arch/um/kernel/process.c

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