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Tue Feb 13 00:12:12 1996 Roland McGrath <roland@charlie-brown.gnu.ai.mit.edu>
* sysdeps/i386/dl-machine.h (ELF_MACHINE_RUNTIME_TRAMPOLINE, elf_machine_relplt): New macros. * elf/dl-runtime.c: New file. * sysdeps/i386/dl-runtime.c, sysdeps/stub/dl-runtime.c: Files removed. * sysdeps/i386/dl-machine.h (ELF_MACHINE_RUNTIME_TRAMPOLINE, elf_machine_relplt): New macros. * elf/dl-runtime.c: New file. * sysdeps/i386/dl-runtime.c, sysdeps/stub/dl-runtime.c: Files removed.
This commit is contained in:
Roland McGrath
parent
dbdb6189d5
commit
38334018ff
@ -1,5 +1,10 @@
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Tue Feb 13 00:12:12 1996 Roland McGrath <roland@charlie-brown.gnu.ai.mit.edu>
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* sysdeps/i386/dl-machine.h (ELF_MACHINE_RUNTIME_TRAMPOLINE,
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elf_machine_relplt): New macros.
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* elf/dl-runtime.c: New file.
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* sysdeps/i386/dl-runtime.c, sysdeps/stub/dl-runtime.c: Files removed.
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* gmon/Makefile (headers): Remove machine-gmon.h.
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* sysdeps/stub/machine-gmon.h, sysdeps/i386/machine-gmon.h: Removed.
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* gmon/mcount.c [! NO_UNDERSCORES] (_mcount): Specify "mcount" as
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@ -1,5 +1,5 @@
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/* On-demand PLT fixup for shared objects. i386 version.
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Copyright (C) 1995 Free Software Foundation, Inc.
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/* On-demand PLT fixup for shared objects.
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Copyright (C) 1995, 1996 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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@ -20,28 +20,42 @@ Cambridge, MA 02139, USA. */
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#include <link.h>
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#include "dynamic-link.h"
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/* This function is not called in the normal way. The PLT jumps here, not
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using a call. The stack looks like this:
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/* Figure out the right type, Rel or Rela. */
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#define elf_machine_rel 1
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#define elf_machine_rela 2
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#if elf_machine_relplt == elf_machine_rel
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#define PLTREL Elf32_Rel
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#elif elf_machine_relplt == elf_machine_rela
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#define PLTREL Elf32_Rela
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#else
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#error "dl-machine.h bug: elf_machine_relplt not rel or rela"
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#endif
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#undef elf_machine_rel
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#undef elf_machine_rela
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-->8(%esp) address to return to the caller of the function in the PLT
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4(%esp) relocation offset for this PLT entry
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0(%esp) identifier for this shared object (struct link_map *)
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/* We need to define the function as a local symbol so that the reference
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in the trampoline code will be a local PC-relative call. Tell the
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compiler not to worry that the function appears not to be called. */
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The user expects the real function the PLT refers to to be entered
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with 8(%esp) as the top of stack. */
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static Elf32_Addr fixup (struct link_map *l, Elf32_Word reloc_offset)
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__attribute__ ((unused));
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void
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_dl_runtime_resolve (Elf32_Word reloc_offset)
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/* This function is called through a special trampoline from the PLT the
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first time each PLT entry is called. We must perform the relocation
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specified in the PLT of the given shared object, and return the resolved
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function address to the trampoline, which will restart the original call
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to that address. Future calls will bounce directly from the PLT to the
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function. */
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static Elf32_Addr
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fixup (struct link_map *l, Elf32_Word reloc_offset)
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{
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__label__ return_insn;
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struct link_map *l = (void *) (&reloc_offset)[-1];
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const Elf32_Sym *const symtab
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= (const Elf32_Sym *) (l->l_addr + l->l_info[DT_SYMTAB]->d_un.d_ptr);
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const char *strtab =
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(const char *) (l->l_addr + l->l_info[DT_STRTAB]->d_un.d_ptr);
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const Elf32_Rel *const reloc
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const PLTREL *const reloc
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= (const void *) (l->l_addr + l->l_info[DT_JMPREL]->d_un.d_ptr +
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reloc_offset);
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@ -72,23 +86,15 @@ _dl_runtime_resolve (Elf32_Word reloc_offset)
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l->l_prev->l_next = l;
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/* Apply the relocation with that value. */
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elf_machine_rel (l, reloc, loadbase, definer);
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elf_machine_relplt (l, reloc, loadbase, definer);
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/* The top of the stack is the word we set L from; but this location
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holds the address we will return to. Store there the address of a
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"ret" instruction, which will pop the stack and run the code at the
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address in the next stack word. */
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(&reloc_offset)[-1] = (Elf32_Word) &&return_insn;
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/* The next stack word is our argument RELOC_OFFSET; but that "ret" will
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pop and jump to this location, and the next stack word is the user's
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return address. So store here the resolved address of the function
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referred to by this PLT entry; once "ret" pops this address, the
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function in the shared object will run with the stack arranged just as
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when the user entered the PLT. */
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(&reloc_offset)[0] = *(Elf32_Word *) (l->l_addr + reloc->r_offset);
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return;
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return_insn: asm volatile ("ret");
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return *(Elf32_Addr *) (l->l_addr + reloc->r_offset);
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}
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/* This macro is defined in dl-machine.h to define the entry point called
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by the PLT. The `fixup' function above does the real work, but a little
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more twiddling is needed to get the stack right and jump to the address
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finally resolved. */
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ELF_MACHINE_RUNTIME_TRAMPOLINE
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@ -1,5 +1,5 @@
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/* Inline functions for dynamic linking.
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Copyright (C) 1995 Free Software Foundation, Inc.
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Copyright (C) 1995, 1996 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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@ -157,8 +157,20 @@ elf_machine_runtime_setup (struct link_map *l, int lazy)
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the offset on the stack, and then jump to the resolved address. */
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got[2] = (Elf32_Addr) &_dl_runtime_resolve;
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}
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}
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/* This code is used in dl-runtime.c to call the `fixup' function
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and then redirect to the address it returns. */
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#define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\
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.globl _dl_runtime_resolve
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.type _dl_runtime_resolve, @function
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_dl_runtime_resolve:
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call fixup # Args pushed by PLT.
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addl $8, %esp # Pop args.
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jmp *%eax # Jump to function address.
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");
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/* The PLT uses Elf32_Rel relocs. */
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#define elf_machine_relplt elf_machine_rel
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}
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/* Mask identifying addresses reserved for the user program,
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where the dynamic linker should not map anything. */
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@ -1,64 +0,0 @@
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/* On-demand PLT fixup for shared objects. Stub version.
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Copyright (C) 1995 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 Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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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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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If
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not, write to the Free Software Foundation, Inc., 675 Mass Ave,
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Cambridge, MA 02139, USA. */
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#include <link.h>
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#include "dynamic-link.h"
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/* This function is not called in the normal way. The PLT jumps here, not
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using a call. */
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void
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_dl_runtime_resolve ()
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{
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struct link_map *l = ???;
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Elf32_Word reloc_offset = ???;
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const Elf32_Sym *const symtab
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= (const Elf32_Sym *) l->l_info[DT_SYMTAB]->d_un.d_ptr;
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const char *strtab
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= ((void *) l->l_addr + l->l_info[DT_STRTAB]->d_un.d_ptr);
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const Elf32_Rel *const reloc = (void *) (l->l_info[DT_JMPREL]->d_un.d_ptr
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+ reloc_offset);
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const Elf32_Sym *definer;
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Elf32_Addr loadbase;
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struct link_map *scope, *real_next;
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/* Look up the symbol's run-time value. */
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real_next = l->l_next;
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if (l->l_info[DT_SYMBOLIC])
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{
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l->l_prev->l_next = real_next;
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l->l_next = _dl_loaded;
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scope = l;
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}
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else
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scope = _dl_loaded;
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definer = &symtab[ELF32_R_SYM (reloc->r_info)];
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loadbase = _dl_lookup_symbol (strtab + definer->st_name, &definer, scope);
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/* Restore list frobnication done above for DT_SYMBOLIC. */
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l->l_next = real_next;
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l->l_prev->l_next = l;
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/* Apply the relocation with that value. */
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elf_machine_rel (l->l_addr, l->l_info, reloc, loadbase, definer);
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}
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