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elf: Unify old and new format cache handling code in ld.so

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struct file_entry_new starts with the fields of struct file_entry,
so the code can be shared if the size computation is made dynamic.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
This commit is contained in:
Florian Weimer 2020-10-30 11:57:59 +01:00
parent cb3a749a22
commit de1a9197af
2 changed files with 157 additions and 145 deletions
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285
elf/dl-cache.c
View File

@ -35,103 +35,141 @@ static struct cache_file *cache;
static struct cache_file_new *cache_new;
static size_t cachesize;
/* 1 if cache_data + PTR points into the cache. */
#define _dl_cache_verify_ptr(ptr) (ptr < cache_data_size)
/* True if PTR is a valid string table index. */
static inline bool
_dl_cache_verify_ptr (uint32_t ptr, size_t string_table_size)
{
return ptr < string_table_size;
}
#define SEARCH_CACHE(cache) \
/* We use binary search since the table is sorted in the cache file. \
The first matching entry in the table is returned. \
It is important to use the same algorithm as used while generating \
the cache file. */ \
do \
{ \
left = 0; \
right = cache->nlibs - 1; \
\
while (left <= right) \
{ \
__typeof__ (cache->libs[0].key) key; \
\
middle = (left + right) / 2; \
\
key = cache->libs[middle].key; \
\
/* Make sure string table indices are not bogus before using \
them. */ \
if (! _dl_cache_verify_ptr (key)) \
{ \
cmpres = 1; \
break; \
} \
\
/* Actually compare the entry with the key. */ \
cmpres = _dl_cache_libcmp (name, cache_data + key); \
if (__glibc_unlikely (cmpres == 0)) \
{ \
/* Found it. LEFT now marks the last entry for which we \
know the name is correct. */ \
left = middle; \
\
/* There might be entries with this name before the one we \
found. So we have to find the beginning. */ \
while (middle > 0) \
{ \
__typeof__ (cache->libs[0].key) key; \
\
key = cache->libs[middle - 1].key; \
/* Make sure string table indices are not bogus before \
using them. */ \
if (! _dl_cache_verify_ptr (key) \
/* Actually compare the entry. */ \
|| _dl_cache_libcmp (name, cache_data + key) != 0) \
break; \
--middle; \
} \
\
do \
{ \
int flags; \
__typeof__ (cache->libs[0]) *lib = &cache->libs[middle]; \
\
/* Only perform the name test if necessary. */ \
if (middle > left \
/* We haven't seen this string so far. Test whether the \
index is ok and whether the name matches. Otherwise \
we are done. */ \
&& (! _dl_cache_verify_ptr (lib->key) \
|| (_dl_cache_libcmp (name, cache_data + lib->key) \
!= 0))) \
break; \
\
flags = lib->flags; \
if (_dl_cache_check_flags (flags) \
&& _dl_cache_verify_ptr (lib->value)) \
{ \
if (best == NULL || flags == GLRO(dl_correct_cache_id)) \
{ \
HWCAP_CHECK; \
best = cache_data + lib->value; \
\
if (flags == GLRO(dl_correct_cache_id)) \
/* We've found an exact match for the shared \
object and no general `ELF' release. Stop \
searching. */ \
break; \
} \
} \
} \
while (++middle <= right); \
break; \
} \
\
if (cmpres < 0) \
left = middle + 1; \
else \
right = middle - 1; \
} \
} \
while (0)
/* Compute the address of the element INDEX of the array at LIBS.
Conceptually, this is &LIBS[INDEX], but use ENTRY_SIZE for the size
of *LIBS. */
static inline const struct file_entry *
_dl_cache_file_entry (const struct file_entry *libs, size_t entry_size,
size_t index)
{
return (const void *) libs + index * entry_size;
}
/* We use binary search since the table is sorted in the cache file.
The first matching entry in the table is returned. It is important
to use the same algorithm as used while generating the cache file.
STRING_TABLE_SIZE indicates the maximum offset in STRING_TABLE at
which data is mapped; it is not exact. */
static const char *
search_cache (const char *string_table, uint32_t string_table_size,
struct file_entry *libs, uint32_t nlibs, uint32_t entry_size,
const char *name)
{
/* Used by the HWCAP check in the struct file_entry_new case. */
uint64_t platform = _dl_string_platform (GLRO (dl_platform));
if (platform != (uint64_t) -1)
platform = 1ULL << platform;
uint64_t hwcap_mask = GET_HWCAP_MASK ();
#define _DL_HWCAP_TLS_MASK (1LL << 63)
uint64_t hwcap_exclude = ~((GLRO (dl_hwcap) & hwcap_mask)
| _DL_HWCAP_PLATFORM | _DL_HWCAP_TLS_MASK);
int left = 0;
int right = nlibs - 1;
const char *best = NULL;
while (left <= right)
{
int middle = (left + right) / 2;
uint32_t key = _dl_cache_file_entry (libs, entry_size, middle)->key;
/* Make sure string table indices are not bogus before using
them. */
if (!_dl_cache_verify_ptr (key, string_table_size))
return NULL;
/* Actually compare the entry with the key. */
int cmpres = _dl_cache_libcmp (name, string_table + key);
if (__glibc_unlikely (cmpres == 0))
{
/* Found it. LEFT now marks the last entry for which we
know the name is correct. */
left = middle;
/* There might be entries with this name before the one we
found. So we have to find the beginning. */
while (middle > 0)
{
key = _dl_cache_file_entry (libs, entry_size, middle - 1)->key;
/* Make sure string table indices are not bogus before
using them. */
if (!_dl_cache_verify_ptr (key, string_table_size)
/* Actually compare the entry. */
|| _dl_cache_libcmp (name, string_table + key) != 0)
break;
--middle;
}
do
{
int flags;
const struct file_entry *lib
= _dl_cache_file_entry (libs, entry_size, middle);
/* Only perform the name test if necessary. */
if (middle > left
/* We haven't seen this string so far. Test whether the
index is ok and whether the name matches. Otherwise
we are done. */
&& (! _dl_cache_verify_ptr (lib->key, string_table_size)
|| (_dl_cache_libcmp (name, string_table + lib->key)
!= 0)))
break;
flags = lib->flags;
if (_dl_cache_check_flags (flags)
&& _dl_cache_verify_ptr (lib->value, string_table_size))
{
if (best == NULL || flags == GLRO (dl_correct_cache_id))
{
if (entry_size >= sizeof (struct file_entry_new))
{
/* The entry is large enough to include
HWCAP data. Check it. */
struct file_entry_new *libnew
= (struct file_entry_new *) lib;
if (libnew->hwcap & hwcap_exclude)
continue;
if (GLRO (dl_osversion)
&& libnew->osversion > GLRO (dl_osversion))
continue;
if (_DL_PLATFORMS_COUNT
&& (libnew->hwcap & _DL_HWCAP_PLATFORM) != 0
&& ((libnew->hwcap & _DL_HWCAP_PLATFORM)
!= platform))
continue;
}
best = string_table + lib->value;
if (flags == GLRO (dl_correct_cache_id))
/* We've found an exact match for the shared
object and no general `ELF' release. Stop
searching. */
break;
}
}
}
while (++middle <= right);
break;
}
if (cmpres < 0)
left = middle + 1;
else
right = middle - 1;
}
return best;
}
int
_dl_cache_libcmp (const char *p1, const char *p2)
@ -182,12 +220,6 @@ _dl_cache_libcmp (const char *p1, const char *p2)
char *
_dl_load_cache_lookup (const char *name)
{
int left, right, middle;
int cmpres;
const char *cache_data;
uint32_t cache_data_size;
const char *best;
/* Print a message if the loading of libs is traced. */
if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_LIBS))
_dl_debug_printf (" search cache=%s\n", LD_SO_CACHE);
@ -247,51 +279,22 @@ _dl_load_cache_lookup (const char *name)
/* Previously looked for the cache file and didn't find it. */
return NULL;
best = NULL;
const char *best;
if (cache_new != (void *) -1)
{
uint64_t platform;
/* This is where the strings start. */
cache_data = (const char *) cache_new;
/* Now we can compute how large the string table is. */
cache_data_size = (const char *) cache + cachesize - cache_data;
platform = _dl_string_platform (GLRO(dl_platform));
if (platform != (uint64_t) -1)
platform = 1ULL << platform;
uint64_t hwcap_mask = GET_HWCAP_MASK();
#define _DL_HWCAP_TLS_MASK (1LL << 63)
uint64_t hwcap_exclude = ~((GLRO(dl_hwcap) & hwcap_mask)
| _DL_HWCAP_PLATFORM | _DL_HWCAP_TLS_MASK);
/* Only accept hwcap if it's for the right platform. */
#define HWCAP_CHECK \
if (lib->hwcap & hwcap_exclude) \
continue; \
if (GLRO(dl_osversion) && lib->osversion > GLRO(dl_osversion)) \
continue; \
if (_DL_PLATFORMS_COUNT \
&& (lib->hwcap & _DL_HWCAP_PLATFORM) != 0 \
&& (lib->hwcap & _DL_HWCAP_PLATFORM) != platform) \
continue
SEARCH_CACHE (cache_new);
const char *string_table = (const char *) cache_new;
best = search_cache (string_table, cachesize,
&cache_new->libs[0].entry, cache_new->nlibs,
sizeof (cache_new->libs[0]), name);
}
else
{
/* This is where the strings start. */
cache_data = (const char *) &cache->libs[cache->nlibs];
/* Now we can compute how large the string table is. */
cache_data_size = (const char *) cache + cachesize - cache_data;
#undef HWCAP_CHECK
#define HWCAP_CHECK do {} while (0)
SEARCH_CACHE (cache);
const char *string_table = (const char *) &cache->libs[cache->nlibs];
uint32_t string_table_size
= (const char *) cache + cachesize - string_table;
best = search_cache (string_table, string_table_size,
&cache->libs[0], cache->nlibs,
sizeof (cache->libs[0]), name);
}
/* Print our result if wanted. */

17
sysdeps/generic/dl-cache.h
View File

@ -59,8 +59,8 @@
*/
struct file_entry
{
int flags; /* This is 1 for an ELF library. */
unsigned int key, value; /* String table indices. */
int32_t flags; /* This is 1 for an ELF library. */
uint32_t key, value; /* String table indices. */
};
struct cache_file
@ -77,8 +77,17 @@ struct cache_file
struct file_entry_new
{
int32_t flags; /* This is 1 for an ELF library. */
uint32_t key, value; /* String table indices. */
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. */
};