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 #if defined(CONFIG_X86_32) && !defined(BUILD_VDSO32_64)
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 
vdso_encode_cpunode(int cpu,unsigned long node)240 static inline unsigned long vdso_encode_cpunode(int cpu, unsigned long node)
241 {
242 	return (node << VDSO_CPUNODE_BITS) | cpu;
243 }
244 
vdso_read_cpunode(unsigned * cpu,unsigned * node)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 
__loadsegment_fs(unsigned short value)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