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 /*
35 * When running on Xen PV, the actual privilege level of the kernel is 1,
36 * not 0. Testing the Requested Privilege Level in a segment selector to
37 * determine whether the context is user mode or kernel mode with
38 * SEGMENT_RPL_MASK is wrong because the PV kernel's privilege level
39 * matches the 0x3 mask.
40 *
41 * Testing with USER_SEGMENT_RPL_MASK is valid for both native and Xen PV
42 * kernels because privilege level 2 is never used.
43 */
44 #define USER_SEGMENT_RPL_MASK 0x2
45
46 /* User mode is privilege level 3: */
47 #define USER_RPL 0x3
48
49 /* Bit 2 is Table Indicator (TI): selects between LDT or GDT */
50 #define SEGMENT_TI_MASK 0x4
51 /* LDT segment has TI set ... */
52 #define SEGMENT_LDT 0x4
53 /* ... GDT has it cleared */
54 #define SEGMENT_GDT 0x0
55
56 #define GDT_ENTRY_INVALID_SEG 0
57
58 #ifdef CONFIG_X86_32
59 /*
60 * The layout of the per-CPU GDT under Linux:
61 *
62 * 0 - null <=== cacheline #1
63 * 1 - reserved
64 * 2 - reserved
65 * 3 - reserved
66 *
67 * 4 - unused <=== cacheline #2
68 * 5 - unused
69 *
70 * ------- start of TLS (Thread-Local Storage) segments:
71 *
72 * 6 - TLS segment #1 [ glibc's TLS segment ]
73 * 7 - TLS segment #2 [ Wine's %fs Win32 segment ]
74 * 8 - TLS segment #3 <=== cacheline #3
75 * 9 - reserved
76 * 10 - reserved
77 * 11 - reserved
78 *
79 * ------- start of kernel segments:
80 *
81 * 12 - kernel code segment <=== cacheline #4
82 * 13 - kernel data segment
83 * 14 - default user CS
84 * 15 - default user DS
85 * 16 - TSS <=== cacheline #5
86 * 17 - LDT
87 * 18 - PNPBIOS support (16->32 gate)
88 * 19 - PNPBIOS support
89 * 20 - PNPBIOS support <=== cacheline #6
90 * 21 - PNPBIOS support
91 * 22 - PNPBIOS support
92 * 23 - APM BIOS support
93 * 24 - APM BIOS support <=== cacheline #7
94 * 25 - APM BIOS support
95 *
96 * 26 - ESPFIX small SS
97 * 27 - per-cpu [ offset to per-cpu data area ]
98 * 28 - stack_canary-20 [ for stack protector ] <=== cacheline #8
99 * 29 - unused
100 * 30 - unused
101 * 31 - TSS for double fault handler
102 */
103 #define GDT_ENTRY_TLS_MIN 6
104 #define GDT_ENTRY_TLS_MAX (GDT_ENTRY_TLS_MIN + GDT_ENTRY_TLS_ENTRIES - 1)
105
106 #define GDT_ENTRY_KERNEL_CS 12
107 #define GDT_ENTRY_KERNEL_DS 13
108 #define GDT_ENTRY_DEFAULT_USER_CS 14
109 #define GDT_ENTRY_DEFAULT_USER_DS 15
110 #define GDT_ENTRY_TSS 16
111 #define GDT_ENTRY_LDT 17
112 #define GDT_ENTRY_PNPBIOS_CS32 18
113 #define GDT_ENTRY_PNPBIOS_CS16 19
114 #define GDT_ENTRY_PNPBIOS_DS 20
115 #define GDT_ENTRY_PNPBIOS_TS1 21
116 #define GDT_ENTRY_PNPBIOS_TS2 22
117 #define GDT_ENTRY_APMBIOS_BASE 23
118
119 #define GDT_ENTRY_ESPFIX_SS 26
120 #define GDT_ENTRY_PERCPU 27
121 #define GDT_ENTRY_STACK_CANARY 28
122
123 #define GDT_ENTRY_DOUBLEFAULT_TSS 31
124
125 /*
126 * Number of entries in the GDT table:
127 */
128 #define GDT_ENTRIES 32
129
130 /*
131 * Segment selector values corresponding to the above entries:
132 */
133
134 #define __KERNEL_CS (GDT_ENTRY_KERNEL_CS*8)
135 #define __KERNEL_DS (GDT_ENTRY_KERNEL_DS*8)
136 #define __USER_DS (GDT_ENTRY_DEFAULT_USER_DS*8 + 3)
137 #define __USER_CS (GDT_ENTRY_DEFAULT_USER_CS*8 + 3)
138 #define __ESPFIX_SS (GDT_ENTRY_ESPFIX_SS*8)
139
140 /* segment for calling fn: */
141 #define PNP_CS32 (GDT_ENTRY_PNPBIOS_CS32*8)
142 /* code segment for BIOS: */
143 #define PNP_CS16 (GDT_ENTRY_PNPBIOS_CS16*8)
144
145 /* "Is this PNP code selector (PNP_CS32 or PNP_CS16)?" */
146 #define SEGMENT_IS_PNP_CODE(x) (((x) & 0xf4) == PNP_CS32)
147
148 /* data segment for BIOS: */
149 #define PNP_DS (GDT_ENTRY_PNPBIOS_DS*8)
150 /* transfer data segment: */
151 #define PNP_TS1 (GDT_ENTRY_PNPBIOS_TS1*8)
152 /* another data segment: */
153 #define PNP_TS2 (GDT_ENTRY_PNPBIOS_TS2*8)
154
155 #ifdef CONFIG_SMP
156 # define __KERNEL_PERCPU (GDT_ENTRY_PERCPU*8)
157 #else
158 # define __KERNEL_PERCPU 0
159 #endif
160
161 #ifdef CONFIG_STACKPROTECTOR
162 # define __KERNEL_STACK_CANARY (GDT_ENTRY_STACK_CANARY*8)
163 #else
164 # define __KERNEL_STACK_CANARY 0
165 #endif
166
167 #else /* 64-bit: */
168
169 #include <asm/cache.h>
170
171 #define GDT_ENTRY_KERNEL32_CS 1
172 #define GDT_ENTRY_KERNEL_CS 2
173 #define GDT_ENTRY_KERNEL_DS 3
174
175 /*
176 * We cannot use the same code segment descriptor for user and kernel mode,
177 * not even in long flat mode, because of different DPL.
178 *
179 * GDT layout to get 64-bit SYSCALL/SYSRET support right. SYSRET hardcodes
180 * selectors:
181 *
182 * if returning to 32-bit userspace: cs = STAR.SYSRET_CS,
183 * if returning to 64-bit userspace: cs = STAR.SYSRET_CS+16,
184 *
185 * ss = STAR.SYSRET_CS+8 (in either case)
186 *
187 * thus USER_DS should be between 32-bit and 64-bit code selectors:
188 */
189 #define GDT_ENTRY_DEFAULT_USER32_CS 4
190 #define GDT_ENTRY_DEFAULT_USER_DS 5
191 #define GDT_ENTRY_DEFAULT_USER_CS 6
192
193 /* Needs two entries */
194 #define GDT_ENTRY_TSS 8
195 /* Needs two entries */
196 #define GDT_ENTRY_LDT 10
197
198 #define GDT_ENTRY_TLS_MIN 12
199 #define GDT_ENTRY_TLS_MAX 14
200
201 #define GDT_ENTRY_CPUNODE 15
202
203 /*
204 * Number of entries in the GDT table:
205 */
206 #define GDT_ENTRIES 16
207
208 /*
209 * Segment selector values corresponding to the above entries:
210 *
211 * Note, selectors also need to have a correct RPL,
212 * expressed with the +3 value for user-space selectors:
213 */
214 #define __KERNEL32_CS (GDT_ENTRY_KERNEL32_CS*8)
215 #define __KERNEL_CS (GDT_ENTRY_KERNEL_CS*8)
216 #define __KERNEL_DS (GDT_ENTRY_KERNEL_DS*8)
217 #define __USER32_CS (GDT_ENTRY_DEFAULT_USER32_CS*8 + 3)
218 #define __USER_DS (GDT_ENTRY_DEFAULT_USER_DS*8 + 3)
219 #define __USER32_DS __USER_DS
220 #define __USER_CS (GDT_ENTRY_DEFAULT_USER_CS*8 + 3)
221 #define __CPUNODE_SEG (GDT_ENTRY_CPUNODE*8 + 3)
222
223 #endif
224
225 #define IDT_ENTRIES 256
226 #define NUM_EXCEPTION_VECTORS 32
227
228 /* Bitmask of exception vectors which push an error code on the stack: */
229 #define EXCEPTION_ERRCODE_MASK 0x20027d00
230
231 #define GDT_SIZE (GDT_ENTRIES*8)
232 #define GDT_ENTRY_TLS_ENTRIES 3
233 #define TLS_SIZE (GDT_ENTRY_TLS_ENTRIES* 8)
234
235 #ifdef CONFIG_X86_64
236
237 /* Bit size and mask of CPU number stored in the per CPU data (and TSC_AUX) */
238 #define VDSO_CPUNODE_BITS 12
239 #define VDSO_CPUNODE_MASK 0xfff
240
241 #ifndef __ASSEMBLY__
242
243 /* Helper functions to store/load CPU and node numbers */
244
vdso_encode_cpunode(int cpu,unsigned long node)245 static inline unsigned long vdso_encode_cpunode(int cpu, unsigned long node)
246 {
247 return (node << VDSO_CPUNODE_BITS) | cpu;
248 }
249
vdso_read_cpunode(unsigned * cpu,unsigned * node)250 static inline void vdso_read_cpunode(unsigned *cpu, unsigned *node)
251 {
252 unsigned int p;
253
254 /*
255 * Load CPU and node number from the GDT. LSL is faster than RDTSCP
256 * and works on all CPUs. This is volatile so that it orders
257 * correctly with respect to barrier() and to keep GCC from cleverly
258 * hoisting it out of the calling function.
259 *
260 * If RDPID is available, use it.
261 */
262 alternative_io ("lsl %[seg],%[p]",
263 ".byte 0xf3,0x0f,0xc7,0xf8", /* RDPID %eax/rax */
264 X86_FEATURE_RDPID,
265 [p] "=a" (p), [seg] "r" (__CPUNODE_SEG));
266
267 if (cpu)
268 *cpu = (p & VDSO_CPUNODE_MASK);
269 if (node)
270 *node = (p >> VDSO_CPUNODE_BITS);
271 }
272
273 #endif /* !__ASSEMBLY__ */
274 #endif /* CONFIG_X86_64 */
275
276 #ifdef __KERNEL__
277
278 /*
279 * early_idt_handler_array is an array of entry points referenced in the
280 * early IDT. For simplicity, it's a real array with one entry point
281 * every nine bytes. That leaves room for an optional 'push $0' if the
282 * vector has no error code (two bytes), a 'push $vector_number' (two
283 * bytes), and a jump to the common entry code (up to five bytes).
284 */
285 #define EARLY_IDT_HANDLER_SIZE 9
286
287 /*
288 * xen_early_idt_handler_array is for Xen pv guests: for each entry in
289 * early_idt_handler_array it contains a prequel in the form of
290 * pop %rcx; pop %r11; jmp early_idt_handler_array[i]; summing up to
291 * max 8 bytes.
292 */
293 #define XEN_EARLY_IDT_HANDLER_SIZE 8
294
295 #ifndef __ASSEMBLY__
296
297 extern const char early_idt_handler_array[NUM_EXCEPTION_VECTORS][EARLY_IDT_HANDLER_SIZE];
298 extern void early_ignore_irq(void);
299
300 #ifdef CONFIG_XEN_PV
301 extern const char xen_early_idt_handler_array[NUM_EXCEPTION_VECTORS][XEN_EARLY_IDT_HANDLER_SIZE];
302 #endif
303
304 /*
305 * Load a segment. Fall back on loading the zero segment if something goes
306 * wrong. This variant assumes that loading zero fully clears the segment.
307 * This is always the case on Intel CPUs and, even on 64-bit AMD CPUs, any
308 * failure to fully clear the cached descriptor is only observable for
309 * FS and GS.
310 */
311 #define __loadsegment_simple(seg, value) \
312 do { \
313 unsigned short __val = (value); \
314 \
315 asm volatile(" \n" \
316 "1: movl %k0,%%" #seg " \n" \
317 \
318 ".section .fixup,\"ax\" \n" \
319 "2: xorl %k0,%k0 \n" \
320 " jmp 1b \n" \
321 ".previous \n" \
322 \
323 _ASM_EXTABLE(1b, 2b) \
324 \
325 : "+r" (__val) : : "memory"); \
326 } while (0)
327
328 #define __loadsegment_ss(value) __loadsegment_simple(ss, (value))
329 #define __loadsegment_ds(value) __loadsegment_simple(ds, (value))
330 #define __loadsegment_es(value) __loadsegment_simple(es, (value))
331
332 #ifdef CONFIG_X86_32
333
334 /*
335 * On 32-bit systems, the hidden parts of FS and GS are unobservable if
336 * the selector is NULL, so there's no funny business here.
337 */
338 #define __loadsegment_fs(value) __loadsegment_simple(fs, (value))
339 #define __loadsegment_gs(value) __loadsegment_simple(gs, (value))
340
341 #else
342
__loadsegment_fs(unsigned short value)343 static inline void __loadsegment_fs(unsigned short value)
344 {
345 asm volatile(" \n"
346 "1: movw %0, %%fs \n"
347 "2: \n"
348
349 _ASM_EXTABLE_HANDLE(1b, 2b, ex_handler_clear_fs)
350
351 : : "rm" (value) : "memory");
352 }
353
354 /* __loadsegment_gs is intentionally undefined. Use load_gs_index instead. */
355
356 #endif
357
358 #define loadsegment(seg, value) __loadsegment_ ## seg (value)
359
360 /*
361 * Save a segment register away:
362 */
363 #define savesegment(seg, value) \
364 asm("mov %%" #seg ",%0":"=r" (value) : : "memory")
365
366 /*
367 * x86-32 user GS accessors:
368 */
369 #ifdef CONFIG_X86_32
370 # ifdef CONFIG_X86_32_LAZY_GS
371 # define get_user_gs(regs) (u16)({ unsigned long v; savesegment(gs, v); v; })
372 # define set_user_gs(regs, v) loadsegment(gs, (unsigned long)(v))
373 # define task_user_gs(tsk) ((tsk)->thread.gs)
374 # define lazy_save_gs(v) savesegment(gs, (v))
375 # define lazy_load_gs(v) loadsegment(gs, (v))
376 # else /* X86_32_LAZY_GS */
377 # define get_user_gs(regs) (u16)((regs)->gs)
378 # define set_user_gs(regs, v) do { (regs)->gs = (v); } while (0)
379 # define task_user_gs(tsk) (task_pt_regs(tsk)->gs)
380 # define lazy_save_gs(v) do { } while (0)
381 # define lazy_load_gs(v) do { } while (0)
382 # endif /* X86_32_LAZY_GS */
383 #endif /* X86_32 */
384
385 #endif /* !__ASSEMBLY__ */
386 #endif /* __KERNEL__ */
387
388 #endif /* _ASM_X86_SEGMENT_H */
389
