ld: don't generate base relocations in PE output for absolute symbols

It is the very nature of absolute symbols that they don't change even
if the loader decides to put the image at other than its link-time base
address. Of the linker-defined (and PE-specific) symbols __image_base__
(and its alias) needs special casing, as it'll still appear to be
absolute at this point.

A new inquiry function in ldexp.c is needed because PE base relocations
get generated before ldexp_finalize_syms() runs, yet whether a
relocation is needed depends on the ultimate property of a symbol.

diff --git a/ld/ChangeLog b/ld/ChangeLog
index 0f1da7fafabaaa509bb942fd93c1016d6776c445..95bb3f6c1a8aab29cc45cc861b46c572b79ad1ba 100644 (file)
--- a/ld/ChangeLog
+++ b/ld/ChangeLog
@@ -1,3 +1,11 @@
+2021-03-04  Jan Beulich  <jbeulich@suse.com>
+
+       * ldexp.c (ldexp_is_final_sym_absolute): New.
+       * ldexp.h (ldexp_is_final_sym_absolute): Declare.
+       * pe-dll.c (generate_reloc): Skip absolute symbols.
+       * testsuite/ld-pe/reloc.s, testsuite/ld-pe/reloc.d: New.
+       * testsuite/ld-pe/pe.exp: Run new test.
+
 2021-03-03  Alan Modra  <amodra@gmail.com>
 
        PR 27500

diff --git a/ld/ldexp.c b/ld/ldexp.c
index 016784505b2b0fad4dc511729f1e52537a39417b..7a95e561a03e203092d9933c9411715660957248 100644 (file)
--- a/ld/ldexp.c
+++ b/ld/ldexp.c
@@ -1699,6 +1699,28 @@ ldexp_finalize_syms (void)
   bfd_hash_traverse (&definedness_table, set_sym_sections, NULL);
 }
 
+/* Determine whether a symbol is going to remain absolute even after
+   ldexp_finalize_syms() has run.  */
+
+bfd_boolean
+ldexp_is_final_sym_absolute (const struct bfd_link_hash_entry *h)
+{
+  if (h->type == bfd_link_hash_defined
+      && h->u.def.section == bfd_abs_section_ptr)
+    {
+      const struct definedness_hash_entry *def;
+
+      if (!h->ldscript_def)
+       return TRUE;
+
+      def = symbol_defined (h->root.string);
+      if (def != NULL)
+       return def->final_sec == bfd_abs_section_ptr;
+    }
+
+  return FALSE;
+}
+
 void
 ldexp_finish (void)
 {

diff --git a/ld/ldexp.h b/ld/ldexp.h
index d6096175c05d0299a0c3956f276c7c784fcf161a..1055053e28dd03f03160aa08223a16a72771060e 100644 (file)
--- a/ld/ldexp.h
+++ b/ld/ldexp.h
@@ -239,6 +239,7 @@ bfd_vma exp_get_abs_int
   (etree_type *, int, char *);
 void ldexp_init (void);
 void ldexp_finalize_syms (void);
+bfd_boolean ldexp_is_final_sym_absolute (const struct bfd_link_hash_entry *);
 void ldexp_finish (void);
 
 #endif

diff --git a/ld/pe-dll.c b/ld/pe-dll.c
index 3c82f8d60d970f856926d5feeac6e586e0c9a1ed..afcf6fea93e4d8071acc3185d06b89df57844dc6 100644 (file)
--- a/ld/pe-dll.c
+++ b/ld/pe-dll.c
@@ -1579,13 +1579,13 @@ generate_reloc (bfd *abfd, struct bfd_link_info *info)
                  && relocs[i]->howto->type != pe_details->imagebase_reloc)
                {
                  struct bfd_symbol *sym = *relocs[i]->sym_ptr_ptr;
+                 const struct bfd_link_hash_entry *blhe
+                   = bfd_wrapped_link_hash_lookup (abfd, info, sym->name,
+                                                   FALSE, FALSE, FALSE);
 
                  /* Don't create relocs for undefined weak symbols.  */
                  if (sym->flags == BSF_WEAK)
                    {
-                     struct bfd_link_hash_entry *blhe
-                       = bfd_wrapped_link_hash_lookup (abfd, info, sym->name,
-                                               FALSE, FALSE, FALSE);
                      if (blhe && blhe->type == bfd_link_hash_undefweak)
                        {
                          /* Check aux sym and see if it is defined or not. */
@@ -1617,6 +1617,12 @@ generate_reloc (bfd *abfd, struct bfd_link_info *info)
                      if (!strcmp (s->name, ".eh_frame"))
                        continue;
                    }
+                 /* Nor for absolute symbols.  */
+                 else if (blhe && ldexp_is_final_sym_absolute (blhe)
+                          && (!blhe->linker_def
+                              || (strcmp (sym->name, "__image_base__")
+                                  && strcmp (sym->name, U ("__ImageBase")))))
+                   continue;
 
                  reloc_data[total_relocs].vma = sec_vma + relocs[i]->address;
                  reloc_data[total_relocs].idx = total_relocs;

diff --git a/ld/testsuite/ld-pe/pe.exp b/ld/testsuite/ld-pe/pe.exp
index de9e104f0f633d0cea43a9c6e976c062bb623d35..b1a200180be58df2371a40b66c3816053e178a76 100644 (file)
--- a/ld/testsuite/ld-pe/pe.exp
+++ b/ld/testsuite/ld-pe/pe.exp
@@ -76,6 +76,8 @@ run_dump_test "longsecn-5"
 run_dump_test "orphan"
 run_dump_test "orphan_nu"
 
+run_dump_test "reloc"
+
 run_dump_test "weakdef-1"
 
 run_dump_test "pr19803"

diff --git a/ld/testsuite/ld-pe/reloc.d b/ld/testsuite/ld-pe/reloc.d
new file mode 100644 (file)
index 0000000..55888c3
--- /dev/null
+++ b/ld/testsuite/ld-pe/reloc.d
@@ -0,0 +1,14 @@
+#name: PE base relocations
+#ld: --enable-reloc-section
+#objdump: -p
+
+.*:     file format .*
+
+#...
+PE File Base Relocations.*
+Virtual Address: .* Number of fixups 4
+[      ]*reloc    0 offset    0 .* (LOW|HIGHLOW|DIR64)
+[      ]*reloc    1 offset    [248] .* (LOW|HIGHLOW|DIR64)
+[      ]*reloc    2 offset   [124]0 .* (LOW|HIGHLOW|DIR64)
+[      ]*reloc    3 offset    0 .* ABSOLUTE
+#pass

diff --git a/ld/testsuite/ld-pe/reloc.s b/ld/testsuite/ld-pe/reloc.s
new file mode 100644 (file)
index 0000000..3ed2e02
--- /dev/null
+++ b/ld/testsuite/ld-pe/reloc.s
@@ -0,0 +1,13 @@
+       .data
+       .p2align 4
+start:
+       .dc.a   __image_base__
+       .dc.a   start
+       .dc.a   __section_alignment__
+       .dc.a   __file_alignment__
+       .dc.a   __major_os_version__
+       .dc.a   __minor_os_version__
+       .dc.a   __major_subsystem_version__
+       .dc.a   __minor_subsystem_version__
+       .dc.a   end
+end: