mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-30 00:31:08 +00:00
58 lines
2.8 KiB
C
58 lines
2.8 KiB
C
/* Resolve function pointers to VDSO functions.
|
|
Copyright (C) 2005-2023 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
|
|
<https://www.gnu.org/licenses/>. */
|
|
|
|
|
|
#ifndef _LIBC_POWERPC_VDSO_H
|
|
#define _LIBC_POWERPC_VDSO_H
|
|
|
|
#include <sysdep.h>
|
|
#include <sysdep-vdso.h>
|
|
|
|
#if (defined(__PPC64__) || defined(__powerpc64__)) && _CALL_ELF != 2
|
|
# include <dl-funcdesc.h>
|
|
/* 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 /* _LIBC_VDSO_H */
|