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db3476aff1
This commit puts all libio vtables in a dedicated, read-only ELF section, so that they are consecutive in memory. Before any indirect jump, the vtable pointer is checked against the section boundaries, and the process is terminated if the vtable pointer does not fall into the special ELF section. To enable backwards compatibility, a special flag variable (_IO_accept_foreign_vtables), protected by the pointer guard, avoids process termination if libio stream object constructor functions have been called earlier. Such constructor functions are called by the GCC 2.95 libstdc++ library, and this mechanism ensures compatibility with old binaries. Existing callers inside glibc of these functions are adjusted to call the original functions, not the wrappers which enable vtable compatiblity. The compatibility mechanism is used to enable passing FILE * objects across a static dlopen boundary, too.
110 lines
3.4 KiB
C
110 lines
3.4 KiB
C
/* Copyright (C) 1993-2016 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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<http://www.gnu.org/licenses/>.
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As a special exception, if you link the code in this file with
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files compiled with a GNU compiler to produce an executable,
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that does not cause the resulting executable to be covered by
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the GNU Lesser General Public License. This exception does not
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however invalidate any other reasons why the executable file
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might be covered by the GNU Lesser General Public License.
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This exception applies to code released by its copyright holders
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in files containing the exception. */
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#include "libioP.h"
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#include <fcntl.h>
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#include <stdlib.h>
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#include <stddef.h>
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#ifdef _LIBC
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# include <shlib-compat.h>
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#else
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# define _IO_new_fopen fopen
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#endif
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_IO_FILE *
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__fopen_maybe_mmap (_IO_FILE *fp)
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{
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#ifdef _G_HAVE_MMAP
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if ((fp->_flags2 & _IO_FLAGS2_MMAP) && (fp->_flags & _IO_NO_WRITES))
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{
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/* Since this is read-only, we might be able to mmap the contents
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directly. We delay the decision until the first read attempt by
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giving it a jump table containing functions that choose mmap or
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vanilla file operations and reset the jump table accordingly. */
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if (fp->_mode <= 0)
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_IO_JUMPS_FILE_plus (fp) = &_IO_file_jumps_maybe_mmap;
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else
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_IO_JUMPS_FILE_plus (fp) = &_IO_wfile_jumps_maybe_mmap;
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fp->_wide_data->_wide_vtable = &_IO_wfile_jumps_maybe_mmap;
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}
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#endif
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return fp;
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}
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_IO_FILE *
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__fopen_internal (const char *filename, const char *mode, int is32)
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{
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struct locked_FILE
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{
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struct _IO_FILE_plus fp;
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#ifdef _IO_MTSAFE_IO
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_IO_lock_t lock;
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#endif
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struct _IO_wide_data wd;
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} *new_f = (struct locked_FILE *) malloc (sizeof (struct locked_FILE));
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if (new_f == NULL)
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return NULL;
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#ifdef _IO_MTSAFE_IO
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new_f->fp.file._lock = &new_f->lock;
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#endif
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#if defined _LIBC || defined _GLIBCPP_USE_WCHAR_T
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_IO_no_init (&new_f->fp.file, 0, 0, &new_f->wd, &_IO_wfile_jumps);
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#else
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_IO_no_init (&new_f->fp.file, 1, 0, NULL, NULL);
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#endif
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_IO_JUMPS (&new_f->fp) = &_IO_file_jumps;
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_IO_new_file_init_internal (&new_f->fp);
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#if !_IO_UNIFIED_JUMPTABLES
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new_f->fp.vtable = NULL;
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#endif
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if (_IO_file_fopen ((_IO_FILE *) new_f, filename, mode, is32) != NULL)
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return __fopen_maybe_mmap (&new_f->fp.file);
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_IO_un_link (&new_f->fp);
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free (new_f);
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return NULL;
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}
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_IO_FILE *
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_IO_new_fopen (const char *filename, const char *mode)
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{
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return __fopen_internal (filename, mode, 1);
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}
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#ifdef _LIBC
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strong_alias (_IO_new_fopen, __new_fopen)
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versioned_symbol (libc, _IO_new_fopen, _IO_fopen, GLIBC_2_1);
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versioned_symbol (libc, __new_fopen, fopen, GLIBC_2_1);
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# if !defined O_LARGEFILE || O_LARGEFILE == 0
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weak_alias (_IO_new_fopen, _IO_fopen64)
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weak_alias (_IO_new_fopen, fopen64)
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# endif
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#endif
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