sysdeps/unix/sysv/linux/setvmaname.c

   1 /* Utilities functions to name memory mappings.
   2    Copyright (C) 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 <ldsodefs.h>
  20 #include <setvmaname.h>
  21 #include <sys/prctl.h>
  22 #include <sysdep.h>
  23 #include <elf/dl-tunables.h>
  24
  25 /* If PR_SET_VMA_ANON_NAME is not supported by the kernel, prctl returns
  26    EINVAL.  However, it also returns the same error for invalid argument.
  27    Since it is an internal-only API, it assumes well formatted input:
  28    aligned START, with (START, START+LEN) being a valid memory range,
  29    and NAME with a limit of 80 characters without invalid one ("\\`$[]").  */
  30
  31 void
  32 __set_vma_name (void *start, size_t len, const char *name)
  33 {
  34   static int prctl_supported = 1;
  35   if (atomic_load_relaxed (&prctl_supported) == 0)
  36     return;
  37
  38   /* Set the prctl as not supported to avoid checking the tunable on every
  39      call.  */
  40   if (TUNABLE_GET (glibc, mem, decorate_maps, int32_t, NULL) != 0)
  41     {
  42       int r = INTERNAL_SYSCALL_CALL (prctl, PR_SET_VMA, PR_SET_VMA_ANON_NAME,
  43                                      start, len, name);
  44       if (r == 0 || r != -EINVAL)
  45         return;
  46     }
  47   atomic_store_relaxed (&prctl_supported, 0);
  48   return;
  49 }