ld.so: Introduce delayed relocation processing fw/bug21242

This makes it possible to use IFUNC resolvers which depend
on relocations themselves, as long as these reloctions do
not depend on IFUNCs.

So far, delayed relocation processing is only implemented for
x86-64.

1 files changed, 97 insertions, 0 deletions

diff --git a/sysdeps/x86_64/dl-delayed-reloc-machine.h b/sysdeps/x86_64/dl-delayed-reloc-machine.h
new file mode 100644
index 0000000000..d49e9ba27e
--- /dev/null
+++ b/sysdeps/x86_64/dl-delayed-reloc-machine.h
@@ -0,0 +1,97 @@
+/* Delayed relocation processing.  x86-64 version.
+   Copyright (C) 2001-2018 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/>.  */
+
+#ifndef _DL_DELAYED_RELOC_MACHINE_H
+#define _DL_DELAYED_RELOC_MACHINE_H
+
+/* This needs to be kept in sync with elf_machine_rela in
+   dl-machine.h.  */
+static inline void
+_dl_delayed_reloc_machine (const struct dl_delayed_reloc *dr)
+{
+  const ElfW(Rela) *reloc = dr->reloc;
+  const unsigned long int r_type = ELFW(R_TYPE) (reloc->r_info);
+  ElfW(Addr) *const reloc_addr = dr->reloc_addr;
+  const ElfW(Sym) *refsym = dr->refsym;
+  const ElfW(Sym) *sym = dr->sym;
+  ElfW(Addr) value = SYMBOL_ADDRESS (dr->sym_map, sym, true);
+
+  if (r_type == R_X86_64_IRELATIVE)
+    {
+      /* Special case: IRELATIVE relocations do not have an associated
+         symbol.  */
+      value = dr->map->l_addr + reloc->r_addend;
+      value = ((ElfW(Addr) (*) (void)) value) ();
+      *reloc_addr = value;
+      return;
+    }
+
+  if (ELFW(ST_TYPE) (sym->st_info) == STT_GNU_IFUNC
+      && sym->st_shndx != SHN_UNDEF)
+    value = ((ElfW(Addr) (*) (void)) value) ();
+
+  /* This switch statement needs to be kept in sync with the switch
+     statement in elf_machine_rela.  */
+  switch (r_type)
+    {
+    case R_X86_64_GLOB_DAT:
+    case R_X86_64_JUMP_SLOT:
+      *reloc_addr = value + reloc->r_addend;
+      break;
+
+    case R_X86_64_64:
+      /* value + r_addend may be > 0xffffffff and R_X86_64_64
+         relocation updates the whole 64-bit entry.  */
+      *(Elf64_Addr *) reloc_addr = (Elf64_Addr) value + reloc->r_addend;
+      break;
+    case R_X86_64_32:
+      value += reloc->r_addend;
+      *(unsigned int *) reloc_addr = value;
+
+      const char *fmt;
+      if (__glibc_unlikely (value > UINT_MAX))
+        {
+          const char *strtab;
+
+          fmt = "\
+%s: Symbol `%s' causes overflow in R_X86_64_32 relocation\n";
+        print_err:
+          strtab = (const char *) D_PTR (dr->map, l_info[DT_STRTAB]);
+
+          _dl_error_printf (fmt, RTLD_PROGNAME, strtab + refsym->st_name);
+        }
+      break;
+    case R_X86_64_PC32:
+      value += reloc->r_addend - (ElfW(Addr)) reloc_addr;
+      *(unsigned int *) reloc_addr = value;
+      if (__glibc_unlikely (value != (int) value))
+        {
+          fmt = "\
+%s: Symbol `%s' causes overflow in R_X86_64_PC32 relocation\n";
+          goto print_err;
+        }
+    case R_X86_64_COPY:
+      memcpy (reloc_addr, (void *) value,
+              MIN (sym->st_size, refsym->st_size));
+      break;
+    default:
+      _dl_reloc_bad_type (dr->map, r_type, 0);
+    }
+}
+
+#endif  /* _DL_DELAYED_RELOC_MACHINE_H */