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1769608794
Various code in glibc uses __strnlen instead of strnlen for namespace reasons. However, __strnlen does not use libc_hidden_proto / libc_hidden_def (as is normally done for any function defined and called within the same library, whether or not exported from the library and whatever namespace it is in), so the compiler does not know that those calls are to a function within libc. This patch uses libc_hidden_proto / libc_hidden_def with __strnlen. On x86_64, it makes no difference to the installed stripped shared libraries. On 32-bit x86, it causes __strnlen calls to go to the same place as strnlen calls (the fallback strnlen implementation), rather than through a PLT entry for the strnlen IFUNC; I'm not sure of the logic behind when calls from within libc should use IFUNCs versus when they should go direct to a particular function implementation, but clearly it doesn't make sense for strnlen and __strnlen to be handled differently in this regard. Tested for x86_64 and x86 (testsuite, and comparison of installed shared libraries as described above). * string/strnlen.c [!STRNLEN] (__strnlen): Use libc_hidden_def. * include/string.h (__strnlen): Use libc_hidden_proto. * sysdeps/aarch64/strnlen.S (__strnlen): Use libc_hidden_def. * sysdeps/i386/i686/multiarch/strnlen-c.c [SHARED] (libc_hidden_def): Define __GI___strnlen as well as __GI_strnlen. * sysdeps/powerpc/powerpc32/power4/multiarch/strnlen-power7.S (libc_hidden_def): Undefine and redefine. * sysdeps/powerpc/powerpc32/power4/multiarch/strnlen-ppc32.c [SHARED] (libc_hidden_def): Define __GI___strnlen as well as __GI_strnlen. * sysdeps/powerpc/powerpc32/power7/strnlen.S (__strnlen): Use libc_hidden_def. * sysdeps/tile/tilegx/strnlen.c (__strnlen): Likewise.
58 lines
1.9 KiB
C
58 lines
1.9 KiB
C
/* Copyright (C) 2013-2015 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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<http://www.gnu.org/licenses/>. */
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#include <string.h>
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#include <stdint.h>
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#include "string-endian.h"
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/* Find the length of S, but scan at most MAXLEN characters. If no
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'\0' terminator is found in that many characters, return MAXLEN. */
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size_t
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__strnlen (const char *s, size_t maxlen)
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{
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/* When maxlen is 0, can't read any bytes or it might cause a page fault. */
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if (maxlen == 0)
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return 0;
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/* Get an aligned pointer. */
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const uintptr_t s_int = (uintptr_t) s;
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const uint64_t *p = (const uint64_t *) (s_int & -8);
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size_t bytes_read = sizeof (*p) - (s_int & (sizeof (*p) - 1));
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/* Read and MASK the first word. */
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uint64_t v = *p | MASK (s_int);
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uint64_t bits;
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while ((bits = __insn_v1cmpeqi (v, 0)) == 0)
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{
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if (bytes_read >= maxlen)
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{
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/* Read maxlen bytes and didn't find the terminator. */
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return maxlen;
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}
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v = *++p;
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bytes_read += sizeof (v);
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}
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/* Found '\0', check it is not larger than maxlen */
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size_t len = ((const char *) p) + (CFZ (bits) >> 3) - s;
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return (len < maxlen ? len : maxlen);
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}
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libc_hidden_def (__strnlen)
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weak_alias (__strnlen, strnlen)
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libc_hidden_def (strnlen)
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