mirror of
git://sourceware.org/git/glibc.git
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f8ed116aa5
Commit a2e8aa0d9e ("Block signals during
the initial part of dlopen") was deemed necessary because of
read-modify-write operations like the one in add_dependency in
elf/dl-lookup.c. In the old code, we check for any kind of NODELETE
status and bail out:
/* Redo the NODELETE check, as when dl_load_lock wasn't held
yet this could have changed. */
if (map->l_nodelete != link_map_nodelete_inactive)
goto out;
And then set pending status (during relocation):
if (flags & DL_LOOKUP_FOR_RELOCATE)
map->l_nodelete = link_map_nodelete_pending;
else
map->l_nodelete = link_map_nodelete_active;
If a signal arrives during relocation and the signal handler, through
lazy binding, adds a global scope dependency on the same map, it will
set map->l_nodelete to link_map_nodelete_active. This will be
overwritten with link_map_nodelete_pending by the dlopen relocation
code.
To avoid such problems in relation to the l_nodelete member, this
commit introduces two flags for active NODELETE status (irrevocable)
and pending NODELETE status (revocable until activate_nodelete is
invoked). As a result, NODELETE processing in dlopen does not
introduce further reasons why lazy binding from signal handlers
is unsafe during dlopen, and a subsequent commit can remove signal
blocking from dlopen.
This does not address pre-existing issues (unrelated to the NODELETE
changes) which make lazy binding in a signal handler during dlopen
unsafe, such as the use of malloc in both cases.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
372 lines
13 KiB
C
372 lines
13 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) 1995-2019 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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/* 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_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_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_symbolic_in_local_scope:1; /* Nonzero if l_local_scope
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during LD_TRACE_PRELINKING=1
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contains any DT_SYMBOLIC
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libraries. */
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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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/* 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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/* End of the executable part of the mapping. */
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ElfW(Addr) l_text_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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/* 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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#if __ELF_NATIVE_CLASS == 32
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# define symbind symbind32
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#elif __ELF_NATIVE_CLASS == 64
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# define symbind 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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