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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.
116 lines
3.3 KiB
C
116 lines
3.3 KiB
C
/* Print output of stream to given obstack.
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Copyright (C) 1996-2016 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
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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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#include <stdlib.h>
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#include <libioP.h>
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#include "../libio/strfile.h"
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#include <assert.h>
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#include <string.h>
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#include <errno.h>
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#include <obstack.h>
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#include <stdarg.h>
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#include <stdio_ext.h>
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struct _IO_obstack_file
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{
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struct _IO_FILE_plus file;
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struct obstack *obstack;
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};
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extern const struct _IO_jump_t _IO_obstack_jumps libio_vtable attribute_hidden;
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int
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__obstack_vprintf_chk (struct obstack *obstack, int flags, const char *format,
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va_list args)
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{
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struct obstack_FILE
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{
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struct _IO_obstack_file ofile;
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} new_f;
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int result;
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int size;
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int room;
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#ifdef _IO_MTSAFE_IO
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new_f.ofile.file.file._lock = NULL;
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#endif
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_IO_no_init (&new_f.ofile.file.file, _IO_USER_LOCK, -1, NULL, NULL);
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_IO_JUMPS (&new_f.ofile.file) = &_IO_obstack_jumps;
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room = obstack_room (obstack);
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size = obstack_object_size (obstack) + room;
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if (size == 0)
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{
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/* We have to handle the allocation a bit different since the
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`_IO_str_init_static' function would handle a size of zero
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different from what we expect. */
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/* Get more memory. */
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obstack_make_room (obstack, 64);
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/* Recompute how much room we have. */
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room = obstack_room (obstack);
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size = room;
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assert (size != 0);
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}
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_IO_str_init_static_internal ((struct _IO_strfile_ *) &new_f.ofile,
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obstack_base (obstack),
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size, obstack_next_free (obstack));
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/* Now allocate the rest of the current chunk. */
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assert (size == (new_f.ofile.file.file._IO_write_end
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- new_f.ofile.file.file._IO_write_base));
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assert (new_f.ofile.file.file._IO_write_ptr
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== (new_f.ofile.file.file._IO_write_base
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+ obstack_object_size (obstack)));
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obstack_blank_fast (obstack, room);
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new_f.ofile.obstack = obstack;
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/* For flags > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
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can only come from read-only format strings. */
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if (flags > 0)
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new_f.ofile.file.file._flags2 |= _IO_FLAGS2_FORTIFY;
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result = _IO_vfprintf (&new_f.ofile.file.file, format, args);
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/* Shrink the buffer to the space we really currently need. */
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obstack_blank_fast (obstack, (new_f.ofile.file.file._IO_write_ptr
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- new_f.ofile.file.file._IO_write_end));
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return result;
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}
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libc_hidden_def (__obstack_vprintf_chk)
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int
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__obstack_printf_chk (struct obstack *obstack, int flags, const char *format,
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...)
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{
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int result;
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va_list ap;
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va_start (ap, format);
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result = __obstack_vprintf_chk (obstack, flags, format, ap);
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va_end (ap);
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return result;
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}
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