142 lines
5.2 KiB
C
142 lines
5.2 KiB
C
/* Locating objects in the process image. ld.so implementation.
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Copyright (C) 2021-2022 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 _DL_FIND_EH_FRAME_H
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#define _DL_FIND_EH_FRAME_H
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#include <assert.h>
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#include <atomic.h>
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#include <dlfcn.h>
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#include <ldsodefs.h>
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#include <stdbool.h>
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#include <stdint.h>
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/* Internal version of struct dl_find_object. Does not include the
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(yet unused) flags member. We need to make a copy of data also in
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struct link_map to support non-contiguous mappings, and to support
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software transactional memory (the link map is not covered by
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transactions). */
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struct dl_find_object_internal
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{
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uintptr_t map_start;
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uintptr_t map_end; /* Set to map_start by dlclose. */
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struct link_map *map; /* Set to NULL by dlclose. */
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void *eh_frame;
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#if DLFO_STRUCT_HAS_EH_DBASE
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void *eh_dbase;
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#endif
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#if DLFO_STRUCT_HAS_EH_COUNT
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int eh_count;
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#endif
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};
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/* Create a copy of *SOURCE in *COPY using relaxed MO loads and
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stores. */
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static inline void
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_dl_find_object_internal_copy (const struct dl_find_object_internal *source,
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struct dl_find_object_internal *copy)
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{
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atomic_store_relaxed (©->map_start,
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atomic_load_relaxed (&source->map_start));
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atomic_store_relaxed (©->map_end,
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atomic_load_relaxed (&source->map_end));
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atomic_store_relaxed (©->map,
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atomic_load_relaxed (&source->map));
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atomic_store_relaxed (©->eh_frame,
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atomic_load_relaxed (&source->eh_frame));
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#if DLFO_STRUCT_HAS_EH_DBASE
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atomic_store_relaxed (©->eh_dbase,
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atomic_load_relaxed (&source->eh_dbase));
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#endif
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#if DLFO_STRUCT_HAS_EH_COUNT
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atomic_store_relaxed (©->eh_count,
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atomic_load_relaxed (&source->eh_count));
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#endif
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}
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static inline void
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_dl_find_object_to_external (struct dl_find_object_internal *internal,
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struct dl_find_object *external)
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{
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external->dlfo_flags = 0;
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external->dlfo_map_start = (void *) internal->map_start;
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external->dlfo_map_end = (void *) internal->map_end;
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external->dlfo_link_map = internal->map;
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external->dlfo_eh_frame = internal->eh_frame;
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# if DLFO_STRUCT_HAS_EH_DBASE
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external->dlfo_eh_dbase = internal->eh_dbase;
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# endif
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# if DLFO_STRUCT_HAS_EH_COUNT
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external->dlfo_eh_count = internal->eh_count;
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# endif
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}
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/* Extract the object location data from a link map and writes it to
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*RESULT using relaxed MO stores. */
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static void __attribute__ ((unused))
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_dl_find_object_from_map (struct link_map *l,
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struct dl_find_object_internal *result)
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{
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atomic_store_relaxed (&result->map_start, (uintptr_t) l->l_map_start);
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atomic_store_relaxed (&result->map_end, (uintptr_t) l->l_map_end);
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atomic_store_relaxed (&result->map, l);
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#if DLFO_STRUCT_HAS_EH_DBASE
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atomic_store_relaxed (&result->eh_dbase, (void *) l->l_info[DT_PLTGOT]);
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#endif
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for (const ElfW(Phdr) *ph = l->l_phdr, *ph_end = l->l_phdr + l->l_phnum;
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ph < ph_end; ++ph)
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if (ph->p_type == DLFO_EH_SEGMENT_TYPE)
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{
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atomic_store_relaxed (&result->eh_frame,
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(void *) (ph->p_vaddr + l->l_addr));
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#if DLFO_STRUCT_HAS_EH_COUNT
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atomic_store_relaxed (&result->eh_count, ph->p_memsz / 8);
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#endif
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return;
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}
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/* Object has no exception handling segment. */
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atomic_store_relaxed (&result->eh_frame, NULL);
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#if DLFO_STRUCT_HAS_EH_COUNT
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atomic_store_relaxed (&result->eh_count, 0);
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#endif
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}
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/* Called by the dynamic linker to set up the data structures for the
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initially loaded objects. This creates a few persistent
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allocations, so it should be called with the minimal malloc. */
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void _dl_find_object_init (void) attribute_hidden;
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/* Called by dlopen/dlmopen to add new objects to the DWARF EH frame
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data structures. NEW_MAP is the dlopen'ed link map. Link maps on
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the l_next list are added if l_object_processed is 0. Needs to
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be protected by loader write lock. Returns true on success, false
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on malloc failure. */
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bool _dl_find_object_update (struct link_map *new_map) attribute_hidden;
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/* Called by dlclose to remove the link map from the DWARF EH frame
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data structures. Needs to be protected by loader write lock. */
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void _dl_find_object_dlclose (struct link_map *l) attribute_hidden;
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/* Called from __libc_freeres to deallocate malloc'ed memory. */
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void _dl_find_object_freeres (void) attribute_hidden;
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#endif /* _DL_FIND_OBJECT_H */
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