRY_PNPBIOS_CS16*8) 146 147 /* "Is this PNP code selector (PNP_CS32 or PNP_CS16)?" */ 148 #define SEGMENT_IS_PNP_CODE(x) (((x) & 0xf4) == PNP_CS32) 149 150 /* data segment for BIOS: */ 151 #define PNP_DS (GDT_ENTRY_PNPBIOS_DS*8) 152 /* transfer data segment: */ 153 #define PNP_TS1 (GDT_ENTRY_PNPBIOS_TS1*8) 154 /* another data segment: */ 155 #define PNP_TS2 (GDT_ENTRY_PNPBIOS_TS2*8) 156 157 #ifdef CONFIG_SMP 158 # define __KERNEL_PERCPU (GDT_ENTRY_PERCPU*8) 159 #else 160 # define __KERNEL_PERCPU 0 161 #endif 162 163 #define __CPUNODE_SEG (GDT_ENTRY_CPUNODE*8 + 3) 164 165 #else /* 64-bit: */ 166 167 #include <asm/cache.h> 168 169 #define GDT_ENTRY_KERNEL32_CS 1 170 #define GDT_ENTRY_KERNEL_CS 2 171 #define GDT_ENTRY_KERNEL_DS 3 172 173 /* 174 * We cannot use the same code segment descriptor for user and kernel mode, 175 * not even in long flat mode, because of different DPL. 176 * 177 * GDT layout to get 64-bit SYSCALL/SYSRET support right. SYSRET hardcodes 178 * selectors: 179 * 180 * if returning to 32-bit userspace: cs = STAR.SYSRET_CS, 181 * if returning to 64-bit userspace: cs = STAR.SYSRET_CS+16, 182 * 183 * ss = STAR.SYSRET_CS+8 (in either case) 184 * 185 * thus USER_DS should be between 32-bit and 64-bit code selectors: 186 */ 187 #define GDT_ENTRY_DEFAULT_USER32_CS 4 188 #define GDT_ENTRY_DEFAULT_USER_DS 5 189 #define GDT_ENTRY_DEFAULT_USER_CS 6 190 191 /* Needs two entries */ 192 #define GDT_ENTRY_TSS 8 193 /* Needs two entries */ 194 #define GDT_ENTRY_LDT 10 195 196 #define GDT_ENTRY_TLS_MIN 12 197 #define GDT_ENTRY_TLS_MAX 14 198 199 #define GDT_ENTRY_CPUNODE 15 200 201 /* 202 * Number of entries in the GDT table: 203 */ 204 #define GDT_ENTRIES 16 205 206 /* 207 * Segment selector values corresponding to the above entries: 208 * 209 * Note, selectors also need to have a correct RPL, 210 * expressed with the +3 value for user-space selectors: 211 */ 212 #define __KERNEL32_CS (GDT_ENTRY_KERNEL32_CS*8) 213 #define __KERNEL_CS (GDT_ENTRY_KERNEL_CS*8) 214 #define __KERNEL_DS (GDT_ENTRY_KERNEL_DS*8) 215 #define __USER32_CS (GDT_ENTRY_DEFAULT_USER32_CS*8 + 3) 216 #define __USER_DS (GDT_ENTRY_DEFAULT_USER_DS*8 + 3) 217 #define __USER_CS (GDT_ENTRY_DEFAULT_USER_CS*8 + 3) 218 #define __CPUNODE_SEG (GDT_ENTRY_CPUNODE*8 + 3) 219 220 #endif 221 222 #define IDT_ENTRIES 256 223 #define NUM_EXCEPTION_VECTORS 32 224 225 /* Bitmask of exception vectors which push an error code on the stack: */ 226 #define EXCEPTION_ERRCODE_MASK 0x20027d00 227 228 #define GDT_SIZE (GDT_ENTRIES*8) 229 #define GDT_ENTRY_TLS_ENTRIES 3 230 #define TLS_SIZE (GDT_ENTRY_TLS_ENTRIES* 8) 231 232 /* Bit size and mask of CPU number stored in the per CPU data (and TSC_AUX) */ 233 #define VDSO_CPUNODE_BITS 12 234 #define VDSO_CPUNODE_MASK 0xfff 235 236 #ifndef __ASSEMBLY__ 237 238 /* Helper functions to store/load CPU and node numbers */ 239 240 static inline unsigned long vdso_encode_cpunode(int cpu, unsigned long node) 241 { 242 return (node << VDSO_CPUNODE_BITS) | cpu; 243 } 244 245 static inline void vdso_read_cpunode(unsigned *cpu, unsigned *node) 246 { 247 unsigned int p; 248 249 /* 250 * Load CPU and node number from the GDT. LSL is faster than RDTSCP 251 * and works on all CPUs. This is volatile so that it orders 252 * correctly with respect to barrier() and to keep GCC from cleverly 253 * hoisting it out of the calling function. 254 * 255 * If RDPID is available, use it. 256 */ 257 alternative_io ("lsl %[seg],%[p]", 258 ".byte 0xf3,0x0f,0xc7,0xf8", /* RDPID %eax/rax */ 259 X86_FEATURE_RDPID, 260 [p] "=a" (p), [seg] "r" (__CPUNODE_SEG)); 261 262 if (cpu) 263 *cpu = (p & VDSO_CPUNODE_MASK); 264 if (node) 265 *node = (p >> VDSO_CPUNODE_BITS); 266 } 267 268 #endif /* !__ASSEMBLY__ */ 269 270 #ifdef __KERNEL__ 271 272 /* 273 * early_idt_handler_array is an array of entry points referenced in the 274 * early IDT. For simplicity, it's a real array with one entry point 275 * every nine bytes. That leaves room for an optional 'push $0' if the 276 * vector has no error code (two bytes), a 'push $vector_number' (two 277 * bytes), and a jump to the common entry code (up to five bytes). 278 */ 279 #define EARLY_IDT_HANDLER_SIZE (9 + ENDBR_INSN_SIZE) 280 281 /* 282 * xen_early_idt_handler_array is for Xen pv guests: for each entry in 283 * early_idt_handler_array it contains a prequel in the form of 284 * pop %rcx; pop %r11; jmp early_idt_handler_array[i]; summing up to 285 * max 8 bytes. 286 */ 287 #define XEN_EARLY_IDT_HANDLER_SIZE (8 + ENDBR_INSN_SIZE) 288 289 #ifndef __ASSEMBLY__ 290 291 extern const char early_idt_handler_array[NUM_EXCEPTION_VECTORS][EARLY_IDT_HANDLER_SIZE]; 292 extern void early_ignore_irq(void); 293 294 #ifdef CONFIG_XEN_PV 295 extern const char xen_early_idt_handler_array[NUM_EXCEPTION_VECTORS][XEN_EARLY_IDT_HANDLER_SIZE]; 296 #endif 297 298 /* 299 * Load a segment. Fall back on loading the zero segment if something goes 300 * wrong. This variant assumes that loading zero fully clears the segment. 301 * This is always the case on Intel CPUs and, even on 64-bit AMD CPUs, any 302 * failure to fully clear the cached descriptor is only observable for 303 * FS and GS. 304 */ 305 #define __loadsegment_simple(seg, value) \ 306 do { \ 307 unsigned short __val = (value); \ 308 \ 309 asm volatile(" \n" \ 310 "1: movl %k0,%%" #seg " \n" \ 311 _ASM_EXTABLE_TYPE_REG(1b, 1b, EX_TYPE_ZERO_REG, %k0)\ 312 : "+r" (__val) : : "memory"); \ 313 } while (0) 314 315 #define __loadsegment_ss(value) __loadsegment_simple(ss, (value)) 316 #define __loadsegment_ds(value) __loadsegment_simple(ds, (value)) 317 #define __loadsegment_es(value) __loadsegment_simple(es, (value)) 318 319 #ifdef CONFIG_X86_32 320 321 /* 322 * On 32-bit systems, the hidden parts of FS and GS are unobservable if 323 * the selector is NULL, so there's no funny business here. 324 */ 325 #define __loadsegment_fs(value) __loadsegment_simple(fs, (value)) 326 #define __loadsegment_gs(value) __loadsegment_simple(gs, (value)) 327 328 #else 329 330 static inline void __loadsegment_fs(unsigned short value) 331 { 332 asm volatile(" \n" 333 "1: movw %0, %%fs \n" 334 "2: \n" 335 336 _ASM_EXTABLE_TYPE(1b, 2b, EX_TYPE_CLEAR_FS) 337 338 : : "rm" (value) : "memory"); 339 } 340 341 /* __loadsegment_gs is intentionally undefined. Use load_gs_index instead. */ 342 343 #endif 344 345 #define loadsegment(seg, value) __loadsegment_ ## seg (value) 346 347 /* 348 * Save a segment register away: 349 */ 350 #define savesegment(seg, value) \ 351 asm("mov %%" #seg ",%0":"=r" (value) : : "memory") 352 353 #endif /* !__ASSEMBLY__ */ 354 #endif /* __KERNEL__ */ 355 356 #endif /* _ASM_X86_SEGMENT_H */ 357