Set up the data structures for vDSO in libc.a

1 files changed, 119 insertions, 0 deletions

diff --git a/elf/setup-vdso.h b/elf/setup-vdso.h
new file mode 100644
index 0000000000..1b969a0718
--- /dev/null
+++ b/elf/setup-vdso.h
@@ -0,0 +1,119 @@
+/* Set up the data structures for the system-supplied DSO.
+   Copyright (C) 2012 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+static inline void __attribute__ ((always_inline))
+setup_vdso (struct link_map *main_map __attribute__ ((unused)),
+	    struct link_map ***first_preload __attribute__ ((unused)))
+{
+#if defined NEED_DL_SYSINFO || defined NEED_DL_SYSINFO_DSO
+  if (GLRO(dl_sysinfo_dso) == NULL)
+    return;
+
+  /* Do an abridged version of the work _dl_map_object_from_fd would do
+     to map in the object.  It's already mapped and prelinked (and
+     better be, since it's read-only and so we couldn't relocate it).
+     We just want our data structures to describe it as if we had just
+     mapped and relocated it normally.  */
+  struct link_map *l = _dl_new_object ((char *) "", "", lt_library, NULL,
+				       0, LM_ID_BASE);
+  if (__builtin_expect (l != NULL, 1))
+    {
+      static ElfW(Dyn) dyn_temp[DL_RO_DYN_TEMP_CNT] attribute_relro;
+
+      l->l_phdr = ((const void *) GLRO(dl_sysinfo_dso)
+		   + GLRO(dl_sysinfo_dso)->e_phoff);
+      l->l_phnum = GLRO(dl_sysinfo_dso)->e_phnum;
+      for (uint_fast16_t i = 0; i < l->l_phnum; ++i)
+	{
+	  const ElfW(Phdr) *const ph = &l->l_phdr[i];
+	  if (ph->p_type == PT_DYNAMIC)
+	    {
+	      l->l_ld = (void *) ph->p_vaddr;
+	      l->l_ldnum = ph->p_memsz / sizeof (ElfW(Dyn));
+	    }
+	  else if (ph->p_type == PT_LOAD)
+	    {
+	      if (! l->l_addr)
+		l->l_addr = ph->p_vaddr;
+	      if (ph->p_vaddr + ph->p_memsz >= l->l_map_end)
+		l->l_map_end = ph->p_vaddr + ph->p_memsz;
+	      if ((ph->p_flags & PF_X)
+		  && ph->p_vaddr + ph->p_memsz >= l->l_text_end)
+		l->l_text_end = ph->p_vaddr + ph->p_memsz;
+	    }
+	  else
+	    /* There must be no TLS segment.  */
+	    assert (ph->p_type != PT_TLS);
+	}
+      l->l_map_start = (ElfW(Addr)) GLRO(dl_sysinfo_dso);
+      l->l_addr = l->l_map_start - l->l_addr;
+      l->l_map_end += l->l_addr;
+      l->l_text_end += l->l_addr;
+      l->l_ld = (void *) ((ElfW(Addr)) l->l_ld + l->l_addr);
+      elf_get_dynamic_info (l, dyn_temp);
+      _dl_setup_hash (l);
+      l->l_relocated = 1;
+
+      /* The vDSO is always used.  */
+      l->l_used = 1;
+
+      /* Initialize l_local_scope to contain just this map.  This allows
+	 the use of dl_lookup_symbol_x to resolve symbols within the vdso.
+	 So we create a single entry list pointing to l_real as its only
+	 element */
+      l->l_local_scope[0]->r_nlist = 1;
+      l->l_local_scope[0]->r_list = &l->l_real;
+
+      /* Now that we have the info handy, use the DSO image's soname
+	 so this object can be looked up by name.  Note that we do not
+	 set l_name here.  That field gives the file name of the DSO,
+	 and this DSO is not associated with any file.  */
+      if (l->l_info[DT_SONAME] != NULL)
+	{
+	  /* Work around a kernel problem.  The kernel cannot handle
+	     addresses in the vsyscall DSO pages in writev() calls.  */
+	  const char *dsoname = ((char *) D_PTR (l, l_info[DT_STRTAB])
+				 + l->l_info[DT_SONAME]->d_un.d_val);
+	  size_t len = strlen (dsoname);
+	  char *copy = malloc (len);
+	  if (copy == NULL)
+	    _dl_fatal_printf ("out of memory\n");
+	  l->l_libname->name = l->l_name = memcpy (copy, dsoname, len);
+	}
+
+      /* Add the vDSO to the object list.  */
+      _dl_add_to_namespace_list (l, LM_ID_BASE);
+
+# ifdef IS_IN_rtld
+      /* Rearrange the list so this DSO appears after rtld_map.  */
+      assert (l->l_next == NULL);
+      assert (l->l_prev == main_map);
+      GL(dl_rtld_map).l_next = l;
+      l->l_prev = &GL(dl_rtld_map);
+      *first_preload = &l->l_next;
+# endif
+
+      /* We have a prelinked DSO preloaded by the system.  */
+      GLRO(dl_sysinfo_map) = l;
+# ifdef NEED_DL_SYSINFO
+      if (GLRO(dl_sysinfo) == DL_SYSINFO_DEFAULT)
+	GLRO(dl_sysinfo) = GLRO(dl_sysinfo_dso)->e_entry + l->l_addr;
+# endif
+    }
+#endif
+}