Joakim Tjernlund wrote:
hmm, STT_COMMON got lost and please use likely/unlikely instead of
__builtin_expect()
Jocke
Hi Jocke,
here it's the updated patch fon GNU hash addressing
your above suggestion.
Cheers,
Carmelo
Index: test/Rules.mak
===================================================================
--- test/Rules.mak (revision 20321)
+++ test/Rules.mak (working copy)
@@ -107,7 +107,12 @@
LDFLAGS += -Wl,--dynamic-linker,$(UCLIBC_LDSO_ABSPATH)/$(UCLIBC_LDSO)
endif
+ifeq ($(LDSO_GNU_HASH_SUPPORT),y)
+# Check for binutils support is done on root Rules.mak
+LDFLAGS += -Wl,${LDFLAGS_GNUHASH}
+endif
+
# Filter output
MAKEFLAGS += --no-print-directory
ifneq ($(findstring s,$(MAKEFLAGS)),)
Index: extra/Configs/Config.in
===================================================================
--- extra/Configs/Config.in (revision 20321)
+++ extra/Configs/Config.in (working copy)
@@ -322,6 +322,21 @@
or dtors and want your binaries to be as small as possible, then
answer N.
+config LDSO_GNU_HASH_SUPPORT
+ bool "Enable GNU hash style support"
+ depends on HAVE_SHARED
+ default n
+ help
+ Newest binutils support a new hash style named GNU-hash. The dynamic
+ linker will use the new GNU-hash section (.gnu.hash) for symbol
lookup
+ if present into the ELF binaries, otherwise it will use the old SysV
+ hash style (.hash). This ensures that it is completely backward
compatible.
+ Further, being the hash table implementation self-contained into each
+ executable and shared libraries, objects with mixed hash style can
+ peacefully coexist in the same process.
+
+ If you want to use this new feature, answer Y
+
config HAS_NO_THREADS
bool
default n
Index: include/elf.h
===================================================================
--- include/elf.h (revision 20321)
+++ include/elf.h (working copy)
@@ -431,6 +431,7 @@
#define SHT_SYMTAB_SHNDX 18 /* Extended section indeces */
#define SHT_NUM 19 /* Number of defined types. */
#define SHT_LOOS 0x60000000 /* Start OS-specific */
+#define SHT_GNU_HASH 0x6ffffff6 /* GNU-style hash table. */
#define SHT_GNU_LIBLIST 0x6ffffff7 /* Prelink library list */
#define SHT_CHECKSUM 0x6ffffff8 /* Checksum for DSO content. */
#define SHT_LOSUNW 0x6ffffffa /* Sun-specific low bound. */
@@ -813,6 +814,7 @@
If any adjustment is made to the ELF object after it has been
built these entries will need to be adjusted. */
#define DT_ADDRRNGLO 0x6ffffe00
+#define DT_GNU_HASH 0x6ffffef5 /* GNU-style hash table. */
#define DT_GNU_CONFLICT 0x6ffffef8 /* Start of conflict section */
#define DT_GNU_LIBLIST 0x6ffffef9 /* Library list */
#define DT_CONFIG 0x6ffffefa /* Configuration information. */
Index: ldso/ldso/dl-hash.c
===================================================================
--- ldso/ldso/dl-hash.c (revision 20321)
+++ ldso/ldso/dl-hash.c (working copy)
@@ -53,6 +53,19 @@
*/
struct dyn_elf *_dl_handles = NULL;
+#ifdef __LDSO_GNU_HASH_SUPPORT__
+/* This is the new hash function that is used by the ELF linker to generate the
+ * GNU hash table that each executable and library will have if
--hash-style=[gnu,both]
+ * is passed to the linker. We need it to decode the GNU hash table. */
+static inline Elf_Symndx _dl_gnu_hash (const unsigned char *name)
+{
+ unsigned long h = 5381;
+ unsigned char c;
+ for (c = *name; c != '\0'; c = *++name)
+ h = h * 33 + c;
+ return h & 0xffffffff;
+}
+#endif
/* This is the hash function that is used by the ELF linker to generate the
* hash table that each executable and library is required to have. We need
@@ -108,7 +121,30 @@
tpnt->libname = _dl_strdup(libname);
tpnt->dynamic_addr = (ElfW(Dyn) *)dynamic_addr;
tpnt->libtype = loaded_file;
+
+#ifdef __LDSO_GNU_HASH_SUPPORT__
+ if (dynamic_info[DT_GNU_HASH_IDX] != 0) {
+
+ Elf32_Word *hash32 =
(Elf_Symndx*)dynamic_info[DT_GNU_HASH_IDX];
+
+ tpnt->nbucket = *hash32++;
+ Elf32_Word symbias = *hash32++;
+ Elf32_Word bitmask_nwords = *hash32++;
+ /* Must be a power of two. */
+ _dl_assert ((bitmask_nwords & (bitmask_nwords - 1)) ==
0);
+ tpnt->l_gnu_bitmask_idxbits = bitmask_nwords - 1;
+ tpnt->l_gnu_shift = *hash32++;
+ tpnt->l_gnu_bitmask = (ElfW(Addr) *) hash32;
+ hash32 += __ELF_NATIVE_CLASS / 32 * bitmask_nwords;
+
+ tpnt->l_gnu_buckets = hash32;
+ hash32 += tpnt->nbucket;
+ tpnt->l_gnu_chain_zero = hash32 - symbias;
+ } else
+ /* Fall using old SysV hash table if GNU hash is not present */
+#endif
+
if (dynamic_info[DT_HASH] != 0) {
hash_addr = (Elf_Symndx*)dynamic_info[DT_HASH];
tpnt->nbucket = *hash_addr++;
@@ -124,22 +160,117 @@
}
+/* Routine to check whether the symbol matches. */
+static __attribute_noinline__ const ElfW(Sym) *
+check_match (const ElfW(Sym) *sym, char *strtab, const char* undef_name, int
type_class) {
+
+ if (type_class & (sym->st_shndx == SHN_UNDEF))
+ /* undefined symbol itself */
+ return NULL;
+
+ if (sym->st_value == 0)
+ /* No value */
+ return NULL;
+
+ if (ELF_ST_TYPE(sym->st_info) > STT_FUNC
+ && ELF_ST_TYPE(sym->st_info) != STT_COMMON)
+ /* Ignore all but STT_NOTYPE, STT_OBJECT, STT_FUNC
+ * and STT_COMMON entries since these are no
+ * code/data definitions
+ */
+ return NULL;
+
+ if (_dl_strcmp(strtab + sym->st_name, undef_name) != 0)
+ return NULL;
+
+ /* This is the matching symbol */
+ return sym;
+}
+
+
+#ifdef __LDSO_GNU_HASH_SUPPORT__
+
+static __always_inline const ElfW(Sym) *
+_dl_lookup_gnu_hash(struct elf_resolve *tpnt, ElfW(Sym) *symtab, unsigned long
hash,
+ const char* undef_name, int type_class)
{
+
+ Elf_Symndx symidx;
+ const ElfW(Sym) *sym;
+ char *strtab;
+
+ const ElfW(Addr) *bitmask = tpnt->l_gnu_bitmask;
+
+ ElfW(Addr) bitmask_word = bitmask[(hash / __ELF_NATIVE_CLASS) &
tpnt->l_gnu_bitmask_idxbits];
+
+ unsigned int hashbit1 = hash & (__ELF_NATIVE_CLASS - 1);
+ unsigned int hashbit2 = ((hash >> tpnt->l_gnu_shift) &
(__ELF_NATIVE_CLASS - 1));
+
+ _dl_assert (bitmask != NULL);
+
+ if (unlikely((bitmask_word >> hashbit1) & (bitmask_word >> hashbit2) &
1)) {
+
+ Elf32_Word bucket = tpnt->l_gnu_buckets[hash % tpnt->nbucket];
+
+ if (bucket != 0) {
+ const Elf32_Word *hasharr =
&tpnt->l_gnu_chain_zero[bucket];
+ do {
+ if (((*hasharr ^ hash) >> 1) == 0) {
+ symidx = hasharr -
tpnt->l_gnu_chain_zero;
+ strtab = (char *)
(tpnt->dynamic_info[DT_STRTAB]);
+ sym = check_match (&symtab[symidx],
strtab, undef_name, type_class);
+ if (sym != NULL)
+ return sym;
+ }
+ } while ((*hasharr++ & 1u) == 0);
+ }
+ }
+ /* No symbol found. */
+ return NULL;
+}
+#endif
+
+static __always_inline const ElfW(Sym) *
+_dl_lookup_sysv_hash(struct elf_resolve *tpnt, ElfW(Sym) *symtab, unsigned
long hash, const char* undef_name, int type_class) {
+
+ unsigned long hn;
+ char *strtab;
+ const ElfW(Sym) *sym;
+ Elf_Symndx symidx;
+
+ /* Avoid calling .urem here. */
+ do_rem(hn, hash, tpnt->nbucket);
+ strtab = (char *) (tpnt->dynamic_info[DT_STRTAB]);
+
+ _dl_assert(tpnt->elf_buckets != NULL);
+
+ for (symidx = tpnt->elf_buckets[hn]; symidx != STN_UNDEF; symidx =
tpnt->chains[symidx]) {
+ sym = check_match (&symtab[symidx], strtab, undef_name,
type_class);
+ if (sym != NULL)
+ /* At this point the symbol is that we are looking for
*/
+ return sym;
+ }
+ /* No symbol found into the current module*/
+ return NULL;
+}
+
/*
* This function resolves externals, and this is either called when we process
* relocations or when we call an entry in the PLT table for the first time.
*/
char *_dl_find_hash(const char *name, struct dyn_elf *rpnt, struct elf_resolve
*mytpnt, int type_class)
{
- struct elf_resolve *tpnt;
- int si;
- char *strtab;
+ struct elf_resolve *tpnt = NULL;
ElfW(Sym) *symtab;
- unsigned long elf_hash_number, hn;
- const ElfW(Sym) *sym;
+
+ unsigned long elf_hash_number = 0xffffffff;
+ const ElfW(Sym) *sym = NULL;
+
char *weak_result = NULL;
- elf_hash_number = _dl_elf_hash((const unsigned char *)name);
-
+#ifdef __LDSO_GNU_HASH_SUPPORT__
+ unsigned long gnu_hash_number = _dl_gnu_hash((const unsigned char
*)name);
+#endif
+
for (; rpnt; rpnt = rpnt->next) {
tpnt = rpnt->dyn;
@@ -165,29 +296,32 @@
if (tpnt->nbucket == 0)
continue;
- /* Avoid calling .urem here. */
- do_rem(hn, elf_hash_number, tpnt->nbucket);
- symtab = (ElfW(Sym) *) tpnt->dynamic_info[DT_SYMTAB];
- strtab = (char *) (tpnt->dynamic_info[DT_STRTAB]);
+ symtab = (ElfW(Sym) *) (intptr_t)
(tpnt->dynamic_info[DT_SYMTAB]);
+
+#ifdef __LDSO_GNU_HASH_SUPPORT__
+ /* Prefer GNU hash style, if any */
+ if(tpnt->l_gnu_bitmask) {
+ if((sym = _dl_lookup_gnu_hash(tpnt, symtab,
gnu_hash_number, name, type_class)) != NULL)
+ /* If sym has been found, do not search further */
+ break;
+ } else {
+#endif
+ /* Use the old SysV-style hash table */
+
+ /* Calculate the old sysv hash number only once */
+ if(elf_hash_number == 0xffffffff)
+ elf_hash_number = _dl_elf_hash((const unsigned char
*)name);
- for (si = tpnt->elf_buckets[hn]; si != STN_UNDEF; si =
tpnt->chains[si]) {
- sym = &symtab[si];
+ if((sym = _dl_lookup_sysv_hash(tpnt, symtab, elf_hash_number,
name, type_class)) != NULL )
+ break;
+#ifdef __LDSO_GNU_HASH_SUPPORT__
+ }
+#endif
+ } /* end of for (; rpnt; rpnt = rpnt->next) { */
- if (type_class & (sym->st_shndx == SHN_UNDEF))
- continue;
- if (sym->st_value == 0)
- continue;
- if (ELF_ST_TYPE(sym->st_info) > STT_FUNC
- && ELF_ST_TYPE(sym->st_info) != STT_COMMON)
- /* Ignore all but STT_NOTYPE, STT_OBJECT, STT_FUNC
- * and STT_COMMON entries since these are no
- * code/data definitions
- */
- continue;
- if (_dl_strcmp(strtab + sym->st_name, name) != 0)
- continue;
-
- switch (ELF_ST_BIND(sym->st_info)) {
+ if(sym) {
+ /* At this point we have found the requested symbol, do binding
*/
+ switch (ELF_ST_BIND(sym->st_info)) {
case STB_WEAK:
#if 0
/* Perhaps we should support old style weak symbol handling
@@ -200,7 +334,6 @@
return (char*) DL_RELOC_ADDR(tpnt->loadaddr,
sym->st_value);
default: /* Local symbols not handled here */
break;
- }
}
}
return weak_result;
Index: ldso/include/dl-hash.h
===================================================================
--- ldso/include/dl-hash.h (revision 20321)
+++ ldso/include/dl-hash.h (working copy)
@@ -40,14 +40,39 @@
unsigned short int init_flag;
unsigned long rtld_flags; /* RTLD_GLOBAL, RTLD_NOW etc. */
Elf_Symndx nbucket;
+
+#ifdef __LDSO_GNU_HASH_SUPPORT__
+ /* Data needed to support GNU hash style */
+ Elf32_Word l_gnu_bitmask_idxbits;
+ Elf32_Word l_gnu_shift;
+ const ElfW(Addr) *l_gnu_bitmask;
+
+ union
+ {
+ const Elf32_Word *l_gnu_chain_zero;
+ const Elf_Symndx *elf_buckets;
+ };
+#else
Elf_Symndx *elf_buckets;
+#endif
+
struct init_fini_list *init_fini;
struct init_fini_list *rtld_local; /* keep tack of RTLD_LOCAL libs in same
group */
/*
* These are only used with ELF style shared libraries
*/
Elf_Symndx nchain;
+
+#ifdef __LDSO_GNU_HASH_SUPPORT__
+ union
+ {
+ const Elf32_Word *l_gnu_buckets;
+ const Elf_Symndx *chains;
+ };
+#else
Elf_Symndx *chains;
+#endif
+
unsigned long dynamic_info[DYNAMIC_SIZE];
unsigned long n_phent;
Index: ldso/include/ldso.h
===================================================================
--- ldso/include/ldso.h (revision 20321)
+++ ldso/include/ldso.h (working copy)
@@ -66,9 +66,17 @@
_dl_dprintf(_dl_debug_file, "%s:%i: " fmt, __FUNCTION__, __LINE__, ##
args);
# define _dl_if_debug_dprint(fmt, args...) \
do { if (_dl_debug) __dl_debug_dprint(fmt, ## args); } while (0)
+# define _dl_assert(expr) \
+ do { \
+ if (!(expr)) { \
+ __dl_debug_dprint("assert(%s)\n", #expr); \
+ _dl_exit(45); \
+ } \
+ } while (0)
#else
-# define _dl_debug_dprint(fmt, args...)
+# define __dl_debug_dprint(fmt, args...)
# define _dl_if_debug_dprint(fmt, args...)
+# define _dl_assert(expr)
# define _dl_debug_file 2
#endif /* __SUPPORT_LD_DEBUG__ */
Index: ldso/include/dl-elf.h
===================================================================
--- ldso/include/dl-elf.h (revision 20321)
+++ ldso/include/dl-elf.h (working copy)
@@ -84,8 +84,11 @@
#endif
/* OS and/or GNU dynamic extensions */
-#define OS_NUM 1
-#define DT_RELCONT_IDX DT_NUM
+#ifdef __LDSO_GNU_HASH_SUPPORT__
+# define OS_NUM 2 /* for DT_RELOCCOUNT and DT_GNU_HASH entries */
+#else
+# define OS_NUM 1 /* for DT_RELOCCOUNT entry */
+#endif
#ifndef ARCH_DYNAMIC_INFO
/* define in arch specific code, if needed */
@@ -93,7 +96,14 @@
#endif
#define DYNAMIC_SIZE (DT_NUM+OS_NUM+ARCH_NUM)
+/* Keep ARCH specific entries into dynamic section at the end of the array */
+#define DT_RELCONT_IDX (DYNAMIC_SIZE - OS_NUM - ARCH_NUM)
+#ifdef __LDSO_GNU_HASH_SUPPORT__
+/* GNU hash comes just after the relocation count */
+# define DT_GNU_HASH_IDX (DT_RELCONT_IDX + 1)
+#endif
+
extern void _dl_parse_dynamic_info(ElfW(Dyn) *dpnt, unsigned long
dynamic_info[],
void *debug_addr, DL_LOADADDR_TYPE
load_off);
@@ -131,6 +141,10 @@
if (dpnt->d_tag == DT_FLAGS_1 &&
(dpnt->d_un.d_val & DF_1_NOW))
dynamic_info[DT_BIND_NOW] = 1;
+#ifdef __LDSO_GNU_HASH_SUPPORT__
+ if (dpnt->d_tag == DT_GNU_HASH)
+ dynamic_info[DT_GNU_HASH_IDX] =
dpnt->d_un.d_ptr;
+#endif
}
#ifdef ARCH_DYNAMIC_INFO
else {
@@ -149,6 +163,9 @@
ADJUST_DYN_INFO(DT_SYMTAB, load_off);
ADJUST_DYN_INFO(DT_RELOC_TABLE_ADDR, load_off);
ADJUST_DYN_INFO(DT_JMPREL, load_off);
+#ifdef __LDSO_GNU_HASH_SUPPORT__
+ ADJUST_DYN_INFO(DT_GNU_HASH_IDX, load_off);
+#endif
#undef ADJUST_DYN_INFO
}
Index: Rules.mak
===================================================================
--- Rules.mak (revision 20321)
+++ Rules.mak (working copy)
@@ -408,6 +408,16 @@
LDFLAGS_NOSTRIP+=-Wl,-z,now
endif
+ifeq ($(LDSO_GNU_HASH_SUPPORT),y)
+# Be sure that binutils support it
+LDFLAGS_GNUHASH :=$(call check_ld,--hash-style=gnu)
+ifeq ($(LDFLAGS_GNUHASH),)
+$(error Your binutils don't support --hash-style option, while you want to use
it)
+else
+LDFLAGS_NOSTRIP += -Wl,$(LDFLAGS_GNUHASH)
+endif
+endif
+
LDFLAGS:=$(LDFLAGS_NOSTRIP) -Wl,-z,defs
ifeq ($(DODEBUG),y)
#CFLAGS += -g3
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