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Linux/arch/um/kernel/process.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * Copyright (C) 2015 Anton Ivanov (aivanov@{brocade.com,kot-begemot.co.uk})
  4  * Copyright (C) 2015 Thomas Meyer (thomas@m3y3r.de)
  5  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  6  * Copyright 2003 PathScale, Inc.
  7  */
  8 
  9 #include <linux/stddef.h>
 10 #include <linux/err.h>
 11 #include <linux/hardirq.h>
 12 #include <linux/mm.h>
 13 #include <linux/module.h>
 14 #include <linux/personality.h>
 15 #include <linux/proc_fs.h>
 16 #include <linux/ptrace.h>
 17 #include <linux/random.h>
 18 #include <linux/slab.h>
 19 #include <linux/sched.h>
 20 #include <linux/sched/debug.h>
 21 #include <linux/sched/task.h>
 22 #include <linux/sched/task_stack.h>
 23 #include <linux/seq_file.h>
 24 #include <linux/tick.h>
 25 #include <linux/threads.h>
 26 #include <linux/tracehook.h>
 27 #include <asm/current.h>
 28 #include <asm/mmu_context.h>
 29 #include <linux/uaccess.h>
 30 #include <as-layout.h>
 31 #include <kern_util.h>
 32 #include <os.h>
 33 #include <skas.h>
 34 #include <linux/time-internal.h>
 35 
 36 /*
 37  * This is a per-cpu array.  A processor only modifies its entry and it only
 38  * cares about its entry, so it's OK if another processor is modifying its
 39  * entry.
 40  */
 41 struct cpu_task cpu_tasks[NR_CPUS] = { [0 ... NR_CPUS - 1] = { -1, NULL } };
 42 
 43 static inline int external_pid(void)
 44 {
 45         /* FIXME: Need to look up userspace_pid by cpu */
 46         return userspace_pid[0];
 47 }
 48 
 49 int pid_to_processor_id(int pid)
 50 {
 51         int i;
 52 
 53         for (i = 0; i < ncpus; i++) {
 54                 if (cpu_tasks[i].pid == pid)
 55                         return i;
 56         }
 57         return -1;
 58 }
 59 
 60 void free_stack(unsigned long stack, int order)
 61 {
 62         free_pages(stack, order);
 63 }
 64 
 65 unsigned long alloc_stack(int order, int atomic)
 66 {
 67         unsigned long page;
 68         gfp_t flags = GFP_KERNEL;
 69 
 70         if (atomic)
 71                 flags = GFP_ATOMIC;
 72         page = __get_free_pages(flags, order);
 73 
 74         return page;
 75 }
 76 
 77 static inline void set_current(struct task_struct *task)
 78 {
 79         cpu_tasks[task_thread_info(task)->cpu] = ((struct cpu_task)
 80                 { external_pid(), task });
 81 }
 82 
 83 extern void arch_switch_to(struct task_struct *to);
 84 
 85 void *__switch_to(struct task_struct *from, struct task_struct *to)
 86 {
 87         to->thread.prev_sched = from;
 88         set_current(to);
 89 
 90         switch_threads(&from->thread.switch_buf, &to->thread.switch_buf);
 91         arch_switch_to(current);
 92 
 93         return current->thread.prev_sched;
 94 }
 95 
 96 void interrupt_end(void)
 97 {
 98         struct pt_regs *regs = &current->thread.regs;
 99 
100         if (need_resched())
101                 schedule();
102         if (test_thread_flag(TIF_SIGPENDING))
103                 do_signal(regs);
104         if (test_and_clear_thread_flag(TIF_NOTIFY_RESUME))
105                 tracehook_notify_resume(regs);
106 }
107 
108 int get_current_pid(void)
109 {
110         return task_pid_nr(current);
111 }
112 
113 /*
114  * This is called magically, by its address being stuffed in a jmp_buf
115  * and being longjmp-d to.
116  */
117 void new_thread_handler(void)
118 {
119         int (*fn)(void *), n;
120         void *arg;
121 
122         if (current->thread.prev_sched != NULL)
123                 schedule_tail(current->thread.prev_sched);
124         current->thread.prev_sched = NULL;
125 
126         fn = current->thread.request.u.thread.proc;
127         arg = current->thread.request.u.thread.arg;
128 
129         /*
130          * callback returns only if the kernel thread execs a process
131          */
132         n = fn(arg);
133         userspace(&current->thread.regs.regs, current_thread_info()->aux_fp_regs);
134 }
135 
136 /* Called magically, see new_thread_handler above */
137 void fork_handler(void)
138 {
139         force_flush_all();
140 
141         schedule_tail(current->thread.prev_sched);
142 
143         /*
144          * XXX: if interrupt_end() calls schedule, this call to
145          * arch_switch_to isn't needed. We could want to apply this to
146          * improve performance. -bb
147          */
148         arch_switch_to(current);
149 
150         current->thread.prev_sched = NULL;
151 
152         userspace(&current->thread.regs.regs, current_thread_info()->aux_fp_regs);
153 }
154 
155 int copy_thread(unsigned long clone_flags, unsigned long sp,
156                 unsigned long arg, struct task_struct * p, unsigned long tls)
157 {
158         void (*handler)(void);
159         int kthread = current->flags & PF_KTHREAD;
160         int ret = 0;
161 
162         p->thread = (struct thread_struct) INIT_THREAD;
163 
164         if (!kthread) {
165                 memcpy(&p->thread.regs.regs, current_pt_regs(),
166                        sizeof(p->thread.regs.regs));
167                 PT_REGS_SET_SYSCALL_RETURN(&p->thread.regs, 0);
168                 if (sp != 0)
169                         REGS_SP(p->thread.regs.regs.gp) = sp;
170 
171                 handler = fork_handler;
172 
173                 arch_copy_thread(&current->thread.arch, &p->thread.arch);
174         } else {
175                 get_safe_registers(p->thread.regs.regs.gp, p->thread.regs.regs.fp);
176                 p->thread.request.u.thread.proc = (int (*)(void *))sp;
177                 p->thread.request.u.thread.arg = (void *)arg;
178                 handler = new_thread_handler;
179         }
180 
181         new_thread(task_stack_page(p), &p->thread.switch_buf, handler);
182 
183         if (!kthread) {
184                 clear_flushed_tls(p);
185 
186                 /*
187                  * Set a new TLS for the child thread?
188                  */
189                 if (clone_flags & CLONE_SETTLS)
190                         ret = arch_set_tls(p, tls);
191         }
192 
193         return ret;
194 }
195 
196 void initial_thread_cb(void (*proc)(void *), void *arg)
197 {
198         int save_kmalloc_ok = kmalloc_ok;
199 
200         kmalloc_ok = 0;
201         initial_thread_cb_skas(proc, arg);
202         kmalloc_ok = save_kmalloc_ok;
203 }
204 
205 static void um_idle_sleep(void)
206 {
207         unsigned long long duration = UM_NSEC_PER_SEC;
208 
209         if (time_travel_mode != TT_MODE_OFF) {
210                 time_travel_sleep(duration);
211         } else {
212                 os_idle_sleep(duration);
213         }
214 }
215 
216 void arch_cpu_idle(void)
217 {
218         cpu_tasks[current_thread_info()->cpu].pid = os_getpid();
219         um_idle_sleep();
220         raw_local_irq_enable();
221 }
222 
223 int __cant_sleep(void) {
224         return in_atomic() || irqs_disabled() || in_interrupt();
225         /* Is in_interrupt() really needed? */
226 }
227 
228 int user_context(unsigned long sp)
229 {
230         unsigned long stack;
231 
232         stack = sp & (PAGE_MASK << CONFIG_KERNEL_STACK_ORDER);
233         return stack != (unsigned long) current_thread_info();
234 }
235 
236 extern exitcall_t __uml_exitcall_begin, __uml_exitcall_end;
237 
238 void do_uml_exitcalls(void)
239 {
240         exitcall_t *call;
241 
242         call = &__uml_exitcall_end;
243         while (--call >= &__uml_exitcall_begin)
244                 (*call)();
245 }
246 
247 char *uml_strdup(const char *string)
248 {
249         return kstrdup(string, GFP_KERNEL);
250 }
251 EXPORT_SYMBOL(uml_strdup);
252 
253 int copy_to_user_proc(void __user *to, void *from, int size)
254 {
255         return copy_to_user(to, from, size);
256 }
257 
258 int copy_from_user_proc(void *to, void __user *from, int size)
259 {
260         return copy_from_user(to, from, size);
261 }
262 
263 int clear_user_proc(void __user *buf, int size)
264 {
265         return clear_user(buf, size);
266 }
267 
268 int cpu(void)
269 {
270         return current_thread_info()->cpu;
271 }
272 
273 static atomic_t using_sysemu = ATOMIC_INIT(0);
274 int sysemu_supported;
275 
276 void set_using_sysemu(int value)
277 {
278         if (value > sysemu_supported)
279                 return;
280         atomic_set(&using_sysemu, value);
281 }
282 
283 int get_using_sysemu(void)
284 {
285         return atomic_read(&using_sysemu);
286 }
287 
288 static int sysemu_proc_show(struct seq_file *m, void *v)
289 {
290         seq_printf(m, "%d\n", get_using_sysemu());
291         return 0;
292 }
293 
294 static int sysemu_proc_open(struct inode *inode, struct file *file)
295 {
296         return single_open(file, sysemu_proc_show, NULL);
297 }
298 
299 static ssize_t sysemu_proc_write(struct file *file, const char __user *buf,
300                                  size_t count, loff_t *pos)
301 {
302         char tmp[2];
303 
304         if (copy_from_user(tmp, buf, 1))
305                 return -EFAULT;
306 
307         if (tmp[0] >= '' && tmp[0] <= '2')
308                 set_using_sysemu(tmp[0] - '');
309         /* We use the first char, but pretend to write everything */
310         return count;
311 }
312 
313 static const struct proc_ops sysemu_proc_ops = {
314         .proc_open      = sysemu_proc_open,
315         .proc_read      = seq_read,
316         .proc_lseek     = seq_lseek,
317         .proc_release   = single_release,
318         .proc_write     = sysemu_proc_write,
319 };
320 
321 int __init make_proc_sysemu(void)
322 {
323         struct proc_dir_entry *ent;
324         if (!sysemu_supported)
325                 return 0;
326 
327         ent = proc_create("sysemu", 0600, NULL, &sysemu_proc_ops);
328 
329         if (ent == NULL)
330         {
331                 printk(KERN_WARNING "Failed to register /proc/sysemu\n");
332                 return 0;
333         }
334 
335         return 0;
336 }
337 
338 late_initcall(make_proc_sysemu);
339 
340 int singlestepping(void * t)
341 {
342         struct task_struct *task = t ? t : current;
343 
344         if (!(task->ptrace & PT_DTRACE))
345                 return 0;
346 
347         if (task->thread.singlestep_syscall)
348                 return 1;
349 
350         return 2;
351 }
352 
353 /*
354  * Only x86 and x86_64 have an arch_align_stack().
355  * All other arches have "#define arch_align_stack(x) (x)"
356  * in their asm/exec.h
357  * As this is included in UML from asm-um/system-generic.h,
358  * we can use it to behave as the subarch does.
359  */
360 #ifndef arch_align_stack
361 unsigned long arch_align_stack(unsigned long sp)
362 {
363         if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
364                 sp -= get_random_int() % 8192;
365         return sp & ~0xf;
366 }
367 #endif
368 
369 unsigned long get_wchan(struct task_struct *p)
370 {
371         unsigned long stack_page, sp, ip;
372         bool seen_sched = 0;
373 
374         if ((p == NULL) || (p == current) || (p->state == TASK_RUNNING))
375                 return 0;
376 
377         stack_page = (unsigned long) task_stack_page(p);
378         /* Bail if the process has no kernel stack for some reason */
379         if (stack_page == 0)
380                 return 0;
381 
382         sp = p->thread.switch_buf->JB_SP;
383         /*
384          * Bail if the stack pointer is below the bottom of the kernel
385          * stack for some reason
386          */
387         if (sp < stack_page)
388                 return 0;
389 
390         while (sp < stack_page + THREAD_SIZE) {
391                 ip = *((unsigned long *) sp);
392                 if (in_sched_functions(ip))
393                         /* Ignore everything until we're above the scheduler */
394                         seen_sched = 1;
395                 else if (kernel_text_address(ip) && seen_sched)
396                         return ip;
397 
398                 sp += sizeof(unsigned long);
399         }
400 
401         return 0;
402 }
403 
404 int elf_core_copy_fpregs(struct task_struct *t, elf_fpregset_t *fpu)
405 {
406         int cpu = current_thread_info()->cpu;
407 
408         return save_i387_registers(userspace_pid[cpu], (unsigned long *) fpu);
409 }
410 
411 

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