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/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 <timer-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 */
  42struct cpu_task cpu_tasks[NR_CPUS] = { [0 ... NR_CPUS - 1] = { -1, NULL } };
  43
  44static inline int external_pid(void)
  45{
  46        /* FIXME: Need to look up userspace_pid by cpu */
  47        return userspace_pid[0];
  48}
  49
  50int 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
  61void free_stack(unsigned long stack, int order)
  62{
  63        free_pages(stack, order);
  64}
  65
  66unsigned 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
  78static 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
  84extern void arch_switch_to(struct task_struct *to);
  85
  86void *__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
  97void 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
 109int 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 */
 118void 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 */
 138void 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
 156int copy_thread(unsigned long clone_flags, unsigned long sp,
 157                unsigned long arg, struct task_struct * p)
 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_copy_tls(p);
 192        }
 193
 194        return ret;
 195}
 196
 197void 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
 206static void time_travel_sleep(unsigned long long duration)
 207{
 208        unsigned long long next = time_travel_time + duration;
 209
 210        if (time_travel_mode != TT_MODE_INFCPU)
 211                os_timer_disable();
 212
 213        while (time_travel_timer_mode == TT_TMR_PERIODIC &&
 214               time_travel_timer_expiry < time_travel_time)
 215                time_travel_set_timer_expiry(time_travel_timer_expiry +
 216                                             time_travel_timer_interval);
 217
 218        if (time_travel_timer_mode != TT_TMR_DISABLED &&
 219            time_travel_timer_expiry < next) {
 220                if (time_travel_timer_mode == TT_TMR_ONESHOT)
 221                        time_travel_set_timer_mode(TT_TMR_DISABLED);
 222                /*
 223                 * In basic mode, time_travel_time will be adjusted in
 224                 * the timer IRQ handler so it works even when the signal
 225                 * comes from the OS timer, see there.
 226                 */
 227                if (time_travel_mode != TT_MODE_BASIC)
 228                        time_travel_set_time(time_travel_timer_expiry);
 229
 230                deliver_alarm();
 231        } else {
 232                time_travel_set_time(next);
 233        }
 234
 235        if (time_travel_mode != TT_MODE_INFCPU) {
 236                if (time_travel_timer_mode == TT_TMR_PERIODIC)
 237                        os_timer_set_interval(time_travel_timer_interval);
 238                else if (time_travel_timer_mode == TT_TMR_ONESHOT)
 239                        os_timer_one_shot(time_travel_timer_expiry - next);
 240        }
 241}
 242
 243static void um_idle_sleep(void)
 244{
 245        unsigned long long duration = UM_NSEC_PER_SEC;
 246
 247        if (time_travel_mode != TT_MODE_OFF) {
 248                time_travel_sleep(duration);
 249        } else {
 250                os_idle_sleep(duration);
 251        }
 252}
 253
 254void arch_cpu_idle(void)
 255{
 256        cpu_tasks[current_thread_info()->cpu].pid = os_getpid();
 257        um_idle_sleep();
 258        local_irq_enable();
 259}
 260
 261int __cant_sleep(void) {
 262        return in_atomic() || irqs_disabled() || in_interrupt();
 263        /* Is in_interrupt() really needed? */
 264}
 265
 266int user_context(unsigned long sp)
 267{
 268        unsigned long stack;
 269
 270        stack = sp & (PAGE_MASK << CONFIG_KERNEL_STACK_ORDER);
 271        return stack != (unsigned long) current_thread_info();
 272}
 273
 274extern exitcall_t __uml_exitcall_begin, __uml_exitcall_end;
 275
 276void do_uml_exitcalls(void)
 277{
 278        exitcall_t *call;
 279
 280        call = &__uml_exitcall_end;
 281        while (--call >= &__uml_exitcall_begin)
 282                (*call)();
 283}
 284
 285char *uml_strdup(const char *string)
 286{
 287        return kstrdup(string, GFP_KERNEL);
 288}
 289EXPORT_SYMBOL(uml_strdup);
 290
 291int copy_to_user_proc(void __user *to, void *from, int size)
 292{
 293        return copy_to_user(to, from, size);
 294}
 295
 296int copy_from_user_proc(void *to, void __user *from, int size)
 297{
 298        return copy_from_user(to, from, size);
 299}
 300
 301int clear_user_proc(void __user *buf, int size)
 302{
 303        return clear_user(buf, size);
 304}
 305
 306int cpu(void)
 307{
 308        return current_thread_info()->cpu;
 309}
 310
 311static atomic_t using_sysemu = ATOMIC_INIT(0);
 312int sysemu_supported;
 313
 314void set_using_sysemu(int value)
 315{
 316        if (value > sysemu_supported)
 317                return;
 318        atomic_set(&using_sysemu, value);
 319}
 320
 321int get_using_sysemu(void)
 322{
 323        return atomic_read(&using_sysemu);
 324}
 325
 326static int sysemu_proc_show(struct seq_file *m, void *v)
 327{
 328        seq_printf(m, "%d\n", get_using_sysemu());
 329        return 0;
 330}
 331
 332static int sysemu_proc_open(struct inode *inode, struct file *file)
 333{
 334        return single_open(file, sysemu_proc_show, NULL);
 335}
 336
 337static ssize_t sysemu_proc_write(struct file *file, const char __user *buf,
 338                                 size_t count, loff_t *pos)
 339{
 340        char tmp[2];
 341
 342        if (copy_from_user(tmp, buf, 1))
 343                return -EFAULT;
 344
 345        if (tmp[0] >= '0' && tmp[0] <= '2')
 346                set_using_sysemu(tmp[0] - '0');
 347        /* We use the first char, but pretend to write everything */
 348        return count;
 349}
 350
 351static const struct file_operations sysemu_proc_fops = {
 352        .owner          = THIS_MODULE,
 353        .open           = sysemu_proc_open,
 354        .read           = seq_read,
 355        .llseek         = seq_lseek,
 356        .release        = single_release,
 357        .write          = sysemu_proc_write,
 358};
 359
 360int __init make_proc_sysemu(void)
 361{
 362        struct proc_dir_entry *ent;
 363        if (!sysemu_supported)
 364                return 0;
 365
 366        ent = proc_create("sysemu", 0600, NULL, &sysemu_proc_fops);
 367
 368        if (ent == NULL)
 369        {
 370                printk(KERN_WARNING "Failed to register /proc/sysemu\n");
 371                return 0;
 372        }
 373
 374        return 0;
 375}
 376
 377late_initcall(make_proc_sysemu);
 378
 379int singlestepping(void * t)
 380{
 381        struct task_struct *task = t ? t : current;
 382
 383        if (!(task->ptrace & PT_DTRACE))
 384                return 0;
 385
 386        if (task->thread.singlestep_syscall)
 387                return 1;
 388
 389        return 2;
 390}
 391
 392/*
 393 * Only x86 and x86_64 have an arch_align_stack().
 394 * All other arches have "#define arch_align_stack(x) (x)"
 395 * in their asm/exec.h
 396 * As this is included in UML from asm-um/system-generic.h,
 397 * we can use it to behave as the subarch does.
 398 */
 399#ifndef arch_align_stack
 400unsigned long arch_align_stack(unsigned long sp)
 401{
 402        if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
 403                sp -= get_random_int() % 8192;
 404        return sp & ~0xf;
 405}
 406#endif
 407
 408unsigned long get_wchan(struct task_struct *p)
 409{
 410        unsigned long stack_page, sp, ip;
 411        bool seen_sched = 0;
 412
 413        if ((p == NULL) || (p == current) || (p->state == TASK_RUNNING))
 414                return 0;
 415
 416        stack_page = (unsigned long) task_stack_page(p);
 417        /* Bail if the process has no kernel stack for some reason */
 418        if (stack_page == 0)
 419                return 0;
 420
 421        sp = p->thread.switch_buf->JB_SP;
 422        /*
 423         * Bail if the stack pointer is below the bottom of the kernel
 424         * stack for some reason
 425         */
 426        if (sp < stack_page)
 427                return 0;
 428
 429        while (sp < stack_page + THREAD_SIZE) {
 430                ip = *((unsigned long *) sp);
 431                if (in_sched_functions(ip))
 432                        /* Ignore everything until we're above the scheduler */
 433                        seen_sched = 1;
 434                else if (kernel_text_address(ip) && seen_sched)
 435                        return ip;
 436
 437                sp += sizeof(unsigned long);
 438        }
 439
 440        return 0;
 441}
 442
 443int elf_core_copy_fpregs(struct task_struct *t, elf_fpregset_t *fpu)
 444{
 445        int cpu = current_thread_info()->cpu;
 446
 447        return save_i387_registers(userspace_pid[cpu], (unsigned long *) fpu);
 448}
 449
 450