/* Support for reading /etc/ld.so.cache files written by Linux ldconfig.
- Copyright (C) 1999 Free Software Foundation, Inc.
+ Copyright (C) 1999-2021 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 Library General Public License as
- published by the Free Software Foundation; either version 2 of the
- License, or (at your option) any later version.
+ 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
- Library General Public License for more details.
+ Lesser General Public License for more details.
- You should have received a copy of the GNU Library General Public
- License along with the GNU C Library; see the file COPYING.LIB. If not,
- write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
- Boston, MA 02111-1307, USA. */
+ 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/>. */
-#define _DL_CACHE_DEFAULT_ID 3
+#ifndef _DL_CACHE_H
+#define _DL_CACHE_H
-#define _dl_cache_check_flags(flags) \
+#include <endian.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <string.h>
+
+#ifndef _DL_CACHE_DEFAULT_ID
+# define _DL_CACHE_DEFAULT_ID 3
+#endif
+
+#ifndef _dl_cache_check_flags
+# define _dl_cache_check_flags(flags) \
((flags) == 1 || (flags) == _DL_CACHE_DEFAULT_ID)
+#endif
+
+#ifndef LD_SO_CACHE
+# define LD_SO_CACHE SYSCONFDIR "/ld.so.cache"
+#endif
+
+#ifndef add_system_dir
+# define add_system_dir(dir) add_dir (dir)
+#endif
+
+#define CACHEMAGIC "ld.so-1.7.0"
+
+/* libc5 and glibc 2.0/2.1 use the same format. For glibc 2.2 another
+ format has been added in a compatible way:
+ The beginning of the string table is used for the new table:
+ old_magic
+ nlibs
+ libs[0]
+ ...
+ libs[nlibs-1]
+ pad, new magic needs to be aligned
+ - this is string[0] for the old format
+ new magic - this is string[0] for the new format
+ newnlibs
+ ...
+ newlibs[0]
+ ...
+ newlibs[newnlibs-1]
+ string 1
+ string 2
+ ...
+*/
+struct file_entry
+{
+ int32_t flags; /* This is 1 for an ELF library. */
+ uint32_t key, value; /* String table indices. */
+};
+
+struct cache_file
+{
+ char magic[sizeof CACHEMAGIC - 1];
+ unsigned int nlibs;
+ struct file_entry libs[0];
+};
+
+#define CACHEMAGIC_NEW "glibc-ld.so.cache"
+#define CACHE_VERSION "1.1"
+#define CACHEMAGIC_VERSION_NEW CACHEMAGIC_NEW CACHE_VERSION
+
+
+struct file_entry_new
+{
+ union
+ {
+ /* Fields shared with struct file_entry. */
+ struct file_entry entry;
+ /* Also expose these fields directly. */
+ struct
+ {
+ int32_t flags; /* This is 1 for an ELF library. */
+ uint32_t key, value; /* String table indices. */
+ };
+ };
+ uint32_t osversion; /* Required OS version. */
+ uint64_t hwcap; /* Hwcap entry. */
+};
+
+/* This bit in the hwcap field of struct file_entry_new indicates that
+ the lower 32 bits contain an index into the
+ cache_extension_tag_glibc_hwcaps section. Older glibc versions do
+ not know about this HWCAP bit, so they will ignore these
+ entries. */
+#define DL_CACHE_HWCAP_EXTENSION (1ULL << 62)
+
+/* Return true if the ENTRY->hwcap value indicates that
+ DL_CACHE_HWCAP_EXTENSION is used. */
+static inline bool
+dl_cache_hwcap_extension (struct file_entry_new *entry)
+{
+ /* If DL_CACHE_HWCAP_EXTENSION is set, but other bits as well, this
+ is a different kind of extension. */
+ return (entry->hwcap >> 32) == (DL_CACHE_HWCAP_EXTENSION >> 32);
+}
+
+/* See flags member of struct cache_file_new below. */
+enum
+ {
+ /* No endianness information available. An old ldconfig version
+ without endianness support wrote the file. */
+ cache_file_new_flags_endian_unset = 0,
+
+ /* Cache is invalid and should be ignored. */
+ cache_file_new_flags_endian_invalid = 1,
+
+ /* Cache format is little endian. */
+ cache_file_new_flags_endian_little = 2,
+
+ /* Cache format is big endian. */
+ cache_file_new_flags_endian_big = 3,
+
+ /* Bit mask to extract the cache_file_new_flags_endian_*
+ values. */
+ cache_file_new_flags_endian_mask = 3,
+
+ /* Expected value of the endian bits in the flags member for the
+ current architecture. */
+ cache_file_new_flags_endian_current
+ = (__BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+ ? cache_file_new_flags_endian_little
+ : cache_file_new_flags_endian_big),
+ };
+
+struct cache_file_new
+{
+ char magic[sizeof CACHEMAGIC_NEW - 1];
+ char version[sizeof CACHE_VERSION - 1];
+ uint32_t nlibs; /* Number of entries. */
+ uint32_t len_strings; /* Size of string table. */
+
+ /* flags & cache_file_new_flags_endian_mask is one of the values
+ cache_file_new_flags_endian_unset, cache_file_new_flags_endian_invalid,
+ cache_file_new_flags_endian_little, cache_file_new_flags_endian_big.
+
+ The remaining bits are unused and should be generated as zero and
+ ignored by readers. */
+ uint8_t flags;
+
+ uint8_t padding_unsed[3]; /* Not used, for future extensions. */
+
+ /* File offset of the extension directory. See struct
+ cache_extension below. Must be a multiple of four. */
+ uint32_t extension_offset;
+
+ uint32_t unused[3]; /* Leave space for future extensions
+ and align to 8 byte boundary. */
+ struct file_entry_new libs[0]; /* Entries describing libraries. */
+ /* After this the string table of size len_strings is found. */
+};
+_Static_assert (sizeof (struct cache_file_new) == 48,
+ "size of struct cache_file_new");
+
+/* Returns false if *CACHE has the wrong endianness for this
+ architecture, and true if the endianness matches (or is
+ unknown). */
+static inline bool
+cache_file_new_matches_endian (const struct cache_file_new *cache)
+{
+ /* A zero value for cache->flags means that no endianness
+ information is available. */
+ return cache->flags == 0
+ || ((cache->flags & cache_file_new_flags_endian_big)
+ == cache_file_new_flags_endian_current);
+}
+
+
+/* Randomly chosen magic value, which allows for additional
+ consistency verification. */
+enum { cache_extension_magic = (uint32_t) -358342284 };
+
+/* Tag values for different kinds of extension sections. Similar to
+ SHT_* constants. */
+enum cache_extension_tag
+ {
+ /* Array of bytes containing the glibc version that generated this
+ cache file. */
+ cache_extension_tag_generator,
+
+ /* glibc-hwcaps subdirectory information. An array of uint32_t
+ values, which are indices into the string table. The strings
+ are sorted lexicographically (according to strcmp). The extra
+ level of indirection (instead of using string table indices
+ directly) allows the dynamic loader to compute the preference
+ order of the hwcaps names more efficiently.
+
+ For this section, 4-byte alignment is required, and the section
+ size must be a multiple of 4. */
+ cache_extension_tag_glibc_hwcaps,
+
+ /* Total number of known cache extension tags. */
+ cache_extension_count
+ };
+
+/* Element in the array following struct cache_extension. Similar to
+ an ELF section header. */
+struct cache_extension_section
+{
+ /* Type of the extension section. A enum cache_extension_tag value. */
+ uint32_t tag;
+
+ /* Extension-specific flags. Currently generated as zero. */
+ uint32_t flags;
+
+ /* Offset from the start of the file for the data in this extension
+ section. Specific extensions can have alignment constraints. */
+ uint32_t offset;
+
+ /* Length in bytes of the extension data. Specific extensions may
+ have size requirements. */
+ uint32_t size;
+};
+
+/* The extension directory in the cache. An array of struct
+ cache_extension_section entries. */
+struct cache_extension
+{
+ uint32_t magic; /* Always cache_extension_magic. */
+ uint32_t count; /* Number of following entries. */
+
+ /* count section descriptors of type struct cache_extension_section
+ follow. */
+ struct cache_extension_section sections[];
+};
+
+/* A relocated version of struct cache_extension_section. */
+struct cache_extension_loaded
+{
+ /* Address and size of this extension section. base is NULL if the
+ section is missing from the file. */
+ const void *base;
+ size_t size;
+
+ /* Flags from struct cache_extension_section. */
+ uint32_t flags;
+};
+
+/* All supported extension sections, relocated. Filled in by
+ cache_extension_load below. */
+struct cache_extension_all_loaded
+{
+ struct cache_extension_loaded sections[cache_extension_count];
+};
+
+/* Performs basic data validation based on section tag, and removes
+ the sections which are invalid. */
+static void
+cache_extension_verify (struct cache_extension_all_loaded *loaded)
+{
+ {
+ /* Section must not be empty, it must be aligned at 4 bytes, and
+ the size must be a multiple of 4. */
+ struct cache_extension_loaded *hwcaps
+ = &loaded->sections[cache_extension_tag_glibc_hwcaps];
+ if (hwcaps->size == 0
+ || ((uintptr_t) hwcaps->base % 4) != 0
+ || (hwcaps->size % 4) != 0)
+ {
+ hwcaps->base = NULL;
+ hwcaps->size = 0;
+ hwcaps->flags = 0;
+ }
+ }
+}
+
+static bool __attribute__ ((unused))
+cache_extension_load (const struct cache_file_new *cache,
+ const void *file_base, size_t file_size,
+ struct cache_extension_all_loaded *loaded)
+{
+ memset (loaded, 0, sizeof (*loaded));
+ if (cache->extension_offset == 0)
+ /* No extensions present. This is not a format error. */
+ return true;
+ if ((cache->extension_offset % 4) != 0)
+ /* Extension offset is misaligned. */
+ return false;
+ size_t size_tmp;
+ if (__builtin_add_overflow (cache->extension_offset,
+ sizeof (struct cache_extension), &size_tmp)
+ || size_tmp > file_size)
+ /* Extension extends beyond the end of the file. */
+ return false;
+ const struct cache_extension *ext = file_base + cache->extension_offset;
+ if (ext->magic != cache_extension_magic)
+ return false;
+ if (__builtin_mul_overflow (ext->count,
+ sizeof (struct cache_extension_section),
+ &size_tmp)
+ || __builtin_add_overflow (cache->extension_offset
+ + sizeof (struct cache_extension), size_tmp,
+ &size_tmp)
+ || size_tmp > file_size)
+ /* Extension array extends beyond the end of the file. */
+ return false;
+ for (uint32_t i = 0; i < ext->count; ++i)
+ {
+ if (__builtin_add_overflow (ext->sections[i].offset,
+ ext->sections[i].size, &size_tmp)
+ || size_tmp > file_size)
+ /* Extension data extends beyond the end of the file. */
+ return false;
+
+ uint32_t tag = ext->sections[i].tag;
+ if (tag >= cache_extension_count)
+ /* Tag is out of range and unrecognized. */
+ continue;
+ loaded->sections[tag].base = file_base + ext->sections[i].offset;
+ loaded->sections[tag].size = ext->sections[i].size;
+ loaded->sections[tag].flags = ext->sections[i].flags;
+ }
+ cache_extension_verify (loaded);
+ return true;
+}
+
+/* Used to align cache_file_new. */
+#define ALIGN_CACHE(addr) \
+(((addr) + __alignof__ (struct cache_file_new) -1) \
+ & (~(__alignof__ (struct cache_file_new) - 1)))
+
+extern int _dl_cache_libcmp (const char *p1, const char *p2) attribute_hidden;
+
+#endif /* _DL_CACHE_H */
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