1 /*
2 * xsave/xrstor support.
3 *
4 * Author: Suresh Siddha <suresh.b.siddha@intel.com>
5 */
6 #include <linux/bootmem.h>
7 #include <linux/compat.h>
8 #include <asm/i387.h>
9 #ifdef CONFIG_IA32_EMULATION
10 #include <asm/sigcontext32.h>
11 #endif
12 #include <asm/xcr.h>
13
14 /*
15 * Supported feature mask by the CPU and the kernel.
16 */
17 u64 pcntxt_mask;
18
19 struct _fpx_sw_bytes fx_sw_reserved;
20 #ifdef CONFIG_IA32_EMULATION
21 struct _fpx_sw_bytes fx_sw_reserved_ia32;
22 #endif
23
24 /*
25 * Check for the presence of extended state information in the
26 * user fpstate pointer in the sigcontext.
27 */
check_for_xstate(struct i387_fxsave_struct __user * buf,void __user * fpstate,struct _fpx_sw_bytes * fx_sw_user)28 int check_for_xstate(struct i387_fxsave_struct __user *buf,
29 void __user *fpstate,
30 struct _fpx_sw_bytes *fx_sw_user)
31 {
32 int min_xstate_size = sizeof(struct i387_fxsave_struct) +
33 sizeof(struct xsave_hdr_struct);
34 unsigned int magic2;
35 int err;
36
37 err = __copy_from_user(fx_sw_user, &buf->sw_reserved[0],
38 sizeof(struct _fpx_sw_bytes));
39
40 if (err)
41 return err;
42
43 /*
44 * First Magic check failed.
45 */
46 if (fx_sw_user->magic1 != FP_XSTATE_MAGIC1)
47 return -1;
48
49 /*
50 * Check for error scenarios.
51 */
52 if (fx_sw_user->xstate_size < min_xstate_size ||
53 fx_sw_user->xstate_size > xstate_size ||
54 fx_sw_user->xstate_size > fx_sw_user->extended_size)
55 return -1;
56
57 err = __get_user(magic2, (__u32 *) (((void *)fpstate) +
58 fx_sw_user->extended_size -
59 FP_XSTATE_MAGIC2_SIZE));
60 /*
61 * Check for the presence of second magic word at the end of memory
62 * layout. This detects the case where the user just copied the legacy
63 * fpstate layout with out copying the extended state information
64 * in the memory layout.
65 */
66 if (err || magic2 != FP_XSTATE_MAGIC2)
67 return -1;
68
69 return 0;
70 }
71
72 #ifdef CONFIG_X86_64
73 /*
74 * Signal frame handlers.
75 */
76
save_i387_xstate(void __user * buf)77 int save_i387_xstate(void __user *buf)
78 {
79 struct task_struct *tsk = current;
80 int err = 0;
81
82 if (!access_ok(VERIFY_WRITE, buf, sig_xstate_size))
83 return -EACCES;
84
85 BUG_ON(sig_xstate_size < xstate_size);
86
87 if ((unsigned long)buf % 64)
88 printk("save_i387_xstate: bad fpstate %p\n", buf);
89
90 if (!used_math())
91 return 0;
92 clear_used_math(); /* trigger finit */
93 if (task_thread_info(tsk)->status & TS_USEDFPU) {
94 /*
95 * Start with clearing the user buffer. This will present a
96 * clean context for the bytes not touched by the fxsave/xsave.
97 */
98 err = __clear_user(buf, sig_xstate_size);
99 if (err)
100 return err;
101
102 if (task_thread_info(tsk)->status & TS_XSAVE)
103 err = xsave_user(buf);
104 else
105 err = fxsave_user(buf);
106
107 if (err)
108 return err;
109 task_thread_info(tsk)->status &= ~TS_USEDFPU;
110 stts();
111 } else {
112 if (__copy_to_user(buf, &tsk->thread.xstate->fxsave,
113 xstate_size))
114 return -1;
115 }
116
117 if (task_thread_info(tsk)->status & TS_XSAVE) {
118 struct _fpstate __user *fx = buf;
119 struct _xstate __user *x = buf;
120 u64 xstate_bv;
121
122 err = __copy_to_user(&fx->sw_reserved, &fx_sw_reserved,
123 sizeof(struct _fpx_sw_bytes));
124
125 err |= __put_user(FP_XSTATE_MAGIC2,
126 (__u32 __user *) (buf + sig_xstate_size
127 - FP_XSTATE_MAGIC2_SIZE));
128
129 /*
130 * Read the xstate_bv which we copied (directly from the cpu or
131 * from the state in task struct) to the user buffers and
132 * set the FP/SSE bits.
133 */
134 err |= __get_user(xstate_bv, &x->xstate_hdr.xstate_bv);
135
136 /*
137 * For legacy compatible, we always set FP/SSE bits in the bit
138 * vector while saving the state to the user context. This will
139 * enable us capturing any changes(during sigreturn) to
140 * the FP/SSE bits by the legacy applications which don't touch
141 * xstate_bv in the xsave header.
142 *
143 * xsave aware apps can change the xstate_bv in the xsave
144 * header as well as change any contents in the memory layout.
145 * xrestore as part of sigreturn will capture all the changes.
146 */
147 xstate_bv |= XSTATE_FPSSE;
148
149 err |= __put_user(xstate_bv, &x->xstate_hdr.xstate_bv);
150
151 if (err)
152 return err;
153 }
154
155 return 1;
156 }
157
158 /*
159 * Restore the extended state if present. Otherwise, restore the FP/SSE
160 * state.
161 */
restore_user_xstate(void __user * buf)162 static int restore_user_xstate(void __user *buf)
163 {
164 struct _fpx_sw_bytes fx_sw_user;
165 u64 mask;
166 int err;
167
168 if (((unsigned long)buf % 64) ||
169 check_for_xstate(buf, buf, &fx_sw_user))
170 goto fx_only;
171
172 mask = fx_sw_user.xstate_bv;
173
174 /*
175 * restore the state passed by the user.
176 */
177 err = xrestore_user(buf, mask);
178 if (err)
179 return err;
180
181 /*
182 * init the state skipped by the user.
183 */
184 mask = pcntxt_mask & ~mask;
185
186 xrstor_state(init_xstate_buf, mask);
187
188 return 0;
189
190 fx_only:
191 /*
192 * couldn't find the extended state information in the
193 * memory layout. Restore just the FP/SSE and init all
194 * the other extended state.
195 */
196 xrstor_state(init_xstate_buf, pcntxt_mask & ~XSTATE_FPSSE);
197 return fxrstor_checking((__force struct i387_fxsave_struct *)buf);
198 }
199
200 /*
201 * This restores directly out of user space. Exceptions are handled.
202 */
restore_i387_xstate(void __user * buf)203 int restore_i387_xstate(void __user *buf)
204 {
205 struct task_struct *tsk = current;
206 int err = 0;
207
208 if (!buf) {
209 if (used_math())
210 goto clear;
211 return 0;
212 } else
213 if (!access_ok(VERIFY_READ, buf, sig_xstate_size))
214 return -EACCES;
215
216 if (!used_math()) {
217 err = init_fpu(tsk);
218 if (err)
219 return err;
220 }
221
222 if (!(task_thread_info(current)->status & TS_USEDFPU)) {
223 clts();
224 task_thread_info(current)->status |= TS_USEDFPU;
225 }
226 if (task_thread_info(tsk)->status & TS_XSAVE)
227 err = restore_user_xstate(buf);
228 else
229 err = fxrstor_checking((__force struct i387_fxsave_struct *)
230 buf);
231 if (unlikely(err)) {
232 /*
233 * Encountered an error while doing the restore from the
234 * user buffer, clear the fpu state.
235 */
236 clear:
237 clear_fpu(tsk);
238 clear_used_math();
239 }
240 return err;
241 }
242 #endif
243
244 /*
245 * Prepare the SW reserved portion of the fxsave memory layout, indicating
246 * the presence of the extended state information in the memory layout
247 * pointed by the fpstate pointer in the sigcontext.
248 * This will be saved when ever the FP and extended state context is
249 * saved on the user stack during the signal handler delivery to the user.
250 */
prepare_fx_sw_frame(void)251 static void prepare_fx_sw_frame(void)
252 {
253 int size_extended = (xstate_size - sizeof(struct i387_fxsave_struct)) +
254 FP_XSTATE_MAGIC2_SIZE;
255
256 sig_xstate_size = sizeof(struct _fpstate) + size_extended;
257
258 #ifdef CONFIG_IA32_EMULATION
259 sig_xstate_ia32_size = sizeof(struct _fpstate_ia32) + size_extended;
260 #endif
261
262 memset(&fx_sw_reserved, 0, sizeof(fx_sw_reserved));
263
264 fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
265 fx_sw_reserved.extended_size = sig_xstate_size;
266 fx_sw_reserved.xstate_bv = pcntxt_mask;
267 fx_sw_reserved.xstate_size = xstate_size;
268 #ifdef CONFIG_IA32_EMULATION
269 memcpy(&fx_sw_reserved_ia32, &fx_sw_reserved,
270 sizeof(struct _fpx_sw_bytes));
271 fx_sw_reserved_ia32.extended_size = sig_xstate_ia32_size;
272 #endif
273 }
274
275 /*
276 * Represents init state for the supported extended state.
277 */
278 struct xsave_struct *init_xstate_buf;
279
280 #ifdef CONFIG_X86_64
281 unsigned int sig_xstate_size = sizeof(struct _fpstate);
282 #endif
283
284 /*
285 * Enable the extended processor state save/restore feature
286 */
xsave_init(void)287 void __cpuinit xsave_init(void)
288 {
289 if (!cpu_has_xsave)
290 return;
291
292 set_in_cr4(X86_CR4_OSXSAVE);
293
294 /*
295 * Enable all the features that the HW is capable of
296 * and the Linux kernel is aware of.
297 */
298 xsetbv(XCR_XFEATURE_ENABLED_MASK, pcntxt_mask);
299 }
300
301 /*
302 * setup the xstate image representing the init state
303 */
setup_xstate_init(void)304 static void __init setup_xstate_init(void)
305 {
306 init_xstate_buf = alloc_bootmem(xstate_size);
307 init_xstate_buf->i387.mxcsr = MXCSR_DEFAULT;
308 }
309
310 /*
311 * Enable and initialize the xsave feature.
312 */
xsave_cntxt_init(void)313 void __ref xsave_cntxt_init(void)
314 {
315 unsigned int eax, ebx, ecx, edx;
316
317 cpuid_count(0xd, 0, &eax, &ebx, &ecx, &edx);
318 pcntxt_mask = eax + ((u64)edx << 32);
319
320 if ((pcntxt_mask & XSTATE_FPSSE) != XSTATE_FPSSE) {
321 printk(KERN_ERR "FP/SSE not shown under xsave features 0x%llx\n",
322 pcntxt_mask);
323 BUG();
324 }
325
326 /*
327 * for now OS knows only about FP/SSE
328 */
329 pcntxt_mask = pcntxt_mask & XCNTXT_MASK;
330 xsave_init();
331
332 /*
333 * Recompute the context size for enabled features
334 */
335 cpuid_count(0xd, 0, &eax, &ebx, &ecx, &edx);
336 xstate_size = ebx;
337
338 prepare_fx_sw_frame();
339
340 setup_xstate_init();
341
342 printk(KERN_INFO "xsave/xrstor: enabled xstate_bv 0x%llx, "
343 "cntxt size 0x%x\n",
344 pcntxt_mask, xstate_size);
345 }
346