i386: Allow copy relocs for building PIE
authorH.J. Lu <hjl.tools@gmail.com>
Wed, 22 Apr 2015 12:24:54 +0000 (05:24 -0700)
committerH.J. Lu <hjl.tools@gmail.com>
Wed, 22 Apr 2015 12:30:01 +0000 (05:30 -0700)
This patch allows copy relocs for R_386_GOTOFF relocations in PIE.  For

extern int glob_a;
int foo ()
{
  return glob_a;
}

compiler now can optimize it from

call __x86.get_pc_thunk.ax
addl $_GLOBAL_OFFSET_TABLE_, %eax
movl glob_a@GOT(%eax), %eax
movl (%eax), %eax
ret

to

call __x86.get_pc_thunk.ax
addl $_GLOBAL_OFFSET_TABLE_, %eax
movl glob_a@GOTOFF(%eax), %eax
ret

bfd/

PR ld/18289
* elf32-i386.c (elf_i386_link_hash_entry): Add gotoff_ref.
(elf_i386_link_hash_newfunc): Initialize gotoff_ref to 0.
(elf_i386_create_dynamic_sections): Always allow copy relocs for
building executables.
(elf_i386_copy_indirect_symbol): Also copy gotoff_ref.
(elf_i386_check_relocs): Set gotoff_ref for R_386_GOTOFF.
(elf_i386_adjust_dynamic_symbol): Also allocate copy relocs for
PIE and R_386_GOTOFF.
(elf_i386_relocate_section): Allow R_386_GOTOFF in executable.

ld/testsuite/

PR ld/18289
* ld-i386/copyreloc-lib.c: New file.
* ld-i386/copyreloc-main.S: Likewise.
* ld-i386/copyreloc-main.out: Likewise.
* ld-i386/copyreloc-main1.rd: Likewise.
* ld-i386/copyreloc-main2.rd: Likewise.
* ld-i386/dummy.c: Likewise.
* ld-i386/pr17689.out: Likewise.
* ld-i386/pr17689.rd: Likewise.
* ld-i386/pr17689a.c: Likewise.
* ld-i386/pr17689b.S: Likewise.
* ld-i386/pr17827.rd: Likewise.
* ld-i386/pr17827ver.rd: Likewise.
* ld-i386/i386.exp: Run copyreloc tests.

17 files changed:
bfd/ChangeLog
bfd/elf32-i386.c
ld/testsuite/ChangeLog
ld/testsuite/ld-i386/copyreloc-lib.c [new file with mode: 0644]
ld/testsuite/ld-i386/copyreloc-main.S [new file with mode: 0644]
ld/testsuite/ld-i386/copyreloc-main.out [new file with mode: 0644]
ld/testsuite/ld-i386/copyreloc-main1.rd [new file with mode: 0644]
ld/testsuite/ld-i386/copyreloc-main2.rd [new file with mode: 0644]
ld/testsuite/ld-i386/dummy.c [new file with mode: 0644]
ld/testsuite/ld-i386/i386.exp
ld/testsuite/ld-i386/pr17689.out [new file with mode: 0644]
ld/testsuite/ld-i386/pr17689.rd [new file with mode: 0644]
ld/testsuite/ld-i386/pr17689a.c [new file with mode: 0644]
ld/testsuite/ld-i386/pr17689a.t [new file with mode: 0644]
ld/testsuite/ld-i386/pr17689b.S [new file with mode: 0644]
ld/testsuite/ld-i386/pr17689ver.rd [new file with mode: 0644]
ld/testsuite/ld-i386/pr17827.rd [new file with mode: 0644]

index 1f95fd5..94aca52 100644 (file)
@@ -1,3 +1,16 @@
+2015-04-22  H.J. Lu  <hongjiu.lu@intel.com>
+
+       PR ld/18289
+       * elf32-i386.c (elf_i386_link_hash_entry): Add gotoff_ref.
+       (elf_i386_link_hash_newfunc): Initialize gotoff_ref to 0.
+       (elf_i386_create_dynamic_sections): Always allow copy relocs for
+       building executables.
+       (elf_i386_copy_indirect_symbol): Also copy gotoff_ref.
+       (elf_i386_check_relocs): Set gotoff_ref for R_386_GOTOFF.
+       (elf_i386_adjust_dynamic_symbol): Also allocate copy relocs for
+       PIE and R_386_GOTOFF.
+       (elf_i386_relocate_section): Allow R_386_GOTOFF in executable.
+
 2015-04-20  H.J. Lu  <hongjiu.lu@intel.com>
 
        * elf.c (assign_section_numbers): Always set up sh_name.
index f71bce1..d76addb 100644 (file)
@@ -756,6 +756,9 @@ struct elf_i386_link_hash_entry
   (GOT_TLS_GD_P (type) || GOT_TLS_GDESC_P (type))
   unsigned char tls_type;
 
+  /* Symbol is referenced by R_386_GOTOFF relocation.  */
+  unsigned int gotoff_ref : 1;
+
   /* Information about the GOT PLT entry. Filled when there are both
      GOT and PLT relocations against the same function.  */
   union gotplt_union plt_got;
@@ -879,6 +882,7 @@ elf_i386_link_hash_newfunc (struct bfd_hash_entry *entry,
       eh = (struct elf_i386_link_hash_entry *) entry;
       eh->dyn_relocs = NULL;
       eh->tls_type = GOT_UNKNOWN;
+      eh->gotoff_ref = 0;
       eh->plt_got.offset = (bfd_vma) -1;
       eh->tlsdesc_got = (bfd_vma) -1;
     }
@@ -1022,13 +1026,28 @@ elf_i386_create_dynamic_sections (bfd *dynobj, struct bfd_link_info *info)
     return FALSE;
 
   htab->sdynbss = bfd_get_linker_section (dynobj, ".dynbss");
-  if (!info->shared)
-    htab->srelbss = bfd_get_linker_section (dynobj, ".rel.bss");
-
-  if (!htab->sdynbss
-      || (!info->shared && !htab->srelbss))
+  if (!htab->sdynbss)
     abort ();
 
+  if (info->executable)
+    {
+      /* Always allow copy relocs for building executables.  */
+      asection *s = bfd_get_linker_section (dynobj, ".rel.bss");
+      if (s == NULL)
+       {
+         const struct elf_backend_data *bed = get_elf_backend_data (dynobj);
+         s = bfd_make_section_anyway_with_flags (dynobj,
+                                                 ".rel.bss",
+                                                 (bed->dynamic_sec_flags
+                                                  | SEC_READONLY));
+         if (s == NULL
+             || ! bfd_set_section_alignment (dynobj, s,
+                                             bed->s->log_file_align))
+           return FALSE;
+       }
+      htab->srelbss = s;
+    }
+
   if (get_elf_i386_backend_data (dynobj)->is_vxworks
       && !elf_vxworks_create_dynamic_sections (dynobj, info,
                                               &htab->srelplt2))
@@ -1101,6 +1120,10 @@ elf_i386_copy_indirect_symbol (struct bfd_link_info *info,
       eind->tls_type = GOT_UNKNOWN;
     }
 
+  /* Copy gotoff_ref so that elf_i386_adjust_dynamic_symbol will
+     generate a R_386_COPY reloc.  */
+  edir->gotoff_ref |= eind->gotoff_ref;
+
   if (ELIMINATE_COPY_RELOCS
       && ind->root.type != bfd_link_hash_indirect
       && dir->dynamic_adjusted)
@@ -1475,6 +1498,7 @@ elf_i386_check_relocs (bfd *abfd,
       unsigned int r_type;
       unsigned long r_symndx;
       struct elf_link_hash_entry *h;
+      struct elf_i386_link_hash_entry *eh;
       Elf_Internal_Sym *isym;
       const char *name;
       bfd_boolean size_reloc;
@@ -1524,6 +1548,7 @@ elf_i386_check_relocs (bfd *abfd,
            h = (struct elf_link_hash_entry *) h->root.u.i.link;
        }
 
+      eh = (struct elf_i386_link_hash_entry *) h;
       if (h != NULL)
        {
          /* Create the ifunc sections for static executables.  If we
@@ -1535,11 +1560,12 @@ elf_i386_check_relocs (bfd *abfd,
            default:
              break;
 
+           case R_386_GOTOFF:
+             eh->gotoff_ref = 1;
            case R_386_32:
            case R_386_PC32:
            case R_386_PLT32:
            case R_386_GOT32:
-           case R_386_GOTOFF:
              if (htab->elf.dynobj == NULL)
                htab->elf.dynobj = abfd;
              if (!_bfd_elf_create_ifunc_sections (htab->elf.dynobj, info))
@@ -1791,7 +1817,7 @@ do_size:
                 relocations we need for this symbol.  */
              if (h != NULL)
                {
-                 head = &((struct elf_i386_link_hash_entry *) h)->dyn_relocs;
+                 head = &eh->dyn_relocs;
                }
              else
                {
@@ -2175,12 +2201,14 @@ elf_i386_adjust_dynamic_symbol (struct bfd_link_info *info,
      only references to the symbol are via the global offset table.
      For such cases we need not do anything here; the relocations will
      be handled correctly by relocate_section.  */
-  if (info->shared)
+  if (!info->executable)
     return TRUE;
 
   /* If there are no references to this symbol that do not use the
-     GOT, we don't need to generate a copy reloc.  */
-  if (!h->non_got_ref)
+     GOT nor R_386_GOTOFF relocation, we don't need to generate a copy
+     reloc.  */
+  eh = (struct elf_i386_link_hash_entry *) h;
+  if (!h->non_got_ref && !eh->gotoff_ref)
     return TRUE;
 
   /* If -z nocopyreloc was given, we won't generate them either.  */
@@ -2194,14 +2222,15 @@ elf_i386_adjust_dynamic_symbol (struct bfd_link_info *info,
   if (htab == NULL)
     return FALSE;
 
-  /* If there aren't any dynamic relocs in read-only sections, then
-     we can keep the dynamic relocs and avoid the copy reloc.  This
-     doesn't work on VxWorks, where we can not have dynamic relocations
-     (other than copy and jump slot relocations) in an executable.  */
+  /* If there aren't any dynamic relocs in read-only sections nor
+     R_386_GOTOFF relocation, then we can keep the dynamic relocs and
+     avoid the copy reloc.  This doesn't work on VxWorks, where we can
+     not have dynamic relocations (other than copy and jump slot
+     relocations) in an executable.  */
   if (ELIMINATE_COPY_RELOCS
+      && !eh->gotoff_ref
       && !get_elf_i386_backend_data (info->output_bfd)->is_vxworks)
     {
-      eh = (struct elf_i386_link_hash_entry *) h;
       for (p = eh->dyn_relocs; p != NULL; p = p->next)
        {
          s = p->sec->output_section;
@@ -3718,7 +3747,7 @@ elf_i386_relocate_section (bfd *output_bfd,
             symbol for shared library since it may not be local when
             used as function address or with copy relocation.  We also
             need to make sure that a symbol is referenced locally.  */
-         if (info->shared && h)
+         if (!info->executable && h)
            {
              if (!h->def_regular)
                {
@@ -3746,8 +3775,7 @@ elf_i386_relocate_section (bfd *output_bfd,
                  bfd_set_error (bfd_error_bad_value);
                  return FALSE;
                }
-             else if (!info->executable
-                      && !SYMBOL_REFERENCES_LOCAL (info, h)
+             else if (!SYMBOL_REFERENCES_LOCAL (info, h)
                       && (h->type == STT_FUNC
                           || h->type == STT_OBJECT)
                       && ELF_ST_VISIBILITY (h->other) == STV_PROTECTED)
index 240a444..ea6a863 100644 (file)
@@ -1,3 +1,20 @@
+2015-04-22  H.J. Lu  <hongjiu.lu@intel.com>
+
+       PR ld/18289
+       * ld-i386/copyreloc-lib.c: New file.
+       * ld-i386/copyreloc-main.S: Likewise.
+       * ld-i386/copyreloc-main.out: Likewise.
+       * ld-i386/copyreloc-main1.rd: Likewise.
+       * ld-i386/copyreloc-main2.rd: Likewise.
+       * ld-i386/dummy.c: Likewise.
+       * ld-i386/pr17689.out: Likewise.
+       * ld-i386/pr17689.rd: Likewise.
+       * ld-i386/pr17689a.c: Likewise.
+       * ld-i386/pr17689b.S: Likewise.
+       * ld-i386/pr17827.rd: Likewise.
+       * ld-i386/pr17827ver.rd: Likewise.
+       * ld-i386/i386.exp: Run copyreloc tests.
+
 2015-04-20  H.J. Lu  <hongjiu.lu@intel.com>
 
        * ld-mmix/bspec1.d: Don't hardcode offset of .shstrtab section.
diff --git a/ld/testsuite/ld-i386/copyreloc-lib.c b/ld/testsuite/ld-i386/copyreloc-lib.c
new file mode 100644 (file)
index 0000000..cbbc5e2
--- /dev/null
@@ -0,0 +1 @@
+int a_glob = 2;
diff --git a/ld/testsuite/ld-i386/copyreloc-main.S b/ld/testsuite/ld-i386/copyreloc-main.S
new file mode 100644 (file)
index 0000000..98aef83
--- /dev/null
@@ -0,0 +1,24 @@
+       .section        .text.startup,"ax",@progbits
+       .p2align 4,,15
+       .globl  main
+       .type   main, @function
+main:
+       .cfi_startproc
+       call    __x86.get_pc_thunk.ax
+       addl    $_GLOBAL_OFFSET_TABLE_, %eax
+       cmpl    $2, a_glob@GOTOFF(%eax)
+       setne   %al
+       movzbl  %al, %eax
+       ret
+       .cfi_endproc
+       .size   main, .-main
+       .section        .text.__x86.get_pc_thunk.ax,"axG",@progbits,__x86.get_pc_thunk.ax,comdat
+       .globl  __x86.get_pc_thunk.ax
+       .hidden __x86.get_pc_thunk.ax
+       .type   __x86.get_pc_thunk.ax, @function
+__x86.get_pc_thunk.ax:
+       .cfi_startproc
+       movl    (%esp), %eax
+       ret
+       .cfi_endproc
+       .section        .note.GNU-stack,"",@progbits
diff --git a/ld/testsuite/ld-i386/copyreloc-main.out b/ld/testsuite/ld-i386/copyreloc-main.out
new file mode 100644 (file)
index 0000000..e69de29
diff --git a/ld/testsuite/ld-i386/copyreloc-main1.rd b/ld/testsuite/ld-i386/copyreloc-main1.rd
new file mode 100644 (file)
index 0000000..a6bd67c
--- /dev/null
@@ -0,0 +1,3 @@
+#...
+[0-9a-f ]+R_386_COPY+[0-9a-f ]+ +a_glob
+#...
diff --git a/ld/testsuite/ld-i386/copyreloc-main2.rd b/ld/testsuite/ld-i386/copyreloc-main2.rd
new file mode 100644 (file)
index 0000000..ed61aa1
--- /dev/null
@@ -0,0 +1,4 @@
+#failif
+#...
+[0-9a-f ]+R_386_NONE.*
+#...
diff --git a/ld/testsuite/ld-i386/dummy.c b/ld/testsuite/ld-i386/dummy.c
new file mode 100644 (file)
index 0000000..5c03287
--- /dev/null
@@ -0,0 +1 @@
+/* An empty file.  */
index f214d89..8399cbc 100644 (file)
@@ -335,6 +335,78 @@ if { [isnative]
            {{readelf {-Wr} plt-main.rd}} \
            "plt-main" \
        ] \
+       [list \
+           "Build copyreloc-lib.so" \
+           "-shared" \
+           "-fPIC" \
+           { copyreloc-lib.c } \
+           {} \
+           "copyreloc-lib.so" \
+       ] \
+       [list \
+           "Build copyreloc-main with PIE and GOTOFF (1)" \
+           "tmpdir/copyreloc-lib.so -pie" \
+           "" \
+           { copyreloc-main.S } \
+           {{readelf {-Wr} copyreloc-main1.rd}} \
+           "copyreloc-main" \
+       ] \
+       [list \
+           "Build copyreloc-main with PIE and GOTOFF (2)" \
+           "tmpdir/copyreloc-lib.so -pie" \
+           "" \
+           { copyreloc-main.S } \
+           {{readelf {-Wr} copyreloc-main2.rd}} \
+           "copyreloc-main" \
+       ] \
+       [list \
+           "Build pr17689.so" \
+           "-shared" \
+           "-fPIC" \
+           { pr17689a.c } \
+           {} \
+           "pr17689.so" \
+       ] \
+       [list \
+           "Build pr17689ver.so" \
+           "-shared -Wl,--version-script,pr17689a.t" \
+           "-fPIC" \
+           { pr17689a.c } \
+           {} \
+           "pr17689ver.so" \
+       ] \
+       [list \
+           "Build pr17689.a" \
+           "" \
+           "" \
+           { pr17689b.S } \
+           {} \
+           "pr17689.a" \
+       ] \
+       [list \
+           "Build pr17689 with PIE and GOTOFF" \
+           "tmpdir/pr17689b.o tmpdir/pr17689.so -pie" \
+           "" \
+           { dummy.c } \
+           {{readelf {-Wr} pr17689.rd}} \
+           "pr17689" \
+       ] \
+       [list \
+           "Build pr17689ver with PIE and GOTOFF" \
+           "tmpdir/pr17689b.o tmpdir/pr17689ver.so -pie" \
+           "" \
+           { dummy.c } \
+           {{readelf {-Wr} pr17689ver.rd}} \
+           "pr17689ver" \
+       ] \
+       [list \
+           "Build pr17827 with PIE and GOTOFF" \
+           "tmpdir/pr17689b.o tmpdir/pr17689.so -pie" \
+           "" \
+           { dummy.c } \
+           {{readelf {-Wr} pr17827.rd}} \
+           "pr17827" \
+       ] \
     ]
 
     run_ld_link_exec_tests [] [list \
@@ -357,5 +429,29 @@ if { [isnative]
            "plt-main.out" \
            "-fPIC" \
        ] \
+       [list \
+           "Run copyreloc-main with PIE and GOTOFF" \
+           "tmpdir/copyreloc-lib.so -pie" \
+           "" \
+           { copyreloc-main.S } \
+           "copyreloc-main" \
+           "copyreloc-main.out" \
+       ] \
+       [list \
+           "Run pr17689 with PIE and GOTOFF" \
+           "tmpdir/pr17689b.o tmpdir/pr17689.so -pie" \
+           "" \
+           { dummy.c } \
+           "pr17689" \
+           "pr17689.out" \
+       ] \
+       [list \
+           "Run pr17689ver with PIE and GOTOFF" \
+           "tmpdir/pr17689b.o tmpdir/pr17689ver.so -pie" \
+           "" \
+           { dummy.c } \
+           "pr17689ver" \
+           "pr17689.out" \
+       ] \
     ]
 }
diff --git a/ld/testsuite/ld-i386/pr17689.out b/ld/testsuite/ld-i386/pr17689.out
new file mode 100644 (file)
index 0000000..38e0352
--- /dev/null
@@ -0,0 +1,2 @@
+PASS
+PASS
diff --git a/ld/testsuite/ld-i386/pr17689.rd b/ld/testsuite/ld-i386/pr17689.rd
new file mode 100644 (file)
index 0000000..dda1850
--- /dev/null
@@ -0,0 +1,3 @@
+#...
+[0-9a-f ]+R_386_COPY+[0-9a-f ]+ +bar
+#...
diff --git a/ld/testsuite/ld-i386/pr17689a.c b/ld/testsuite/ld-i386/pr17689a.c
new file mode 100644 (file)
index 0000000..5317668
--- /dev/null
@@ -0,0 +1,10 @@
+#include <stdio.h>
+
+char *bar = "PASS";
+extern char *bar_alias __attribute__ ((weak, alias ("bar")));
+
+void
+foo (char *x)
+{
+  printf ("%s\n", x);
+}
diff --git a/ld/testsuite/ld-i386/pr17689a.t b/ld/testsuite/ld-i386/pr17689a.t
new file mode 100644 (file)
index 0000000..7f0efef
--- /dev/null
@@ -0,0 +1,6 @@
+VERSION {
+  global:
+    bar_alias; bar; foo;
+  local:
+    *;
+};
diff --git a/ld/testsuite/ld-i386/pr17689b.S b/ld/testsuite/ld-i386/pr17689b.S
new file mode 100644 (file)
index 0000000..24daf36
--- /dev/null
@@ -0,0 +1,44 @@
+       .text
+       .globl  main
+       .type   main, @function
+main:
+       leal    4(%esp), %ecx
+       andl    $-16, %esp
+       pushl   -4(%ecx)
+       pushl   %ebp
+       movl    %esp, %ebp
+       pushl   %ebx
+       pushl   %ecx
+       call    __x86.get_pc_thunk.bx
+       addl    $_GLOBAL_OFFSET_TABLE_, %ebx
+       subl    $12, %esp
+       pushl   bar_alias@GOTOFF(%ebx)
+       call    foo@PLT
+       popl    %eax
+       movl    ptr@GOTOFF(%ebx), %eax
+       pushl   (%eax)
+       call    foo@PLT
+       addl    $16, %esp
+       leal    -8(%ebp), %esp
+       xorl    %eax, %eax
+       popl    %ecx
+       popl    %ebx
+       popl    %ebp
+       leal    -4(%ecx), %esp
+       ret
+       .size   main, .-main
+       .globl  ptr
+       .section        .data.rel.local,"aw",@progbits
+       .align 4
+       .type   ptr, @object
+       .size   ptr, 4
+ptr:
+       .long   bar_alias
+       .section        .text.__x86.get_pc_thunk.bx,"axG",@progbits,__x86.get_pc_thunk.bx,comdat
+       .globl  __x86.get_pc_thunk.bx
+       .hidden __x86.get_pc_thunk.bx
+       .type   __x86.get_pc_thunk.bx, @function
+__x86.get_pc_thunk.bx:
+       movl    (%esp), %ebx
+       ret
+       .section        .note.GNU-stack,"",@progbits
diff --git a/ld/testsuite/ld-i386/pr17689ver.rd b/ld/testsuite/ld-i386/pr17689ver.rd
new file mode 100644 (file)
index 0000000..6cebe73
--- /dev/null
@@ -0,0 +1,3 @@
+#...
+[0-9a-f ]+R_386_COPY+[0-9a-f ]+ +bar@VERSION
+#...
diff --git a/ld/testsuite/ld-i386/pr17827.rd b/ld/testsuite/ld-i386/pr17827.rd
new file mode 100644 (file)
index 0000000..ed61aa1
--- /dev/null
@@ -0,0 +1,4 @@
+#failif
+#...
+[0-9a-f ]+R_386_NONE.*
+#...