| /* Hardware capability support for run-time dynamic loader. |
| Copyright (C) 2012-2018 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 |
| <http://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> |
| |
| #ifdef _DL_FIRST_PLATFORM |
| # define _DL_FIRST_EXTRA (_DL_FIRST_PLATFORM + _DL_PLATFORMS_COUNT) |
| #else |
| # define _DL_FIRST_EXTRA _DL_HWCAP_COUNT |
| #endif |
| |
| /* Return an array of useful/necessary hardware capability names. */ |
| const struct r_strlenpair * |
| _dl_important_hwcaps (const char *platform, size_t platform_len, 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 = 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; |
| |
| #ifdef NEED_DL_SYSINFO_DSO |
| /* The system-supplied DSO can contain a note of type 2, vendor "GNU". |
| This gives us a list of names to treat as fake hwcap bits. */ |
| |
| const char *dsocaps = NULL; |
| size_t dsocapslen = 0; |
| if (GLRO(dl_sysinfo_map) != NULL) |
| { |
| const ElfW(Phdr) *const phdr = GLRO(dl_sysinfo_map)->l_phdr; |
| const ElfW(Word) phnum = GLRO(dl_sysinfo_map)->l_phnum; |
| for (uint_fast16_t i = 0; i < phnum; ++i) |
| if (phdr[i].p_type == PT_NOTE) |
| { |
| const ElfW(Addr) start = (phdr[i].p_vaddr |
| + GLRO(dl_sysinfo_map)->l_addr); |
| /* NB: Some PT_NOTE segment may have alignment value of 0 |
| or 1. gABI specifies that PT_NOTE segments should be |
| aligned to 4 bytes in 32-bit objects and to 8 bytes in |
| 64-bit objects. As a Linux extension, we also support |
| 4 byte alignment in 64-bit objects. If p_align is less |
| than 4, we treate alignment as 4 bytes since some note |
| segments have 0 or 1 byte alignment. */ |
| ElfW(Addr) align = phdr[i].p_align; |
| if (align < 4) |
| align = 4; |
| else if (align != 4 && align != 8) |
| continue; |
| /* The standard ELF note layout is exactly as the anonymous struct. |
| The next element is a variable length vendor name of length |
| VENDORLEN (with a real length rounded to ElfW(Word)), followed |
| by the data of length DATALEN (with a real length rounded to |
| ElfW(Word)). */ |
| const struct |
| { |
| ElfW(Word) vendorlen; |
| ElfW(Word) datalen; |
| ElfW(Word) type; |
| } *note = (const void *) start; |
| while ((ElfW(Addr)) (note + 1) - start < phdr[i].p_memsz) |
| { |
| /* The layout of the type 2, vendor "GNU" note is as follows: |
| .long <Number of capabilities enabled by this note> |
| .long <Capabilities mask> (as mask >> _DL_FIRST_EXTRA). |
| .byte <The bit number for the next capability> |
| .asciz <The name of the capability>. */ |
| if (note->type == NT_GNU_HWCAP |
| && note->vendorlen == sizeof "GNU" |
| && !memcmp ((note + 1), "GNU", sizeof "GNU") |
| && note->datalen > 2 * sizeof (ElfW(Word)) + 2) |
| { |
| const ElfW(Word) *p |
| = ((const void *) note |
| + ELF_NOTE_DESC_OFFSET (sizeof "GNU", align)); |
| cnt += *p++; |
| ++p; /* Skip mask word. */ |
| dsocaps = (const char *) p; /* Pseudo-string "<b>name" */ |
| dsocapslen = note->datalen - sizeof *p * 2; |
| break; |
| } |
| note = ((const void *) note |
| + ELF_NOTE_NEXT_OFFSET (note->vendorlen, |
| note->datalen, align)); |
| } |
| if (dsocaps != NULL) |
| break; |
| } |
| } |
| #endif |
| |
| /* For TLS enabled builds always add 'tls'. */ |
| ++cnt; |
| |
| /* Create temporary data structure to generate result table. */ |
| struct r_strlenpair temp[cnt]; |
| m = 0; |
| #ifdef NEED_DL_SYSINFO_DSO |
| if (dsocaps != NULL) |
| { |
| /* dsocaps points to the .asciz string, and -1 points to the mask |
| .long just before the string. */ |
| const ElfW(Word) mask = ((const ElfW(Word) *) dsocaps)[-1]; |
| GLRO(dl_hwcap) |= (uint64_t) mask << _DL_FIRST_EXTRA; |
| /* Note that we add the dsocaps to the set already chosen by the |
| LD_HWCAP_MASK environment variable (or default HWCAP_IMPORTANT). |
| So there is no way to request ignoring an OS-supplied dsocap |
| string and bit like you can ignore an OS-supplied HWCAP bit. */ |
| hwcap_mask |= (uint64_t) mask << _DL_FIRST_EXTRA; |
| #if HAVE_TUNABLES |
| TUNABLE_SET (glibc, tune, hwcap_mask, uint64_t, hwcap_mask); |
| #else |
| GLRO(dl_hwcap_mask) = hwcap_mask; |
| #endif |
| size_t len; |
| for (const char *p = dsocaps; p < dsocaps + dsocapslen; p += len + 1) |
| { |
| uint_fast8_t bit = *p++; |
| len = strlen (p); |
| |
| /* Skip entries that are not enabled in the mask word. */ |
| if (__glibc_likely (mask & ((ElfW(Word)) 1 << bit))) |
| { |
| temp[m].str = p; |
| temp[m].len = len; |
| ++m; |
| } |
| else |
| --cnt; |
| } |
| } |
| #endif |
| 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 (platform != NULL) |
| { |
| temp[m].str = platform; |
| temp[m].len = platform_len; |
| ++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; |
| } |
