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 #ifdef CONFIG_IA32_EMULATION
14 #include <asm/sigcontext32.h>
19 * Supported feature mask by the CPU and the kernel.
24 * Represents init state for the supported extended state.
26 static struct xsave_struct *init_xstate_buf;
28 struct _fpx_sw_bytes fx_sw_reserved;
29 #ifdef CONFIG_IA32_EMULATION
30 struct _fpx_sw_bytes fx_sw_reserved_ia32;
33 static unsigned int *xstate_offsets, *xstate_sizes, xstate_features;
36 * If a processor implementation discern that a processor state component is
37 * in its initialized state it may modify the corresponding bit in the
38 * xsave_hdr.xstate_bv as '0', with out modifying the corresponding memory
39 * layout in the case of xsaveopt. While presenting the xstate information to
40 * the user, we always ensure that the memory layout of a feature will be in
41 * the init state if the corresponding header bit is zero. This is to ensure
42 * that the user doesn't see some stale state in the memory layout during
43 * signal handling, debugging etc.
45 void __sanitize_i387_state(struct task_struct *tsk)
48 int feature_bit = 0x2;
49 struct i387_fxsave_struct *fx = &tsk->thread.fpu.state->fxsave;
54 xstate_bv = tsk->thread.fpu.state->xsave.xsave_hdr.xstate_bv;
57 * None of the feature bits are in init state. So nothing else
58 * to do for us, as the memory layout is up to date.
60 if ((xstate_bv & pcntxt_mask) == pcntxt_mask)
66 if (!(xstate_bv & XSTATE_FP)) {
73 memset(&fx->st_space[0], 0, 128);
77 * SSE is in init state
79 if (!(xstate_bv & XSTATE_SSE))
80 memset(&fx->xmm_space[0], 0, 256);
82 xstate_bv = (pcntxt_mask & ~xstate_bv) >> 2;
85 * Update all the other memory layouts for which the corresponding
86 * header bit is in the init state.
89 if (xstate_bv & 0x1) {
90 int offset = xstate_offsets[feature_bit];
91 int size = xstate_sizes[feature_bit];
93 memcpy(((void *) fx) + offset,
94 ((void *) init_xstate_buf) + offset,
104 * Check for the presence of extended state information in the
105 * user fpstate pointer in the sigcontext.
107 int check_for_xstate(struct i387_fxsave_struct __user *buf,
108 void __user *fpstate,
109 struct _fpx_sw_bytes *fx_sw_user)
111 int min_xstate_size = sizeof(struct i387_fxsave_struct) +
112 sizeof(struct xsave_hdr_struct);
116 err = __copy_from_user(fx_sw_user, &buf->sw_reserved[0],
117 sizeof(struct _fpx_sw_bytes));
122 * First Magic check failed.
124 if (fx_sw_user->magic1 != FP_XSTATE_MAGIC1)
128 * Check for error scenarios.
130 if (fx_sw_user->xstate_size < min_xstate_size ||
131 fx_sw_user->xstate_size > xstate_size ||
132 fx_sw_user->xstate_size > fx_sw_user->extended_size)
135 err = __get_user(magic2, (__u32 __user *) (fpstate +
136 fx_sw_user->extended_size -
137 FP_XSTATE_MAGIC2_SIZE));
141 * Check for the presence of second magic word at the end of memory
142 * layout. This detects the case where the user just copied the legacy
143 * fpstate layout with out copying the extended state information
144 * in the memory layout.
146 if (magic2 != FP_XSTATE_MAGIC2)
154 * Signal frame handlers.
157 int save_i387_xstate(void __user *buf)
159 struct task_struct *tsk = current;
162 if (!access_ok(VERIFY_WRITE, buf, sig_xstate_size))
165 BUG_ON(sig_xstate_size < xstate_size);
167 if ((unsigned long)buf % 64)
168 pr_err("%s: bad fpstate %p\n", __func__, buf);
173 if (user_has_fpu()) {
175 err = xsave_user(buf);
177 err = fxsave_user(buf);
180 __clear_user(buf, xstate_size);
185 sanitize_i387_state(tsk);
186 if (__copy_to_user(buf, &tsk->thread.fpu.state->fxsave,
191 clear_used_math(); /* trigger finit */
194 struct _fpstate __user *fx = buf;
195 struct _xstate __user *x = buf;
198 err = __copy_to_user(&fx->sw_reserved, &fx_sw_reserved,
199 sizeof(struct _fpx_sw_bytes));
201 err |= __put_user(FP_XSTATE_MAGIC2,
202 (__u32 __user *) (buf + sig_xstate_size
203 - FP_XSTATE_MAGIC2_SIZE));
206 * Read the xstate_bv which we copied (directly from the cpu or
207 * from the state in task struct) to the user buffers and
208 * set the FP/SSE bits.
210 err |= __get_user(xstate_bv, &x->xstate_hdr.xstate_bv);
213 * For legacy compatible, we always set FP/SSE bits in the bit
214 * vector while saving the state to the user context. This will
215 * enable us capturing any changes(during sigreturn) to
216 * the FP/SSE bits by the legacy applications which don't touch
217 * xstate_bv in the xsave header.
219 * xsave aware apps can change the xstate_bv in the xsave
220 * header as well as change any contents in the memory layout.
221 * xrestore as part of sigreturn will capture all the changes.
223 xstate_bv |= XSTATE_FPSSE;
225 err |= __put_user(xstate_bv, &x->xstate_hdr.xstate_bv);
235 * Restore the extended state if present. Otherwise, restore the FP/SSE
238 static int restore_user_xstate(void __user *buf)
240 struct _fpx_sw_bytes fx_sw_user;
244 if (((unsigned long)buf % 64) ||
245 check_for_xstate(buf, buf, &fx_sw_user))
248 mask = fx_sw_user.xstate_bv;
251 * restore the state passed by the user.
253 err = xrestore_user(buf, mask);
258 * init the state skipped by the user.
260 mask = pcntxt_mask & ~mask;
262 xrstor_state(init_xstate_buf, mask);
268 * couldn't find the extended state information in the
269 * memory layout. Restore just the FP/SSE and init all
270 * the other extended state.
272 xrstor_state(init_xstate_buf, pcntxt_mask & ~XSTATE_FPSSE);
273 return fxrstor_checking((__force struct i387_fxsave_struct *)buf);
277 * This restores directly out of user space. Exceptions are handled.
279 int restore_i387_xstate(void __user *buf)
281 struct task_struct *tsk = current;
289 if (!access_ok(VERIFY_READ, buf, sig_xstate_size))
300 err = restore_user_xstate(buf);
302 err = fxrstor_checking((__force struct i387_fxsave_struct *)
306 * Encountered an error while doing the restore from the
307 * user buffer, clear the fpu state.
318 * Prepare the SW reserved portion of the fxsave memory layout, indicating
319 * the presence of the extended state information in the memory layout
320 * pointed by the fpstate pointer in the sigcontext.
321 * This will be saved when ever the FP and extended state context is
322 * saved on the user stack during the signal handler delivery to the user.
324 static void prepare_fx_sw_frame(void)
326 int size_extended = (xstate_size - sizeof(struct i387_fxsave_struct)) +
327 FP_XSTATE_MAGIC2_SIZE;
329 sig_xstate_size = sizeof(struct _fpstate) + size_extended;
331 #ifdef CONFIG_IA32_EMULATION
332 sig_xstate_ia32_size = sizeof(struct _fpstate_ia32) + size_extended;
335 memset(&fx_sw_reserved, 0, sizeof(fx_sw_reserved));
337 fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
338 fx_sw_reserved.extended_size = sig_xstate_size;
339 fx_sw_reserved.xstate_bv = pcntxt_mask;
340 fx_sw_reserved.xstate_size = xstate_size;
341 #ifdef CONFIG_IA32_EMULATION
342 memcpy(&fx_sw_reserved_ia32, &fx_sw_reserved,
343 sizeof(struct _fpx_sw_bytes));
344 fx_sw_reserved_ia32.extended_size = sig_xstate_ia32_size;
349 unsigned int sig_xstate_size = sizeof(struct _fpstate);
353 * Enable the extended processor state save/restore feature
355 static inline void xstate_enable(void)
357 set_in_cr4(X86_CR4_OSXSAVE);
358 xsetbv(XCR_XFEATURE_ENABLED_MASK, pcntxt_mask);
362 * Record the offsets and sizes of different state managed by the xsave
365 static void __init setup_xstate_features(void)
367 int eax, ebx, ecx, edx, leaf = 0x2;
369 xstate_features = fls64(pcntxt_mask);
370 xstate_offsets = alloc_bootmem(xstate_features * sizeof(int));
371 xstate_sizes = alloc_bootmem(xstate_features * sizeof(int));
374 cpuid_count(XSTATE_CPUID, leaf, &eax, &ebx, &ecx, &edx);
379 xstate_offsets[leaf] = ebx;
380 xstate_sizes[leaf] = eax;
387 * setup the xstate image representing the init state
389 static void __init setup_xstate_init(void)
391 setup_xstate_features();
394 * Setup init_xstate_buf to represent the init state of
395 * all the features managed by the xsave
397 init_xstate_buf = alloc_bootmem_align(xstate_size,
398 __alignof__(struct xsave_struct));
399 init_xstate_buf->i387.mxcsr = MXCSR_DEFAULT;
403 * Init all the features state with header_bv being 0x0
405 xrstor_state(init_xstate_buf, -1);
407 * Dump the init state again. This is to identify the init state
408 * of any feature which is not represented by all zero's.
410 xsave_state(init_xstate_buf, -1);
415 * Enable and initialize the xsave feature.
417 static void __init xstate_enable_boot_cpu(void)
419 unsigned int eax, ebx, ecx, edx;
421 if (boot_cpu_data.cpuid_level < XSTATE_CPUID) {
422 WARN(1, KERN_ERR "XSTATE_CPUID missing\n");
426 cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
427 pcntxt_mask = eax + ((u64)edx << 32);
429 if ((pcntxt_mask & XSTATE_FPSSE) != XSTATE_FPSSE) {
430 pr_err("FP/SSE not shown under xsave features 0x%llx\n",
436 * Support only the state known to OS.
438 pcntxt_mask = pcntxt_mask & XCNTXT_MASK;
443 * Recompute the context size for enabled features
445 cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
448 update_regset_xstate_info(xstate_size, pcntxt_mask);
449 prepare_fx_sw_frame();
453 pr_info("enabled xstate_bv 0x%llx, cntxt size 0x%x\n",
454 pcntxt_mask, xstate_size);
458 * For the very first instance, this calls xstate_enable_boot_cpu();
459 * for all subsequent instances, this calls xstate_enable().
461 * This is somewhat obfuscated due to the lack of powerful enough
462 * overrides for the section checks.
464 void __cpuinit xsave_init(void)
466 static __refdata void (*next_func)(void) = xstate_enable_boot_cpu;
467 void (*this_func)(void);
472 this_func = next_func;
473 next_func = xstate_enable;