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When an executable is invoked directly, we calculate $ORIGIN by calling
readlink on /proc/self/exe, which the Linux kernel resolves to the
target of any symlinks. However, if an executable is run through ld.so,
we cannot use /proc/self/exe and instead use the path given as an
argument. This leads to a different calculation of $ORIGIN, which is
most notable in that it causes ldd to behave differently (e.g., by not
finding a library) from directly running the program.
To make the behavior consistent, take advantage of the fact that the
kernel also resolves /proc/self/fd/ symlinks to the target of any
symlinks in the same manner, so once we have opened the main executable
in order to load it, replace the user-provided path with the result of
calling readlink("/proc/self/fd/N").
(On non-Linux platforms this resolution does not happen and so no
behavior change is needed.)
The __fd_to_filename requires _fitoa_word and _itoa_word, which for
32-bits pulls a lot of definitions from _itoa.c (due _ITOA_NEEDED
being defined). To simplify the build move the required function
to a new file, _fitoa_word.c.
Checked on x86_64-linux-gnu and i686-linux-gnu.
Co-authored-by: Geoffrey Thomas <geofft@ldpreload.com>
Reviewed-by: Geoffrey Thomas <geofft@ldpreload.com>
Tested-by: Geoffrey Thomas <geofft@ldpreload.com>
75 lines
2.7 KiB
C
75 lines
2.7 KiB
C
/* Internal function for converting integers to ASCII.
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Copyright (C) 1994-2025 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 _ITOA_H
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#define _ITOA_H
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#include <limits.h>
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/* When long long is different from long, by default, _itoa_word is
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provided to convert long to ASCII and _itoa is provided to convert
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long long. A sysdeps _itoa.h can define _ITOA_NEEDED to 0 and define
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_ITOA_WORD_TYPE to unsigned long long int to override it so that
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_itoa_word is changed to convert long long to ASCII and _itoa is
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mapped to _itoa_word. */
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#ifndef _ITOA_NEEDED
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# define _ITOA_NEEDED (LONG_MAX != LLONG_MAX)
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#endif
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#ifndef _ITOA_WORD_TYPE
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# define _ITOA_WORD_TYPE unsigned long int
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#endif
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/* Convert VALUE into ASCII in base BASE (2..36).
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Write backwards starting the character just before BUFLIM.
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Return the address of the first (left-to-right) character in the number.
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Use upper case letters iff UPPER_CASE is nonzero. */
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extern char *_itoa (unsigned long long int value, char *buflim,
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unsigned int base, int upper_case) attribute_hidden;
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extern const char _itoa_upper_digits[];
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extern const char _itoa_lower_digits[];
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#if IS_IN (libc) || IS_IN (rtld)
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hidden_proto (_itoa_upper_digits)
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hidden_proto (_itoa_lower_digits)
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#endif
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extern char *_itoa_word (_ITOA_WORD_TYPE value, char *buflim,
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unsigned int base,
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int upper_case) attribute_hidden;
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/* Similar to the _itoa functions, but output starts at buf and pointer
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after the last written character is returned. */
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extern char *_fitoa_word (_ITOA_WORD_TYPE value, char *buf,
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unsigned int base,
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int upper_case) attribute_hidden;
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extern char *_fitoa (unsigned long long value, char *buf, unsigned int base,
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int upper_case) attribute_hidden;
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#if !_ITOA_NEEDED
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/* No need for special long long versions. */
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# define _itoa(value, buf, base, upper_case) \
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_itoa_word (value, buf, base, upper_case)
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# define _fitoa(value, buf, base, upper_case) \
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_fitoa_word (value, buf, base, upper_case)
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#endif
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#endif /* itoa.h */
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