1/*
  2 * x86 FPU boot time init code:
  3 */
  4#include <asm/fpu/internal.h>
  5#include <asm/tlbflush.h>
  6#include <asm/setup.h>
  7#include <asm/cmdline.h>
  8
  9#include <linux/sched.h>
 10#include <linux/sched/task.h>
 11#include <linux/init.h>
 12
 13/*
 14 * Initialize the registers found in all CPUs, CR0 and CR4:
 15 */
 16static void fpu__init_cpu_generic(void)
 17{
 18	unsigned long cr0;
 19	unsigned long cr4_mask = 0;
 20
 21	if (boot_cpu_has(X86_FEATURE_FXSR))
 22		cr4_mask |= X86_CR4_OSFXSR;
 23	if (boot_cpu_has(X86_FEATURE_XMM))
 24		cr4_mask |= X86_CR4_OSXMMEXCPT;
 25	if (cr4_mask)
 26		cr4_set_bits(cr4_mask);
 27
 28	cr0 = read_cr0();
 29	cr0 &= ~(X86_CR0_TS|X86_CR0_EM); /* clear TS and EM */
 30	if (!boot_cpu_has(X86_FEATURE_FPU))
 31		cr0 |= X86_CR0_EM;
 32	write_cr0(cr0);
 33
 34	/* Flush out any pending x87 state: */
 35#ifdef CONFIG_MATH_EMULATION
 36	if (!boot_cpu_has(X86_FEATURE_FPU))
 37		fpstate_init_soft(&current->thread.fpu.state.soft);
 38	else
 39#endif
 40		asm volatile ("fninit");
 41}
 42
 43/*
 44 * Enable all supported FPU features. Called when a CPU is brought online:
 45 */
 46void fpu__init_cpu(void)
 47{
 48	fpu__init_cpu_generic();
 49	fpu__init_cpu_xstate();
 50}
 51
 52static bool fpu__probe_without_cpuid(void)
 53{
 54	unsigned long cr0;
 55	u16 fsw, fcw;
 56
 57	fsw = fcw = 0xffff;
 58
 59	cr0 = read_cr0();
 60	cr0 &= ~(X86_CR0_TS | X86_CR0_EM);
 61	write_cr0(cr0);
 62
 63	asm volatile("fninit ; fnstsw %0 ; fnstcw %1" : "+m" (fsw), "+m" (fcw));
 64
 65	pr_info("x86/fpu: Probing for FPU: FSW=0x%04hx FCW=0x%04hx\n", fsw, fcw);
 66
 67	return fsw == 0 && (fcw & 0x103f) == 0x003f;
 68}
 69
 70static void fpu__init_system_early_generic(struct cpuinfo_x86 *c)
 71{
 72	if (!boot_cpu_has(X86_FEATURE_CPUID) &&
 73	    !test_bit(X86_FEATURE_FPU, (unsigned long *)cpu_caps_cleared)) {
 74		if (fpu__probe_without_cpuid())
 75			setup_force_cpu_cap(X86_FEATURE_FPU);
 76		else
 77			setup_clear_cpu_cap(X86_FEATURE_FPU);
 78	}
 79
 80#ifndef CONFIG_MATH_EMULATION
 81	if (!test_cpu_cap(&boot_cpu_data, X86_FEATURE_FPU)) {
 82		pr_emerg("x86/fpu: Giving up, no FPU found and no math emulation present\n");
 83		for (;;)
 84			asm volatile("hlt");
 85	}
 86#endif
 87}
 88
 89/*
 90 * Boot time FPU feature detection code:
 91 */
 92unsigned int mxcsr_feature_mask __read_mostly = 0xffffffffu;
 93EXPORT_SYMBOL_GPL(mxcsr_feature_mask);
 94
 95static void __init fpu__init_system_mxcsr(void)
 96{
 97	unsigned int mask = 0;
 98
 99	if (boot_cpu_has(X86_FEATURE_FXSR)) {
100		/* Static because GCC does not get 16-byte stack alignment right: */
101		static struct fxregs_state fxregs __initdata;
102
103		asm volatile("fxsave %0" : "+m" (fxregs));
104
105		mask = fxregs.mxcsr_mask;
106
107		/*
108		 * If zero then use the default features mask,
109		 * which has all features set, except the
110		 * denormals-are-zero feature bit:
111		 */
112		if (mask == 0)
113			mask = 0x0000ffbf;
114	}
115	mxcsr_feature_mask &= mask;
116}
117
118/*
119 * Once per bootup FPU initialization sequences that will run on most x86 CPUs:
120 */
121static void __init fpu__init_system_generic(void)
122{
123	/*
124	 * Set up the legacy init FPU context. (xstate init might overwrite this
125	 * with a more modern format, if the CPU supports it.)
126	 */
127	fpstate_init(&init_fpstate);
128
129	fpu__init_system_mxcsr();
130}
131
132/*
133 * Size of the FPU context state. All tasks in the system use the
134 * same context size, regardless of what portion they use.
135 * This is inherent to the XSAVE architecture which puts all state
136 * components into a single, continuous memory block:
137 */
138unsigned int fpu_kernel_xstate_size;
139EXPORT_SYMBOL_GPL(fpu_kernel_xstate_size);
140
141/* Get alignment of the TYPE. */
142#define TYPE_ALIGN(TYPE) offsetof(struct { char x; TYPE test; }, test)
143
144/*
145 * Enforce that 'MEMBER' is the last field of 'TYPE'.
146 *
147 * Align the computed size with alignment of the TYPE,
148 * because that's how C aligns structs.
149 */
150#define CHECK_MEMBER_AT_END_OF(TYPE, MEMBER) \
151	BUILD_BUG_ON(sizeof(TYPE) != ALIGN(offsetofend(TYPE, MEMBER), \
152					   TYPE_ALIGN(TYPE)))
153
154/*
155 * We append the 'struct fpu' to the task_struct:
156 */
157static void __init fpu__init_task_struct_size(void)
158{
159	int task_size = sizeof(struct task_struct);
160
161	/*
162	 * Subtract off the static size of the register state.
163	 * It potentially has a bunch of padding.
164	 */
165	task_size -= sizeof(((struct task_struct *)0)->thread.fpu.state);
166
167	/*
168	 * Add back the dynamically-calculated register state
169	 * size.
170	 */
171	task_size += fpu_kernel_xstate_size;
172
173	/*
174	 * We dynamically size 'struct fpu', so we require that
175	 * it be at the end of 'thread_struct' and that
176	 * 'thread_struct' be at the end of 'task_struct'.  If
177	 * you hit a compile error here, check the structure to
178	 * see if something got added to the end.
179	 */
180	CHECK_MEMBER_AT_END_OF(struct fpu, state);
181	CHECK_MEMBER_AT_END_OF(struct thread_struct, fpu);
182	CHECK_MEMBER_AT_END_OF(struct task_struct, thread);
183
184	arch_task_struct_size = task_size;
185}
186
187/*
188 * Set up the user and kernel xstate sizes based on the legacy FPU context size.
189 *
190 * We set this up first, and later it will be overwritten by
191 * fpu__init_system_xstate() if the CPU knows about xstates.
192 */
193static void __init fpu__init_system_xstate_size_legacy(void)
194{
195	static int on_boot_cpu __initdata = 1;
196
197	WARN_ON_FPU(!on_boot_cpu);
198	on_boot_cpu = 0;
199
200	/*
201	 * Note that xstate sizes might be overwritten later during
202	 * fpu__init_system_xstate().
203	 */
204
205	if (!boot_cpu_has(X86_FEATURE_FPU)) {
206		/*
207		 * Disable xsave as we do not support it if i387
208		 * emulation is enabled.
209		 */
210		setup_clear_cpu_cap(X86_FEATURE_XSAVE);
211		setup_clear_cpu_cap(X86_FEATURE_XSAVEOPT);
212		fpu_kernel_xstate_size = sizeof(struct swregs_state);
213	} else {
214		if (boot_cpu_has(X86_FEATURE_FXSR))
215			fpu_kernel_xstate_size =
216				sizeof(struct fxregs_state);
217		else
218			fpu_kernel_xstate_size =
219				sizeof(struct fregs_state);
220	}
221
222	fpu_user_xstate_size = fpu_kernel_xstate_size;
223}
224
225/*
226 * Find supported xfeatures based on cpu features and command-line input.
227 * This must be called after fpu__init_parse_early_param() is called and
228 * xfeatures_mask is enumerated.
229 */
230u64 __init fpu__get_supported_xfeatures_mask(void)
231{
232	return XCNTXT_MASK;
233}
234
235/* Legacy code to initialize eager fpu mode. */
236static void __init fpu__init_system_ctx_switch(void)
237{
238	static bool on_boot_cpu __initdata = 1;
239
240	WARN_ON_FPU(!on_boot_cpu);
241	on_boot_cpu = 0;
242
243	WARN_ON_FPU(current->thread.fpu.initialized);
244}
245
246/*
247 * We parse fpu parameters early because fpu__init_system() is executed
248 * before parse_early_param().
249 */
250static void __init fpu__init_parse_early_param(void)
251{
252	char arg[32];
253	char *argptr = arg;
254	int bit;
255
256	if (cmdline_find_option_bool(boot_command_line, "no387"))
257		setup_clear_cpu_cap(X86_FEATURE_FPU);
258
259	if (cmdline_find_option_bool(boot_command_line, "nofxsr")) {
260		setup_clear_cpu_cap(X86_FEATURE_FXSR);
261		setup_clear_cpu_cap(X86_FEATURE_FXSR_OPT);
262		setup_clear_cpu_cap(X86_FEATURE_XMM);
263	}
264
265	if (cmdline_find_option_bool(boot_command_line, "noxsave"))
266		fpu__xstate_clear_all_cpu_caps();
267
268	if (cmdline_find_option_bool(boot_command_line, "noxsaveopt"))
269		setup_clear_cpu_cap(X86_FEATURE_XSAVEOPT);
270
271	if (cmdline_find_option_bool(boot_command_line, "noxsaves"))
272		setup_clear_cpu_cap(X86_FEATURE_XSAVES);
273
274	if (cmdline_find_option(boot_command_line, "clearcpuid", arg,
275				sizeof(arg)) &&
276	    get_option(&argptr, &bit) &&
277	    bit >= 0 &&
278	    bit < NCAPINTS * 32)
279		setup_clear_cpu_cap(bit);
280}
281
282/*
283 * Called on the boot CPU once per system bootup, to set up the initial
284 * FPU state that is later cloned into all processes:
285 */
286void __init fpu__init_system(struct cpuinfo_x86 *c)
287{
288	fpu__init_parse_early_param();
289	fpu__init_system_early_generic(c);
290
291	/*
292	 * The FPU has to be operational for some of the
293	 * later FPU init activities:
294	 */
295	fpu__init_cpu();
296
297	fpu__init_system_generic();
298	fpu__init_system_xstate_size_legacy();
299	fpu__init_system_xstate();
300	fpu__init_task_struct_size();
301
302	fpu__init_system_ctx_switch();
303}