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 - unused
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 
122 #define GDT_ENTRY_DOUBLEFAULT_TSS	31
123 
124 /*
125  * Number of entries in the GDT table:
126  */
127 #define GDT_ENTRIES			32
128 
129 /*
130  * Segment selector values corresponding to the above entries:
131  */
132 
133 #define __KERNEL_CS			(GDT_ENTRY_KERNEL_CS*8)
134 #define __KERNEL_DS			(GDT_ENTRY_KERNEL_DS*8)
135 #define __USER_DS			(GDT_ENTRY_DEFAULT_USER_DS*8 + 3)
136 #define __USER_CS			(GDT_ENTRY_DEFAULT_USER_CS*8 + 3)
137 #define __ESPFIX_SS			(GDT_ENTRY_ESPFIX_SS*8)
138 
139 /* segment for calling fn: */
140 #define PNP_CS32			(GDT_ENTRY_PNPBIOS_CS32*8)
141 /* code segment for BIOS: */
142 #define PNP_CS16			(GDT_ENTRY_PNPBIOS_CS16*8)
143 
144 /* "Is this PNP code selector (PNP_CS32 or PNP_CS16)?" */
145 #define SEGMENT_IS_PNP_CODE(x)		(((x) & 0xf4) == PNP_CS32)
146 
147 /* data segment for BIOS: */
148 #define PNP_DS				(GDT_ENTRY_PNPBIOS_DS*8)
149 /* transfer data segment: */
150 #define PNP_TS1				(GDT_ENTRY_PNPBIOS_TS1*8)
151 /* another data segment: */
152 #define PNP_TS2				(GDT_ENTRY_PNPBIOS_TS2*8)
153 
154 #ifdef CONFIG_SMP
155 # define __KERNEL_PERCPU		(GDT_ENTRY_PERCPU*8)
156 #else
157 # define __KERNEL_PERCPU		0
158 #endif
159 
160 #else /* 64-bit: */
161 
162 #include <asm/cache.h>
163 
164 #define GDT_ENTRY_KERNEL32_CS		1
165 #define GDT_ENTRY_KERNEL_CS		2
166 #define GDT_ENTRY_KERNEL_DS		3
167 
168 /*
169  * We cannot use the same code segment descriptor for user and kernel mode,
170  * not even in long flat mode, because of different DPL.
171  *
172  * GDT layout to get 64-bit SYSCALL/SYSRET support right. SYSRET hardcodes
173  * selectors:
174  *
175  *   if returning to 32-bit userspace: cs = STAR.SYSRET_CS,
176  *   if returning to 64-bit userspace: cs = STAR.SYSRET_CS+16,
177  *
178  * ss = STAR.SYSRET_CS+8 (in either case)
179  *
180  * thus USER_DS should be between 32-bit and 64-bit code selectors:
181  */
182 #define GDT_ENTRY_DEFAULT_USER32_CS	4
183 #define GDT_ENTRY_DEFAULT_USER_DS	5
184 #define GDT_ENTRY_DEFAULT_USER_CS	6
185 
186 /* Needs two entries */
187 #define GDT_ENTRY_TSS			8
188 /* Needs two entries */
189 #define GDT_ENTRY_LDT			10
190 
191 #define GDT_ENTRY_TLS_MIN		12
192 #define GDT_ENTRY_TLS_MAX		14
193 
194 #define GDT_ENTRY_CPUNODE		15
195 
196 /*
197  * Number of entries in the GDT table:
198  */
199 #define GDT_ENTRIES			16
200 
201 /*
202  * Segment selector values corresponding to the above entries:
203  *
204  * Note, selectors also need to have a correct RPL,
205  * expressed with the +3 value for user-space selectors:
206  */
207 #define __KERNEL32_CS			(GDT_ENTRY_KERNEL32_CS*8)
208 #define __KERNEL_CS			(GDT_ENTRY_KERNEL_CS*8)
209 #define __KERNEL_DS			(GDT_ENTRY_KERNEL_DS*8)
210 #define __USER32_CS			(GDT_ENTRY_DEFAULT_USER32_CS*8 + 3)
211 #define __USER_DS			(GDT_ENTRY_DEFAULT_USER_DS*8 + 3)
212 #define __USER32_DS			__USER_DS
213 #define __USER_CS			(GDT_ENTRY_DEFAULT_USER_CS*8 + 3)
214 #define __CPUNODE_SEG			(GDT_ENTRY_CPUNODE*8 + 3)
215 
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		0x20027d00
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 CONFIG_X86_64
229 
230 /* Bit size and mask of CPU number stored in the per CPU data (and TSC_AUX) */
231 #define VDSO_CPUNODE_BITS		12
232 #define VDSO_CPUNODE_MASK		0xfff
233 
234 #ifndef __ASSEMBLY__
235 
236 /* Helper functions to store/load CPU and node numbers */
237 
vdso_encode_cpunode(int cpu,unsigned long node)238 static inline unsigned long vdso_encode_cpunode(int cpu, unsigned long node)
239 {
240 	return (node << VDSO_CPUNODE_BITS) | cpu;
241 }
242 
vdso_read_cpunode(unsigned * cpu,unsigned * node)243 static inline void vdso_read_cpunode(unsigned *cpu, unsigned *node)
244 {
245 	unsigned int p;
246 
247 	/*
248 	 * Load CPU and node number from the GDT.  LSL is faster than RDTSCP
249 	 * and works on all CPUs.  This is volatile so that it orders
250 	 * correctly with respect to barrier() and to keep GCC from cleverly
251 	 * hoisting it out of the calling function.
252 	 *
253 	 * If RDPID is available, use it.
254 	 */
255 	alternative_io ("lsl %[seg],%[p]",
256 			".byte 0xf3,0x0f,0xc7,0xf8", /* RDPID %eax/rax */
257 			X86_FEATURE_RDPID,
258 			[p] "=a" (p), [seg] "r" (__CPUNODE_SEG));
259 
260 	if (cpu)
261 		*cpu = (p & VDSO_CPUNODE_MASK);
262 	if (node)
263 		*node = (p >> VDSO_CPUNODE_BITS);
264 }
265 
266 #endif /* !__ASSEMBLY__ */
267 #endif /* CONFIG_X86_64 */
268 
269 #ifdef __KERNEL__
270 
271 /*
272  * early_idt_handler_array is an array of entry points referenced in the
273  * early IDT.  For simplicity, it's a real array with one entry point
274  * every nine bytes.  That leaves room for an optional 'push $0' if the
275  * vector has no error code (two bytes), a 'push $vector_number' (two
276  * bytes), and a jump to the common entry code (up to five bytes).
277  */
278 #define EARLY_IDT_HANDLER_SIZE 9
279 
280 /*
281  * xen_early_idt_handler_array is for Xen pv guests: for each entry in
282  * early_idt_handler_array it contains a prequel in the form of
283  * pop %rcx; pop %r11; jmp early_idt_handler_array[i]; summing up to
284  * max 8 bytes.
285  */
286 #define XEN_EARLY_IDT_HANDLER_SIZE 8
287 
288 #ifndef __ASSEMBLY__
289 
290 extern const char early_idt_handler_array[NUM_EXCEPTION_VECTORS][EARLY_IDT_HANDLER_SIZE];
291 extern void early_ignore_irq(void);
292 
293 #ifdef CONFIG_XEN_PV
294 extern const char xen_early_idt_handler_array[NUM_EXCEPTION_VECTORS][XEN_EARLY_IDT_HANDLER_SIZE];
295 #endif
296 
297 /*
298  * Load a segment. Fall back on loading the zero segment if something goes
299  * wrong.  This variant assumes that loading zero fully clears the segment.
300  * This is always the case on Intel CPUs and, even on 64-bit AMD CPUs, any
301  * failure to fully clear the cached descriptor is only observable for
302  * FS and GS.
303  */
304 #define __loadsegment_simple(seg, value)				\
305 do {									\
306 	unsigned short __val = (value);					\
307 									\
308 	asm volatile("						\n"	\
309 		     "1:	movl %k0,%%" #seg "		\n"	\
310 									\
311 		     ".section .fixup,\"ax\"			\n"	\
312 		     "2:	xorl %k0,%k0			\n"	\
313 		     "		jmp 1b				\n"	\
314 		     ".previous					\n"	\
315 									\
316 		     _ASM_EXTABLE(1b, 2b)				\
317 									\
318 		     : "+r" (__val) : : "memory");			\
319 } while (0)
320 
321 #define __loadsegment_ss(value) __loadsegment_simple(ss, (value))
322 #define __loadsegment_ds(value) __loadsegment_simple(ds, (value))
323 #define __loadsegment_es(value) __loadsegment_simple(es, (value))
324 
325 #ifdef CONFIG_X86_32
326 
327 /*
328  * On 32-bit systems, the hidden parts of FS and GS are unobservable if
329  * the selector is NULL, so there's no funny business here.
330  */
331 #define __loadsegment_fs(value) __loadsegment_simple(fs, (value))
332 #define __loadsegment_gs(value) __loadsegment_simple(gs, (value))
333 
334 #else
335 
__loadsegment_fs(unsigned short value)336 static inline void __loadsegment_fs(unsigned short value)
337 {
338 	asm volatile("						\n"
339 		     "1:	movw %0, %%fs			\n"
340 		     "2:					\n"
341 
342 		     _ASM_EXTABLE_TYPE(1b, 2b, EX_TYPE_CLEAR_FS)
343 
344 		     : : "rm" (value) : "memory");
345 }
346 
347 /* __loadsegment_gs is intentionally undefined.  Use load_gs_index instead. */
348 
349 #endif
350 
351 #define loadsegment(seg, value) __loadsegment_ ## seg (value)
352 
353 /*
354  * Save a segment register away:
355  */
356 #define savesegment(seg, value)				\
357 	asm("mov %%" #seg ",%0":"=r" (value) : : "memory")
358 
359 /*
360  * x86-32 user GS accessors.  This is ugly and could do with some cleaning up.
361  */
362 #ifdef CONFIG_X86_32
363 # define get_user_gs(regs)		(u16)({ unsigned long v; savesegment(gs, v); v; })
364 # define set_user_gs(regs, v)		loadsegment(gs, (unsigned long)(v))
365 # define task_user_gs(tsk)		((tsk)->thread.gs)
366 # define lazy_save_gs(v)		savesegment(gs, (v))
367 # define lazy_load_gs(v)		loadsegment(gs, (v))
368 # define load_gs_index(v)		loadsegment(gs, (v))
369 #endif	/* X86_32 */
370 
371 #endif /* !__ASSEMBLY__ */
372 #endif /* __KERNEL__ */
373 
374 #endif /* _ASM_X86_SEGMENT_H */
375