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Linux/arch/x86/um/syscalls_64.c

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  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/sched.h>
  9 #include <asm/prctl.h> /* XXX This should get the constants from libc */
 10 #include <os.h>
 11 
 12 long arch_prctl(struct task_struct *task, int code, unsigned long __user *addr)
 13 {
 14         unsigned long *ptr = addr, tmp;
 15         long ret;
 16         int pid = task->mm->context.id.u.pid;
 17 
 18         /*
 19          * With ARCH_SET_FS (and ARCH_SET_GS is treated similarly to
 20          * be safe), we need to call arch_prctl on the host because
 21          * setting %fs may result in something else happening (like a
 22          * GDT or thread.fs being set instead).  So, we let the host
 23          * fiddle the registers and thread struct and restore the
 24          * registers afterwards.
 25          *
 26          * So, the saved registers are stored to the process (this
 27          * needed because a stub may have been the last thing to run),
 28          * arch_prctl is run on the host, then the registers are read
 29          * back.
 30          */
 31         switch (code) {
 32         case ARCH_SET_FS:
 33         case ARCH_SET_GS:
 34                 ret = restore_registers(pid, &current->thread.regs.regs);
 35                 if (ret)
 36                         return ret;
 37                 break;
 38         case ARCH_GET_FS:
 39         case ARCH_GET_GS:
 40                 /*
 41                  * With these two, we read to a local pointer and
 42                  * put_user it to the userspace pointer that we were
 43                  * given.  If addr isn't valid (because it hasn't been
 44                  * faulted in or is just bogus), we want put_user to
 45                  * fault it in (or return -EFAULT) instead of having
 46                  * the host return -EFAULT.
 47                  */
 48                 ptr = &tmp;
 49         }
 50 
 51         ret = os_arch_prctl(pid, code, ptr);
 52         if (ret)
 53                 return ret;
 54 
 55         switch (code) {
 56         case ARCH_SET_FS:
 57                 current->thread.arch.fs = (unsigned long) ptr;
 58                 ret = save_registers(pid, &current->thread.regs.regs);
 59                 break;
 60         case ARCH_SET_GS:
 61                 ret = save_registers(pid, &current->thread.regs.regs);
 62                 break;
 63         case ARCH_GET_FS:
 64                 ret = put_user(tmp, addr);
 65                 break;
 66         case ARCH_GET_GS:
 67                 ret = put_user(tmp, addr);
 68                 break;
 69         }
 70 
 71         return ret;
 72 }
 73 
 74 long sys_arch_prctl(int code, unsigned long addr)
 75 {
 76         return arch_prctl(current, code, (unsigned long __user *) addr);
 77 }
 78 
 79 void arch_switch_to(struct task_struct *to)
 80 {
 81         if ((to->thread.arch.fs == 0) || (to->mm == NULL))
 82                 return;
 83 
 84         arch_prctl(to, ARCH_SET_FS, (void __user *) to->thread.arch.fs);
 85 }
 86 

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