2 * xsave/xrstor support.
4 * Author: Suresh Siddha <suresh.b.siddha@intel.com>
7 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
9 #include <linux/bootmem.h>
10 #include <linux/compat.h>
12 #include <asm/fpu-internal.h>
13 #include <asm/sigframe.h>
17 * Supported feature mask by the CPU and the kernel.
22 * Represents init state for the supported extended state.
24 static struct xsave_struct *init_xstate_buf;
26 static struct _fpx_sw_bytes fx_sw_reserved, fx_sw_reserved_ia32;
27 static unsigned int *xstate_offsets, *xstate_sizes, xstate_features;
30 * If a processor implementation discern that a processor state component is
31 * in its initialized state it may modify the corresponding bit in the
32 * xsave_hdr.xstate_bv as '0', with out modifying the corresponding memory
33 * layout in the case of xsaveopt. While presenting the xstate information to
34 * the user, we always ensure that the memory layout of a feature will be in
35 * the init state if the corresponding header bit is zero. This is to ensure
36 * that the user doesn't see some stale state in the memory layout during
37 * signal handling, debugging etc.
39 void __sanitize_i387_state(struct task_struct *tsk)
41 struct i387_fxsave_struct *fx = &tsk->thread.fpu.state->fxsave;
42 int feature_bit = 0x2;
48 xstate_bv = tsk->thread.fpu.state->xsave.xsave_hdr.xstate_bv;
51 * None of the feature bits are in init state. So nothing else
52 * to do for us, as the memory layout is up to date.
54 if ((xstate_bv & pcntxt_mask) == pcntxt_mask)
60 if (!(xstate_bv & XSTATE_FP)) {
67 memset(&fx->st_space[0], 0, 128);
71 * SSE is in init state
73 if (!(xstate_bv & XSTATE_SSE))
74 memset(&fx->xmm_space[0], 0, 256);
76 xstate_bv = (pcntxt_mask & ~xstate_bv) >> 2;
79 * Update all the other memory layouts for which the corresponding
80 * header bit is in the init state.
83 if (xstate_bv & 0x1) {
84 int offset = xstate_offsets[feature_bit];
85 int size = xstate_sizes[feature_bit];
87 memcpy(((void *) fx) + offset,
88 ((void *) init_xstate_buf) + offset,
98 * Check for the presence of extended state information in the
99 * user fpstate pointer in the sigcontext.
101 static inline int check_for_xstate(struct i387_fxsave_struct __user *buf,
102 void __user *fpstate,
103 struct _fpx_sw_bytes *fx_sw)
105 int min_xstate_size = sizeof(struct i387_fxsave_struct) +
106 sizeof(struct xsave_hdr_struct);
109 if (__copy_from_user(fx_sw, &buf->sw_reserved[0], sizeof(*fx_sw)))
112 /* Check for the first magic field and other error scenarios. */
113 if (fx_sw->magic1 != FP_XSTATE_MAGIC1 ||
114 fx_sw->xstate_size < min_xstate_size ||
115 fx_sw->xstate_size > xstate_size ||
116 fx_sw->xstate_size > fx_sw->extended_size)
120 * Check for the presence of second magic word at the end of memory
121 * layout. This detects the case where the user just copied the legacy
122 * fpstate layout with out copying the extended state information
123 * in the memory layout.
125 if (__get_user(magic2, (__u32 __user *)(fpstate + fx_sw->xstate_size))
126 || magic2 != FP_XSTATE_MAGIC2)
133 * Signal frame handlers.
135 static inline int save_fsave_header(struct task_struct *tsk, void __user *buf)
138 struct xsave_struct *xsave = &tsk->thread.fpu.state->xsave;
139 struct user_i387_ia32_struct env;
140 struct _fpstate_ia32 __user *fp = buf;
142 convert_from_fxsr(&env, tsk);
144 if (__copy_to_user(buf, &env, sizeof(env)) ||
145 __put_user(xsave->i387.swd, &fp->status) ||
146 __put_user(X86_FXSR_MAGIC, &fp->magic))
149 struct i387_fsave_struct __user *fp = buf;
151 if (__get_user(swd, &fp->swd) || __put_user(swd, &fp->status))
158 static inline int save_xstate_epilog(void __user *buf, int ia32_frame)
160 struct xsave_struct __user *x = buf;
161 struct _fpx_sw_bytes *sw_bytes;
165 /* Setup the bytes not touched by the [f]xsave and reserved for SW. */
166 sw_bytes = ia32_frame ? &fx_sw_reserved_ia32 : &fx_sw_reserved;
167 err = __copy_to_user(&x->i387.sw_reserved, sw_bytes, sizeof(*sw_bytes));
172 err |= __put_user(FP_XSTATE_MAGIC2, (__u32 *)(buf + xstate_size));
175 * Read the xstate_bv which we copied (directly from the cpu or
176 * from the state in task struct) to the user buffers.
178 err |= __get_user(xstate_bv, (__u32 *)&x->xsave_hdr.xstate_bv);
181 * For legacy compatible, we always set FP/SSE bits in the bit
182 * vector while saving the state to the user context. This will
183 * enable us capturing any changes(during sigreturn) to
184 * the FP/SSE bits by the legacy applications which don't touch
185 * xstate_bv in the xsave header.
187 * xsave aware apps can change the xstate_bv in the xsave
188 * header as well as change any contents in the memory layout.
189 * xrestore as part of sigreturn will capture all the changes.
191 xstate_bv |= XSTATE_FPSSE;
193 err |= __put_user(xstate_bv, (__u32 *)&x->xsave_hdr.xstate_bv);
198 static inline int save_user_xstate(struct xsave_struct __user *buf)
203 err = xsave_user(buf);
205 err = fxsave_user((struct i387_fxsave_struct __user *) buf);
207 err = fsave_user((struct i387_fsave_struct __user *) buf);
209 if (unlikely(err) && __clear_user(buf, xstate_size))
215 * Save the fpu, extended register state to the user signal frame.
217 * 'buf_fx' is the 64-byte aligned pointer at which the [f|fx|x]save
219 * 'buf' points to the 'buf_fx' or to the fsave header followed by 'buf_fx'.
221 * buf == buf_fx for 64-bit frames and 32-bit fsave frame.
222 * buf != buf_fx for 32-bit frames with fxstate.
224 * If the fpu, extended register state is live, save the state directly
225 * to the user frame pointed by the aligned pointer 'buf_fx'. Otherwise,
226 * copy the thread's fpu state to the user frame starting at 'buf_fx'.
228 * If this is a 32-bit frame with fxstate, put a fsave header before
229 * the aligned state at 'buf_fx'.
231 * For [f]xsave state, update the SW reserved fields in the [f]xsave frame
232 * indicating the absence/presence of the extended state to the user.
234 int save_xstate_sig(void __user *buf, void __user *buf_fx, int size)
236 struct xsave_struct *xsave = ¤t->thread.fpu.state->xsave;
237 struct task_struct *tsk = current;
238 int ia32_fxstate = (buf != buf_fx);
240 ia32_fxstate &= (config_enabled(CONFIG_X86_32) ||
241 config_enabled(CONFIG_IA32_EMULATION));
243 if (!access_ok(VERIFY_WRITE, buf, size))
247 return fpregs_soft_get(current, NULL, 0,
248 sizeof(struct user_i387_ia32_struct), NULL,
249 (struct _fpstate_ia32 __user *) buf) ? -1 : 1;
251 if (user_has_fpu()) {
252 /* Save the live register state to the user directly. */
253 if (save_user_xstate(buf_fx))
255 /* Update the thread's fxstate to save the fsave header. */
257 fpu_fxsave(&tsk->thread.fpu);
260 sanitize_i387_state(tsk);
261 if (__copy_to_user(buf_fx, xsave, xstate_size))
265 /* Save the fsave header for the 32-bit frames. */
266 if ((ia32_fxstate || !use_fxsr()) && save_fsave_header(tsk, buf))
269 if (use_fxsr() && save_xstate_epilog(buf_fx, ia32_fxstate))
272 drop_fpu(tsk); /* trigger finit */
278 sanitize_restored_xstate(struct task_struct *tsk,
279 struct user_i387_ia32_struct *ia32_env,
280 u64 xstate_bv, int fx_only)
282 struct xsave_struct *xsave = &tsk->thread.fpu.state->xsave;
283 struct xsave_hdr_struct *xsave_hdr = &xsave->xsave_hdr;
286 /* These bits must be zero. */
287 xsave_hdr->reserved1[0] = xsave_hdr->reserved1[1] = 0;
290 * Init the state that is not present in the memory
291 * layout and not enabled by the OS.
294 xsave_hdr->xstate_bv = XSTATE_FPSSE;
296 xsave_hdr->xstate_bv &= (pcntxt_mask & xstate_bv);
301 * mscsr reserved bits must be masked to zero for security
304 xsave->i387.mxcsr &= mxcsr_feature_mask;
306 convert_to_fxsr(tsk, ia32_env);
311 * Restore the extended state if present. Otherwise, restore the FP/SSE state.
313 static inline int restore_user_xstate(void __user *buf, u64 xbv, int fx_only)
316 if ((unsigned long)buf % 64 || fx_only) {
317 u64 init_bv = pcntxt_mask & ~XSTATE_FPSSE;
318 xrstor_state(init_xstate_buf, init_bv);
319 return fxrstor_checking((__force void *) buf);
321 u64 init_bv = pcntxt_mask & ~xbv;
322 if (unlikely(init_bv))
323 xrstor_state(init_xstate_buf, init_bv);
324 return xrestore_user(buf, xbv);
326 } else if (use_fxsr()) {
327 return fxrstor_checking((__force void *) buf);
329 return frstor_checking((__force void *) buf);
332 int __restore_xstate_sig(void __user *buf, void __user *buf_fx, int size)
334 int ia32_fxstate = (buf != buf_fx);
335 struct task_struct *tsk = current;
336 int state_size = xstate_size;
340 ia32_fxstate &= (config_enabled(CONFIG_X86_32) ||
341 config_enabled(CONFIG_IA32_EMULATION));
348 if (!access_ok(VERIFY_READ, buf, size))
351 if (!used_math() && init_fpu(tsk))
355 return fpregs_soft_set(current, NULL,
356 0, sizeof(struct user_i387_ia32_struct),
361 struct _fpx_sw_bytes fx_sw_user;
362 if (unlikely(check_for_xstate(buf_fx, buf_fx, &fx_sw_user))) {
364 * Couldn't find the extended state information in the
365 * memory layout. Restore just the FP/SSE and init all
366 * the other extended state.
368 state_size = sizeof(struct i387_fxsave_struct);
371 state_size = fx_sw_user.xstate_size;
372 xstate_bv = fx_sw_user.xstate_bv;
378 * For 32-bit frames with fxstate, copy the user state to the
379 * thread's fpu state, reconstruct fxstate from the fsave
380 * header. Sanitize the copied state etc.
382 struct xsave_struct *xsave = &tsk->thread.fpu.state->xsave;
383 struct user_i387_ia32_struct env;
385 stop_fpu_preload(tsk);
388 if (__copy_from_user(xsave, buf_fx, state_size) ||
389 __copy_from_user(&env, buf, sizeof(env))) {
394 sanitize_restored_xstate(tsk, &env, xstate_bv, fx_only);
397 * For 64-bit frames and 32-bit fsave frames, restore the user
398 * state to the registers directly (with exceptions handled).
401 if (restore_user_xstate(buf_fx, xstate_bv, fx_only)) {
411 * Prepare the SW reserved portion of the fxsave memory layout, indicating
412 * the presence of the extended state information in the memory layout
413 * pointed by the fpstate pointer in the sigcontext.
414 * This will be saved when ever the FP and extended state context is
415 * saved on the user stack during the signal handler delivery to the user.
417 static void prepare_fx_sw_frame(void)
419 int fsave_header_size = sizeof(struct i387_fsave_struct);
420 int size = xstate_size + FP_XSTATE_MAGIC2_SIZE;
422 if (config_enabled(CONFIG_X86_32))
423 size += fsave_header_size;
425 fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
426 fx_sw_reserved.extended_size = size;
427 fx_sw_reserved.xstate_bv = pcntxt_mask;
428 fx_sw_reserved.xstate_size = xstate_size;
430 if (config_enabled(CONFIG_IA32_EMULATION)) {
431 fx_sw_reserved_ia32 = fx_sw_reserved;
432 fx_sw_reserved_ia32.extended_size += fsave_header_size;
437 * Enable the extended processor state save/restore feature
439 static inline void xstate_enable(void)
441 set_in_cr4(X86_CR4_OSXSAVE);
442 xsetbv(XCR_XFEATURE_ENABLED_MASK, pcntxt_mask);
446 * Record the offsets and sizes of different state managed by the xsave
449 static void __init setup_xstate_features(void)
451 int eax, ebx, ecx, edx, leaf = 0x2;
453 xstate_features = fls64(pcntxt_mask);
454 xstate_offsets = alloc_bootmem(xstate_features * sizeof(int));
455 xstate_sizes = alloc_bootmem(xstate_features * sizeof(int));
458 cpuid_count(XSTATE_CPUID, leaf, &eax, &ebx, &ecx, &edx);
463 xstate_offsets[leaf] = ebx;
464 xstate_sizes[leaf] = eax;
471 * setup the xstate image representing the init state
473 static void __init setup_xstate_init(void)
475 setup_xstate_features();
478 * Setup init_xstate_buf to represent the init state of
479 * all the features managed by the xsave
481 init_xstate_buf = alloc_bootmem_align(xstate_size,
482 __alignof__(struct xsave_struct));
483 init_xstate_buf->i387.mxcsr = MXCSR_DEFAULT;
487 * Init all the features state with header_bv being 0x0
489 xrstor_state(init_xstate_buf, -1);
491 * Dump the init state again. This is to identify the init state
492 * of any feature which is not represented by all zero's.
494 xsave_state(init_xstate_buf, -1);
499 * Enable and initialize the xsave feature.
501 static void __init xstate_enable_boot_cpu(void)
503 unsigned int eax, ebx, ecx, edx;
505 if (boot_cpu_data.cpuid_level < XSTATE_CPUID) {
506 WARN(1, KERN_ERR "XSTATE_CPUID missing\n");
510 cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
511 pcntxt_mask = eax + ((u64)edx << 32);
513 if ((pcntxt_mask & XSTATE_FPSSE) != XSTATE_FPSSE) {
514 pr_err("FP/SSE not shown under xsave features 0x%llx\n",
520 * Support only the state known to OS.
522 pcntxt_mask = pcntxt_mask & XCNTXT_MASK;
527 * Recompute the context size for enabled features
529 cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
532 update_regset_xstate_info(xstate_size, pcntxt_mask);
533 prepare_fx_sw_frame();
537 pr_info("enabled xstate_bv 0x%llx, cntxt size 0x%x\n",
538 pcntxt_mask, xstate_size);
542 * For the very first instance, this calls xstate_enable_boot_cpu();
543 * for all subsequent instances, this calls xstate_enable().
545 * This is somewhat obfuscated due to the lack of powerful enough
546 * overrides for the section checks.
548 void __cpuinit xsave_init(void)
550 static __refdata void (*next_func)(void) = xstate_enable_boot_cpu;
551 void (*this_func)(void);
556 this_func = next_func;
557 next_func = xstate_enable;