1/*
  2 * FPU signal frame handling routines.
  3 */
  4
  5#include <linux/compat.h>
  6#include <linux/cpu.h>
  7
  8#include <asm/fpu/internal.h>
  9#include <asm/fpu/signal.h>
 10#include <asm/fpu/regset.h>
 11#include <asm/fpu/xstate.h>
 12
 13#include <asm/sigframe.h>
 14#include <asm/trace/fpu.h>
 15
 16static struct _fpx_sw_bytes fx_sw_reserved, fx_sw_reserved_ia32;
 17
 18/*
 19 * Check for the presence of extended state information in the
 20 * user fpstate pointer in the sigcontext.
 21 */
 22static inline int check_for_xstate(struct fxregs_state __user *buf,
 23				   void __user *fpstate,
 24				   struct _fpx_sw_bytes *fx_sw)
 25{
 26	int min_xstate_size = sizeof(struct fxregs_state) +
 27			      sizeof(struct xstate_header);
 28	unsigned int magic2;
 29
 30	if (__copy_from_user(fx_sw, &buf->sw_reserved[0], sizeof(*fx_sw)))
 31		return -1;
 32
 33	/* Check for the first magic field and other error scenarios. */
 34	if (fx_sw->magic1 != FP_XSTATE_MAGIC1 ||
 35	    fx_sw->xstate_size < min_xstate_size ||
 36	    fx_sw->xstate_size > fpu_user_xstate_size ||
 37	    fx_sw->xstate_size > fx_sw->extended_size)
 38		return -1;
 39
 40	/*
 41	 * Check for the presence of second magic word at the end of memory
 42	 * layout. This detects the case where the user just copied the legacy
 43	 * fpstate layout with out copying the extended state information
 44	 * in the memory layout.
 45	 */
 46	if (__get_user(magic2, (__u32 __user *)(fpstate + fx_sw->xstate_size))
 47	    || magic2 != FP_XSTATE_MAGIC2)
 48		return -1;
 49
 50	return 0;
 51}
 52
 53/*
 54 * Signal frame handlers.
 55 */
 56static inline int save_fsave_header(struct task_struct *tsk, void __user *buf)
 57{
 58	if (use_fxsr()) {
 59		struct xregs_state *xsave = &tsk->thread.fpu.state.xsave;
 60		struct user_i387_ia32_struct env;
 61		struct _fpstate_32 __user *fp = buf;
 62
 63		convert_from_fxsr(&env, tsk);
 64
 65		if (__copy_to_user(buf, &env, sizeof(env)) ||
 66		    __put_user(xsave->i387.swd, &fp->status) ||
 67		    __put_user(X86_FXSR_MAGIC, &fp->magic))
 68			return -1;
 69	} else {
 70		struct fregs_state __user *fp = buf;
 71		u32 swd;
 72		if (__get_user(swd, &fp->swd) || __put_user(swd, &fp->status))
 73			return -1;
 74	}
 75
 76	return 0;
 77}
 78
 79static inline int save_xstate_epilog(void __user *buf, int ia32_frame)
 80{
 81	struct xregs_state __user *x = buf;
 82	struct _fpx_sw_bytes *sw_bytes;
 83	u32 xfeatures;
 84	int err;
 85
 86	/* Setup the bytes not touched by the [f]xsave and reserved for SW. */
 87	sw_bytes = ia32_frame ? &fx_sw_reserved_ia32 : &fx_sw_reserved;
 88	err = __copy_to_user(&x->i387.sw_reserved, sw_bytes, sizeof(*sw_bytes));
 89
 90	if (!use_xsave())
 91		return err;
 92
 93	err |= __put_user(FP_XSTATE_MAGIC2,
 94			  (__u32 *)(buf + fpu_user_xstate_size));
 95
 96	/*
 97	 * Read the xfeatures which we copied (directly from the cpu or
 98	 * from the state in task struct) to the user buffers.
 99	 */
100	err |= __get_user(xfeatures, (__u32 *)&x->header.xfeatures);
101
102	/*
103	 * For legacy compatible, we always set FP/SSE bits in the bit
104	 * vector while saving the state to the user context. This will
105	 * enable us capturing any changes(during sigreturn) to
106	 * the FP/SSE bits by the legacy applications which don't touch
107	 * xfeatures in the xsave header.
108	 *
109	 * xsave aware apps can change the xfeatures in the xsave
110	 * header as well as change any contents in the memory layout.
111	 * xrestore as part of sigreturn will capture all the changes.
112	 */
113	xfeatures |= XFEATURE_MASK_FPSSE;
114
115	err |= __put_user(xfeatures, (__u32 *)&x->header.xfeatures);
116
117	return err;
118}
119
120static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf)
121{
122	int err;
123
124	if (use_xsave())
125		err = copy_xregs_to_user(buf);
126	else if (use_fxsr())
127		err = copy_fxregs_to_user((struct fxregs_state __user *) buf);
128	else
129		err = copy_fregs_to_user((struct fregs_state __user *) buf);
130
131	if (unlikely(err) && __clear_user(buf, fpu_user_xstate_size))
132		err = -EFAULT;
133	return err;
134}
135
136/*
137 * Save the fpu, extended register state to the user signal frame.
138 *
139 * 'buf_fx' is the 64-byte aligned pointer at which the [f|fx|x]save
140 *  state is copied.
141 *  'buf' points to the 'buf_fx' or to the fsave header followed by 'buf_fx'.
142 *
143 *	buf == buf_fx for 64-bit frames and 32-bit fsave frame.
144 *	buf != buf_fx for 32-bit frames with fxstate.
145 *
146 * If the fpu, extended register state is live, save the state directly
147 * to the user frame pointed by the aligned pointer 'buf_fx'. Otherwise,
148 * copy the thread's fpu state to the user frame starting at 'buf_fx'.
149 *
150 * If this is a 32-bit frame with fxstate, put a fsave header before
151 * the aligned state at 'buf_fx'.
152 *
153 * For [f]xsave state, update the SW reserved fields in the [f]xsave frame
154 * indicating the absence/presence of the extended state to the user.
155 */
156int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
157{
158	struct xregs_state *xsave = &current->thread.fpu.state.xsave;
159	struct task_struct *tsk = current;
160	int ia32_fxstate = (buf != buf_fx);
161
162	ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) ||
163			 IS_ENABLED(CONFIG_IA32_EMULATION));
164
165	if (!access_ok(VERIFY_WRITE, buf, size))
166		return -EACCES;
167
168	if (!static_cpu_has(X86_FEATURE_FPU))
169		return fpregs_soft_get(current, NULL, 0,
170			sizeof(struct user_i387_ia32_struct), NULL,
171			(struct _fpstate_32 __user *) buf) ? -1 : 1;
172
173	if (fpregs_active() || using_compacted_format()) {
174		/* Save the live register state to the user directly. */
175		if (copy_fpregs_to_sigframe(buf_fx))
176			return -1;
177		/* Update the thread's fxstate to save the fsave header. */
178		if (ia32_fxstate)
179			copy_fxregs_to_kernel(&tsk->thread.fpu);
180	} else {
181		/*
182		 * It is a *bug* if kernel uses compacted-format for xsave
183		 * area and we copy it out directly to a signal frame. It
184		 * should have been handled above by saving the registers
185		 * directly.
186		 */
187		if (boot_cpu_has(X86_FEATURE_XSAVES)) {
188			WARN_ONCE(1, "x86/fpu: saving compacted-format xsave area to a signal frame!\n");
189			return -1;
190		}
191
192		fpstate_sanitize_xstate(&tsk->thread.fpu);
193		if (__copy_to_user(buf_fx, xsave, fpu_user_xstate_size))
194			return -1;
195	}
196
197	/* Save the fsave header for the 32-bit frames. */
198	if ((ia32_fxstate || !use_fxsr()) && save_fsave_header(tsk, buf))
199		return -1;
200
201	if (use_fxsr() && save_xstate_epilog(buf_fx, ia32_fxstate))
202		return -1;
203
204	return 0;
205}
206
207static inline void
208sanitize_restored_xstate(struct task_struct *tsk,
209			 struct user_i387_ia32_struct *ia32_env,
210			 u64 xfeatures, int fx_only)
211{
212	struct xregs_state *xsave = &tsk->thread.fpu.state.xsave;
213	struct xstate_header *header = &xsave->header;
214
215	if (use_xsave()) {
216		/* These bits must be zero. */
217		memset(header->reserved, 0, 48);
218
219		/*
220		 * Init the state that is not present in the memory
221		 * layout and not enabled by the OS.
222		 */
223		if (fx_only)
224			header->xfeatures = XFEATURE_MASK_FPSSE;
225		else
226			header->xfeatures &= (xfeatures_mask & xfeatures);
227	}
228
229	if (use_fxsr()) {
230		/*
231		 * mscsr reserved bits must be masked to zero for security
232		 * reasons.
233		 */
234		xsave->i387.mxcsr &= mxcsr_feature_mask;
235
236		convert_to_fxsr(tsk, ia32_env);
237	}
238}
239
240/*
241 * Restore the extended state if present. Otherwise, restore the FP/SSE state.
242 */
243static inline int copy_user_to_fpregs_zeroing(void __user *buf, u64 xbv, int fx_only)
244{
245	if (use_xsave()) {
246		if ((unsigned long)buf % 64 || fx_only) {
247			u64 init_bv = xfeatures_mask & ~XFEATURE_MASK_FPSSE;
248			copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
249			return copy_user_to_fxregs(buf);
250		} else {
251			u64 init_bv = xfeatures_mask & ~xbv;
252			if (unlikely(init_bv))
253				copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
254			return copy_user_to_xregs(buf, xbv);
255		}
256	} else if (use_fxsr()) {
257		return copy_user_to_fxregs(buf);
258	} else
259		return copy_user_to_fregs(buf);
260}
261
262static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
263{
264	int ia32_fxstate = (buf != buf_fx);
265	struct task_struct *tsk = current;
266	struct fpu *fpu = &tsk->thread.fpu;
267	int state_size = fpu_kernel_xstate_size;
268	u64 xfeatures = 0;
269	int fx_only = 0;
270
271	ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) ||
272			 IS_ENABLED(CONFIG_IA32_EMULATION));
273
274	if (!buf) {
275		fpu__clear(fpu);
276		return 0;
277	}
278
279	if (!access_ok(VERIFY_READ, buf, size))
280		return -EACCES;
281
282	fpu__activate_curr(fpu);
283
284	if (!static_cpu_has(X86_FEATURE_FPU))
285		return fpregs_soft_set(current, NULL,
286				       0, sizeof(struct user_i387_ia32_struct),
287				       NULL, buf) != 0;
288
289	if (use_xsave()) {
290		struct _fpx_sw_bytes fx_sw_user;
291		if (unlikely(check_for_xstate(buf_fx, buf_fx, &fx_sw_user))) {
292			/*
293			 * Couldn't find the extended state information in the
294			 * memory layout. Restore just the FP/SSE and init all
295			 * the other extended state.
296			 */
297			state_size = sizeof(struct fxregs_state);
298			fx_only = 1;
299			trace_x86_fpu_xstate_check_failed(fpu);
300		} else {
301			state_size = fx_sw_user.xstate_size;
302			xfeatures = fx_sw_user.xfeatures;
303		}
304	}
305
306	if (ia32_fxstate) {
307		/*
308		 * For 32-bit frames with fxstate, copy the user state to the
309		 * thread's fpu state, reconstruct fxstate from the fsave
310		 * header. Sanitize the copied state etc.
311		 */
312		struct fpu *fpu = &tsk->thread.fpu;
313		struct user_i387_ia32_struct env;
314		int err = 0;
315
316		/*
317		 * Drop the current fpu which clears fpu->fpstate_active. This ensures
318		 * that any context-switch during the copy of the new state,
319		 * avoids the intermediate state from getting restored/saved.
320		 * Thus avoiding the new restored state from getting corrupted.
321		 * We will be ready to restore/save the state only after
322		 * fpu->fpstate_active is again set.
323		 */
324		fpu__drop(fpu);
325
326		if (using_compacted_format()) {
327			err = copyin_to_xsaves(NULL, buf_fx,
328					       &fpu->state.xsave);
329		} else {
330			err = __copy_from_user(&fpu->state.xsave,
331					       buf_fx, state_size);
332		}
333
334		if (err || __copy_from_user(&env, buf, sizeof(env))) {
335			fpstate_init(&fpu->state);
336			trace_x86_fpu_init_state(fpu);
337			err = -1;
338		} else {
339			sanitize_restored_xstate(tsk, &env, xfeatures, fx_only);
340		}
341
342		fpu->fpstate_active = 1;
343		preempt_disable();
344		fpu__restore(fpu);
345		preempt_enable();
346
347		return err;
348	} else {
349		/*
350		 * For 64-bit frames and 32-bit fsave frames, restore the user
351		 * state to the registers directly (with exceptions handled).
352		 */
353		user_fpu_begin();
354		if (copy_user_to_fpregs_zeroing(buf_fx, xfeatures, fx_only)) {
355			fpu__clear(fpu);
356			return -1;
357		}
358	}
359
360	return 0;
361}
362
363static inline int xstate_sigframe_size(void)
364{
365	return use_xsave() ? fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE :
366			fpu_user_xstate_size;
367}
368
369/*
370 * Restore FPU state from a sigframe:
371 */
372int fpu__restore_sig(void __user *buf, int ia32_frame)
373{
374	void __user *buf_fx = buf;
375	int size = xstate_sigframe_size();
376
377	if (ia32_frame && use_fxsr()) {
378		buf_fx = buf + sizeof(struct fregs_state);
379		size += sizeof(struct fregs_state);
380	}
381
382	return __fpu__restore_sig(buf, buf_fx, size);
383}
384
385unsigned long
386fpu__alloc_mathframe(unsigned long sp, int ia32_frame,
387		     unsigned long *buf_fx, unsigned long *size)
388{
389	unsigned long frame_size = xstate_sigframe_size();
390
391	*buf_fx = sp = round_down(sp - frame_size, 64);
392	if (ia32_frame && use_fxsr()) {
393		frame_size += sizeof(struct fregs_state);
394		sp -= sizeof(struct fregs_state);
395	}
396
397	*size = frame_size;
398
399	return sp;
400}
401/*
402 * Prepare the SW reserved portion of the fxsave memory layout, indicating
403 * the presence of the extended state information in the memory layout
404 * pointed by the fpstate pointer in the sigcontext.
405 * This will be saved when ever the FP and extended state context is
406 * saved on the user stack during the signal handler delivery to the user.
407 */
408void fpu__init_prepare_fx_sw_frame(void)
409{
410	int size = fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE;
411
412	fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
413	fx_sw_reserved.extended_size = size;
414	fx_sw_reserved.xfeatures = xfeatures_mask;
415	fx_sw_reserved.xstate_size = fpu_user_xstate_size;
416
417	if (IS_ENABLED(CONFIG_IA32_EMULATION) ||
418	    IS_ENABLED(CONFIG_X86_32)) {
419		int fsave_header_size = sizeof(struct fregs_state);
420
421		fx_sw_reserved_ia32 = fx_sw_reserved;
422		fx_sw_reserved_ia32.extended_size = size + fsave_header_size;
423	}
424}
425