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68 lines
3.0 KiB
C
68 lines
3.0 KiB
C
/* Resolve function pointers to VDSO functions.
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Copyright (C) 2005-2020 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#ifndef _LIBC_POWERPC_VDSO_H
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#define _LIBC_POWERPC_VDSO_H
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#include <sysdep.h>
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#include <sysdep-vdso.h>
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#if (defined(__PPC64__) || defined(__powerpc64__)) && _CALL_ELF != 2
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# include <dl-machine.h>
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/* The correct solution is for _dl_vdso_vsym to return the address of the OPD
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for the kernel VDSO function. That address would then be stored in the
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__vdso_* variables and returned as the result of the IFUNC resolver function.
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Yet, the kernel does not contain any OPD entries for the VDSO functions
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(incomplete implementation). However, PLT relocations for IFUNCs still expect
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the address of an OPD to be returned from the IFUNC resolver function (since
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PLT entries on PPC64 are just copies of OPDs). The solution for now is to
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create an artificial static OPD for each VDSO function returned by a resolver
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function. The TOC value is set to a non-zero value to avoid triggering lazy
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symbol resolution via .glink0/.plt0 for a zero TOC (requires thread-safe PLT
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sequences) when the dynamic linker isn't prepared for it e.g. RTLD_NOW. None
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of the kernel VDSO routines use the TOC or AUX values so any non-zero value
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will work. Note that function pointer comparisons will not use this artificial
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static OPD since those are resolved via ADDR64 relocations and will point at
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the non-IFUNC default OPD for the symbol. Lastly, because the IFUNC relocations
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are processed immediately at startup the resolver functions and this code need
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not be thread-safe, but if the caller writes to a PLT slot it must do so in a
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thread-safe manner with all the required barriers. */
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# define VDSO_IFUNC_RET(value) \
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({ \
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static Elf64_FuncDesc vdso_opd = { .fd_toc = ~0x0 }; \
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vdso_opd.fd_func = (Elf64_Addr)value; \
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&vdso_opd; \
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})
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#else
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# define VDSO_IFUNC_RET(value) ((void *) (value))
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#endif
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#include_next <libc-vdso.h>
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extern unsigned long long (*VDSO_SYMBOL(get_tbfreq)) (void);
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#if defined(__PPC64__) || defined(__powerpc64__)
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extern void *VDSO_SYMBOL(sigtramp_rt64);
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#else
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extern void *VDSO_SYMBOL(sigtramp32);
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extern void *VDSO_SYMBOL(sigtramp_rt32);
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#endif
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#endif /* _LIBC_VDSO_H */
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