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ebcf45a16c
The kernel does not put the vDSO at special addresses, so writev can write the name directly. Also remove the incorrect comment about not setting l_name. Andy Lutomirski confirmed in <https://lore.kernel.org/linux-api/442A16C0-AE5A-4A44-B261-FE6F817EAF3C@amacapital.net/> that this copy is not necessary. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
115 lines
4.0 KiB
C
115 lines
4.0 KiB
C
/* Set up the data structures for the system-supplied DSO.
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Copyright (C) 2012-2021 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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static inline void __attribute__ ((always_inline))
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setup_vdso (struct link_map *main_map __attribute__ ((unused)),
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struct link_map ***first_preload __attribute__ ((unused)))
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{
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#ifdef NEED_DL_SYSINFO_DSO
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if (GLRO(dl_sysinfo_dso) == NULL)
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return;
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/* Do an abridged version of the work _dl_map_object_from_fd would do
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to map in the object. It's already mapped and prelinked (and
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better be, since it's read-only and so we couldn't relocate it).
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We just want our data structures to describe it as if we had just
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mapped and relocated it normally. */
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struct link_map *l = _dl_new_object ((char *) "", "", lt_library, NULL,
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0, LM_ID_BASE);
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if (__glibc_likely (l != NULL))
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{
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static ElfW(Dyn) dyn_temp[DL_RO_DYN_TEMP_CNT] attribute_relro;
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l->l_phdr = ((const void *) GLRO(dl_sysinfo_dso)
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+ GLRO(dl_sysinfo_dso)->e_phoff);
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l->l_phnum = GLRO(dl_sysinfo_dso)->e_phnum;
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for (uint_fast16_t i = 0; i < l->l_phnum; ++i)
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{
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const ElfW(Phdr) *const ph = &l->l_phdr[i];
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if (ph->p_type == PT_DYNAMIC)
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{
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l->l_ld = (void *) ph->p_vaddr;
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l->l_ldnum = ph->p_memsz / sizeof (ElfW(Dyn));
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}
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else if (ph->p_type == PT_LOAD)
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{
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if (! l->l_addr)
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l->l_addr = ph->p_vaddr;
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if (ph->p_vaddr + ph->p_memsz >= l->l_map_end)
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l->l_map_end = ph->p_vaddr + ph->p_memsz;
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if ((ph->p_flags & PF_X)
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&& ph->p_vaddr + ph->p_memsz >= l->l_text_end)
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l->l_text_end = ph->p_vaddr + ph->p_memsz;
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}
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else
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/* There must be no TLS segment. */
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assert (ph->p_type != PT_TLS);
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}
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l->l_map_start = (ElfW(Addr)) GLRO(dl_sysinfo_dso);
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l->l_addr = l->l_map_start - l->l_addr;
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l->l_map_end += l->l_addr;
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l->l_text_end += l->l_addr;
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l->l_ld = (void *) ((ElfW(Addr)) l->l_ld + l->l_addr);
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elf_get_dynamic_info (l, dyn_temp);
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_dl_setup_hash (l);
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l->l_relocated = 1;
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/* The vDSO is always used. */
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l->l_used = 1;
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/* Initialize l_local_scope to contain just this map. This allows
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the use of dl_lookup_symbol_x to resolve symbols within the vdso.
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So we create a single entry list pointing to l_real as its only
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element */
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l->l_local_scope[0]->r_nlist = 1;
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l->l_local_scope[0]->r_list = &l->l_real;
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/* Now that we have the info handy, use the DSO image's soname
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so this object can be looked up by name. */
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if (l->l_info[DT_SONAME] != NULL)
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{
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char *dsoname = ((char *) D_PTR (l, l_info[DT_STRTAB])
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+ l->l_info[DT_SONAME]->d_un.d_val);
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l->l_libname->name = dsoname;
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l->l_name = dsoname;
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}
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/* Add the vDSO to the object list. */
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_dl_add_to_namespace_list (l, LM_ID_BASE);
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# if IS_IN (rtld)
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/* Rearrange the list so this DSO appears after rtld_map. */
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assert (l->l_next == NULL);
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assert (l->l_prev == main_map);
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GL(dl_rtld_map).l_next = l;
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l->l_prev = &GL(dl_rtld_map);
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*first_preload = &l->l_next;
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# else
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GL(dl_nns) = 1;
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# endif
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/* We have a prelinked DSO preloaded by the system. */
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GLRO(dl_sysinfo_map) = l;
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# ifdef NEED_DL_SYSINFO
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if (GLRO(dl_sysinfo) == DL_SYSINFO_DEFAULT)
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GLRO(dl_sysinfo) = GLRO(dl_sysinfo_dso)->e_entry + l->l_addr;
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# endif
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}
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#endif
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}
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