Promote do_lookup_x:check_match to a full function.
While it may be argued that nested functions make the resulting code easier to read, or worse to read the following two bugs make it difficult to debug: Bug 8300 - no local symbol information within nested or nesting procedures https://sourceware.org/bugzilla/show_bug.cgi?id=8300 Bug 53927 - wrong value for DW_AT_static_link http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53927 Until these are fixed I've made check_match a full function. After they are fixed we can resume arguing about the merits of nested functions on readability and maintenance.
This commit is contained in:
Carlos O'Donell
parent
7b3551e3a8
commit
8e25d1e772
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@ -1,3 +1,10 @@
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2014-02-28 Carlos O'Donell <carlos@redhat.com>
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* elf/dl-lookup.c (check_match): New function.
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(ELF_MACHINE_SYM_NO_MATCH): Adjust comment.
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(do_lookup_x): Remove nested function check_match. Use non-nested
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function check_match.
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2014-02-28 Roland McGrath <roland@hack.frob.com>
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* csu/Makefile (generated, before-compile): Use += rather than =.
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226
elf/dl-lookup.c
226
elf/dl-lookup.c
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@ -31,9 +31,8 @@
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#include <assert.h>
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/* Return nonzero if do_lookup_x:check_match should consider SYM to
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fail to match a symbol reference for some machine-specific
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reason. */
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/* Return nonzero if check_match should consider SYM to fail to match a
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symbol reference for some machine-specific reason. */
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#ifndef ELF_MACHINE_SYM_NO_MATCH
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# define ELF_MACHINE_SYM_NO_MATCH(sym) 0
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#endif
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@ -75,6 +74,118 @@ struct sym_val
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# define bump_num_relocations() ((void) 0)
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#endif
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/* Utility function for do_lookup_x. The caller is called with undef_name,
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ref, version, flags and type_class, and those are passed as the first
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five arguments. The caller then computes sym, symidx, strtab, and map
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and passes them as the next four arguments. Lastly the caller passes in
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versioned_sym and num_versions which are modified by check_match during
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the checking process. */
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static const ElfW(Sym) *
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check_match (const char *const undef_name,
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const ElfW(Sym) *const ref,
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const struct r_found_version *const version,
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const int flags,
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const int type_class,
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const ElfW(Sym) *const sym,
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const Elf_Symndx symidx,
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const char *const strtab,
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const struct link_map *const map,
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const ElfW(Sym) **const versioned_sym,
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int *const num_versions)
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{
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unsigned int stt = ELFW(ST_TYPE) (sym->st_info);
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assert (ELF_RTYPE_CLASS_PLT == 1);
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if (__builtin_expect ((sym->st_value == 0 /* No value. */
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&& stt != STT_TLS)
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|| ELF_MACHINE_SYM_NO_MATCH (sym)
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|| (type_class & (sym->st_shndx == SHN_UNDEF)),
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0))
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return NULL;
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/* Ignore all but STT_NOTYPE, STT_OBJECT, STT_FUNC,
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STT_COMMON, STT_TLS, and STT_GNU_IFUNC since these are no
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code/data definitions. */
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#define ALLOWED_STT \
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((1 << STT_NOTYPE) | (1 << STT_OBJECT) | (1 << STT_FUNC) \
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| (1 << STT_COMMON) | (1 << STT_TLS) | (1 << STT_GNU_IFUNC))
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if (__glibc_unlikely (((1 << stt) & ALLOWED_STT) == 0))
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return NULL;
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if (sym != ref && strcmp (strtab + sym->st_name, undef_name))
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/* Not the symbol we are looking for. */
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return NULL;
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const ElfW(Half) *verstab = map->l_versyms;
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if (version != NULL)
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{
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if (__glibc_unlikely (verstab == NULL))
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{
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/* We need a versioned symbol but haven't found any. If
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this is the object which is referenced in the verneed
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entry it is a bug in the library since a symbol must
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not simply disappear.
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It would also be a bug in the object since it means that
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the list of required versions is incomplete and so the
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tests in dl-version.c haven't found a problem.*/
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assert (version->filename == NULL
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|| ! _dl_name_match_p (version->filename, map));
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/* Otherwise we accept the symbol. */
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}
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else
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{
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/* We can match the version information or use the
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default one if it is not hidden. */
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ElfW(Half) ndx = verstab[symidx] & 0x7fff;
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if ((map->l_versions[ndx].hash != version->hash
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|| strcmp (map->l_versions[ndx].name, version->name))
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&& (version->hidden || map->l_versions[ndx].hash
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|| (verstab[symidx] & 0x8000)))
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/* It's not the version we want. */
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return NULL;
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}
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}
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else
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{
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/* No specific version is selected. There are two ways we
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can got here:
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- a binary which does not include versioning information
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is loaded
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- dlsym() instead of dlvsym() is used to get a symbol which
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might exist in more than one form
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If the library does not provide symbol version information
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there is no problem at all: we simply use the symbol if it
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is defined.
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These two lookups need to be handled differently if the
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library defines versions. In the case of the old
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unversioned application the oldest (default) version
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should be used. In case of a dlsym() call the latest and
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public interface should be returned. */
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if (verstab != NULL)
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{
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if ((verstab[symidx] & 0x7fff)
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>= ((flags & DL_LOOKUP_RETURN_NEWEST) ? 2 : 3))
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{
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/* Don't accept hidden symbols. */
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if ((verstab[symidx] & 0x8000) == 0
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&& (*num_versions)++ == 0)
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/* No version so far. */
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*versioned_sym = sym;
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return NULL;
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}
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}
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}
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/* There cannot be another entry for this symbol so stop here. */
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return sym;
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}
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/* Inner part of the lookup functions. We return a value > 0 if we
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found the symbol, the value 0 if nothing is found and < 0 if
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@ -130,105 +241,6 @@ do_lookup_x (const char *undef_name, uint_fast32_t new_hash,
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const ElfW(Sym) *symtab = (const void *) D_PTR (map, l_info[DT_SYMTAB]);
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const char *strtab = (const void *) D_PTR (map, l_info[DT_STRTAB]);
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/* Nested routine to check whether the symbol matches. */
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const ElfW(Sym) *
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__attribute_noinline__
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check_match (const ElfW(Sym) *sym)
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{
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unsigned int stt = ELFW(ST_TYPE) (sym->st_info);
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assert (ELF_RTYPE_CLASS_PLT == 1);
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if (__builtin_expect ((sym->st_value == 0 /* No value. */
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&& stt != STT_TLS)
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|| ELF_MACHINE_SYM_NO_MATCH (sym)
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|| (type_class & (sym->st_shndx == SHN_UNDEF)),
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0))
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return NULL;
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/* Ignore all but STT_NOTYPE, STT_OBJECT, STT_FUNC,
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STT_COMMON, STT_TLS, and STT_GNU_IFUNC since these are no
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code/data definitions. */
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#define ALLOWED_STT \
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((1 << STT_NOTYPE) | (1 << STT_OBJECT) | (1 << STT_FUNC) \
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| (1 << STT_COMMON) | (1 << STT_TLS) | (1 << STT_GNU_IFUNC))
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if (__glibc_unlikely (((1 << stt) & ALLOWED_STT) == 0))
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return NULL;
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if (sym != ref && strcmp (strtab + sym->st_name, undef_name))
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/* Not the symbol we are looking for. */
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return NULL;
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const ElfW(Half) *verstab = map->l_versyms;
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if (version != NULL)
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{
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if (__glibc_unlikely (verstab == NULL))
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{
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/* We need a versioned symbol but haven't found any. If
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this is the object which is referenced in the verneed
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entry it is a bug in the library since a symbol must
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not simply disappear.
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It would also be a bug in the object since it means that
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the list of required versions is incomplete and so the
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tests in dl-version.c haven't found a problem.*/
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assert (version->filename == NULL
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|| ! _dl_name_match_p (version->filename, map));
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/* Otherwise we accept the symbol. */
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}
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else
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{
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/* We can match the version information or use the
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default one if it is not hidden. */
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ElfW(Half) ndx = verstab[symidx] & 0x7fff;
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if ((map->l_versions[ndx].hash != version->hash
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|| strcmp (map->l_versions[ndx].name, version->name))
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&& (version->hidden || map->l_versions[ndx].hash
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|| (verstab[symidx] & 0x8000)))
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/* It's not the version we want. */
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return NULL;
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}
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}
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else
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{
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/* No specific version is selected. There are two ways we
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can got here:
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- a binary which does not include versioning information
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is loaded
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- dlsym() instead of dlvsym() is used to get a symbol which
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might exist in more than one form
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If the library does not provide symbol version information
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there is no problem at all: we simply use the symbol if it
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is defined.
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These two lookups need to be handled differently if the
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library defines versions. In the case of the old
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unversioned application the oldest (default) version
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should be used. In case of a dlsym() call the latest and
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public interface should be returned. */
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if (verstab != NULL)
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{
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if ((verstab[symidx] & 0x7fff)
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>= ((flags & DL_LOOKUP_RETURN_NEWEST) ? 2 : 3))
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{
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/* Don't accept hidden symbols. */
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if ((verstab[symidx] & 0x8000) == 0
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&& num_versions++ == 0)
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/* No version so far. */
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versioned_sym = sym;
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return NULL;
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}
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}
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}
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/* There cannot be another entry for this symbol so stop here. */
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return sym;
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}
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const ElfW(Sym) *sym;
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const ElfW(Addr) *bitmask = map->l_gnu_bitmask;
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if (__glibc_likely (bitmask != NULL))
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@ -254,7 +266,10 @@ do_lookup_x (const char *undef_name, uint_fast32_t new_hash,
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if (((*hasharr ^ new_hash) >> 1) == 0)
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{
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symidx = hasharr - map->l_gnu_chain_zero;
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sym = check_match (&symtab[symidx]);
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sym = check_match (undef_name, ref, version, flags,
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type_class, &symtab[symidx], symidx,
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strtab, map, &versioned_sym,
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&num_versions);
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if (sym != NULL)
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goto found_it;
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}
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@ -276,7 +291,10 @@ do_lookup_x (const char *undef_name, uint_fast32_t new_hash,
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symidx != STN_UNDEF;
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symidx = map->l_chain[symidx])
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{
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sym = check_match (&symtab[symidx]);
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sym = check_match (undef_name, ref, version, flags,
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type_class, &symtab[symidx], symidx,
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strtab, map, &versioned_sym,
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&num_versions);
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if (sym != NULL)
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goto found_it;
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}
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