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3a0ecccb59
Exporting functions and relying on symbol interposition from libc.so
makes the choice of implementation dependent on DT_NEEDED order, which
is not what some compiler drivers expect.
This commit replaces one magic mechanism (symbol interposition) with
another one (preprocessor-/compiler-based redirection). This makes
the hand-over from the minimal malloc to the full malloc more
explicit.
Removing the ABI symbols is backwards-compatible because libc.so is
always in scope, and the dynamic loader will find the malloc-related
symbols there since commit f0b2132b35
("ld.so: Support moving versioned symbols between sonames
[BZ #24741]").
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
86 lines
2.8 KiB
C
86 lines
2.8 KiB
C
/* Redirection of malloc inside the dynamic linker.
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Copyright (C) 2020 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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/* The dynamic linker needs to use its own minimal malloc before libc
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has been relocated, and the libc malloc afterwards. The active
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malloc implementation is reached via the __rtld_* function pointers
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declared below. They are initialized to the minimal malloc by
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__rtld_malloc_init_stubs, and set to the final implementation by
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__rtld_malloc_init_real. */
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#ifndef _RTLD_MALLOC_H
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#define _RTLD_MALLOC_H
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#if IS_IN (rtld)
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extern __typeof (calloc) *__rtld_calloc attribute_hidden;
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extern __typeof (free) *__rtld_free attribute_hidden;
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extern __typeof (malloc) *__rtld_malloc attribute_hidden;
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extern __typeof (realloc) *__rtld_realloc attribute_hidden;
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/* Wrapper functions which call through the function pointers above.
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Note that it is not supported to take the address of those
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functions. Instead the function pointers must be used
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directly. */
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__extern_inline void *
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calloc (size_t a, size_t b)
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{
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return __rtld_calloc (a, b);
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}
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__extern_inline void
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free (void *ptr)
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{
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__rtld_free (ptr);
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}
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__extern_inline void *
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malloc (size_t size)
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{
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return __rtld_malloc (size);
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}
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__extern_inline void *
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realloc (void *ptr, size_t size)
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{
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return __rtld_realloc (ptr, size);
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}
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/* Called after the first self-relocation to activate the minimal malloc
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implementation. */
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void __rtld_malloc_init_stubs (void) attribute_hidden;
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/* Called shortly before the final self-relocation (when RELRO
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variables are still writable) to activate the real malloc
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implementation. MAIN_MAP is the link map of the executable. */
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struct link_map;
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void __rtld_malloc_init_real (struct link_map *main_map) attribute_hidden;
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#else /* !IS_IN (rtld) */
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/* This allows static/non-rtld builds to get a pointer to the
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functions, in the same way that is required inside rtld. */
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# define __rtld_calloc (&calloc)
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# define __rtld_free (&free)
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# define __rtld_malloc (&malloc)
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# define __rtld_realloc (&realloc)
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#endif /* !IS_IN (rtld) */
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#endif /* _RTLD_MALLOC_H */
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