Line data Source code
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 :
245 7 : static inline unsigned long vdso_encode_cpunode(int cpu, unsigned long node)
246 : {
247 7 : return (node << VDSO_CPUNODE_BITS) | cpu;
248 : }
249 :
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 :
343 5749 : static inline void __loadsegment_fs(unsigned short value)
344 : {
345 5749 : 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 5749 : }
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 */
|
