1 files changed, 90 insertions, 0 deletions
diff --git a/arch/x86/um/syscalls_64.c b/arch/x86/um/syscalls_64.c
new file mode 100644
index 000000000..8249685b4
--- /dev/null
+++ b/arch/x86/um/syscalls_64.c
@@ -0,0 +1,90 @@
+/*
+ * Copyright (C) 2003 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ * Copyright 2003 PathScale, Inc.
+ *
+ * Licensed under the GPL
+ */
+
+#include <linux/sched.h>
+#include <linux/sched/mm.h>
+#include <linux/syscalls.h>
+#include <linux/uaccess.h>
+#include <asm/prctl.h> /* XXX This should get the constants from libc */
+#include <os.h>
+#include <registers.h>
+
+long arch_prctl(struct task_struct *task, int option,
+		unsigned long __user *arg2)
+{
+	unsigned long *ptr = arg2, tmp;
+	long ret;
+	int pid = task->mm->context.id.u.pid;
+
+	/*
+	 * With ARCH_SET_FS (and ARCH_SET_GS is treated similarly to
+	 * be safe), we need to call arch_prctl on the host because
+	 * setting %fs may result in something else happening (like a
+	 * GDT or thread.fs being set instead).  So, we let the host
+	 * fiddle the registers and thread struct and restore the
+	 * registers afterwards.
+	 *
+	 * So, the saved registers are stored to the process (this
+	 * needed because a stub may have been the last thing to run),
+	 * arch_prctl is run on the host, then the registers are read
+	 * back.
+	 */
+	switch (option) {
+	case ARCH_SET_FS:
+	case ARCH_SET_GS:
+		ret = restore_pid_registers(pid, &current->thread.regs.regs);
+		if (ret)
+			return ret;
+		break;
+	case ARCH_GET_FS:
+	case ARCH_GET_GS:
+		/*
+		 * With these two, we read to a local pointer and
+		 * put_user it to the userspace pointer that we were
+		 * given.  If addr isn't valid (because it hasn't been
+		 * faulted in or is just bogus), we want put_user to
+		 * fault it in (or return -EFAULT) instead of having
+		 * the host return -EFAULT.
+		 */
+		ptr = &tmp;
+	}
+
+	ret = os_arch_prctl(pid, option, ptr);
+	if (ret)
+		return ret;
+
+	switch (option) {
+	case ARCH_SET_FS:
+		current->thread.arch.fs = (unsigned long) ptr;
+		ret = save_registers(pid, &current->thread.regs.regs);
+		break;
+	case ARCH_SET_GS:
+		ret = save_registers(pid, &current->thread.regs.regs);
+		break;
+	case ARCH_GET_FS:
+		ret = put_user(tmp, arg2);
+		break;
+	case ARCH_GET_GS:
+		ret = put_user(tmp, arg2);
+		break;
+	}
+
+	return ret;
+}
+
+SYSCALL_DEFINE2(arch_prctl, int, option, unsigned long, arg2)
+{
+	return arch_prctl(current, option, (unsigned long __user *) arg2);
+}
+
+void arch_switch_to(struct task_struct *to)
+{
+	if ((to->thread.arch.fs == 0) || (to->mm == NULL))
+		return;
+
+	arch_prctl(to, ARCH_SET_FS, (void __user *) to->thread.arch.fs);
+}