1  /* arch_prctl call for Linux/x32.
       2     Copyright (C) 2012-2023 Free Software Foundation, Inc.
       3     This file is part of the GNU C Library.
       4  
       5     The GNU C Library is free software; you can redistribute it and/or
       6     modify it under the terms of the GNU Lesser General Public
       7     License as published by the Free Software Foundation; either
       8     version 2.1 of the License, or (at your option) any later version.
       9  
      10     The GNU C Library is distributed in the hope that it will be useful,
      11     but WITHOUT ANY WARRANTY; without even the implied warranty of
      12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      13     Lesser General Public License for more details.
      14  
      15     You should have received a copy of the GNU Lesser General Public
      16     License along with the GNU C Library; if not, see
      17     <https://www.gnu.org/licenses/>.  */
      18  
      19  #include <errno.h>
      20  #include <sys/prctl.h>
      21  #include <sys/syscall.h>
      22  #include <sysdep.h>
      23  #include <stdint.h>
      24  
      25  /* Since x32 arch_prctl stores 32-bit base address of segment registers
      26     %fs and %gs as unsigned 64-bit value via ARCH_GET_FS and ARCH_GET_GS,
      27     we use an unsigned 64-bit variable to hold the base address and copy
      28     it to ADDR after the system call returns.  */
      29  
      30  int
      31  __arch_prctl (int code, uintptr_t *addr)
      32  {
      33    int res;
      34    uint64_t addr64;
      35    void *prctl_arg = addr;
      36  
      37    switch (code)
      38      {
      39      case ARCH_GET_FS:
      40      case ARCH_GET_GS:
      41        prctl_arg = &addr64;
      42        break;
      43      }
      44  
      45    res = INLINE_SYSCALL (arch_prctl, 2, code, prctl_arg);
      46    if (res == 0)
      47      switch (code)
      48        {
      49        case ARCH_GET_FS:
      50        case ARCH_GET_GS:
      51  	 /* Check for a large value that overflows.  */
      52  	if ((uintptr_t) addr64 != addr64)
      53  	  {
      54  	    __set_errno (EOVERFLOW);
      55  	    return -1;
      56  	  }
      57  	*addr = (uintptr_t) addr64;
      58  	break;
      59        }
      60  
      61    return res;
      62  }
      63  weak_alias (__arch_prctl, arch_prctl)