arch/um/kernel/process.c

   1 /*
   2  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
   3  * Copyright 2003 PathScale, Inc.
   4  * Licensed under the GPL
   5  */
   6
   7 #include <linux/stddef.h>
   8 #include <linux/err.h>
   9 #include <linux/hardirq.h>
  10 #include <linux/gfp.h>
  11 #include <linux/mm.h>
  12 #include <linux/personality.h>
  13 #include <linux/proc_fs.h>
  14 #include <linux/ptrace.h>
  15 #include <linux/random.h>
  16 #include <linux/sched.h>
  17 #include <linux/tick.h>
  18 #include <linux/threads.h>
  19 #include <asm/current.h>
  20 #include <asm/pgtable.h>
  21 #include <asm/uaccess.h>
  22 #include "as-layout.h"
  23 #include "kern_util.h"
  24 #include "os.h"
  25 #include "skas.h"
  26 #include "tlb.h"
  27
  28 /*
  29  * This is a per-cpu array.  A processor only modifies its entry and it only
  30  * cares about its entry, so it's OK if another processor is modifying its
  31  * entry.
  32  */
  33 struct cpu_task cpu_tasks[NR_CPUS] = { [0 ... NR_CPUS - 1] = { -1, NULL } };
  34
  35 static inline int external_pid(void)
  36 {
  37         /* FIXME: Need to look up userspace_pid by cpu */
  38         return userspace_pid[0];
  39 }
  40
  41 int pid_to_processor_id(int pid)
  42 {
  43         int i;
  44
  45         for (i = 0; i < ncpus; i++) {
  46                 if (cpu_tasks[i].pid == pid)
  47                         return i;
  48         }
  49         return -1;
  50 }
  51
  52 void free_stack(unsigned long stack, int order)
  53 {
  54         free_pages(stack, order);
  55 }
  56
  57 unsigned long alloc_stack(int order, int atomic)
  58 {
  59         unsigned long page;
  60         gfp_t flags = GFP_KERNEL;
  61
  62         if (atomic)
  63                 flags = GFP_ATOMIC;
  64         page = __get_free_pages(flags, order);
  65
  66         return page;
  67 }
  68
  69 int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
  70 {
  71         int pid;
  72
  73         current->thread.request.u.thread.proc = fn;
  74         current->thread.request.u.thread.arg = arg;
  75         pid = do_fork(CLONE_VM | CLONE_UNTRACED | flags, 0,
  76                       &current->thread.regs, 0, NULL, NULL);
  77         return pid;
  78 }
  79
  80 static inline void set_current(struct task_struct *task)
  81 {
  82         cpu_tasks[task_thread_info(task)->cpu] = ((struct cpu_task)
  83                 { external_pid(), task });
  84 }
  85
  86 extern void arch_switch_to(struct task_struct *to);
  87
  88 void *_switch_to(void *prev, void *next, void *last)
  89 {
  90         struct task_struct *from = prev;
  91         struct task_struct *to = next;
  92
  93         to->thread.prev_sched = from;
  94         set_current(to);
  95
  96         do {
  97                 current->thread.saved_task = NULL;
  98
  99                 switch_threads(&from->thread.switch_buf,
 100                                &to->thread.switch_buf);
 101
 102                 arch_switch_to(current);
 103
 104                 if (current->thread.saved_task)
 105                         show_regs(&(current->thread.regs));
 106                 to = current->thread.saved_task;
 107                 from = current;
 108         } while (current->thread.saved_task);
 109
 110         return current->thread.prev_sched;
 111
 112 }
 113
 114 void interrupt_end(void)
 115 {
 116         if (need_resched())
 117                 schedule();
 118         if (test_tsk_thread_flag(current, TIF_SIGPENDING))
 119                 do_signal();
 120 }
 121
 122 void exit_thread(void)
 123 {
 124 }
 125
 126 void *get_current(void)
 127 {
 128         return current;
 129 }
 130
 131 /*
 132  * This is called magically, by its address being stuffed in a jmp_buf
 133  * and being longjmp-d to.
 134  */
 135 void new_thread_handler(void)
 136 {
 137         int (*fn)(void *), n;
 138         void *arg;
 139
 140         if (current->thread.prev_sched != NULL)
 141                 schedule_tail(current->thread.prev_sched);
 142         current->thread.prev_sched = NULL;
 143
 144         fn = current->thread.request.u.thread.proc;
 145         arg = current->thread.request.u.thread.arg;
 146
 147         /*
 148          * The return value is 1 if the kernel thread execs a process,
 149          * 0 if it just exits
 150          */
 151         n = run_kernel_thread(fn, arg, &current->thread.exec_buf);
 152         if (n == 1) {
 153                 /* Handle any immediate reschedules or signals */
 154                 interrupt_end();
 155                 userspace(&current->thread.regs.regs);
 156         }
 157         else do_exit(0);
 158 }
 159
 160 /* Called magically, see new_thread_handler above */
 161 void fork_handler(void)
 162 {
 163         force_flush_all();
 164
 165         schedule_tail(current->thread.prev_sched);
 166
 167         /*
 168          * XXX: if interrupt_end() calls schedule, this call to
 169          * arch_switch_to isn't needed. We could want to apply this to
 170          * improve performance. -bb
 171          */
 172         arch_switch_to(current);
 173
 174         current->thread.prev_sched = NULL;
 175
 176         /* Handle any immediate reschedules or signals */
 177         interrupt_end();
 178
 179         userspace(&current->thread.regs.regs);
 180 }
 181
 182 int copy_thread(int nr, unsigned long clone_flags, unsigned long sp,
 183                 unsigned long stack_top, struct task_struct * p,
 184                 struct pt_regs *regs)
 185 {
 186         void (*handler)(void);
 187         int ret = 0;
 188
 189         p->thread = (struct thread_struct) INIT_THREAD;
 190
 191         if (current->thread.forking) {
 192                 memcpy(&p->thread.regs.regs, &regs->regs,
 193                        sizeof(p->thread.regs.regs));
 194                 REGS_SET_SYSCALL_RETURN(p->thread.regs.regs.gp, 0);
 195                 if (sp != 0)
 196                         REGS_SP(p->thread.regs.regs.gp) = sp;
 197
 198                 handler = fork_handler;
 199
 200                 arch_copy_thread(&current->thread.arch, &p->thread.arch);
 201         }
 202         else {
 203                 get_safe_registers(p->thread.regs.regs.gp);
 204                 p->thread.request.u.thread = current->thread.request.u.thread;
 205                 handler = new_thread_handler;
 206         }
 207
 208         new_thread(task_stack_page(p), &p->thread.switch_buf, handler);
 209
 210         if (current->thread.forking) {
 211                 clear_flushed_tls(p);
 212
 213                 /*
 214                  * Set a new TLS for the child thread?
 215                  */
 216                 if (clone_flags & CLONE_SETTLS)
 217                         ret = arch_copy_tls(p);
 218         }
 219
 220         return ret;
 221 }
 222
 223 void initial_thread_cb(void (*proc)(void *), void *arg)
 224 {
 225         int save_kmalloc_ok = kmalloc_ok;
 226
 227         kmalloc_ok = 0;
 228         initial_thread_cb_skas(proc, arg);
 229         kmalloc_ok = save_kmalloc_ok;
 230 }
 231
 232 void default_idle(void)
 233 {
 234         unsigned long long nsecs;
 235
 236         while (1) {
 237                 /* endless idle loop with no priority at all */
 238
 239                 /*
 240                  * although we are an idle CPU, we do not want to
 241                  * get into the scheduler unnecessarily.
 242                  */
 243                 if (need_resched())
 244                         schedule();
 245
 246                 tick_nohz_stop_sched_tick();
 247                 nsecs = disable_timer();
 248                 idle_sleep(nsecs);
 249                 tick_nohz_restart_sched_tick();
 250         }
 251 }
 252
 253 void cpu_idle(void)
 254 {
 255         cpu_tasks[current_thread_info()->cpu].pid = os_getpid();
 256         default_idle();
 257 }
 258
 259 int __cant_sleep(void) {
 260         return in_atomic() || irqs_disabled() || in_interrupt();
 261         /* Is in_interrupt() really needed? */
 262 }
 263
 264 int user_context(unsigned long sp)
 265 {
 266         unsigned long stack;
 267
 268         stack = sp & (PAGE_MASK << CONFIG_KERNEL_STACK_ORDER);
 269         return stack != (unsigned long) current_thread_info();
 270 }
 271
 272 extern exitcall_t __uml_exitcall_begin, __uml_exitcall_end;
 273
 274 void do_uml_exitcalls(void)
 275 {
 276         exitcall_t *call;
 277
 278         call = &__uml_exitcall_end;
 279         while (--call >= &__uml_exitcall_begin)
 280                 (*call)();
 281 }
 282
 283 char *uml_strdup(const char *string)
 284 {
 285         return kstrdup(string, GFP_KERNEL);
 286 }
 287
 288 int copy_to_user_proc(void __user *to, void *from, int size)
 289 {
 290         return copy_to_user(to, from, size);
 291 }
 292
 293 int copy_from_user_proc(void *to, void __user *from, int size)
 294 {
 295         return copy_from_user(to, from, size);
 296 }
 297
 298 int clear_user_proc(void __user *buf, int size)
 299 {
 300         return clear_user(buf, size);
 301 }
 302
 303 int strlen_user_proc(char __user *str)
 304 {
 305         return strlen_user(str);
 306 }
 307
 308 int smp_sigio_handler(void)
 309 {
 310 #ifdef CONFIG_SMP
 311         int cpu = current_thread_info()->cpu;
 312         IPI_handler(cpu);
 313         if (cpu != 0)
 314                 return 1;
 315 #endif
 316         return 0;
 317 }
 318
 319 int cpu(void)
 320 {
 321         return current_thread_info()->cpu;
 322 }
 323
 324 static atomic_t using_sysemu = ATOMIC_INIT(0);
 325 int sysemu_supported;
 326
 327 void set_using_sysemu(int value)
 328 {
 329         if (value > sysemu_supported)
 330                 return;
 331         atomic_set(&using_sysemu, value);
 332 }
 333
 334 int get_using_sysemu(void)
 335 {
 336         return atomic_read(&using_sysemu);
 337 }
 338
 339 static int proc_read_sysemu(char *buf, char **start, off_t offset, int size,int *eof, void *data)
 340 {
 341         if (snprintf(buf, size, "%d\n", get_using_sysemu()) < size)
 342                 /* No overflow */
 343                 *eof = 1;
 344
 345         return strlen(buf);
 346 }
 347
 348 static int proc_write_sysemu(struct file *file,const char __user *buf, unsigned long count,void *data)
 349 {
 350         char tmp[2];
 351
 352         if (copy_from_user(tmp, buf, 1))
 353                 return -EFAULT;
 354
 355         if (tmp[0] >= '0' && tmp[0] <= '2')
 356                 set_using_sysemu(tmp[0] - '0');
 357         /* We use the first char, but pretend to write everything */
 358         return count;
 359 }
 360
 361 int __init make_proc_sysemu(void)
 362 {
 363         struct proc_dir_entry *ent;
 364         if (!sysemu_supported)
 365                 return 0;
 366
 367         ent = create_proc_entry("sysemu", 0600, &proc_root);
 368
 369         if (ent == NULL)
 370         {
 371                 printk(KERN_WARNING "Failed to register /proc/sysemu\n");
 372                 return 0;
 373         }
 374
 375         ent->read_proc  = proc_read_sysemu;
 376         ent->write_proc = proc_write_sysemu;
 377
 378         return 0;
 379 }
 380
 381 late_initcall(make_proc_sysemu);
 382
 383 int singlestepping(void * t)
 384 {
 385         struct task_struct *task = t ? t : current;
 386
 387         if (!(task->ptrace & PT_DTRACE))
 388                 return 0;
 389
 390         if (task->thread.singlestep_syscall)
 391                 return 1;
 392
 393         return 2;
 394 }
 395
 396 /*
 397  * Only x86 and x86_64 have an arch_align_stack().
 398  * All other arches have "#define arch_align_stack(x) (x)"
 399  * in their asm/system.h
 400  * As this is included in UML from asm-um/system-generic.h,
 401  * we can use it to behave as the subarch does.
 402  */
 403 #ifndef arch_align_stack
 404 unsigned long arch_align_stack(unsigned long sp)
 405 {
 406         if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
 407                 sp -= get_random_int() % 8192;
 408         return sp & ~0xf;
 409 }
 410 #endif
 411
 412 unsigned long get_wchan(struct task_struct *p)
 413 {
 414         unsigned long stack_page, sp, ip;
 415         bool seen_sched = 0;
 416
 417         if ((p == NULL) || (p == current) || (p->state == TASK_RUNNING))
 418                 return 0;
 419
 420         stack_page = (unsigned long) task_stack_page(p);
 421         /* Bail if the process has no kernel stack for some reason */
 422         if (stack_page == 0)
 423                 return 0;
 424
 425         sp = p->thread.switch_buf->JB_SP;
 426         /*
 427          * Bail if the stack pointer is below the bottom of the kernel
 428          * stack for some reason
 429          */
 430         if (sp < stack_page)
 431                 return 0;
 432
 433         while (sp < stack_page + THREAD_SIZE) {
 434                 ip = *((unsigned long *) sp);
 435                 if (in_sched_functions(ip))
 436                         /* Ignore everything until we're above the scheduler */
 437                         seen_sched = 1;
 438                 else if (kernel_text_address(ip) && seen_sched)
 439                         return ip;
 440
 441                 sp += sizeof(unsigned long);
 442         }
 443
 444         return 0;
 445 }
 446
 447 int elf_core_copy_fpregs(struct task_struct *t, elf_fpregset_t *fpu)
 448 {
 449         int cpu = current_thread_info()->cpu;
 450
 451         return save_fp_registers(userspace_pid[cpu], (unsigned long *) fpu);
 452 }
 453