/* Resolve function pointers to VDSO functions.

   Copyright (C) 2005-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or

   modify it under the terms of the GNU Lesser General Public

   License as published by the Free Software Foundation; either

   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with the GNU C Library; if not, see

   <http://www.gnu.org/licenses/>.  */

#ifndef _LIBC_VDSO_H

#define _LIBC_VDSO_H

#ifdef SHARED

#include <sysdep-vdso.h>

extern int (*VDSO_SYMBOL(gettimeofday)) (struct timeval *, void *)

  attribute_hidden;

extern int (*VDSO_SYMBOL(clock_gettime)) (clockid_t, struct timespec *);

extern int (*VDSO_SYMBOL(clock_getres)) (clockid_t, struct timespec *);

extern unsigned long long (*VDSO_SYMBOL(get_tbfreq)) (void);

extern int (*VDSO_SYMBOL(getcpu)) (unsigned *, unsigned *);

extern time_t (*VDSO_SYMBOL(time)) (time_t *);

#if defined(__PPC64__) || defined(__powerpc64__)

extern void *VDSO_SYMBOL(sigtramp_rt64);

#else

extern void *VDSO_SYMBOL(sigtramp32);

extern void *VDSO_SYMBOL(sigtramp_rt32);

#endif

#if (defined(__PPC64__) || defined(__powerpc64__)) && _CALL_ELF != 2

/* The correct solution is for _dl_vdso_vsym to return the address of the OPD

   for the kernel VDSO function.  That address would then be stored in the

   __vdso_* variables and returned as the result of the IFUNC resolver function.

   Yet, the kernel does not contain any OPD entries for the VDSO functions

   (incomplete implementation).  However, PLT relocations for IFUNCs still expect

   the address of an OPD to be returned from the IFUNC resolver function (since

   PLT entries on PPC64 are just copies of OPDs).  The solution for now is to

   create an artificial static OPD for each VDSO function returned by a resolver

   function.  The TOC value is set to a non-zero value to avoid triggering lazy

   symbol resolution via .glink0/.plt0 for a zero TOC (requires thread-safe PLT

   sequences) when the dynamic linker isn't prepared for it e.g. RTLD_NOW.  None

   of the kernel VDSO routines use the TOC or AUX values so any non-zero value

   will work.  Note that function pointer comparisons will not use this artificial

   static OPD since those are resolved via ADDR64 relocations and will point at

   the non-IFUNC default OPD for the symbol.  Lastly, because the IFUNC relocations

   are processed immediately at startup the resolver functions and this code need

   not be thread-safe, but if the caller writes to a PLT slot it must do so in a

   thread-safe manner with all the required barriers.  */

#define VDSO_IFUNC_RET(value)                            \

  ({                                                     \

    static Elf64_FuncDesc vdso_opd = { .fd_toc = ~0x0 }; \

    vdso_opd.fd_func = (Elf64_Addr)value;                \

    &vdso_opd;                                           \

  })

#else

#define VDSO_IFUNC_RET(value)  ((void *) (value))

#endif

#endif

#endif /* _LIBC_VDSO_H */