1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * FPU register's regset abstraction, for ptrace, core dumps, etc.
4 */
5 #include <asm/fpu/internal.h>
6 #include <asm/fpu/signal.h>
7 #include <asm/fpu/regset.h>
8 #include <asm/fpu/xstate.h>
9 #include <linux/sched/task_stack.h>
10
11 /*
12 * The xstateregs_active() routine is the same as the regset_fpregs_active() routine,
13 * as the "regset->n" for the xstate regset will be updated based on the feature
14 * capabilities supported by the xsave.
15 */
regset_fpregs_active(struct task_struct * target,const struct user_regset * regset)16 int regset_fpregs_active(struct task_struct *target, const struct user_regset *regset)
17 {
18 return regset->n;
19 }
20
regset_xregset_fpregs_active(struct task_struct * target,const struct user_regset * regset)21 int regset_xregset_fpregs_active(struct task_struct *target, const struct user_regset *regset)
22 {
23 if (boot_cpu_has(X86_FEATURE_FXSR))
24 return regset->n;
25 else
26 return 0;
27 }
28
xfpregs_get(struct task_struct * target,const struct user_regset * regset,struct membuf to)29 int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
30 struct membuf to)
31 {
32 struct fpu *fpu = &target->thread.fpu;
33
34 if (!boot_cpu_has(X86_FEATURE_FXSR))
35 return -ENODEV;
36
37 fpu__prepare_read(fpu);
38 fpstate_sanitize_xstate(fpu);
39
40 return membuf_write(&to, &fpu->state.fxsave, sizeof(struct fxregs_state));
41 }
42
xfpregs_set(struct task_struct * target,const struct user_regset * regset,unsigned int pos,unsigned int count,const void * kbuf,const void __user * ubuf)43 int xfpregs_set(struct task_struct *target, const struct user_regset *regset,
44 unsigned int pos, unsigned int count,
45 const void *kbuf, const void __user *ubuf)
46 {
47 struct fpu *fpu = &target->thread.fpu;
48 int ret;
49
50 if (!boot_cpu_has(X86_FEATURE_FXSR))
51 return -ENODEV;
52
53 fpu__prepare_write(fpu);
54 fpstate_sanitize_xstate(fpu);
55
56 ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
57 &fpu->state.fxsave, 0, -1);
58
59 /*
60 * mxcsr reserved bits must be masked to zero for security reasons.
61 */
62 fpu->state.fxsave.mxcsr &= mxcsr_feature_mask;
63
64 /*
65 * update the header bits in the xsave header, indicating the
66 * presence of FP and SSE state.
67 */
68 if (boot_cpu_has(X86_FEATURE_XSAVE))
69 fpu->state.xsave.header.xfeatures |= XFEATURE_MASK_FPSSE;
70
71 return ret;
72 }
73
xstateregs_get(struct task_struct * target,const struct user_regset * regset,struct membuf to)74 int xstateregs_get(struct task_struct *target, const struct user_regset *regset,
75 struct membuf to)
76 {
77 struct fpu *fpu = &target->thread.fpu;
78 struct xregs_state *xsave;
79
80 if (!boot_cpu_has(X86_FEATURE_XSAVE))
81 return -ENODEV;
82
83 xsave = &fpu->state.xsave;
84
85 fpu__prepare_read(fpu);
86
87 if (using_compacted_format()) {
88 copy_xstate_to_kernel(to, xsave);
89 return 0;
90 } else {
91 fpstate_sanitize_xstate(fpu);
92 /*
93 * Copy the 48 bytes defined by the software into the xsave
94 * area in the thread struct, so that we can copy the whole
95 * area to user using one user_regset_copyout().
96 */
97 memcpy(&xsave->i387.sw_reserved, xstate_fx_sw_bytes, sizeof(xstate_fx_sw_bytes));
98
99 /*
100 * Copy the xstate memory layout.
101 */
102 return membuf_write(&to, xsave, fpu_user_xstate_size);
103 }
104 }
105
xstateregs_set(struct task_struct * target,const struct user_regset * regset,unsigned int pos,unsigned int count,const void * kbuf,const void __user * ubuf)106 int xstateregs_set(struct task_struct *target, const struct user_regset *regset,
107 unsigned int pos, unsigned int count,
108 const void *kbuf, const void __user *ubuf)
109 {
110 struct fpu *fpu = &target->thread.fpu;
111 struct xregs_state *xsave;
112 int ret;
113
114 if (!boot_cpu_has(X86_FEATURE_XSAVE))
115 return -ENODEV;
116
117 /*
118 * A whole standard-format XSAVE buffer is needed:
119 */
120 if (pos != 0 || count != fpu_user_xstate_size)
121 return -EFAULT;
122
123 xsave = &fpu->state.xsave;
124
125 fpu__prepare_write(fpu);
126
127 if (using_compacted_format()) {
128 if (kbuf)
129 ret = copy_kernel_to_xstate(xsave, kbuf);
130 else
131 ret = copy_user_to_xstate(xsave, ubuf);
132 } else {
133 ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, xsave, 0, -1);
134 if (!ret)
135 ret = validate_user_xstate_header(&xsave->header);
136 }
137
138 /*
139 * mxcsr reserved bits must be masked to zero for security reasons.
140 */
141 xsave->i387.mxcsr &= mxcsr_feature_mask;
142
143 /*
144 * In case of failure, mark all states as init:
145 */
146 if (ret)
147 fpstate_init(&fpu->state);
148
149 return ret;
150 }
151
152 #if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
153
154 /*
155 * FPU tag word conversions.
156 */
157
twd_i387_to_fxsr(unsigned short twd)158 static inline unsigned short twd_i387_to_fxsr(unsigned short twd)
159 {
160 unsigned int tmp; /* to avoid 16 bit prefixes in the code */
161
162 /* Transform each pair of bits into 01 (valid) or 00 (empty) */
163 tmp = ~twd;
164 tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
165 /* and move the valid bits to the lower byte. */
166 tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
167 tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
168 tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */
169
170 return tmp;
171 }
172
173 #define FPREG_ADDR(f, n) ((void *)&(f)->st_space + (n) * 16)
174 #define FP_EXP_TAG_VALID 0
175 #define FP_EXP_TAG_ZERO 1
176 #define FP_EXP_TAG_SPECIAL 2
177 #define FP_EXP_TAG_EMPTY 3
178
twd_fxsr_to_i387(struct fxregs_state * fxsave)179 static inline u32 twd_fxsr_to_i387(struct fxregs_state *fxsave)
180 {
181 struct _fpxreg *st;
182 u32 tos = (fxsave->swd >> 11) & 7;
183 u32 twd = (unsigned long) fxsave->twd;
184 u32 tag;
185 u32 ret = 0xffff0000u;
186 int i;
187
188 for (i = 0; i < 8; i++, twd >>= 1) {
189 if (twd & 0x1) {
190 st = FPREG_ADDR(fxsave, (i - tos) & 7);
191
192 switch (st->exponent & 0x7fff) {
193 case 0x7fff:
194 tag = FP_EXP_TAG_SPECIAL;
195 break;
196 case 0x0000:
197 if (!st->significand[0] &&
198 !st->significand[1] &&
199 !st->significand[2] &&
200 !st->significand[3])
201 tag = FP_EXP_TAG_ZERO;
202 else
203 tag = FP_EXP_TAG_SPECIAL;
204 break;
205 default:
206 if (st->significand[3] & 0x8000)
207 tag = FP_EXP_TAG_VALID;
208 else
209 tag = FP_EXP_TAG_SPECIAL;
210 break;
211 }
212 } else {
213 tag = FP_EXP_TAG_EMPTY;
214 }
215 ret |= tag << (2 * i);
216 }
217 return ret;
218 }
219
220 /*
221 * FXSR floating point environment conversions.
222 */
223
224 void
convert_from_fxsr(struct user_i387_ia32_struct * env,struct task_struct * tsk)225 convert_from_fxsr(struct user_i387_ia32_struct *env, struct task_struct *tsk)
226 {
227 struct fxregs_state *fxsave = &tsk->thread.fpu.state.fxsave;
228 struct _fpreg *to = (struct _fpreg *) &env->st_space[0];
229 struct _fpxreg *from = (struct _fpxreg *) &fxsave->st_space[0];
230 int i;
231
232 env->cwd = fxsave->cwd | 0xffff0000u;
233 env->swd = fxsave->swd | 0xffff0000u;
234 env->twd = twd_fxsr_to_i387(fxsave);
235
236 #ifdef CONFIG_X86_64
237 env->fip = fxsave->rip;
238 env->foo = fxsave->rdp;
239 /*
240 * should be actually ds/cs at fpu exception time, but
241 * that information is not available in 64bit mode.
242 */
243 env->fcs = task_pt_regs(tsk)->cs;
244 if (tsk == current) {
245 savesegment(ds, env->fos);
246 } else {
247 env->fos = tsk->thread.ds;
248 }
249 env->fos |= 0xffff0000;
250 #else
251 env->fip = fxsave->fip;
252 env->fcs = (u16) fxsave->fcs | ((u32) fxsave->fop << 16);
253 env->foo = fxsave->foo;
254 env->fos = fxsave->fos;
255 #endif
256
257 for (i = 0; i < 8; ++i)
258 memcpy(&to[i], &from[i], sizeof(to[0]));
259 }
260
convert_to_fxsr(struct fxregs_state * fxsave,const struct user_i387_ia32_struct * env)261 void convert_to_fxsr(struct fxregs_state *fxsave,
262 const struct user_i387_ia32_struct *env)
263
264 {
265 struct _fpreg *from = (struct _fpreg *) &env->st_space[0];
266 struct _fpxreg *to = (struct _fpxreg *) &fxsave->st_space[0];
267 int i;
268
269 fxsave->cwd = env->cwd;
270 fxsave->swd = env->swd;
271 fxsave->twd = twd_i387_to_fxsr(env->twd);
272 fxsave->fop = (u16) ((u32) env->fcs >> 16);
273 #ifdef CONFIG_X86_64
274 fxsave->rip = env->fip;
275 fxsave->rdp = env->foo;
276 /* cs and ds ignored */
277 #else
278 fxsave->fip = env->fip;
279 fxsave->fcs = (env->fcs & 0xffff);
280 fxsave->foo = env->foo;
281 fxsave->fos = env->fos;
282 #endif
283
284 for (i = 0; i < 8; ++i)
285 memcpy(&to[i], &from[i], sizeof(from[0]));
286 }
287
fpregs_get(struct task_struct * target,const struct user_regset * regset,struct membuf to)288 int fpregs_get(struct task_struct *target, const struct user_regset *regset,
289 struct membuf to)
290 {
291 struct fpu *fpu = &target->thread.fpu;
292 struct user_i387_ia32_struct env;
293
294 fpu__prepare_read(fpu);
295
296 if (!boot_cpu_has(X86_FEATURE_FPU))
297 return fpregs_soft_get(target, regset, to);
298
299 if (!boot_cpu_has(X86_FEATURE_FXSR)) {
300 return membuf_write(&to, &fpu->state.fsave,
301 sizeof(struct fregs_state));
302 }
303
304 fpstate_sanitize_xstate(fpu);
305
306 if (to.left == sizeof(env)) {
307 convert_from_fxsr(to.p, target);
308 return 0;
309 }
310
311 convert_from_fxsr(&env, target);
312 return membuf_write(&to, &env, sizeof(env));
313 }
314
fpregs_set(struct task_struct * target,const struct user_regset * regset,unsigned int pos,unsigned int count,const void * kbuf,const void __user * ubuf)315 int fpregs_set(struct task_struct *target, const struct user_regset *regset,
316 unsigned int pos, unsigned int count,
317 const void *kbuf, const void __user *ubuf)
318 {
319 struct fpu *fpu = &target->thread.fpu;
320 struct user_i387_ia32_struct env;
321 int ret;
322
323 fpu__prepare_write(fpu);
324 fpstate_sanitize_xstate(fpu);
325
326 if (!boot_cpu_has(X86_FEATURE_FPU))
327 return fpregs_soft_set(target, regset, pos, count, kbuf, ubuf);
328
329 if (!boot_cpu_has(X86_FEATURE_FXSR))
330 return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
331 &fpu->state.fsave, 0,
332 -1);
333
334 if (pos > 0 || count < sizeof(env))
335 convert_from_fxsr(&env, target);
336
337 ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
338 if (!ret)
339 convert_to_fxsr(&target->thread.fpu.state.fxsave, &env);
340
341 /*
342 * update the header bit in the xsave header, indicating the
343 * presence of FP.
344 */
345 if (boot_cpu_has(X86_FEATURE_XSAVE))
346 fpu->state.xsave.header.xfeatures |= XFEATURE_MASK_FP;
347 return ret;
348 }
349
350 #endif /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */
351