arch/um/sys-x86_64/syscalls.c

   1 /*
   2  * Copyright (C) 2003 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
   3  * Copyright 2003 PathScale, Inc.
   4  *
   5  * Licensed under the GPL
   6  */
   7
   8 #include "linux/linkage.h"
   9 #include "linux/personality.h"
  10 #include "linux/utsname.h"
  11 #include "asm/prctl.h" /* XXX This should get the constants from libc */
  12 #include "asm/uaccess.h"
  13 #include "os.h"
  14
  15 long arch_prctl(struct task_struct *task, int code, unsigned long __user *addr)
  16 {
  17         unsigned long *ptr = addr, tmp;
  18         long ret;
  19         int pid = task->mm->context.id.u.pid;
  20
  21         /*
  22          * With ARCH_SET_FS (and ARCH_SET_GS is treated similarly to
  23          * be safe), we need to call arch_prctl on the host because
  24          * setting %fs may result in something else happening (like a
  25          * GDT or thread.fs being set instead).  So, we let the host
  26          * fiddle the registers and thread struct and restore the
  27          * registers afterwards.
  28          *
  29          * So, the saved registers are stored to the process (this
  30          * needed because a stub may have been the last thing to run),
  31          * arch_prctl is run on the host, then the registers are read
  32          * back.
  33          */
  34         switch (code) {
  35         case ARCH_SET_FS:
  36         case ARCH_SET_GS:
  37                 ret = restore_registers(pid, &current->thread.regs.regs);
  38                 if (ret)
  39                         return ret;
  40                 break;
  41         case ARCH_GET_FS:
  42         case ARCH_GET_GS:
  43                 /*
  44                  * With these two, we read to a local pointer and
  45                  * put_user it to the userspace pointer that we were
  46                  * given.  If addr isn't valid (because it hasn't been
  47                  * faulted in or is just bogus), we want put_user to
  48                  * fault it in (or return -EFAULT) instead of having
  49                  * the host return -EFAULT.
  50                  */
  51                 ptr = &tmp;
  52         }
  53
  54         ret = os_arch_prctl(pid, code, ptr);
  55         if (ret)
  56                 return ret;
  57
  58         switch (code) {
  59         case ARCH_SET_FS:
  60                 current->thread.arch.fs = (unsigned long) ptr;
  61                 ret = save_registers(pid, &current->thread.regs.regs);
  62                 break;
  63         case ARCH_SET_GS:
  64                 ret = save_registers(pid, &current->thread.regs.regs);
  65                 break;
  66         case ARCH_GET_FS:
  67                 ret = put_user(tmp, addr);
  68                 break;
  69         case ARCH_GET_GS:
  70                 ret = put_user(tmp, addr);
  71                 break;
  72         }
  73
  74         return ret;
  75 }
  76
  77 long sys_arch_prctl(int code, unsigned long addr)
  78 {
  79         return arch_prctl(current, code, (unsigned long __user *) addr);
  80 }
  81
  82 long sys_clone(unsigned long clone_flags, unsigned long newsp,
  83                void __user *parent_tid, void __user *child_tid)
  84 {
  85         long ret;
  86
  87         if (!newsp)
  88                 newsp = UPT_SP(&current->thread.regs.regs);
  89         current->thread.forking = 1;
  90         ret = do_fork(clone_flags, newsp, &current->thread.regs, 0, parent_tid,
  91                       child_tid);
  92         current->thread.forking = 0;
  93         return ret;
  94 }
  95
  96 void arch_switch_to(struct task_struct *to)
  97 {
  98         if ((to->thread.arch.fs == 0) || (to->mm == NULL))
  99                 return;
 100
 101         arch_prctl(to, ARCH_SET_FS, (void __user *) to->thread.arch.fs);
 102 }