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 8 /* 9 * Constructor for a conventional segment GDT (or LDT) entry. 10 * This is a macro so it can be used in initializers. 11 */ 12 #define GDT_ENTRY(flags, base, limit) \ 13 ((((base) & _AC(0xff000000,ULL)) << (56-24)) | \ 14 (((flags) & _AC(0x0000f0ff,ULL)) << 40) | \ 15 (((limit) & _AC(0x000f0000,ULL)) << (48-16)) | \ 16 (((base) & _AC(0x00ffffff,ULL)) << 16) | \ 17 (((limit) & _AC(0x0000ffff,ULL)))) 18 19 /* Simple and small GDT entries for booting only: */ 20 21 #define GDT_ENTRY_BOOT_CS 2 22 #define GDT_ENTRY_BOOT_DS 3 23 #define GDT_ENTRY_BOOT_TSS 4 24 #define __BOOT_CS (GDT_ENTRY_BOOT_CS*8) 25 #define __BOOT_DS (GDT_ENTRY_BOOT_DS*8) 26 #define __BOOT_TSS (GDT_ENTRY_BOOT_TSS*8) 27 28 /* 29 * Bottom two bits of selector give the ring 30 * privilege level 31 */ 32 #define SEGMENT_RPL_MASK 0x3 33 34 /* User mode is privilege level 3: */ 35 #define USER_RPL 0x3 36 37 /* Bit 2 is Table Indicator (TI): selects between LDT or GDT */ 38 #define SEGMENT_TI_MASK 0x4 39 /* LDT segment has TI set ... */ 40 #define SEGMENT_LDT 0x4 41 /* ... GDT has it cleared */ 42 #define SEGMENT_GDT 0x0 43 44 #define GDT_ENTRY_INVALID_SEG 0 45 46 #ifdef CONFIG_X86_32 47 /* 48 * The layout of the per-CPU GDT under Linux: 49 * 50 * 0 - null <=== cacheline #1 51 * 1 - reserved 52 * 2 - reserved 53 * 3 - reserved 54 * 55 * 4 - unused <=== cacheline #2 56 * 5 - unused 57 * 58 * ------- start of TLS (Thread-Local Storage) segments: 59 * 60 * 6 - TLS segment #1 [ glibc's TLS segment ] 61 * 7 - TLS segment #2 [ Wine's %fs Win32 segment ] 62 * 8 - TLS segment #3 <=== cacheline #3 63 * 9 - reserved 64 * 10 - reserved 65 * 11 - reserved 66 * 67 * ------- start of kernel segments: 68 * 69 * 12 - kernel code segment <=== cacheline #4 70 * 13 - kernel data segment 71 * 14 - default user CS 72 * 15 - default user DS 73 * 16 - TSS <=== cacheline #5 74 * 17 - LDT 75 * 18 - PNPBIOS support (16->32 gate) 76 * 19 - PNPBIOS support 77 * 20 - PNPBIOS support <=== cacheline #6 78 * 21 - PNPBIOS support 79 * 22 - PNPBIOS support 80 * 23 - APM BIOS support 81 * 24 - APM BIOS support <=== cacheline #7 82 * 25 - APM BIOS support 83 * 84 * 26 - ESPFIX small SS 85 * 27 - per-cpu [ offset to per-cpu data area ] 86 * 28 - stack_canary-20 [ for stack protector ] <=== cacheline #8 87 * 29 - unused 88 * 30 - unused 89 * 31 - TSS for double fault handler 90 */ 91 #define GDT_ENTRY_TLS_MIN 6 92 #define GDT_ENTRY_TLS_MAX (GDT_ENTRY_TLS_MIN + GDT_ENTRY_TLS_ENTRIES - 1) 93 94 #define GDT_ENTRY_KERNEL_CS 12 95 #define GDT_ENTRY_KERNEL_DS 13 96 #define GDT_ENTRY_DEFAULT_USER_CS 14 97 #define GDT_ENTRY_DEFAULT_USER_DS 15 98 #define GDT_ENTRY_TSS 16 99 #define GDT_ENTRY_LDT 17 100 #define GDT_ENTRY_PNPBIOS_CS32 18 101 #define GDT_ENTRY_PNPBIOS_CS16 19 102 #define GDT_ENTRY_PNPBIOS_DS 20 103 #define GDT_ENTRY_PNPBIOS_TS1 21 104 #define GDT_ENTRY_PNPBIOS_TS2 22 105 #define GDT_ENTRY_APMBIOS_BASE 23 106 107 #define GDT_ENTRY_ESPFIX_SS 26 108 #define GDT_ENTRY_PERCPU 27 109 #define GDT_ENTRY_STACK_CANARY 28 110 111 #define GDT_ENTRY_DOUBLEFAULT_TSS 31 112 113 /* 114 * Number of entries in the GDT table: 115 */ 116 #define GDT_ENTRIES 32 117 118 /* 119 * Segment selector values corresponding to the above entries: 120 */ 121 122 #define __KERNEL_CS (GDT_ENTRY_KERNEL_CS*8) 123 #define __KERNEL_DS (GDT_ENTRY_KERNEL_DS*8) 124 #define __USER_DS (GDT_ENTRY_DEFAULT_USER_DS*8 + 3) 125 #define __USER_CS (GDT_ENTRY_DEFAULT_USER_CS*8 + 3) 126 #define __ESPFIX_SS (GDT_ENTRY_ESPFIX_SS*8) 127 128 /* segment for calling fn: */ 129 #define PNP_CS32 (GDT_ENTRY_PNPBIOS_CS32*8) 130 /* code segment for BIOS: */ 131 #define PNP_CS16 (GDT_ENTRY_PNPBIOS_CS16*8) 132 133 /* "Is this PNP code selector (PNP_CS32 or PNP_CS16)?" */ 134 #define SEGMENT_IS_PNP_CODE(x) (((x) & 0xf4) == PNP_CS32) 135 136 /* data segment for BIOS: */ 137 #define PNP_DS (GDT_ENTRY_PNPBIOS_DS*8) 138 /* transfer data segment: */ 139 #define PNP_TS1 (GDT_ENTRY_PNPBIOS_TS1*8) 140 /* another data segment: */ 141 #define PNP_TS2 (GDT_ENTRY_PNPBIOS_TS2*8) 142 143 #ifdef CONFIG_SMP 144 # define __KERNEL_PERCPU (GDT_ENTRY_PERCPU*8) 145 #else 146 # define __KERNEL_PERCPU 0 147 #endif 148 149 #ifdef CONFIG_CC_STACKPROTECTOR 150 # define __KERNEL_STACK_CANARY (GDT_ENTRY_STACK_CANARY*8) 151 #else 152 # define __KERNEL_STACK_CANARY 0 153 #endif 154 155 #else /* 64-bit: */ 156 157 #include <asm/cache.h> 158 159 #define GDT_ENTRY_KERNEL32_CS 1 160 #define GDT_ENTRY_KERNEL_CS 2 161 #define GDT_ENTRY_KERNEL_DS 3 162 163 /* 164 * We cannot use the same code segment descriptor for user and kernel mode, 165 * not even in long flat mode, because of different DPL. 166 * 167 * GDT layout to get 64-bit SYSCALL/SYSRET support right. SYSRET hardcodes 168 * selectors: 169 * 170 * if returning to 32-bit userspace: cs = STAR.SYSRET_CS, 171 * if returning to 64-bit userspace: cs = STAR.SYSRET_CS+16, 172 * 173 * ss = STAR.SYSRET_CS+8 (in either case) 174 * 175 * thus USER_DS should be between 32-bit and 64-bit code selectors: 176 */ 177 #define GDT_ENTRY_DEFAULT_USER32_CS 4 178 #define GDT_ENTRY_DEFAULT_USER_DS 5 179 #define GDT_ENTRY_DEFAULT_USER_CS 6 180 181 /* Needs two entries */ 182 #define GDT_ENTRY_TSS 8 183 /* Needs two entries */ 184 #define GDT_ENTRY_LDT 10 185 186 #define GDT_ENTRY_TLS_MIN 12 187 #define GDT_ENTRY_TLS_MAX 14 188 189 /* Abused to load per CPU data from limit */ 190 #define GDT_ENTRY_PER_CPU 15 191 192 /* 193 * Number of entries in the GDT table: 194 */ 195 #define GDT_ENTRIES 16 196 197 /* 198 * Segment selector values corresponding to the above entries: 199 * 200 * Note, selectors also need to have a correct RPL, 201 * expressed with the +3 value for user-space selectors: 202 */ 203 #define __KERNEL32_CS (GDT_ENTRY_KERNEL32_CS*8) 204 #define __KERNEL_CS (GDT_ENTRY_KERNEL_CS*8) 205 #define __KERNEL_DS (GDT_ENTRY_KERNEL_DS*8) 206 #define __USER32_CS (GDT_ENTRY_DEFAULT_USER32_CS*8 + 3) 207 #define __USER_DS (GDT_ENTRY_DEFAULT_USER_DS*8 + 3) 208 #define __USER32_DS __USER_DS 209 #define __USER_CS (GDT_ENTRY_DEFAULT_USER_CS*8 + 3) 210 #define __PER_CPU_SEG (GDT_ENTRY_PER_CPU*8 + 3) 211 212 #endif 213 214 #ifndef CONFIG_PARAVIRT 215 # define get_kernel_rpl() 0 216 #endif 217 218 #define IDT_ENTRIES 256 219 #define NUM_EXCEPTION_VECTORS 32 220 221 /* Bitmask of exception vectors which push an error code on the stack: */ 222 #define EXCEPTION_ERRCODE_MASK 0x00027d00 223 224 #define GDT_SIZE (GDT_ENTRIES*8) 225 #define GDT_ENTRY_TLS_ENTRIES 3 226 #define TLS_SIZE (GDT_ENTRY_TLS_ENTRIES* 8) 227 228 #ifdef __KERNEL__ 229 230 /* 231 * early_idt_handler_array is an array of entry points referenced in the 232 * early IDT. For simplicity, it's a real array with one entry point 233 * every nine bytes. That leaves room for an optional 'push $0' if the 234 * vector has no error code (two bytes), a 'push $vector_number' (two 235 * bytes), and a jump to the common entry code (up to five bytes). 236 */ 237 #define EARLY_IDT_HANDLER_SIZE 9 238 239 /* 240 * xen_early_idt_handler_array is for Xen pv guests: for each entry in 241 * early_idt_handler_array it contains a prequel in the form of 242 * pop %rcx; pop %r11; jmp early_idt_handler_array[i]; summing up to 243 * max 8 bytes. 244 */ 245 #define XEN_EARLY_IDT_HANDLER_SIZE 8 246 247 #ifndef __ASSEMBLY__ 248 249 extern const char early_idt_handler_array[NUM_EXCEPTION_VECTORS][EARLY_IDT_HANDLER_SIZE]; 250 extern void early_ignore_irq(void); 251 252 #if defined(CONFIG_X86_64) && defined(CONFIG_XEN_PV) 253 extern const char xen_early_idt_handler_array[NUM_EXCEPTION_VECTORS][XEN_EARLY_IDT_HANDLER_SIZE]; 254 #endif 255 256 /* 257 * Load a segment. Fall back on loading the zero segment if something goes 258 * wrong. This variant assumes that loading zero fully clears the segment. 259 * This is always the case on Intel CPUs and, even on 64-bit AMD CPUs, any 260 * failure to fully clear the cached descriptor is only observable for 261 * FS and GS. 262 */ 263 #define __loadsegment_simple(seg, value) \ 264 do { \ 265 unsigned short __val = (value); \ 266 \ 267 asm volatile(" \n" \ 268 "1: movl %k0,%%" #seg " \n" \ 269 \ 270 ".section .fixup,\"ax\" \n" \ 271 "2: xorl %k0,%k0 \n" \ 272 " jmp 1b \n" \ 273 ".previous \n" \ 274 \ 275 _ASM_EXTABLE(1b, 2b) \ 276 \ 277 : "+r" (__val) : : "memory"); \ 278 } while (0) 279 280 #define __loadsegment_ss(value) __loadsegment_simple(ss, (value)) 281 #define __loadsegment_ds(value) __loadsegment_simple(ds, (value)) 282 #define __loadsegment_es(value) __loadsegment_simple(es, (value)) 283 284 #ifdef CONFIG_X86_32 285 286 /* 287 * On 32-bit systems, the hidden parts of FS and GS are unobservable if 288 * the selector is NULL, so there's no funny business here. 289 */ 290 #define __loadsegment_fs(value) __loadsegment_simple(fs, (value)) 291 #define __loadsegment_gs(value) __loadsegment_simple(gs, (value)) 292 293 #else 294 295 static inline void __loadsegment_fs(unsigned short value) 296 { 297 asm volatile(" \n" 298 "1: movw %0, %%fs \n" 299 "2: \n" 300 301 _ASM_EXTABLE_HANDLE(1b, 2b, ex_handler_clear_fs) 302 303 : : "rm" (value) : "memory"); 304 } 305 306 /* __loadsegment_gs is intentionally undefined. Use load_gs_index instead. */ 307 308 #endif 309 310 #define loadsegment(seg, value) __loadsegment_ ## seg (value) 311 312 /* 313 * Save a segment register away: 314 */ 315 #define savesegment(seg, value) \ 316 asm("mov %%" #seg ",%0":"=r" (value) : : "memory") 317 318 /* 319 * x86-32 user GS accessors: 320 */ 321 #ifdef CONFIG_X86_32 322 # ifdef CONFIG_X86_32_LAZY_GS 323 # define get_user_gs(regs) (u16)({ unsigned long v; savesegment(gs, v); v; }) 324 # define set_user_gs(regs, v) loadsegment(gs, (unsigned long)(v)) 325 # define task_user_gs(tsk) ((tsk)->thread.gs) 326 # define lazy_save_gs(v) savesegment(gs, (v)) 327 # define lazy_load_gs(v) loadsegment(gs, (v)) 328 # else /* X86_32_LAZY_GS */ 329 # define get_user_gs(regs) (u16)((regs)->gs) 330 # define set_user_gs(regs, v) do { (regs)->gs = (v); } while (0) 331 # define task_user_gs(tsk) (task_pt_regs(tsk)->gs) 332 # define lazy_save_gs(v) do { } while (0) 333 # define lazy_load_gs(v) do { } while (0) 334 # endif /* X86_32_LAZY_GS */ 335 #endif /* X86_32 */ 336 337 #endif /* !__ASSEMBLY__ */ 338 #endif /* __KERNEL__ */ 339 340 #endif /* _ASM_X86_SEGMENT_H */ 341