mirror of
https://sourceware.org/git/glibc.git
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dd32e1db38
This reverts commit6985865bc3. Reason for revert: The commit changes the order of ELF destructor calls too much relative to what applications expect or can handle. In particular, during process exit and _dl_fini, after the revert commit, we no longer call the destructors of the main program first; that only happens after some dlopen'ed objects have been destructed. This robs applications of an opportunity to influence destructor order by calling dlclose explicitly from the main program's ELF destructors. A couple of different approaches involving reverse constructor order were tried, and none of them worked really well. It seems we need to keep the dependency sorting in _dl_fini. There is also an ambiguity regarding nested dlopen calls from ELF constructors: Should those destructors run before or after the object that called dlopen? Commit6985865bc3used reverse order of the start of ELF constructor calls for destructors, but arguably using completion of constructors is more correct. However, that alone is not sufficient to address application compatibility issues (it does not change _dl_fini ordering at all).
389 lines
14 KiB
C
389 lines
14 KiB
C
/* Data structure for communication from the run-time dynamic linker for
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loaded ELF shared objects.
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Copyright (C) 1995-2023 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#ifndef _PRIVATE_LINK_H
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#define _PRIVATE_LINK_H 1
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#ifdef _LINK_H
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# error this should be impossible
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#endif
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# ifndef _ISOMAC
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/* Get most of the contents from the public header, but we define a
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different `struct link_map' type for private use. The la_objopen
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prototype uses the type, so we have to declare it separately. */
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# define link_map link_map_public
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# define la_objopen la_objopen_wrongproto
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# endif
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#include <elf/link.h>
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# ifndef _ISOMAC
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#undef link_map
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#undef la_objopen
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struct link_map;
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extern unsigned int la_objopen (struct link_map *__map, Lmid_t __lmid,
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uintptr_t *__cookie);
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#include <stdint.h>
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#include <stddef.h>
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#include <linkmap.h>
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#include <dl-fileid.h>
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#include <dl-lookupcfg.h>
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#include <tls.h>
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#include <libc-lock.h>
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/* Some internal data structures of the dynamic linker used in the
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linker map. We only provide forward declarations. */
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struct libname_list;
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struct r_found_version;
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struct r_search_path_elem;
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/* Forward declaration. */
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struct link_map;
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/* Structure to describe a single list of scope elements. The lookup
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functions get passed an array of pointers to such structures. */
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struct r_scope_elem
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{
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/* Array of maps for the scope. */
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struct link_map **r_list;
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/* Number of entries in the scope. */
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unsigned int r_nlist;
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};
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/* Structure to record search path and allocation mechanism. */
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struct r_search_path_struct
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{
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struct r_search_path_elem **dirs;
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int malloced;
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};
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/* Search path information computed by _dl_init_paths. */
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extern struct r_search_path_struct __rtld_search_dirs attribute_hidden;
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extern struct r_search_path_struct __rtld_env_path_list attribute_hidden;
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/* Structure describing a loaded shared object. The `l_next' and `l_prev'
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members form a chain of all the shared objects loaded at startup.
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These data structures exist in space used by the run-time dynamic linker;
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modifying them may have disastrous results.
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This data structure might change in future, if necessary. User-level
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programs must avoid defining objects of this type. */
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struct link_map
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{
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/* These first few members are part of the protocol with the debugger.
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This is the same format used in SVR4. */
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ElfW(Addr) l_addr; /* Difference between the address in the ELF
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file and the addresses in memory. */
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char *l_name; /* Absolute file name object was found in. */
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ElfW(Dyn) *l_ld; /* Dynamic section of the shared object. */
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struct link_map *l_next, *l_prev; /* Chain of loaded objects. */
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/* All following members are internal to the dynamic linker.
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They may change without notice. */
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/* This is an element which is only ever different from a pointer to
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the very same copy of this type for ld.so when it is used in more
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than one namespace. */
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struct link_map *l_real;
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/* Number of the namespace this link map belongs to. */
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Lmid_t l_ns;
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struct libname_list *l_libname;
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/* Indexed pointers to dynamic section.
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[0,DT_NUM) are indexed by the processor-independent tags.
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[DT_NUM,DT_NUM+DT_THISPROCNUM) are indexed by the tag minus DT_LOPROC.
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[DT_NUM+DT_THISPROCNUM,DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM) are
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indexed by DT_VERSIONTAGIDX(tagvalue).
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[DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM,
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DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM+DT_EXTRANUM) are indexed by
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DT_EXTRATAGIDX(tagvalue).
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[DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM+DT_EXTRANUM,
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DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM+DT_EXTRANUM+DT_VALNUM) are
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indexed by DT_VALTAGIDX(tagvalue) and
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[DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM+DT_EXTRANUM+DT_VALNUM,
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DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM+DT_EXTRANUM+DT_VALNUM+DT_ADDRNUM)
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are indexed by DT_ADDRTAGIDX(tagvalue), see <elf.h>. */
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ElfW(Dyn) *l_info[DT_NUM + DT_THISPROCNUM + DT_VERSIONTAGNUM
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+ DT_EXTRANUM + DT_VALNUM + DT_ADDRNUM];
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const ElfW(Phdr) *l_phdr; /* Pointer to program header table in core. */
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ElfW(Addr) l_entry; /* Entry point location. */
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ElfW(Half) l_phnum; /* Number of program header entries. */
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ElfW(Half) l_ldnum; /* Number of dynamic segment entries. */
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/* Array of DT_NEEDED dependencies and their dependencies, in
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dependency order for symbol lookup (with and without
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duplicates). There is no entry before the dependencies have
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been loaded. */
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struct r_scope_elem l_searchlist;
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/* We need a special searchlist to process objects marked with
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DT_SYMBOLIC. */
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struct r_scope_elem l_symbolic_searchlist;
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/* Dependent object that first caused this object to be loaded. */
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struct link_map *l_loader;
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/* Array with version names. */
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struct r_found_version *l_versions;
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unsigned int l_nversions;
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/* Symbol hash table. */
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Elf_Symndx l_nbuckets;
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Elf32_Word l_gnu_bitmask_idxbits;
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Elf32_Word l_gnu_shift;
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const ElfW(Addr) *l_gnu_bitmask;
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union
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{
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const Elf32_Word *l_gnu_buckets;
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const Elf_Symndx *l_chain;
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};
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union
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{
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const Elf32_Word *l_gnu_chain_zero;
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const Elf_Symndx *l_buckets;
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};
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unsigned int l_direct_opencount; /* Reference count for dlopen/dlclose. */
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enum /* Where this object came from. */
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{
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lt_executable, /* The main executable program. */
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lt_library, /* Library needed by main executable. */
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lt_loaded /* Extra run-time loaded shared object. */
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} l_type:2;
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unsigned int l_dt_relr_ref:1; /* Nonzero if GLIBC_ABI_DT_RELR is
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referenced. */
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unsigned int l_relocated:1; /* Nonzero if object's relocations done. */
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unsigned int l_init_called:1; /* Nonzero if DT_INIT function called. */
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unsigned int l_global:1; /* Nonzero if object in _dl_global_scope. */
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unsigned int l_reserved:2; /* Reserved for internal use. */
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unsigned int l_main_map:1; /* Nonzero for the map of the main program. */
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unsigned int l_visited:1; /* Used internally for map dependency
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graph traversal. */
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unsigned int l_map_used:1; /* These two bits are used during traversal */
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unsigned int l_map_done:1; /* of maps in _dl_close_worker. */
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unsigned int l_phdr_allocated:1; /* Nonzero if the data structure pointed
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to by `l_phdr' is allocated. */
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unsigned int l_soname_added:1; /* Nonzero if the SONAME is for sure in
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the l_libname list. */
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unsigned int l_faked:1; /* Nonzero if this is a faked descriptor
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without associated file. */
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unsigned int l_need_tls_init:1; /* Nonzero if GL(dl_init_static_tls)
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should be called on this link map
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when relocation finishes. */
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unsigned int l_auditing:1; /* Nonzero if the DSO is used in auditing. */
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unsigned int l_audit_any_plt:1; /* Nonzero if at least one audit module
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is interested in the PLT interception.*/
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unsigned int l_removed:1; /* Nozero if the object cannot be used anymore
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since it is removed. */
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unsigned int l_contiguous:1; /* Nonzero if inter-segment holes are
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mprotected or if no holes are present at
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all. */
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unsigned int l_free_initfini:1; /* Nonzero if l_initfini can be
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freed, ie. not allocated with
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the dummy malloc in ld.so. */
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unsigned int l_ld_readonly:1; /* Nonzero if dynamic section is readonly. */
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unsigned int l_find_object_processed:1; /* Zero if _dl_find_object_update
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needs to process this
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lt_library map. */
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/* NODELETE status of the map. Only valid for maps of type
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lt_loaded. Lazy binding sets l_nodelete_active directly,
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potentially from signal handlers. Initial loading of an
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DF_1_NODELETE object set l_nodelete_pending. Relocation may
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set l_nodelete_pending as well. l_nodelete_pending maps are
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promoted to l_nodelete_active status in the final stages of
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dlopen, prior to calling ELF constructors. dlclose only
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refuses to unload l_nodelete_active maps, the pending status is
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ignored. */
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bool l_nodelete_active;
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bool l_nodelete_pending;
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#include <link_map.h>
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/* Collected information about own RPATH directories. */
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struct r_search_path_struct l_rpath_dirs;
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/* Collected results of relocation while profiling. */
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struct reloc_result
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{
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DL_FIXUP_VALUE_TYPE addr;
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struct link_map *bound;
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unsigned int boundndx;
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uint32_t enterexit;
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unsigned int flags;
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/* CONCURRENCY NOTE: This is used to guard the concurrent initialization
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of the relocation result across multiple threads. See the more
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detailed notes in elf/dl-runtime.c. */
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unsigned int init;
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} *l_reloc_result;
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/* Pointer to the version information if available. */
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ElfW(Versym) *l_versyms;
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/* String specifying the path where this object was found. */
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const char *l_origin;
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/* Start and finish of memory map for this object. l_map_start
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need not be the same as l_addr. */
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ElfW(Addr) l_map_start, l_map_end;
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/* Default array for 'l_scope'. */
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struct r_scope_elem *l_scope_mem[4];
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/* Size of array allocated for 'l_scope'. */
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size_t l_scope_max;
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/* This is an array defining the lookup scope for this link map.
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There are initially at most three different scope lists. */
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struct r_scope_elem **l_scope;
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/* A similar array, this time only with the local scope. This is
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used occasionally. */
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struct r_scope_elem *l_local_scope[2];
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/* This information is kept to check for sure whether a shared
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object is the same as one already loaded. */
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struct r_file_id l_file_id;
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/* Collected information about own RUNPATH directories. */
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struct r_search_path_struct l_runpath_dirs;
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/* List of object in order of the init and fini calls. */
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struct link_map **l_initfini;
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/* List of the dependencies introduced through symbol binding. */
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struct link_map_reldeps
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{
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unsigned int act;
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struct link_map *list[];
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} *l_reldeps;
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unsigned int l_reldepsmax;
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/* Nonzero if the DSO is used. */
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unsigned int l_used;
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/* Various flag words. */
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ElfW(Word) l_feature_1;
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ElfW(Word) l_flags_1;
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ElfW(Word) l_flags;
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/* Temporarily used in `dl_close'. */
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int l_idx;
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struct link_map_machine l_mach;
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struct
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{
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const ElfW(Sym) *sym;
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int type_class;
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struct link_map *value;
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const ElfW(Sym) *ret;
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} l_lookup_cache;
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/* Thread-local storage related info. */
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/* Start of the initialization image. */
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void *l_tls_initimage;
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/* Size of the initialization image. */
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size_t l_tls_initimage_size;
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/* Size of the TLS block. */
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size_t l_tls_blocksize;
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/* Alignment requirement of the TLS block. */
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size_t l_tls_align;
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/* Offset of first byte module alignment. */
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size_t l_tls_firstbyte_offset;
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#ifndef NO_TLS_OFFSET
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# define NO_TLS_OFFSET 0
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#endif
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#ifndef FORCED_DYNAMIC_TLS_OFFSET
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# if NO_TLS_OFFSET == 0
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# define FORCED_DYNAMIC_TLS_OFFSET -1
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# elif NO_TLS_OFFSET == -1
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# define FORCED_DYNAMIC_TLS_OFFSET -2
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# else
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# error "FORCED_DYNAMIC_TLS_OFFSET is not defined"
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# endif
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#endif
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/* For objects present at startup time: offset in the static TLS block. */
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ptrdiff_t l_tls_offset;
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/* Index of the module in the dtv array. */
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size_t l_tls_modid;
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/* Number of thread_local objects constructed by this DSO. This is
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atomically accessed and modified and is not always protected by the load
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lock. See also: CONCURRENCY NOTES in cxa_thread_atexit_impl.c. */
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size_t l_tls_dtor_count;
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/* Information used to change permission after the relocations are
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done. */
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ElfW(Addr) l_relro_addr;
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size_t l_relro_size;
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unsigned long long int l_serial;
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};
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#include <dl-relocate-ld.h>
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/* Information used by audit modules. For most link maps, this data
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immediate follows the link map in memory. For the dynamic linker,
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it is allocated separately. See link_map_audit_state in
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<ldsodefs.h>. */
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struct auditstate
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{
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uintptr_t cookie;
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unsigned int bindflags;
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};
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/* This is the hidden instance of struct r_debug_extended used by the
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dynamic linker. */
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extern struct r_debug_extended _r_debug_extended attribute_hidden;
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#if __ELF_NATIVE_CLASS == 32
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# define symbind symbind32
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# define LA_SYMBIND "la_symbind32"
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#elif __ELF_NATIVE_CLASS == 64
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# define symbind symbind64
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# define LA_SYMBIND "la_symbind64"
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#else
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# error "__ELF_NATIVE_CLASS must be defined"
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#endif
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extern int __dl_iterate_phdr (int (*callback) (struct dl_phdr_info *info,
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size_t size, void *data),
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void *data);
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hidden_proto (__dl_iterate_phdr)
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/* We use this macro to refer to ELF macros independent of the native
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wordsize. `ELFW(R_TYPE)' is used in place of `ELF32_R_TYPE' or
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`ELF64_R_TYPE'. */
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#define ELFW(type) _ElfW (ELF, __ELF_NATIVE_CLASS, type)
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# endif /* !_ISOMAC */
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#endif /* include/link.h */
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