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/* Hardware capability support for run-time dynamic loader.
Copyright (C) 2012-2020 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 <assert.h>
#include <elf.h>
#include <errno.h>
#include <libintl.h>
#include <unistd.h>
#include <ldsodefs.h>
#include <dl-procinfo.h>
#include <dl-hwcaps.h>
/* Return an array of useful/necessary hardware capability names. */
const struct r_strlenpair *
_dl_important_hwcaps (size_t *sz, size_t *max_capstrlen)
{
uint64_t hwcap_mask = GET_HWCAP_MASK();
/* Determine how many important bits are set. */
uint64_t masked = GLRO(dl_hwcap) & hwcap_mask;
size_t cnt = GLRO (dl_platform) != NULL;
size_t n, m;
size_t total;
struct r_strlenpair *result;
struct r_strlenpair *rp;
char *cp;
/* Count the number of bits set in the masked value. */
for (n = 0; (~((1ULL << n) - 1) & masked) != 0; ++n)
if ((masked & (1ULL << n)) != 0)
++cnt;
/* For TLS enabled builds always add 'tls'. */
++cnt;
/* Create temporary data structure to generate result table. */
struct r_strlenpair temp[cnt];
m = 0;
for (n = 0; masked != 0; ++n)
if ((masked & (1ULL << n)) != 0)
{
temp[m].str = _dl_hwcap_string (n);
temp[m].len = strlen (temp[m].str);
masked ^= 1ULL << n;
++m;
}
if (GLRO (dl_platform) != NULL)
{
temp[m].str = GLRO (dl_platform);
temp[m].len = GLRO (dl_platformlen);
++m;
}
temp[m].str = "tls";
temp[m].len = 3;
++m;
assert (m == cnt);
/* Determine the total size of all strings together. */
if (cnt == 1)
total = temp[0].len + 1;
else
{
total = temp[0].len + temp[cnt - 1].len + 2;
if (cnt > 2)
{
total <<= 1;
for (n = 1; n + 1 < cnt; ++n)
total += temp[n].len + 1;
if (cnt > 3
&& (cnt >= sizeof (size_t) * 8
|| total + (sizeof (*result) << 3)
>= (1UL << (sizeof (size_t) * 8 - cnt + 3))))
_dl_signal_error (ENOMEM, NULL, NULL,
N_("cannot create capability list"));
total <<= cnt - 3;
}
}
/* The result structure: we use a very compressed way to store the
various combinations of capability names. */
*sz = 1 << cnt;
result = (struct r_strlenpair *) malloc (*sz * sizeof (*result) + total);
if (result == NULL)
_dl_signal_error (ENOMEM, NULL, NULL,
N_("cannot create capability list"));
if (cnt == 1)
{
result[0].str = (char *) (result + *sz);
result[0].len = temp[0].len + 1;
result[1].str = (char *) (result + *sz);
result[1].len = 0;
cp = __mempcpy ((char *) (result + *sz), temp[0].str, temp[0].len);
*cp = '/';
*sz = 2;
*max_capstrlen = result[0].len;
return result;
}
/* Fill in the information. This follows the following scheme
(indices from TEMP for four strings):
entry #0: 0, 1, 2, 3 binary: 1111
#1: 0, 1, 3 1101
#2: 0, 2, 3 1011
#3: 0, 3 1001
This allows the representation of all possible combinations of
capability names in the string. First generate the strings. */
result[1].str = result[0].str = cp = (char *) (result + *sz);
#define add(idx) \
cp = __mempcpy (__mempcpy (cp, temp[idx].str, temp[idx].len), "/", 1);
if (cnt == 2)
{
add (1);
add (0);
}
else
{
n = 1 << (cnt - 1);
do
{
n -= 2;
/* We always add the last string. */
add (cnt - 1);
/* Add the strings which have the bit set in N. */
for (m = cnt - 2; m > 0; --m)
if ((n & (1 << m)) != 0)
add (m);
/* Always add the first string. */
add (0);
}
while (n != 0);
}
#undef add
/* Now we are ready to install the string pointers and length. */
for (n = 0; n < (1UL << cnt); ++n)
result[n].len = 0;
n = cnt;
do
{
size_t mask = 1 << --n;
rp = result;
for (m = 1 << cnt; m > 0; ++rp)
if ((--m & mask) != 0)
rp->len += temp[n].len + 1;
}
while (n != 0);
/* The first half of the strings all include the first string. */
n = (1 << cnt) - 2;
rp = &result[2];
while (n != (1UL << (cnt - 1)))
{
if ((--n & 1) != 0)
rp[0].str = rp[-2].str + rp[-2].len;
else
rp[0].str = rp[-1].str;
++rp;
}
/* The second half starts right after the first part of the string of
the corresponding entry in the first half. */
do
{
rp[0].str = rp[-(1 << (cnt - 1))].str + temp[cnt - 1].len + 1;
++rp;
}
while (--n != 0);
/* The maximum string length. */
*max_capstrlen = result[0].len;
return result;
}
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