v4.19.13 snapshot.
diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
new file mode 100644
index 0000000..691b83b
--- /dev/null
+++ b/arch/um/kernel/process.c
@@ -0,0 +1,401 @@
+/*
+ * Copyright (C) 2015 Anton Ivanov (aivanov@{brocade.com,kot-begemot.co.uk})
+ * Copyright (C) 2015 Thomas Meyer (thomas@m3y3r.de)
+ * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ * Copyright 2003 PathScale, Inc.
+ * Licensed under the GPL
+ */
+
+#include <linux/stddef.h>
+#include <linux/err.h>
+#include <linux/hardirq.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/personality.h>
+#include <linux/proc_fs.h>
+#include <linux/ptrace.h>
+#include <linux/random.h>
+#include <linux/slab.h>
+#include <linux/sched.h>
+#include <linux/sched/debug.h>
+#include <linux/sched/task.h>
+#include <linux/sched/task_stack.h>
+#include <linux/seq_file.h>
+#include <linux/tick.h>
+#include <linux/threads.h>
+#include <linux/tracehook.h>
+#include <asm/current.h>
+#include <asm/pgtable.h>
+#include <asm/mmu_context.h>
+#include <linux/uaccess.h>
+#include <as-layout.h>
+#include <kern_util.h>
+#include <os.h>
+#include <skas.h>
+#include <timer-internal.h>
+
+/*
+ * This is a per-cpu array. A processor only modifies its entry and it only
+ * cares about its entry, so it's OK if another processor is modifying its
+ * entry.
+ */
+struct cpu_task cpu_tasks[NR_CPUS] = { [0 ... NR_CPUS - 1] = { -1, NULL } };
+
+static inline int external_pid(void)
+{
+ /* FIXME: Need to look up userspace_pid by cpu */
+ return userspace_pid[0];
+}
+
+int pid_to_processor_id(int pid)
+{
+ int i;
+
+ for (i = 0; i < ncpus; i++) {
+ if (cpu_tasks[i].pid == pid)
+ return i;
+ }
+ return -1;
+}
+
+void free_stack(unsigned long stack, int order)
+{
+ free_pages(stack, order);
+}
+
+unsigned long alloc_stack(int order, int atomic)
+{
+ unsigned long page;
+ gfp_t flags = GFP_KERNEL;
+
+ if (atomic)
+ flags = GFP_ATOMIC;
+ page = __get_free_pages(flags, order);
+
+ return page;
+}
+
+static inline void set_current(struct task_struct *task)
+{
+ cpu_tasks[task_thread_info(task)->cpu] = ((struct cpu_task)
+ { external_pid(), task });
+}
+
+extern void arch_switch_to(struct task_struct *to);
+
+void *__switch_to(struct task_struct *from, struct task_struct *to)
+{
+ to->thread.prev_sched = from;
+ set_current(to);
+
+ switch_threads(&from->thread.switch_buf, &to->thread.switch_buf);
+ arch_switch_to(current);
+
+ return current->thread.prev_sched;
+}
+
+void interrupt_end(void)
+{
+ struct pt_regs *regs = ¤t->thread.regs;
+
+ if (need_resched())
+ schedule();
+ if (test_thread_flag(TIF_SIGPENDING))
+ do_signal(regs);
+ if (test_and_clear_thread_flag(TIF_NOTIFY_RESUME))
+ tracehook_notify_resume(regs);
+}
+
+int get_current_pid(void)
+{
+ return task_pid_nr(current);
+}
+
+/*
+ * This is called magically, by its address being stuffed in a jmp_buf
+ * and being longjmp-d to.
+ */
+void new_thread_handler(void)
+{
+ int (*fn)(void *), n;
+ void *arg;
+
+ if (current->thread.prev_sched != NULL)
+ schedule_tail(current->thread.prev_sched);
+ current->thread.prev_sched = NULL;
+
+ fn = current->thread.request.u.thread.proc;
+ arg = current->thread.request.u.thread.arg;
+
+ /*
+ * callback returns only if the kernel thread execs a process
+ */
+ n = fn(arg);
+ userspace(¤t->thread.regs.regs, current_thread_info()->aux_fp_regs);
+}
+
+/* Called magically, see new_thread_handler above */
+void fork_handler(void)
+{
+ force_flush_all();
+
+ schedule_tail(current->thread.prev_sched);
+
+ /*
+ * XXX: if interrupt_end() calls schedule, this call to
+ * arch_switch_to isn't needed. We could want to apply this to
+ * improve performance. -bb
+ */
+ arch_switch_to(current);
+
+ current->thread.prev_sched = NULL;
+
+ userspace(¤t->thread.regs.regs, current_thread_info()->aux_fp_regs);
+}
+
+int copy_thread(unsigned long clone_flags, unsigned long sp,
+ unsigned long arg, struct task_struct * p)
+{
+ void (*handler)(void);
+ int kthread = current->flags & PF_KTHREAD;
+ int ret = 0;
+
+ p->thread = (struct thread_struct) INIT_THREAD;
+
+ if (!kthread) {
+ memcpy(&p->thread.regs.regs, current_pt_regs(),
+ sizeof(p->thread.regs.regs));
+ PT_REGS_SET_SYSCALL_RETURN(&p->thread.regs, 0);
+ if (sp != 0)
+ REGS_SP(p->thread.regs.regs.gp) = sp;
+
+ handler = fork_handler;
+
+ arch_copy_thread(¤t->thread.arch, &p->thread.arch);
+ } else {
+ get_safe_registers(p->thread.regs.regs.gp, p->thread.regs.regs.fp);
+ p->thread.request.u.thread.proc = (int (*)(void *))sp;
+ p->thread.request.u.thread.arg = (void *)arg;
+ handler = new_thread_handler;
+ }
+
+ new_thread(task_stack_page(p), &p->thread.switch_buf, handler);
+
+ if (!kthread) {
+ clear_flushed_tls(p);
+
+ /*
+ * Set a new TLS for the child thread?
+ */
+ if (clone_flags & CLONE_SETTLS)
+ ret = arch_copy_tls(p);
+ }
+
+ return ret;
+}
+
+void initial_thread_cb(void (*proc)(void *), void *arg)
+{
+ int save_kmalloc_ok = kmalloc_ok;
+
+ kmalloc_ok = 0;
+ initial_thread_cb_skas(proc, arg);
+ kmalloc_ok = save_kmalloc_ok;
+}
+
+void arch_cpu_idle(void)
+{
+ cpu_tasks[current_thread_info()->cpu].pid = os_getpid();
+ os_idle_sleep(UM_NSEC_PER_SEC);
+ local_irq_enable();
+}
+
+int __cant_sleep(void) {
+ return in_atomic() || irqs_disabled() || in_interrupt();
+ /* Is in_interrupt() really needed? */
+}
+
+int user_context(unsigned long sp)
+{
+ unsigned long stack;
+
+ stack = sp & (PAGE_MASK << CONFIG_KERNEL_STACK_ORDER);
+ return stack != (unsigned long) current_thread_info();
+}
+
+extern exitcall_t __uml_exitcall_begin, __uml_exitcall_end;
+
+void do_uml_exitcalls(void)
+{
+ exitcall_t *call;
+
+ call = &__uml_exitcall_end;
+ while (--call >= &__uml_exitcall_begin)
+ (*call)();
+}
+
+char *uml_strdup(const char *string)
+{
+ return kstrdup(string, GFP_KERNEL);
+}
+EXPORT_SYMBOL(uml_strdup);
+
+int copy_to_user_proc(void __user *to, void *from, int size)
+{
+ return copy_to_user(to, from, size);
+}
+
+int copy_from_user_proc(void *to, void __user *from, int size)
+{
+ return copy_from_user(to, from, size);
+}
+
+int clear_user_proc(void __user *buf, int size)
+{
+ return clear_user(buf, size);
+}
+
+int cpu(void)
+{
+ return current_thread_info()->cpu;
+}
+
+static atomic_t using_sysemu = ATOMIC_INIT(0);
+int sysemu_supported;
+
+void set_using_sysemu(int value)
+{
+ if (value > sysemu_supported)
+ return;
+ atomic_set(&using_sysemu, value);
+}
+
+int get_using_sysemu(void)
+{
+ return atomic_read(&using_sysemu);
+}
+
+static int sysemu_proc_show(struct seq_file *m, void *v)
+{
+ seq_printf(m, "%d\n", get_using_sysemu());
+ return 0;
+}
+
+static int sysemu_proc_open(struct inode *inode, struct file *file)
+{
+ return single_open(file, sysemu_proc_show, NULL);
+}
+
+static ssize_t sysemu_proc_write(struct file *file, const char __user *buf,
+ size_t count, loff_t *pos)
+{
+ char tmp[2];
+
+ if (copy_from_user(tmp, buf, 1))
+ return -EFAULT;
+
+ if (tmp[0] >= '0' && tmp[0] <= '2')
+ set_using_sysemu(tmp[0] - '0');
+ /* We use the first char, but pretend to write everything */
+ return count;
+}
+
+static const struct file_operations sysemu_proc_fops = {
+ .owner = THIS_MODULE,
+ .open = sysemu_proc_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = single_release,
+ .write = sysemu_proc_write,
+};
+
+int __init make_proc_sysemu(void)
+{
+ struct proc_dir_entry *ent;
+ if (!sysemu_supported)
+ return 0;
+
+ ent = proc_create("sysemu", 0600, NULL, &sysemu_proc_fops);
+
+ if (ent == NULL)
+ {
+ printk(KERN_WARNING "Failed to register /proc/sysemu\n");
+ return 0;
+ }
+
+ return 0;
+}
+
+late_initcall(make_proc_sysemu);
+
+int singlestepping(void * t)
+{
+ struct task_struct *task = t ? t : current;
+
+ if (!(task->ptrace & PT_DTRACE))
+ return 0;
+
+ if (task->thread.singlestep_syscall)
+ return 1;
+
+ return 2;
+}
+
+/*
+ * Only x86 and x86_64 have an arch_align_stack().
+ * All other arches have "#define arch_align_stack(x) (x)"
+ * in their asm/exec.h
+ * As this is included in UML from asm-um/system-generic.h,
+ * we can use it to behave as the subarch does.
+ */
+#ifndef arch_align_stack
+unsigned long arch_align_stack(unsigned long sp)
+{
+ if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
+ sp -= get_random_int() % 8192;
+ return sp & ~0xf;
+}
+#endif
+
+unsigned long get_wchan(struct task_struct *p)
+{
+ unsigned long stack_page, sp, ip;
+ bool seen_sched = 0;
+
+ if ((p == NULL) || (p == current) || (p->state == TASK_RUNNING))
+ return 0;
+
+ stack_page = (unsigned long) task_stack_page(p);
+ /* Bail if the process has no kernel stack for some reason */
+ if (stack_page == 0)
+ return 0;
+
+ sp = p->thread.switch_buf->JB_SP;
+ /*
+ * Bail if the stack pointer is below the bottom of the kernel
+ * stack for some reason
+ */
+ if (sp < stack_page)
+ return 0;
+
+ while (sp < stack_page + THREAD_SIZE) {
+ ip = *((unsigned long *) sp);
+ if (in_sched_functions(ip))
+ /* Ignore everything until we're above the scheduler */
+ seen_sched = 1;
+ else if (kernel_text_address(ip) && seen_sched)
+ return ip;
+
+ sp += sizeof(unsigned long);
+ }
+
+ return 0;
+}
+
+int elf_core_copy_fpregs(struct task_struct *t, elf_fpregset_t *fpu)
+{
+ int cpu = current_thread_info()->cpu;
+
+ return save_i387_registers(userspace_pid[cpu], (unsigned long *) fpu);
+}
+