191 lines
6.3 KiB
Diff
191 lines
6.3 KiB
Diff
commit 84ba719b260551918965d0a433914de683087645
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Author: Florian Weimer <fweimer@redhat.com>
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Date: Fri Dec 4 09:13:43 2020 +0100
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elf: Add endianness markup to ld.so.cache (bug 27008)
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Use a reserved byte in the new format cache header to indicate whether
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the file is in little endian or big endian format. Eventually, this
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information could be used to provide a unified cache for qemu-user
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and similiar scenarios.
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Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
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diff --git a/elf/cache.c b/elf/cache.c
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index edcdd4b7cc1a6a0b..28e4889d006d2f0b 100644
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--- a/elf/cache.c
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+++ b/elf/cache.c
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@@ -152,6 +152,14 @@ print_entry (const char *lib, int flag, unsigned int osversion,
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printf (") => %s\n", key);
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}
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+/* Print an error and exit if the new-file cache is internally
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+ inconsistent. */
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+static void
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+check_new_cache (struct cache_file_new *cache)
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+{
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+ if (! cache_file_new_matches_endian (cache))
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+ error (EXIT_FAILURE, 0, _("Cache file has wrong endianness.\n"));
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+}
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/* Print the whole cache file, if a file contains the new cache format
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hidden in the old one, print the contents of the new format. */
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@@ -193,6 +201,7 @@ print_cache (const char *cache_name)
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|| memcmp (cache_new->version, CACHE_VERSION,
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sizeof CACHE_VERSION - 1))
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error (EXIT_FAILURE, 0, _("File is not a cache file.\n"));
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+ check_new_cache (cache_new);
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format = 1;
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/* This is where the strings start. */
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cache_data = (const char *) cache_new;
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@@ -222,6 +231,7 @@ print_cache (const char *cache_name)
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&& memcmp (cache_new->version, CACHE_VERSION,
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sizeof CACHE_VERSION - 1) == 0)
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{
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+ check_new_cache (cache_new);
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cache_data = (const char *) cache_new;
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format = 1;
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}
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@@ -361,6 +371,7 @@ save_cache (const char *cache_name)
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file_entries_new->nlibs = cache_entry_count;
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file_entries_new->len_strings = total_strlen;
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+ file_entries_new->flags = cache_file_new_flags_endian_current;
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}
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/* Pad for alignment of cache_file_new. */
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diff --git a/elf/dl-cache.c b/elf/dl-cache.c
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index 366a051dfcd26132..de063faa8b2c88ae 100644
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--- a/elf/dl-cache.c
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+++ b/elf/dl-cache.c
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@@ -242,6 +242,11 @@ _dl_load_cache_lookup (const char *name)
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&& ((cachesize - sizeof *cache_new) / sizeof (struct file_entry_new)
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>= ((struct cache_file_new *) file)->nlibs))
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{
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+ if (! cache_file_new_matches_endian (file))
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+ {
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+ __munmap (file, cachesize);
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+ file = (void *) -1;
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+ }
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cache_new = file;
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cache = file;
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}
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@@ -263,7 +268,20 @@ _dl_load_cache_lookup (const char *name)
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if (cachesize < (offset + sizeof (struct cache_file_new))
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|| memcmp (cache_new->magic, CACHEMAGIC_VERSION_NEW,
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sizeof CACHEMAGIC_VERSION_NEW - 1) != 0)
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- cache_new = (void *) -1;
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+ cache_new = (void *) -1;
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+ else
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+ {
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+ if (! cache_file_new_matches_endian (cache_new))
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+ {
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+ /* The old-format part of the cache is bogus as well
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+ if the endianness does not match. (But it is
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+ unclear how the new header can be located if the
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+ endianess does not match.) */
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+ cache = (void *) -1;
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+ cache_new = (void *) -1;
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+ __munmap (file, cachesize);
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+ }
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+ }
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}
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else
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{
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diff --git a/sysdeps/generic/dl-cache.h b/sysdeps/generic/dl-cache.h
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index 3c5730dfe42c7c88..6ecfd6da0e59329c 100644
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--- a/sysdeps/generic/dl-cache.h
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+++ b/sysdeps/generic/dl-cache.h
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@@ -16,6 +16,11 @@
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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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+#ifndef _DL_CACHE_H
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+#define _DL_CACHE_H
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+
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+#include <endian.h>
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+#include <stdbool.h>
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#include <stdint.h>
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#ifndef _DL_CACHE_DEFAULT_ID
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@@ -92,17 +97,72 @@ struct file_entry_new
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uint64_t hwcap; /* Hwcap entry. */
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};
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+/* See flags member of struct cache_file_new below. */
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+enum
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+ {
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+ /* No endianness information available. An old ldconfig version
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+ without endianness support wrote the file. */
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+ cache_file_new_flags_endian_unset = 0,
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+
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+ /* Cache is invalid and should be ignored. */
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+ cache_file_new_flags_endian_invalid = 1,
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+
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+ /* Cache format is little endian. */
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+ cache_file_new_flags_endian_little = 2,
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+
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+ /* Cache format is big endian. */
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+ cache_file_new_flags_endian_big = 3,
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+
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+ /* Bit mask to extract the cache_file_new_flags_endian_*
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+ values. */
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+ cache_file_new_flags_endian_mask = 3,
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+
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+ /* Expected value of the endian bits in the flags member for the
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+ current architecture. */
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+ cache_file_new_flags_endian_current
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+ = (__BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
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+ ? cache_file_new_flags_endian_little
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+ : cache_file_new_flags_endian_big),
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+ };
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+
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struct cache_file_new
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{
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char magic[sizeof CACHEMAGIC_NEW - 1];
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char version[sizeof CACHE_VERSION - 1];
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uint32_t nlibs; /* Number of entries. */
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uint32_t len_strings; /* Size of string table. */
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- uint32_t unused[5]; /* Leave space for future extensions
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+
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+ /* flags & cache_file_new_flags_endian_mask is one of the values
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+ cache_file_new_flags_endian_unset, cache_file_new_flags_endian_invalid,
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+ cache_file_new_flags_endian_little, cache_file_new_flags_endian_big.
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+
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+ The remaining bits are unused and should be generated as zero and
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+ ignored by readers. */
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+ uint8_t flags;
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+
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+ uint8_t padding_unsed[3]; /* Not used, for future extensions. */
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+
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+ uint32_t unused[4]; /* Leave space for future extensions
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and align to 8 byte boundary. */
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struct file_entry_new libs[0]; /* Entries describing libraries. */
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/* After this the string table of size len_strings is found. */
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};
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+_Static_assert (sizeof (struct cache_file_new) == 48,
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+ "size of struct cache_file_new");
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+
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+/* Returns false if *CACHE has the wrong endianness for this
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+ architecture, and true if the endianness matches (or is
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+ unknown). */
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+static inline bool
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+cache_file_new_matches_endian (const struct cache_file_new *cache)
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+{
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+ /* A zero value for cache->flags means that no endianness
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+ information is available. */
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+ return cache->flags == 0
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+ || ((cache->flags & cache_file_new_flags_endian_big)
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+ == cache_file_new_flags_endian_current);
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+}
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+
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/* Used to align cache_file_new. */
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#define ALIGN_CACHE(addr) \
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@@ -110,3 +170,5 @@ struct cache_file_new
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& (~(__alignof__ (struct cache_file_new) - 1)))
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extern int _dl_cache_libcmp (const char *p1, const char *p2) attribute_hidden;
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+
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+#endif /* _DL_CACHE_H */
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