sysdeps/unix/sysv/linux/powerpc/libc-vdso.h

   1 /* Resolve function pointers to VDSO functions.
   2    Copyright (C) 2005-2015 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    <http://www.gnu.org/licenses/>.  */
  18
  19
  20 #ifndef _LIBC_VDSO_H
  21 #define _LIBC_VDSO_H
  22
  23 #ifdef SHARED
  24
  25 #include <sysdep-vdso.h>
  26
  27 extern int (*VDSO_SYMBOL(gettimeofday)) (struct timeval *, void *)
  28   attribute_hidden;
  29 extern int (*VDSO_SYMBOL(clock_gettime)) (clockid_t, struct timespec *);
  30 extern int (*VDSO_SYMBOL(clock_getres)) (clockid_t, struct timespec *);
  31 extern unsigned long long (*VDSO_SYMBOL(get_tbfreq)) (void);
  32 extern int (*VDSO_SYMBOL(getcpu)) (unsigned *, unsigned *);
  33 extern time_t (*VDSO_SYMBOL(time)) (time_t *);
  34
  35 #if defined(__PPC64__) || defined(__powerpc64__)
  36 extern void *VDSO_SYMBOL(sigtramp_rt64);
  37 #else
  38 extern void *VDSO_SYMBOL(sigtramp32);
  39 extern void *VDSO_SYMBOL(sigtramp_rt32);
  40 #endif
  41
  42 #if (defined(__PPC64__) || defined(__powerpc64__)) && _CALL_ELF != 2
  43 /* The correct solution is for _dl_vdso_vsym to return the address of the OPD
  44    for the kernel VDSO function.  That address would then be stored in the
  45    __vdso_* variables and returned as the result of the IFUNC resolver function.
  46    Yet, the kernel does not contain any OPD entries for the VDSO functions
  47    (incomplete implementation).  However, PLT relocations for IFUNCs still expect
  48    the address of an OPD to be returned from the IFUNC resolver function (since
  49    PLT entries on PPC64 are just copies of OPDs).  The solution for now is to
  50    create an artificial static OPD for each VDSO function returned by a resolver
  51    function.  The TOC value is set to a non-zero value to avoid triggering lazy
  52    symbol resolution via .glink0/.plt0 for a zero TOC (requires thread-safe PLT
  53    sequences) when the dynamic linker isn't prepared for it e.g. RTLD_NOW.  None
  54    of the kernel VDSO routines use the TOC or AUX values so any non-zero value
  55    will work.  Note that function pointer comparisons will not use this artificial
  56    static OPD since those are resolved via ADDR64 relocations and will point at
  57    the non-IFUNC default OPD for the symbol.  Lastly, because the IFUNC relocations
  58    are processed immediately at startup the resolver functions and this code need
  59    not be thread-safe, but if the caller writes to a PLT slot it must do so in a
  60    thread-safe manner with all the required barriers.  */
  61 #define VDSO_IFUNC_RET(value)                            \
  62   ({                                                     \
  63     static Elf64_FuncDesc vdso_opd = { .fd_toc = ~0x0 }; \
  64     vdso_opd.fd_func = (Elf64_Addr)value;                \
  65     &vdso_opd;                                           \
  66   })
  67
  68 #else
  69 #define VDSO_IFUNC_RET(value)  ((void *) (value))
  70 #endif
  71
  72 #endif
  73
  74 #endif /* _LIBC_VDSO_H */