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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>
60 lines
1.8 KiB
C
60 lines
1.8 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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#include <_itoa.h>
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char *
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_itoa_word (_ITOA_WORD_TYPE value, char *buflim,
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unsigned int base, int upper_case)
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{
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const char *digits = (upper_case
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? _itoa_upper_digits
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: _itoa_lower_digits);
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switch (base)
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{
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#define SPECIAL(Base) \
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case Base: \
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do \
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*--buflim = digits[value % Base]; \
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while ((value /= Base) != 0); \
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break
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SPECIAL (10);
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SPECIAL (16);
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SPECIAL (8);
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default:
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do
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*--buflim = digits[value % base];
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while ((value /= base) != 0);
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}
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return buflim;
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}
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#undef SPECIAL
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char *
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_fitoa_word (_ITOA_WORD_TYPE value, char *buf, unsigned int base,
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int upper_case)
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{
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char tmpbuf[sizeof (value) * 4]; /* Worst case length: base 2. */
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char *cp = _itoa_word (value, tmpbuf + sizeof (value) * 4, base, upper_case);
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while (cp < tmpbuf + sizeof (value) * 4)
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*buf++ = *cp++;
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return buf;
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}
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