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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>
27 lines
930 B
C
27 lines
930 B
C
/* Test if $ORIGIN works correctly with symlinks (BZ 25263)
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Copyright (C) 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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extern void foo (void);
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int
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main (int argc, char *argv[])
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{
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foo ();
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return 0;
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}
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