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1#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
2
3#include <linux/errno.h>
4#include <linux/kernel.h>
5#include <linux/mm.h>
6#include <linux/smp.h>
7#include <linux/prctl.h>
8#include <linux/slab.h>
9#include <linux/sched.h>
10#include <linux/init.h>
11#include <linux/export.h>
12#include <linux/pm.h>
13#include <linux/tick.h>
14#include <linux/random.h>
15#include <linux/user-return-notifier.h>
16#include <linux/dmi.h>
17#include <linux/utsname.h>
18#include <linux/stackprotector.h>
19#include <linux/tick.h>
20#include <linux/cpuidle.h>
21#include <trace/events/power.h>
22#include <linux/hw_breakpoint.h>
23#include <asm/cpu.h>
24#include <asm/apic.h>
25#include <asm/syscalls.h>
26#include <linux/uaccess.h>
27#include <asm/mwait.h>
28#include <asm/fpu/internal.h>
29#include <asm/debugreg.h>
30#include <asm/nmi.h>
31#include <asm/tlbflush.h>
32#include <asm/mce.h>
33#include <asm/vm86.h>
34#include <asm/switch_to.h>
35
36/*
37 * per-CPU TSS segments. Threads are completely 'soft' on Linux,
38 * no more per-task TSS's. The TSS size is kept cacheline-aligned
39 * so they are allowed to end up in the .data..cacheline_aligned
40 * section. Since TSS's are completely CPU-local, we want them
41 * on exact cacheline boundaries, to eliminate cacheline ping-pong.
42 */
43__visible DEFINE_PER_CPU_SHARED_ALIGNED(struct tss_struct, cpu_tss) = {
44 .x86_tss = {
45 .sp0 = TOP_OF_INIT_STACK,
46#ifdef CONFIG_X86_32
47 .ss0 = __KERNEL_DS,
48 .ss1 = __KERNEL_CS,
49 .io_bitmap_base = INVALID_IO_BITMAP_OFFSET,
50#endif
51 },
52#ifdef CONFIG_X86_32
53 /*
54 * Note that the .io_bitmap member must be extra-big. This is because
55 * the CPU will access an additional byte beyond the end of the IO
56 * permission bitmap. The extra byte must be all 1 bits, and must
57 * be within the limit.
58 */
59 .io_bitmap = { [0 ... IO_BITMAP_LONGS] = ~0 },
60#endif
61#ifdef CONFIG_X86_32
62 .SYSENTER_stack_canary = STACK_END_MAGIC,
63#endif
64};
65EXPORT_PER_CPU_SYMBOL(cpu_tss);
66
67/*
68 * this gets called so that we can store lazy state into memory and copy the
69 * current task into the new thread.
70 */
71int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
72{
73 memcpy(dst, src, arch_task_struct_size);
74#ifdef CONFIG_VM86
75 dst->thread.vm86 = NULL;
76#endif
77
78 return fpu__copy(&dst->thread.fpu, &src->thread.fpu);
79}
80
81/*
82 * Free current thread data structures etc..
83 */
84void exit_thread(struct task_struct *tsk)
85{
86 struct thread_struct *t = &tsk->thread;
87 unsigned long *bp = t->io_bitmap_ptr;
88 struct fpu *fpu = &t->fpu;
89
90 if (bp) {
91 struct tss_struct *tss = &per_cpu(cpu_tss, get_cpu());
92
93 t->io_bitmap_ptr = NULL;
94 clear_thread_flag(TIF_IO_BITMAP);
95 /*
96 * Careful, clear this in the TSS too:
97 */
98 memset(tss->io_bitmap, 0xff, t->io_bitmap_max);
99 t->io_bitmap_max = 0;
100 put_cpu();
101 kfree(bp);
102 }
103
104 free_vm86(t);
105
106 fpu__drop(fpu);
107}
108
109void flush_thread(void)
110{
111 struct task_struct *tsk = current;
112
113 flush_ptrace_hw_breakpoint(tsk);
114 memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array));
115
116 fpu__clear(&tsk->thread.fpu);
117}
118
119static void hard_disable_TSC(void)
120{
121 cr4_set_bits(X86_CR4_TSD);
122}
123
124void disable_TSC(void)
125{
126 preempt_disable();
127 if (!test_and_set_thread_flag(TIF_NOTSC))
128 /*
129 * Must flip the CPU state synchronously with
130 * TIF_NOTSC in the current running context.
131 */
132 hard_disable_TSC();
133 preempt_enable();
134}
135
136static void hard_enable_TSC(void)
137{
138 cr4_clear_bits(X86_CR4_TSD);
139}
140
141static void enable_TSC(void)
142{
143 preempt_disable();
144 if (test_and_clear_thread_flag(TIF_NOTSC))
145 /*
146 * Must flip the CPU state synchronously with
147 * TIF_NOTSC in the current running context.
148 */
149 hard_enable_TSC();
150 preempt_enable();
151}
152
153int get_tsc_mode(unsigned long adr)
154{
155 unsigned int val;
156
157 if (test_thread_flag(TIF_NOTSC))
158 val = PR_TSC_SIGSEGV;
159 else
160 val = PR_TSC_ENABLE;
161
162 return put_user(val, (unsigned int __user *)adr);
163}
164
165int set_tsc_mode(unsigned int val)
166{
167 if (val == PR_TSC_SIGSEGV)
168 disable_TSC();
169 else if (val == PR_TSC_ENABLE)
170 enable_TSC();
171 else
172 return -EINVAL;
173
174 return 0;
175}
176
177void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
178 struct tss_struct *tss)
179{
180 struct thread_struct *prev, *next;
181
182 prev = &prev_p->thread;
183 next = &next_p->thread;
184
185 if (test_tsk_thread_flag(prev_p, TIF_BLOCKSTEP) ^
186 test_tsk_thread_flag(next_p, TIF_BLOCKSTEP)) {
187 unsigned long debugctl = get_debugctlmsr();
188
189 debugctl &= ~DEBUGCTLMSR_BTF;
190 if (test_tsk_thread_flag(next_p, TIF_BLOCKSTEP))
191 debugctl |= DEBUGCTLMSR_BTF;
192
193 update_debugctlmsr(debugctl);
194 }
195
196 if (test_tsk_thread_flag(prev_p, TIF_NOTSC) ^
197 test_tsk_thread_flag(next_p, TIF_NOTSC)) {
198 /* prev and next are different */
199 if (test_tsk_thread_flag(next_p, TIF_NOTSC))
200 hard_disable_TSC();
201 else
202 hard_enable_TSC();
203 }
204
205 if (test_tsk_thread_flag(next_p, TIF_IO_BITMAP)) {
206 /*
207 * Copy the relevant range of the IO bitmap.
208 * Normally this is 128 bytes or less:
209 */
210 memcpy(tss->io_bitmap, next->io_bitmap_ptr,
211 max(prev->io_bitmap_max, next->io_bitmap_max));
212 } else if (test_tsk_thread_flag(prev_p, TIF_IO_BITMAP)) {
213 /*
214 * Clear any possible leftover bits:
215 */
216 memset(tss->io_bitmap, 0xff, prev->io_bitmap_max);
217 }
218 propagate_user_return_notify(prev_p, next_p);
219}
220
221/*
222 * Idle related variables and functions
223 */
224unsigned long boot_option_idle_override = IDLE_NO_OVERRIDE;
225EXPORT_SYMBOL(boot_option_idle_override);
226
227static void (*x86_idle)(void);
228
229#ifndef CONFIG_SMP
230static inline void play_dead(void)
231{
232 BUG();
233}
234#endif
235
236void arch_cpu_idle_enter(void)
237{
238 tsc_verify_tsc_adjust(false);
239 local_touch_nmi();
240}
241
242void arch_cpu_idle_dead(void)
243{
244 play_dead();
245}
246
247/*
248 * Called from the generic idle code.
249 */
250void arch_cpu_idle(void)
251{
252 x86_idle();
253}
254
255/*
256 * We use this if we don't have any better idle routine..
257 */
258void __cpuidle default_idle(void)
259{
260 trace_cpu_idle_rcuidle(1, smp_processor_id());
261 safe_halt();
262 trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
263}
264#ifdef CONFIG_APM_MODULE
265EXPORT_SYMBOL(default_idle);
266#endif
267
268#ifdef CONFIG_XEN
269bool xen_set_default_idle(void)
270{
271 bool ret = !!x86_idle;
272
273 x86_idle = default_idle;
274
275 return ret;
276}
277#endif
278void stop_this_cpu(void *dummy)
279{
280 local_irq_disable();
281 /*
282 * Remove this CPU:
283 */
284 set_cpu_online(smp_processor_id(), false);
285 disable_local_APIC();
286 mcheck_cpu_clear(this_cpu_ptr(&cpu_info));
287
288 for (;;)
289 halt();
290}
291
292/*
293 * AMD Erratum 400 aware idle routine. We handle it the same way as C3 power
294 * states (local apic timer and TSC stop).
295 */
296static void amd_e400_idle(void)
297{
298 /*
299 * We cannot use static_cpu_has_bug() here because X86_BUG_AMD_APIC_C1E
300 * gets set after static_cpu_has() places have been converted via
301 * alternatives.
302 */
303 if (!boot_cpu_has_bug(X86_BUG_AMD_APIC_C1E)) {
304 default_idle();
305 return;
306 }
307
308 tick_broadcast_enter();
309
310 default_idle();
311
312 /*
313 * The switch back from broadcast mode needs to be called with
314 * interrupts disabled.
315 */
316 local_irq_disable();
317 tick_broadcast_exit();
318 local_irq_enable();
319}
320
321/*
322 * Intel Core2 and older machines prefer MWAIT over HALT for C1.
323 * We can't rely on cpuidle installing MWAIT, because it will not load
324 * on systems that support only C1 -- so the boot default must be MWAIT.
325 *
326 * Some AMD machines are the opposite, they depend on using HALT.
327 *
328 * So for default C1, which is used during boot until cpuidle loads,
329 * use MWAIT-C1 on Intel HW that has it, else use HALT.
330 */
331static int prefer_mwait_c1_over_halt(const struct cpuinfo_x86 *c)
332{
333 if (c->x86_vendor != X86_VENDOR_INTEL)
334 return 0;
335
336 if (!cpu_has(c, X86_FEATURE_MWAIT) || static_cpu_has_bug(X86_BUG_MONITOR))
337 return 0;
338
339 return 1;
340}
341
342/*
343 * MONITOR/MWAIT with no hints, used for default C1 state. This invokes MWAIT
344 * with interrupts enabled and no flags, which is backwards compatible with the
345 * original MWAIT implementation.
346 */
347static __cpuidle void mwait_idle(void)
348{
349 if (!current_set_polling_and_test()) {
350 trace_cpu_idle_rcuidle(1, smp_processor_id());
351 if (this_cpu_has(X86_BUG_CLFLUSH_MONITOR)) {
352 mb(); /* quirk */
353 clflush((void *)¤t_thread_info()->flags);
354 mb(); /* quirk */
355 }
356
357 __monitor((void *)¤t_thread_info()->flags, 0, 0);
358 if (!need_resched())
359 __sti_mwait(0, 0);
360 else
361 local_irq_enable();
362 trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
363 } else {
364 local_irq_enable();
365 }
366 __current_clr_polling();
367}
368
369void select_idle_routine(const struct cpuinfo_x86 *c)
370{
371#ifdef CONFIG_SMP
372 if (boot_option_idle_override == IDLE_POLL && smp_num_siblings > 1)
373 pr_warn_once("WARNING: polling idle and HT enabled, performance may degrade\n");
374#endif
375 if (x86_idle || boot_option_idle_override == IDLE_POLL)
376 return;
377
378 if (boot_cpu_has_bug(X86_BUG_AMD_E400)) {
379 pr_info("using AMD E400 aware idle routine\n");
380 x86_idle = amd_e400_idle;
381 } else if (prefer_mwait_c1_over_halt(c)) {
382 pr_info("using mwait in idle threads\n");
383 x86_idle = mwait_idle;
384 } else
385 x86_idle = default_idle;
386}
387
388void amd_e400_c1e_apic_setup(void)
389{
390 if (boot_cpu_has_bug(X86_BUG_AMD_APIC_C1E)) {
391 pr_info("Switch to broadcast mode on CPU%d\n", smp_processor_id());
392 local_irq_disable();
393 tick_broadcast_force();
394 local_irq_enable();
395 }
396}
397
398void __init arch_post_acpi_subsys_init(void)
399{
400 u32 lo, hi;
401
402 if (!boot_cpu_has_bug(X86_BUG_AMD_E400))
403 return;
404
405 /*
406 * AMD E400 detection needs to happen after ACPI has been enabled. If
407 * the machine is affected K8_INTP_C1E_ACTIVE_MASK bits are set in
408 * MSR_K8_INT_PENDING_MSG.
409 */
410 rdmsr(MSR_K8_INT_PENDING_MSG, lo, hi);
411 if (!(lo & K8_INTP_C1E_ACTIVE_MASK))
412 return;
413
414 boot_cpu_set_bug(X86_BUG_AMD_APIC_C1E);
415
416 if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
417 mark_tsc_unstable("TSC halt in AMD C1E");
418 pr_info("System has AMD C1E enabled\n");
419}
420
421static int __init idle_setup(char *str)
422{
423 if (!str)
424 return -EINVAL;
425
426 if (!strcmp(str, "poll")) {
427 pr_info("using polling idle threads\n");
428 boot_option_idle_override = IDLE_POLL;
429 cpu_idle_poll_ctrl(true);
430 } else if (!strcmp(str, "halt")) {
431 /*
432 * When the boot option of idle=halt is added, halt is
433 * forced to be used for CPU idle. In such case CPU C2/C3
434 * won't be used again.
435 * To continue to load the CPU idle driver, don't touch
436 * the boot_option_idle_override.
437 */
438 x86_idle = default_idle;
439 boot_option_idle_override = IDLE_HALT;
440 } else if (!strcmp(str, "nomwait")) {
441 /*
442 * If the boot option of "idle=nomwait" is added,
443 * it means that mwait will be disabled for CPU C2/C3
444 * states. In such case it won't touch the variable
445 * of boot_option_idle_override.
446 */
447 boot_option_idle_override = IDLE_NOMWAIT;
448 } else
449 return -1;
450
451 return 0;
452}
453early_param("idle", idle_setup);
454
455unsigned long arch_align_stack(unsigned long sp)
456{
457 if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
458 sp -= get_random_int() % 8192;
459 return sp & ~0xf;
460}
461
462unsigned long arch_randomize_brk(struct mm_struct *mm)
463{
464 return randomize_page(mm->brk, 0x02000000);
465}
466
467/*
468 * Return saved PC of a blocked thread.
469 * What is this good for? it will be always the scheduler or ret_from_fork.
470 */
471unsigned long thread_saved_pc(struct task_struct *tsk)
472{
473 struct inactive_task_frame *frame =
474 (struct inactive_task_frame *) READ_ONCE(tsk->thread.sp);
475 return READ_ONCE_NOCHECK(frame->ret_addr);
476}
477
478/*
479 * Called from fs/proc with a reference on @p to find the function
480 * which called into schedule(). This needs to be done carefully
481 * because the task might wake up and we might look at a stack
482 * changing under us.
483 */
484unsigned long get_wchan(struct task_struct *p)
485{
486 unsigned long start, bottom, top, sp, fp, ip, ret = 0;
487 int count = 0;
488
489 if (!p || p == current || p->state == TASK_RUNNING)
490 return 0;
491
492 if (!try_get_task_stack(p))
493 return 0;
494
495 start = (unsigned long)task_stack_page(p);
496 if (!start)
497 goto out;
498
499 /*
500 * Layout of the stack page:
501 *
502 * ----------- topmax = start + THREAD_SIZE - sizeof(unsigned long)
503 * PADDING
504 * ----------- top = topmax - TOP_OF_KERNEL_STACK_PADDING
505 * stack
506 * ----------- bottom = start
507 *
508 * The tasks stack pointer points at the location where the
509 * framepointer is stored. The data on the stack is:
510 * ... IP FP ... IP FP
511 *
512 * We need to read FP and IP, so we need to adjust the upper
513 * bound by another unsigned long.
514 */
515 top = start + THREAD_SIZE - TOP_OF_KERNEL_STACK_PADDING;
516 top -= 2 * sizeof(unsigned long);
517 bottom = start;
518
519 sp = READ_ONCE(p->thread.sp);
520 if (sp < bottom || sp > top)
521 goto out;
522
523 fp = READ_ONCE_NOCHECK(((struct inactive_task_frame *)sp)->bp);
524 do {
525 if (fp < bottom || fp > top)
526 goto out;
527 ip = READ_ONCE_NOCHECK(*(unsigned long *)(fp + sizeof(unsigned long)));
528 if (!in_sched_functions(ip)) {
529 ret = ip;
530 goto out;
531 }
532 fp = READ_ONCE_NOCHECK(*(unsigned long *)fp);
533 } while (count++ < 16 && p->state != TASK_RUNNING);
534
535out:
536 put_task_stack(p);
537 return ret;
538}
1// SPDX-License-Identifier: GPL-2.0
2#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
3
4#include <linux/errno.h>
5#include <linux/kernel.h>
6#include <linux/mm.h>
7#include <linux/smp.h>
8#include <linux/prctl.h>
9#include <linux/slab.h>
10#include <linux/sched.h>
11#include <linux/sched/idle.h>
12#include <linux/sched/debug.h>
13#include <linux/sched/task.h>
14#include <linux/sched/task_stack.h>
15#include <linux/init.h>
16#include <linux/export.h>
17#include <linux/pm.h>
18#include <linux/tick.h>
19#include <linux/random.h>
20#include <linux/user-return-notifier.h>
21#include <linux/dmi.h>
22#include <linux/utsname.h>
23#include <linux/stackprotector.h>
24#include <linux/cpuidle.h>
25#include <linux/acpi.h>
26#include <linux/elf-randomize.h>
27#include <trace/events/power.h>
28#include <linux/hw_breakpoint.h>
29#include <asm/cpu.h>
30#include <asm/apic.h>
31#include <linux/uaccess.h>
32#include <asm/mwait.h>
33#include <asm/fpu/internal.h>
34#include <asm/debugreg.h>
35#include <asm/nmi.h>
36#include <asm/tlbflush.h>
37#include <asm/mce.h>
38#include <asm/vm86.h>
39#include <asm/switch_to.h>
40#include <asm/desc.h>
41#include <asm/prctl.h>
42#include <asm/spec-ctrl.h>
43#include <asm/io_bitmap.h>
44#include <asm/proto.h>
45#include <asm/frame.h>
46
47#include "process.h"
48
49/*
50 * per-CPU TSS segments. Threads are completely 'soft' on Linux,
51 * no more per-task TSS's. The TSS size is kept cacheline-aligned
52 * so they are allowed to end up in the .data..cacheline_aligned
53 * section. Since TSS's are completely CPU-local, we want them
54 * on exact cacheline boundaries, to eliminate cacheline ping-pong.
55 */
56__visible DEFINE_PER_CPU_PAGE_ALIGNED(struct tss_struct, cpu_tss_rw) = {
57 .x86_tss = {
58 /*
59 * .sp0 is only used when entering ring 0 from a lower
60 * privilege level. Since the init task never runs anything
61 * but ring 0 code, there is no need for a valid value here.
62 * Poison it.
63 */
64 .sp0 = (1UL << (BITS_PER_LONG-1)) + 1,
65
66#ifdef CONFIG_X86_32
67 .sp1 = TOP_OF_INIT_STACK,
68
69 .ss0 = __KERNEL_DS,
70 .ss1 = __KERNEL_CS,
71#endif
72 .io_bitmap_base = IO_BITMAP_OFFSET_INVALID,
73 },
74};
75EXPORT_PER_CPU_SYMBOL(cpu_tss_rw);
76
77DEFINE_PER_CPU(bool, __tss_limit_invalid);
78EXPORT_PER_CPU_SYMBOL_GPL(__tss_limit_invalid);
79
80/*
81 * this gets called so that we can store lazy state into memory and copy the
82 * current task into the new thread.
83 */
84int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
85{
86 memcpy(dst, src, arch_task_struct_size);
87#ifdef CONFIG_VM86
88 dst->thread.vm86 = NULL;
89#endif
90 return fpu_clone(dst);
91}
92
93/*
94 * Free thread data structures etc..
95 */
96void exit_thread(struct task_struct *tsk)
97{
98 struct thread_struct *t = &tsk->thread;
99 struct fpu *fpu = &t->fpu;
100
101 if (test_thread_flag(TIF_IO_BITMAP))
102 io_bitmap_exit(tsk);
103
104 free_vm86(t);
105
106 fpu__drop(fpu);
107}
108
109static int set_new_tls(struct task_struct *p, unsigned long tls)
110{
111 struct user_desc __user *utls = (struct user_desc __user *)tls;
112
113 if (in_ia32_syscall())
114 return do_set_thread_area(p, -1, utls, 0);
115 else
116 return do_set_thread_area_64(p, ARCH_SET_FS, tls);
117}
118
119int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned long arg,
120 struct task_struct *p, unsigned long tls)
121{
122 struct inactive_task_frame *frame;
123 struct fork_frame *fork_frame;
124 struct pt_regs *childregs;
125 int ret = 0;
126
127 childregs = task_pt_regs(p);
128 fork_frame = container_of(childregs, struct fork_frame, regs);
129 frame = &fork_frame->frame;
130
131 frame->bp = encode_frame_pointer(childregs);
132 frame->ret_addr = (unsigned long) ret_from_fork;
133 p->thread.sp = (unsigned long) fork_frame;
134 p->thread.io_bitmap = NULL;
135 memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
136
137#ifdef CONFIG_X86_64
138 current_save_fsgs();
139 p->thread.fsindex = current->thread.fsindex;
140 p->thread.fsbase = current->thread.fsbase;
141 p->thread.gsindex = current->thread.gsindex;
142 p->thread.gsbase = current->thread.gsbase;
143
144 savesegment(es, p->thread.es);
145 savesegment(ds, p->thread.ds);
146#else
147 p->thread.sp0 = (unsigned long) (childregs + 1);
148 /*
149 * Clear all status flags including IF and set fixed bit. 64bit
150 * does not have this initialization as the frame does not contain
151 * flags. The flags consistency (especially vs. AC) is there
152 * ensured via objtool, which lacks 32bit support.
153 */
154 frame->flags = X86_EFLAGS_FIXED;
155#endif
156
157 /* Kernel thread ? */
158 if (unlikely(p->flags & PF_KTHREAD)) {
159 p->thread.pkru = pkru_get_init_value();
160 memset(childregs, 0, sizeof(struct pt_regs));
161 kthread_frame_init(frame, sp, arg);
162 return 0;
163 }
164
165 /*
166 * Clone current's PKRU value from hardware. tsk->thread.pkru
167 * is only valid when scheduled out.
168 */
169 p->thread.pkru = read_pkru();
170
171 frame->bx = 0;
172 *childregs = *current_pt_regs();
173 childregs->ax = 0;
174 if (sp)
175 childregs->sp = sp;
176
177#ifdef CONFIG_X86_32
178 task_user_gs(p) = get_user_gs(current_pt_regs());
179#endif
180
181 if (unlikely(p->flags & PF_IO_WORKER)) {
182 /*
183 * An IO thread is a user space thread, but it doesn't
184 * return to ret_after_fork().
185 *
186 * In order to indicate that to tools like gdb,
187 * we reset the stack and instruction pointers.
188 *
189 * It does the same kernel frame setup to return to a kernel
190 * function that a kernel thread does.
191 */
192 childregs->sp = 0;
193 childregs->ip = 0;
194 kthread_frame_init(frame, sp, arg);
195 return 0;
196 }
197
198 /* Set a new TLS for the child thread? */
199 if (clone_flags & CLONE_SETTLS)
200 ret = set_new_tls(p, tls);
201
202 if (!ret && unlikely(test_tsk_thread_flag(current, TIF_IO_BITMAP)))
203 io_bitmap_share(p);
204
205 return ret;
206}
207
208static void pkru_flush_thread(void)
209{
210 /*
211 * If PKRU is enabled the default PKRU value has to be loaded into
212 * the hardware right here (similar to context switch).
213 */
214 pkru_write_default();
215}
216
217void flush_thread(void)
218{
219 struct task_struct *tsk = current;
220
221 flush_ptrace_hw_breakpoint(tsk);
222 memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array));
223
224 fpu_flush_thread();
225 pkru_flush_thread();
226}
227
228void disable_TSC(void)
229{
230 preempt_disable();
231 if (!test_and_set_thread_flag(TIF_NOTSC))
232 /*
233 * Must flip the CPU state synchronously with
234 * TIF_NOTSC in the current running context.
235 */
236 cr4_set_bits(X86_CR4_TSD);
237 preempt_enable();
238}
239
240static void enable_TSC(void)
241{
242 preempt_disable();
243 if (test_and_clear_thread_flag(TIF_NOTSC))
244 /*
245 * Must flip the CPU state synchronously with
246 * TIF_NOTSC in the current running context.
247 */
248 cr4_clear_bits(X86_CR4_TSD);
249 preempt_enable();
250}
251
252int get_tsc_mode(unsigned long adr)
253{
254 unsigned int val;
255
256 if (test_thread_flag(TIF_NOTSC))
257 val = PR_TSC_SIGSEGV;
258 else
259 val = PR_TSC_ENABLE;
260
261 return put_user(val, (unsigned int __user *)adr);
262}
263
264int set_tsc_mode(unsigned int val)
265{
266 if (val == PR_TSC_SIGSEGV)
267 disable_TSC();
268 else if (val == PR_TSC_ENABLE)
269 enable_TSC();
270 else
271 return -EINVAL;
272
273 return 0;
274}
275
276DEFINE_PER_CPU(u64, msr_misc_features_shadow);
277
278static void set_cpuid_faulting(bool on)
279{
280 u64 msrval;
281
282 msrval = this_cpu_read(msr_misc_features_shadow);
283 msrval &= ~MSR_MISC_FEATURES_ENABLES_CPUID_FAULT;
284 msrval |= (on << MSR_MISC_FEATURES_ENABLES_CPUID_FAULT_BIT);
285 this_cpu_write(msr_misc_features_shadow, msrval);
286 wrmsrl(MSR_MISC_FEATURES_ENABLES, msrval);
287}
288
289static void disable_cpuid(void)
290{
291 preempt_disable();
292 if (!test_and_set_thread_flag(TIF_NOCPUID)) {
293 /*
294 * Must flip the CPU state synchronously with
295 * TIF_NOCPUID in the current running context.
296 */
297 set_cpuid_faulting(true);
298 }
299 preempt_enable();
300}
301
302static void enable_cpuid(void)
303{
304 preempt_disable();
305 if (test_and_clear_thread_flag(TIF_NOCPUID)) {
306 /*
307 * Must flip the CPU state synchronously with
308 * TIF_NOCPUID in the current running context.
309 */
310 set_cpuid_faulting(false);
311 }
312 preempt_enable();
313}
314
315static int get_cpuid_mode(void)
316{
317 return !test_thread_flag(TIF_NOCPUID);
318}
319
320static int set_cpuid_mode(struct task_struct *task, unsigned long cpuid_enabled)
321{
322 if (!boot_cpu_has(X86_FEATURE_CPUID_FAULT))
323 return -ENODEV;
324
325 if (cpuid_enabled)
326 enable_cpuid();
327 else
328 disable_cpuid();
329
330 return 0;
331}
332
333/*
334 * Called immediately after a successful exec.
335 */
336void arch_setup_new_exec(void)
337{
338 /* If cpuid was previously disabled for this task, re-enable it. */
339 if (test_thread_flag(TIF_NOCPUID))
340 enable_cpuid();
341
342 /*
343 * Don't inherit TIF_SSBD across exec boundary when
344 * PR_SPEC_DISABLE_NOEXEC is used.
345 */
346 if (test_thread_flag(TIF_SSBD) &&
347 task_spec_ssb_noexec(current)) {
348 clear_thread_flag(TIF_SSBD);
349 task_clear_spec_ssb_disable(current);
350 task_clear_spec_ssb_noexec(current);
351 speculation_ctrl_update(task_thread_info(current)->flags);
352 }
353}
354
355#ifdef CONFIG_X86_IOPL_IOPERM
356static inline void switch_to_bitmap(unsigned long tifp)
357{
358 /*
359 * Invalidate I/O bitmap if the previous task used it. This prevents
360 * any possible leakage of an active I/O bitmap.
361 *
362 * If the next task has an I/O bitmap it will handle it on exit to
363 * user mode.
364 */
365 if (tifp & _TIF_IO_BITMAP)
366 tss_invalidate_io_bitmap();
367}
368
369static void tss_copy_io_bitmap(struct tss_struct *tss, struct io_bitmap *iobm)
370{
371 /*
372 * Copy at least the byte range of the incoming tasks bitmap which
373 * covers the permitted I/O ports.
374 *
375 * If the previous task which used an I/O bitmap had more bits
376 * permitted, then the copy needs to cover those as well so they
377 * get turned off.
378 */
379 memcpy(tss->io_bitmap.bitmap, iobm->bitmap,
380 max(tss->io_bitmap.prev_max, iobm->max));
381
382 /*
383 * Store the new max and the sequence number of this bitmap
384 * and a pointer to the bitmap itself.
385 */
386 tss->io_bitmap.prev_max = iobm->max;
387 tss->io_bitmap.prev_sequence = iobm->sequence;
388}
389
390/**
391 * tss_update_io_bitmap - Update I/O bitmap before exiting to usermode
392 */
393void native_tss_update_io_bitmap(void)
394{
395 struct tss_struct *tss = this_cpu_ptr(&cpu_tss_rw);
396 struct thread_struct *t = ¤t->thread;
397 u16 *base = &tss->x86_tss.io_bitmap_base;
398
399 if (!test_thread_flag(TIF_IO_BITMAP)) {
400 native_tss_invalidate_io_bitmap();
401 return;
402 }
403
404 if (IS_ENABLED(CONFIG_X86_IOPL_IOPERM) && t->iopl_emul == 3) {
405 *base = IO_BITMAP_OFFSET_VALID_ALL;
406 } else {
407 struct io_bitmap *iobm = t->io_bitmap;
408
409 /*
410 * Only copy bitmap data when the sequence number differs. The
411 * update time is accounted to the incoming task.
412 */
413 if (tss->io_bitmap.prev_sequence != iobm->sequence)
414 tss_copy_io_bitmap(tss, iobm);
415
416 /* Enable the bitmap */
417 *base = IO_BITMAP_OFFSET_VALID_MAP;
418 }
419
420 /*
421 * Make sure that the TSS limit is covering the IO bitmap. It might have
422 * been cut down by a VMEXIT to 0x67 which would cause a subsequent I/O
423 * access from user space to trigger a #GP because tbe bitmap is outside
424 * the TSS limit.
425 */
426 refresh_tss_limit();
427}
428#else /* CONFIG_X86_IOPL_IOPERM */
429static inline void switch_to_bitmap(unsigned long tifp) { }
430#endif
431
432#ifdef CONFIG_SMP
433
434struct ssb_state {
435 struct ssb_state *shared_state;
436 raw_spinlock_t lock;
437 unsigned int disable_state;
438 unsigned long local_state;
439};
440
441#define LSTATE_SSB 0
442
443static DEFINE_PER_CPU(struct ssb_state, ssb_state);
444
445void speculative_store_bypass_ht_init(void)
446{
447 struct ssb_state *st = this_cpu_ptr(&ssb_state);
448 unsigned int this_cpu = smp_processor_id();
449 unsigned int cpu;
450
451 st->local_state = 0;
452
453 /*
454 * Shared state setup happens once on the first bringup
455 * of the CPU. It's not destroyed on CPU hotunplug.
456 */
457 if (st->shared_state)
458 return;
459
460 raw_spin_lock_init(&st->lock);
461
462 /*
463 * Go over HT siblings and check whether one of them has set up the
464 * shared state pointer already.
465 */
466 for_each_cpu(cpu, topology_sibling_cpumask(this_cpu)) {
467 if (cpu == this_cpu)
468 continue;
469
470 if (!per_cpu(ssb_state, cpu).shared_state)
471 continue;
472
473 /* Link it to the state of the sibling: */
474 st->shared_state = per_cpu(ssb_state, cpu).shared_state;
475 return;
476 }
477
478 /*
479 * First HT sibling to come up on the core. Link shared state of
480 * the first HT sibling to itself. The siblings on the same core
481 * which come up later will see the shared state pointer and link
482 * themselves to the state of this CPU.
483 */
484 st->shared_state = st;
485}
486
487/*
488 * Logic is: First HT sibling enables SSBD for both siblings in the core
489 * and last sibling to disable it, disables it for the whole core. This how
490 * MSR_SPEC_CTRL works in "hardware":
491 *
492 * CORE_SPEC_CTRL = THREAD0_SPEC_CTRL | THREAD1_SPEC_CTRL
493 */
494static __always_inline void amd_set_core_ssb_state(unsigned long tifn)
495{
496 struct ssb_state *st = this_cpu_ptr(&ssb_state);
497 u64 msr = x86_amd_ls_cfg_base;
498
499 if (!static_cpu_has(X86_FEATURE_ZEN)) {
500 msr |= ssbd_tif_to_amd_ls_cfg(tifn);
501 wrmsrl(MSR_AMD64_LS_CFG, msr);
502 return;
503 }
504
505 if (tifn & _TIF_SSBD) {
506 /*
507 * Since this can race with prctl(), block reentry on the
508 * same CPU.
509 */
510 if (__test_and_set_bit(LSTATE_SSB, &st->local_state))
511 return;
512
513 msr |= x86_amd_ls_cfg_ssbd_mask;
514
515 raw_spin_lock(&st->shared_state->lock);
516 /* First sibling enables SSBD: */
517 if (!st->shared_state->disable_state)
518 wrmsrl(MSR_AMD64_LS_CFG, msr);
519 st->shared_state->disable_state++;
520 raw_spin_unlock(&st->shared_state->lock);
521 } else {
522 if (!__test_and_clear_bit(LSTATE_SSB, &st->local_state))
523 return;
524
525 raw_spin_lock(&st->shared_state->lock);
526 st->shared_state->disable_state--;
527 if (!st->shared_state->disable_state)
528 wrmsrl(MSR_AMD64_LS_CFG, msr);
529 raw_spin_unlock(&st->shared_state->lock);
530 }
531}
532#else
533static __always_inline void amd_set_core_ssb_state(unsigned long tifn)
534{
535 u64 msr = x86_amd_ls_cfg_base | ssbd_tif_to_amd_ls_cfg(tifn);
536
537 wrmsrl(MSR_AMD64_LS_CFG, msr);
538}
539#endif
540
541static __always_inline void amd_set_ssb_virt_state(unsigned long tifn)
542{
543 /*
544 * SSBD has the same definition in SPEC_CTRL and VIRT_SPEC_CTRL,
545 * so ssbd_tif_to_spec_ctrl() just works.
546 */
547 wrmsrl(MSR_AMD64_VIRT_SPEC_CTRL, ssbd_tif_to_spec_ctrl(tifn));
548}
549
550/*
551 * Update the MSRs managing speculation control, during context switch.
552 *
553 * tifp: Previous task's thread flags
554 * tifn: Next task's thread flags
555 */
556static __always_inline void __speculation_ctrl_update(unsigned long tifp,
557 unsigned long tifn)
558{
559 unsigned long tif_diff = tifp ^ tifn;
560 u64 msr = x86_spec_ctrl_base;
561 bool updmsr = false;
562
563 lockdep_assert_irqs_disabled();
564
565 /* Handle change of TIF_SSBD depending on the mitigation method. */
566 if (static_cpu_has(X86_FEATURE_VIRT_SSBD)) {
567 if (tif_diff & _TIF_SSBD)
568 amd_set_ssb_virt_state(tifn);
569 } else if (static_cpu_has(X86_FEATURE_LS_CFG_SSBD)) {
570 if (tif_diff & _TIF_SSBD)
571 amd_set_core_ssb_state(tifn);
572 } else if (static_cpu_has(X86_FEATURE_SPEC_CTRL_SSBD) ||
573 static_cpu_has(X86_FEATURE_AMD_SSBD)) {
574 updmsr |= !!(tif_diff & _TIF_SSBD);
575 msr |= ssbd_tif_to_spec_ctrl(tifn);
576 }
577
578 /* Only evaluate TIF_SPEC_IB if conditional STIBP is enabled. */
579 if (IS_ENABLED(CONFIG_SMP) &&
580 static_branch_unlikely(&switch_to_cond_stibp)) {
581 updmsr |= !!(tif_diff & _TIF_SPEC_IB);
582 msr |= stibp_tif_to_spec_ctrl(tifn);
583 }
584
585 if (updmsr)
586 wrmsrl(MSR_IA32_SPEC_CTRL, msr);
587}
588
589static unsigned long speculation_ctrl_update_tif(struct task_struct *tsk)
590{
591 if (test_and_clear_tsk_thread_flag(tsk, TIF_SPEC_FORCE_UPDATE)) {
592 if (task_spec_ssb_disable(tsk))
593 set_tsk_thread_flag(tsk, TIF_SSBD);
594 else
595 clear_tsk_thread_flag(tsk, TIF_SSBD);
596
597 if (task_spec_ib_disable(tsk))
598 set_tsk_thread_flag(tsk, TIF_SPEC_IB);
599 else
600 clear_tsk_thread_flag(tsk, TIF_SPEC_IB);
601 }
602 /* Return the updated threadinfo flags*/
603 return task_thread_info(tsk)->flags;
604}
605
606void speculation_ctrl_update(unsigned long tif)
607{
608 unsigned long flags;
609
610 /* Forced update. Make sure all relevant TIF flags are different */
611 local_irq_save(flags);
612 __speculation_ctrl_update(~tif, tif);
613 local_irq_restore(flags);
614}
615
616/* Called from seccomp/prctl update */
617void speculation_ctrl_update_current(void)
618{
619 preempt_disable();
620 speculation_ctrl_update(speculation_ctrl_update_tif(current));
621 preempt_enable();
622}
623
624static inline void cr4_toggle_bits_irqsoff(unsigned long mask)
625{
626 unsigned long newval, cr4 = this_cpu_read(cpu_tlbstate.cr4);
627
628 newval = cr4 ^ mask;
629 if (newval != cr4) {
630 this_cpu_write(cpu_tlbstate.cr4, newval);
631 __write_cr4(newval);
632 }
633}
634
635void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p)
636{
637 unsigned long tifp, tifn;
638
639 tifn = READ_ONCE(task_thread_info(next_p)->flags);
640 tifp = READ_ONCE(task_thread_info(prev_p)->flags);
641
642 switch_to_bitmap(tifp);
643
644 propagate_user_return_notify(prev_p, next_p);
645
646 if ((tifp & _TIF_BLOCKSTEP || tifn & _TIF_BLOCKSTEP) &&
647 arch_has_block_step()) {
648 unsigned long debugctl, msk;
649
650 rdmsrl(MSR_IA32_DEBUGCTLMSR, debugctl);
651 debugctl &= ~DEBUGCTLMSR_BTF;
652 msk = tifn & _TIF_BLOCKSTEP;
653 debugctl |= (msk >> TIF_BLOCKSTEP) << DEBUGCTLMSR_BTF_SHIFT;
654 wrmsrl(MSR_IA32_DEBUGCTLMSR, debugctl);
655 }
656
657 if ((tifp ^ tifn) & _TIF_NOTSC)
658 cr4_toggle_bits_irqsoff(X86_CR4_TSD);
659
660 if ((tifp ^ tifn) & _TIF_NOCPUID)
661 set_cpuid_faulting(!!(tifn & _TIF_NOCPUID));
662
663 if (likely(!((tifp | tifn) & _TIF_SPEC_FORCE_UPDATE))) {
664 __speculation_ctrl_update(tifp, tifn);
665 } else {
666 speculation_ctrl_update_tif(prev_p);
667 tifn = speculation_ctrl_update_tif(next_p);
668
669 /* Enforce MSR update to ensure consistent state */
670 __speculation_ctrl_update(~tifn, tifn);
671 }
672
673 if ((tifp ^ tifn) & _TIF_SLD)
674 switch_to_sld(tifn);
675}
676
677/*
678 * Idle related variables and functions
679 */
680unsigned long boot_option_idle_override = IDLE_NO_OVERRIDE;
681EXPORT_SYMBOL(boot_option_idle_override);
682
683static void (*x86_idle)(void);
684
685#ifndef CONFIG_SMP
686static inline void play_dead(void)
687{
688 BUG();
689}
690#endif
691
692void arch_cpu_idle_enter(void)
693{
694 tsc_verify_tsc_adjust(false);
695 local_touch_nmi();
696}
697
698void arch_cpu_idle_dead(void)
699{
700 play_dead();
701}
702
703/*
704 * Called from the generic idle code.
705 */
706void arch_cpu_idle(void)
707{
708 x86_idle();
709}
710
711/*
712 * We use this if we don't have any better idle routine..
713 */
714void __cpuidle default_idle(void)
715{
716 raw_safe_halt();
717}
718#if defined(CONFIG_APM_MODULE) || defined(CONFIG_HALTPOLL_CPUIDLE_MODULE)
719EXPORT_SYMBOL(default_idle);
720#endif
721
722#ifdef CONFIG_XEN
723bool xen_set_default_idle(void)
724{
725 bool ret = !!x86_idle;
726
727 x86_idle = default_idle;
728
729 return ret;
730}
731#endif
732
733void stop_this_cpu(void *dummy)
734{
735 local_irq_disable();
736 /*
737 * Remove this CPU:
738 */
739 set_cpu_online(smp_processor_id(), false);
740 disable_local_APIC();
741 mcheck_cpu_clear(this_cpu_ptr(&cpu_info));
742
743 /*
744 * Use wbinvd on processors that support SME. This provides support
745 * for performing a successful kexec when going from SME inactive
746 * to SME active (or vice-versa). The cache must be cleared so that
747 * if there are entries with the same physical address, both with and
748 * without the encryption bit, they don't race each other when flushed
749 * and potentially end up with the wrong entry being committed to
750 * memory.
751 */
752 if (boot_cpu_has(X86_FEATURE_SME))
753 native_wbinvd();
754 for (;;) {
755 /*
756 * Use native_halt() so that memory contents don't change
757 * (stack usage and variables) after possibly issuing the
758 * native_wbinvd() above.
759 */
760 native_halt();
761 }
762}
763
764/*
765 * AMD Erratum 400 aware idle routine. We handle it the same way as C3 power
766 * states (local apic timer and TSC stop).
767 *
768 * XXX this function is completely buggered vs RCU and tracing.
769 */
770static void amd_e400_idle(void)
771{
772 /*
773 * We cannot use static_cpu_has_bug() here because X86_BUG_AMD_APIC_C1E
774 * gets set after static_cpu_has() places have been converted via
775 * alternatives.
776 */
777 if (!boot_cpu_has_bug(X86_BUG_AMD_APIC_C1E)) {
778 default_idle();
779 return;
780 }
781
782 tick_broadcast_enter();
783
784 default_idle();
785
786 /*
787 * The switch back from broadcast mode needs to be called with
788 * interrupts disabled.
789 */
790 raw_local_irq_disable();
791 tick_broadcast_exit();
792 raw_local_irq_enable();
793}
794
795/*
796 * Intel Core2 and older machines prefer MWAIT over HALT for C1.
797 * We can't rely on cpuidle installing MWAIT, because it will not load
798 * on systems that support only C1 -- so the boot default must be MWAIT.
799 *
800 * Some AMD machines are the opposite, they depend on using HALT.
801 *
802 * So for default C1, which is used during boot until cpuidle loads,
803 * use MWAIT-C1 on Intel HW that has it, else use HALT.
804 */
805static int prefer_mwait_c1_over_halt(const struct cpuinfo_x86 *c)
806{
807 if (c->x86_vendor != X86_VENDOR_INTEL)
808 return 0;
809
810 if (!cpu_has(c, X86_FEATURE_MWAIT) || boot_cpu_has_bug(X86_BUG_MONITOR))
811 return 0;
812
813 return 1;
814}
815
816/*
817 * MONITOR/MWAIT with no hints, used for default C1 state. This invokes MWAIT
818 * with interrupts enabled and no flags, which is backwards compatible with the
819 * original MWAIT implementation.
820 */
821static __cpuidle void mwait_idle(void)
822{
823 if (!current_set_polling_and_test()) {
824 if (this_cpu_has(X86_BUG_CLFLUSH_MONITOR)) {
825 mb(); /* quirk */
826 clflush((void *)¤t_thread_info()->flags);
827 mb(); /* quirk */
828 }
829
830 __monitor((void *)¤t_thread_info()->flags, 0, 0);
831 if (!need_resched())
832 __sti_mwait(0, 0);
833 else
834 raw_local_irq_enable();
835 } else {
836 raw_local_irq_enable();
837 }
838 __current_clr_polling();
839}
840
841void select_idle_routine(const struct cpuinfo_x86 *c)
842{
843#ifdef CONFIG_SMP
844 if (boot_option_idle_override == IDLE_POLL && smp_num_siblings > 1)
845 pr_warn_once("WARNING: polling idle and HT enabled, performance may degrade\n");
846#endif
847 if (x86_idle || boot_option_idle_override == IDLE_POLL)
848 return;
849
850 if (boot_cpu_has_bug(X86_BUG_AMD_E400)) {
851 pr_info("using AMD E400 aware idle routine\n");
852 x86_idle = amd_e400_idle;
853 } else if (prefer_mwait_c1_over_halt(c)) {
854 pr_info("using mwait in idle threads\n");
855 x86_idle = mwait_idle;
856 } else
857 x86_idle = default_idle;
858}
859
860void amd_e400_c1e_apic_setup(void)
861{
862 if (boot_cpu_has_bug(X86_BUG_AMD_APIC_C1E)) {
863 pr_info("Switch to broadcast mode on CPU%d\n", smp_processor_id());
864 local_irq_disable();
865 tick_broadcast_force();
866 local_irq_enable();
867 }
868}
869
870void __init arch_post_acpi_subsys_init(void)
871{
872 u32 lo, hi;
873
874 if (!boot_cpu_has_bug(X86_BUG_AMD_E400))
875 return;
876
877 /*
878 * AMD E400 detection needs to happen after ACPI has been enabled. If
879 * the machine is affected K8_INTP_C1E_ACTIVE_MASK bits are set in
880 * MSR_K8_INT_PENDING_MSG.
881 */
882 rdmsr(MSR_K8_INT_PENDING_MSG, lo, hi);
883 if (!(lo & K8_INTP_C1E_ACTIVE_MASK))
884 return;
885
886 boot_cpu_set_bug(X86_BUG_AMD_APIC_C1E);
887
888 if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
889 mark_tsc_unstable("TSC halt in AMD C1E");
890 pr_info("System has AMD C1E enabled\n");
891}
892
893static int __init idle_setup(char *str)
894{
895 if (!str)
896 return -EINVAL;
897
898 if (!strcmp(str, "poll")) {
899 pr_info("using polling idle threads\n");
900 boot_option_idle_override = IDLE_POLL;
901 cpu_idle_poll_ctrl(true);
902 } else if (!strcmp(str, "halt")) {
903 /*
904 * When the boot option of idle=halt is added, halt is
905 * forced to be used for CPU idle. In such case CPU C2/C3
906 * won't be used again.
907 * To continue to load the CPU idle driver, don't touch
908 * the boot_option_idle_override.
909 */
910 x86_idle = default_idle;
911 boot_option_idle_override = IDLE_HALT;
912 } else if (!strcmp(str, "nomwait")) {
913 /*
914 * If the boot option of "idle=nomwait" is added,
915 * it means that mwait will be disabled for CPU C2/C3
916 * states. In such case it won't touch the variable
917 * of boot_option_idle_override.
918 */
919 boot_option_idle_override = IDLE_NOMWAIT;
920 } else
921 return -1;
922
923 return 0;
924}
925early_param("idle", idle_setup);
926
927unsigned long arch_align_stack(unsigned long sp)
928{
929 if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
930 sp -= get_random_int() % 8192;
931 return sp & ~0xf;
932}
933
934unsigned long arch_randomize_brk(struct mm_struct *mm)
935{
936 return randomize_page(mm->brk, 0x02000000);
937}
938
939/*
940 * Called from fs/proc with a reference on @p to find the function
941 * which called into schedule(). This needs to be done carefully
942 * because the task might wake up and we might look at a stack
943 * changing under us.
944 */
945unsigned long get_wchan(struct task_struct *p)
946{
947 unsigned long start, bottom, top, sp, fp, ip, ret = 0;
948 int count = 0;
949
950 if (p == current || task_is_running(p))
951 return 0;
952
953 if (!try_get_task_stack(p))
954 return 0;
955
956 start = (unsigned long)task_stack_page(p);
957 if (!start)
958 goto out;
959
960 /*
961 * Layout of the stack page:
962 *
963 * ----------- topmax = start + THREAD_SIZE - sizeof(unsigned long)
964 * PADDING
965 * ----------- top = topmax - TOP_OF_KERNEL_STACK_PADDING
966 * stack
967 * ----------- bottom = start
968 *
969 * The tasks stack pointer points at the location where the
970 * framepointer is stored. The data on the stack is:
971 * ... IP FP ... IP FP
972 *
973 * We need to read FP and IP, so we need to adjust the upper
974 * bound by another unsigned long.
975 */
976 top = start + THREAD_SIZE - TOP_OF_KERNEL_STACK_PADDING;
977 top -= 2 * sizeof(unsigned long);
978 bottom = start;
979
980 sp = READ_ONCE(p->thread.sp);
981 if (sp < bottom || sp > top)
982 goto out;
983
984 fp = READ_ONCE_NOCHECK(((struct inactive_task_frame *)sp)->bp);
985 do {
986 if (fp < bottom || fp > top)
987 goto out;
988 ip = READ_ONCE_NOCHECK(*(unsigned long *)(fp + sizeof(unsigned long)));
989 if (!in_sched_functions(ip)) {
990 ret = ip;
991 goto out;
992 }
993 fp = READ_ONCE_NOCHECK(*(unsigned long *)fp);
994 } while (count++ < 16 && !task_is_running(p));
995
996out:
997 put_task_stack(p);
998 return ret;
999}
1000
1001long do_arch_prctl_common(struct task_struct *task, int option,
1002 unsigned long cpuid_enabled)
1003{
1004 switch (option) {
1005 case ARCH_GET_CPUID:
1006 return get_cpuid_mode();
1007 case ARCH_SET_CPUID:
1008 return set_cpuid_mode(task, cpuid_enabled);
1009 }
1010
1011 return -EINVAL;
1012}