glibc/elf/dl-hwcaps_split.c
Florian Weimer dad90d5282 elf: Add glibc-hwcaps support for LD_LIBRARY_PATH
This hacks non-power-set processing into _dl_important_hwcaps.
Once the legacy hwcaps handling goes away, the subdirectory
handling needs to be reworked, but it is premature to do this
while both approaches are still supported.

ld.so supports two new arguments, --glibc-hwcaps-prepend and
--glibc-hwcaps-mask.  Each accepts a colon-separated list of
glibc-hwcaps subdirectory names.  The prepend option adds additional
subdirectories that are searched first, in the specified order.  The
mask option restricts the automatically selected subdirectories to
those listed in the option argument.  For example, on systems where
/usr/lib64 is on the library search path,
--glibc-hwcaps-prepend=valgrind:debug causes the dynamic loader to
search the directories /usr/lib64/glibc-hwcaps/valgrind and
/usr/lib64/glibc-hwcaps/debug just before /usr/lib64 is searched.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2020-12-04 09:13:43 +01:00

78 lines
2.2 KiB
C

/* Hardware capability support for run-time dynamic loader. String splitting.
Copyright (C) 2020 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <dl-hwcaps.h>
#include <stdbool.h>
#include <string.h>
_Bool
_dl_hwcaps_split (struct dl_hwcaps_split *s)
{
if (s->segment == NULL)
return false;
/* Skip over the previous segment. */
s->segment += s->length;
/* Consume delimiters. This also avoids returning an empty
segment. */
while (*s->segment == ':')
++s->segment;
if (*s->segment == '\0')
return false;
/* This could use strchrnul, but we would have to link the function
into ld.so for that. */
const char *colon = strchr (s->segment, ':');
if (colon == NULL)
s->length = strlen (s->segment);
else
s->length = colon - s->segment;
return true;
}
_Bool
_dl_hwcaps_split_masked (struct dl_hwcaps_split_masked *s)
{
while (true)
{
if (!_dl_hwcaps_split (&s->split))
return false;
bool active = s->bitmask & 1;
s->bitmask >>= 1;
if (active && _dl_hwcaps_contains (s->mask,
s->split.segment, s->split.length))
return true;
}
}
_Bool
_dl_hwcaps_contains (const char *hwcaps, const char *name, size_t name_length)
{
if (hwcaps == NULL)
return true;
struct dl_hwcaps_split split;
_dl_hwcaps_split_init (&split, hwcaps);
while (_dl_hwcaps_split (&split))
if (split.length == name_length
&& memcmp (split.segment, name, name_length) == 0)
return true;
return false;
}