Fix objcopy for little-endian MIPS64 objects.
MIPS64 does not store the 'r_info' field of a relocation table entry as a 64-bit value consisting of a 32-bit symbol index in the high 32 bits and a 32-bit type in the low 32 bits as on other architectures. Instead, the 64-bit 'r_info' field is really a 32-bit symbol index followed by four individual byte type fields. For big-endian MIPS64, treating this as a 64-bit integer happens to be compatible with the layout expected by other architectures (symbol index in upper 32-bits of resulting "native" 64-bit integer). However, for little-endian MIPS64 the parsed 64-bit integer contains the symbol index in the low 32 bits and the 4 individual byte type fields in the upper 32-bits (but as if the upper 32-bits were byte-swapped). To cope, add two helper routines in gelf_getrel.c to translate between the correct native 'r_info' value and the value obtained after the normal byte-swap translation. Use these routines in gelf_getrel(), gelf_getrela(), gelf_update_rel(), and gelf_update_rela(). This fixes 'readelf -r' on little-endian MIPS64 objects which was previously decoding incorrect relocations as well as 'objcopy: invalid symbox index' warnings from objcopy when extracting debug symbols from kernel modules. Even with this fixed, objcopy was still crashing when trying to extract debug symbols from little-endian MIPS64 modules. The workaround in gelf_*rel*() depends on the current ELF object having a valid ELF header so that the 'e_machine' field can be compared against EM_MIPS. objcopy was parsing the relocation entries to possibly rewrite the 'r_info' fields in the update_relocs() function before writing the initial ELF header to the destination object file. Move the initial write of the ELF header earlier before copy_contents() so that update_relocs() uses the correct symbol index values. Note that this change should really go upstream. The binutils readelf source has a similar hack for MIPS64EL though I implemented this version from scratch using the MIPS64 ABI PDF as a reference. Discussed with: jkoshy Reviewed by: emaste, imp Approved by: re (gjb, kib) MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D15734
This commit is contained in:
parent
0125fb6352
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eb81f38a62
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=338478
@ -371,6 +371,14 @@ create_elf(struct elfcopy *ecp)
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if ((ecp->flags & SYMTAB_EXIST) != 0)
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create_symtab(ecp);
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/*
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* Write the underlying ehdr. Note that it should be called
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* before elf_setshstrndx() since it will overwrite e->e_shstrndx.
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*/
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if (gelf_update_ehdr(ecp->eout, &oeh) == 0)
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errx(EXIT_FAILURE, "gelf_update_ehdr() failed: %s",
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elf_errmsg(-1));
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/*
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* First processing of output sections: at this stage we copy the
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* content of each section from input to output object. Section
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@ -380,14 +388,6 @@ create_elf(struct elfcopy *ecp)
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*/
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copy_content(ecp);
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/*
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* Write the underlying ehdr. Note that it should be called
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* before elf_setshstrndx() since it will overwrite e->e_shstrndx.
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*/
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if (gelf_update_ehdr(ecp->eout, &oeh) == 0)
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errx(EXIT_FAILURE, "gelf_update_ehdr() failed: %s",
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elf_errmsg(-1));
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/* Generate section name string table (.shstrtab). */
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set_shstrtab(ecp);
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@ -35,6 +35,7 @@ SRCS= elf.c \
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gelf_ehdr.c \
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gelf_getclass.c \
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gelf_fsize.c \
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gelf_mips64el.c \
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gelf_move.c \
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gelf_phdr.c \
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gelf_rel.c \
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@ -216,12 +216,15 @@ int (*_libelf_get_translator(Elf_Type _t, int _direction, int _elfclass))
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void *_libelf_getphdr(Elf *_e, int _elfclass);
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void *_libelf_getshdr(Elf_Scn *_scn, int _elfclass);
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void _libelf_init_elf(Elf *_e, Elf_Kind _kind);
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int _libelf_is_mips64el(Elf *e);
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int _libelf_load_section_headers(Elf *e, void *ehdr);
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unsigned int _libelf_malign(Elf_Type _t, int _elfclass);
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Elf *_libelf_memory(unsigned char *_image, size_t _sz, int _reporterror);
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size_t _libelf_msize(Elf_Type _t, int _elfclass, unsigned int _version);
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void *_libelf_newphdr(Elf *_e, int _elfclass, size_t _count);
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Elf *_libelf_open_object(int _fd, Elf_Cmd _c, int _reporterror);
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Elf64_Xword _libelf_mips64el_r_info_tof(Elf64_Xword r_info);
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Elf64_Xword _libelf_mips64el_r_info_tom(Elf64_Xword r_info);
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struct _Libelf_Data *_libelf_release_data(struct _Libelf_Data *_d);
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Elf *_libelf_release_elf(Elf *_e);
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Elf_Scn *_libelf_release_scn(Elf_Scn *_s);
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81
contrib/elftoolchain/libelf/gelf_mips64el.c
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81
contrib/elftoolchain/libelf/gelf_mips64el.c
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@ -0,0 +1,81 @@
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/*-
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* Copyright (c) 2018 John Baldwin
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <gelf.h>
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#include "_libelf.h"
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ELFTC_VCSID("$Id$");
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int
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_libelf_is_mips64el(Elf *e)
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{
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return (e->e_kind == ELF_K_ELF && e->e_byteorder == ELFDATA2LSB &&
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e->e_u.e_elf.e_ehdr.e_ehdr64->e_machine == EM_MIPS);
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}
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/*
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* For MIPS64, the r_info field is actually stored as a 32-bit symbol
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* index (r_sym) followed by four single-byte fields (r_ssym, r_type3,
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* r_type2, and r_type). The byte-swap for the little-endian case
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* jumbles this incorrectly so compensate.
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*/
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Elf64_Xword
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_libelf_mips64el_r_info_tof(Elf64_Xword r_info)
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{
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Elf64_Xword new_info;
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uint8_t ssym, type3, type2, type;
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ssym = r_info >> 24;
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type3 = r_info >> 16;
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type2 = r_info >> 8;
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type = r_info;
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new_info = r_info >> 32;
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new_info |= (Elf64_Xword)ssym << 32;
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new_info |= (Elf64_Xword)type3 << 40;
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new_info |= (Elf64_Xword)type2 << 48;
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new_info |= (Elf64_Xword)type << 56;
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return (new_info);
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}
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Elf64_Xword
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_libelf_mips64el_r_info_tom(Elf64_Xword r_info)
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{
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Elf64_Xword new_info;
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uint8_t ssym, type3, type2, type;
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ssym = r_info >> 32;
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type3 = r_info >> 40;
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type2 = r_info >> 48;
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type = r_info >> 56;
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new_info = (r_info & 0xffffffff) << 32;
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new_info |= (Elf64_Xword)ssym << 24;
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new_info |= (Elf64_Xword)type3 << 16;
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new_info |= (Elf64_Xword)type2 << 8;
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new_info |= (Elf64_Xword)type;
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return (new_info);
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}
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@ -90,6 +90,9 @@ gelf_getrel(Elf_Data *ed, int ndx, GElf_Rel *dst)
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rel64 = (Elf64_Rel *) d->d_data.d_buf + ndx;
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*dst = *rel64;
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if (_libelf_is_mips64el(e))
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dst->r_info = _libelf_mips64el_r_info_tom(rel64->r_info);
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}
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return (dst);
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@ -156,6 +159,9 @@ gelf_update_rel(Elf_Data *ed, int ndx, GElf_Rel *dr)
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rel64 = (Elf64_Rel *) d->d_data.d_buf + ndx;
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*rel64 = *dr;
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if (_libelf_is_mips64el(e))
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rel64->r_info = _libelf_mips64el_r_info_tof(dr->r_info);
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}
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return (1);
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@ -91,6 +91,10 @@ gelf_getrela(Elf_Data *ed, int ndx, GElf_Rela *dst)
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rela64 = (Elf64_Rela *) d->d_data.d_buf + ndx;
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*dst = *rela64;
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if (_libelf_is_mips64el(e))
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dst->r_info =
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_libelf_mips64el_r_info_tom(rela64->r_info);
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}
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return (dst);
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@ -159,6 +163,9 @@ gelf_update_rela(Elf_Data *ed, int ndx, GElf_Rela *dr)
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rela64 = (Elf64_Rela *) d->d_data.d_buf + ndx;
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*rela64 = *dr;
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if (_libelf_is_mips64el(e))
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rela64->r_info = _libelf_mips64el_r_info_tof(dr->r_info);
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}
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return (1);
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@ -60,7 +60,7 @@
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* in the range 5 to 9.
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*/
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#undef __FreeBSD_version
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#define __FreeBSD_version 1200083 /* Master, propagated to newvers */
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#define __FreeBSD_version 1200084 /* Master, propagated to newvers */
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/*
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* __FreeBSD_kernel__ indicates that this system uses the kernel of FreeBSD,
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