x86-64: Use PLT address for PC-relative reloc
authorH.J. Lu <hjl.tools@gmail.com>
Wed, 14 Feb 2018 11:50:40 +0000 (03:50 -0800)
committerH.J. Lu <hjl.tools@gmail.com>
Wed, 14 Feb 2018 11:50:55 +0000 (03:50 -0800)
Since PLT in PDE and PC-relative PLT in PIE can be used as function
address, there is no need for dynamic PC-relative relocation against
a dynamic function definition in PIE.  Linker should resolve PC-relative
reference to its PLT address.

NB: i386 has non-PIC PLT and PIC PLT.  Only non-PIC PLT in PDE can
be used as function address.  PIC PLT in PIE can't be used as
function address.

bfd/

PR ld/22842
* elf32-i386.c (elf_i386_check_relocs): Pass FALSE for non
PC-relative PLT to NEED_DYNAMIC_RELOCATION_P.
* elf64-x86-64.c (elf_x86_64_check_relocs): Create PLT for
R_X86_64_PC32 reloc against dynamic function in data section.
Pass TRUE for PC-relative PLT to NEED_DYNAMIC_RELOCATION_P.
(elf_x86_64_relocate_section): Use PLT for R_X86_64_PC32 reloc
against dynamic function in data section.
* elfxx-x86.c (elf_x86_allocate_dynrelocs): Use PLT in PIE as
function address only if pcrel_plt is true.
(_bfd_x86_elf_link_hash_table_create): Set pcrel_plt.
* elfxx-x86.h (NEED_DYNAMIC_RELOCATION_P): Add PCREL_PLT for
PC-relative PLT.  If PLT is PC-relative, don't generate dynamic
PC-relative relocation against a function definition in data
secton in PIE.  Remove the obsolete comments.
(elf_x86_link_hash_table): Add pcrel_plt.

ld/

PR ld/22842
* testsuite/ld-i386/i386.exp: Run PR ld/22842 tests.
* testsuite/ld-x86-64/x86-64.exp: Likewise.
* testsuite/ld-i386/pr22842a.c: New file.
* testsuite/ld-i386/pr22842b.S: Likewise.
* testsuite/ld-x86-64/pr22842a.c: Likewise.
* testsuite/ld-x86-64/pr22842a.rd: Likewise.
* testsuite/ld-x86-64/pr22842b.S: Likewise.
* testsuite/ld-x86-64/pr22842b.rd: Likewise.

14 files changed:
bfd/ChangeLog
bfd/elf32-i386.c
bfd/elf64-x86-64.c
bfd/elfxx-x86.c
bfd/elfxx-x86.h
ld/ChangeLog
ld/testsuite/ld-i386/i386.exp
ld/testsuite/ld-i386/pr22842a.c [new file with mode: 0644]
ld/testsuite/ld-i386/pr22842b.S [new file with mode: 0644]
ld/testsuite/ld-x86-64/pr22842a.c [new file with mode: 0644]
ld/testsuite/ld-x86-64/pr22842a.rd [new file with mode: 0644]
ld/testsuite/ld-x86-64/pr22842b.S [new file with mode: 0644]
ld/testsuite/ld-x86-64/pr22842b.rd [new file with mode: 0644]
ld/testsuite/ld-x86-64/x86-64.exp

index 77cdfe86bc8806538f7535d3da052fed75dbe875..b3afd99cd50c5b8e9ee0fec9292f44ebd227329f 100644 (file)
@@ -1,3 +1,22 @@
+2018-02-14  H.J. Lu  <hongjiu.lu@intel.com>
+
+       PR ld/22842
+       * elf32-i386.c (elf_i386_check_relocs): Pass FALSE for non
+       PC-relative PLT to NEED_DYNAMIC_RELOCATION_P.
+       * elf64-x86-64.c (elf_x86_64_check_relocs): Create PLT for
+       R_X86_64_PC32 reloc against dynamic function in data section.
+       Pass TRUE for PC-relative PLT to NEED_DYNAMIC_RELOCATION_P.
+       (elf_x86_64_relocate_section): Use PLT for R_X86_64_PC32 reloc
+       against dynamic function in data section.
+       * elfxx-x86.c (elf_x86_allocate_dynrelocs): Use PLT in PIE as
+       function address only if pcrel_plt is true.
+       (_bfd_x86_elf_link_hash_table_create): Set pcrel_plt.
+       * elfxx-x86.h (NEED_DYNAMIC_RELOCATION_P): Add PCREL_PLT for
+       PC-relative PLT.  If PLT is PC-relative, don't generate dynamic
+       PC-relative relocation against a function definition in data
+       secton in PIE.  Remove the obsolete comments.
+       (elf_x86_link_hash_table): Add pcrel_plt.
+
 2018-02-13  H.J. Lu  <hongjiu.lu@intel.com>
 
        * elfxx-x86.c (elf_x86_allocate_dynrelocs): Check bfd_link_dll,
index e74da3af620b16769b3a413775d793abb962cceb..1a4b53ae3055331592b043ef34b518d690ee2c1b 100644 (file)
@@ -1812,7 +1812,7 @@ do_relocation:
 
          size_reloc = FALSE;
 do_size:
-         if (NEED_DYNAMIC_RELOCATION_P (info, h, sec, r_type,
+         if (NEED_DYNAMIC_RELOCATION_P (info, FALSE, h, sec, r_type,
                                         R_386_32))
            {
              struct elf_dyn_relocs *p;
index 0e4bb2e4a5f95e14499fed05bcb07a50a0816bcf..00ed5d17a5a60b87b1d301c6dbe62d71868a0c70 100644 (file)
@@ -2135,7 +2135,17 @@ pointer:
                     as pointer, make sure that PLT is used if foo is
                     a function defined in a shared library.  */
                  if ((sec->flags & SEC_CODE) == 0)
-                   h->pointer_equality_needed = 1;
+                   {
+                     h->pointer_equality_needed = 1;
+                     if (bfd_link_pie (info)
+                         && h->type == STT_FUNC
+                         && !h->def_regular
+                         && h->def_dynamic)
+                       {
+                         h->needs_plt = 1;
+                         h->plt.refcount = 1;
+                       }
+                   }
                }
              else if (r_type != R_X86_64_PC32_BND
                       && r_type != R_X86_64_PC64)
@@ -2173,7 +2183,7 @@ pointer:
 
          size_reloc = FALSE;
 do_size:
-         if (NEED_DYNAMIC_RELOCATION_P (info, h, sec, r_type,
+         if (NEED_DYNAMIC_RELOCATION_P (info, TRUE, h, sec, r_type,
                                         htab->pointer_r_type))
            {
              struct elf_dyn_relocs *p;
@@ -2968,6 +2978,7 @@ do_ifunc_pointer:
              break;
            }
 
+use_plt:
          if (h->plt.offset != (bfd_vma) -1)
            {
              if (htab->plt_second != NULL)
@@ -3046,6 +3057,15 @@ do_ifunc_pointer:
                return elf_x86_64_need_pic (info, input_bfd, input_section,
                                            h, NULL, NULL, howto);
            }
+         /* Since x86-64 has PC-relative PLT, we can use PLT in PIE
+            as function address.  */
+         else if (h != NULL
+                  && (input_section->flags & SEC_CODE) == 0
+                  && bfd_link_pie (info)
+                  && h->type == STT_FUNC
+                  && !h->def_regular
+                  && h->def_dynamic)
+           goto use_plt;
          /* Fall through.  */
 
        case R_X86_64_8:
index bd36707fc03f3770a24233e1e75bf1505abfeaaa..05d283b4fe548b45d1a87d1d17828e0ffa56026e 100644 (file)
@@ -179,6 +179,7 @@ elf_x86_allocate_dynrelocs (struct elf_link_hash_entry *h, void *inf)
          asection *s = htab->elf.splt;
          asection *second_s = htab->plt_second;
          asection *got_s = htab->plt_got;
+         bfd_boolean use_plt;
 
          /* If this is the first .plt entry, make room for the special
             first entry.  The .plt section is used by prelink to undo
@@ -196,12 +197,19 @@ elf_x86_allocate_dynrelocs (struct elf_link_hash_entry *h, void *inf)
            }
 
          /* If this symbol is not defined in a regular file, and we are
-            not generating a shared library, then set the symbol to this
-            location in the .plt.  This is required to make function
-            pointers compare as equal between the normal executable and
-            the shared library.  */
-         if (! bfd_link_dll (info)
-             && !h->def_regular)
+            generating PDE, then set the symbol to this location in the
+            .plt.  This is required to make function pointers compare
+            as equal between PDE and the shared library.
+
+            NB: If PLT is PC-relative, we can use the .plt in PIE for
+            function address. */
+         if (h->def_regular)
+           use_plt = FALSE;
+         else if (htab->pcrel_plt)
+           use_plt = ! bfd_link_dll (info);
+         else
+           use_plt = bfd_link_pde (info);
+         if (use_plt)
            {
              if (use_plt_got)
                {
@@ -771,6 +779,7 @@ _bfd_x86_elf_link_hash_table_create (bfd *abfd)
       ret->dt_reloc_sz = DT_RELASZ;
       ret->dt_reloc_ent = DT_RELAENT;
       ret->got_entry_size = 8;
+      ret->pcrel_plt = TRUE;
       ret->tls_get_addr = "__tls_get_addr";
     }
   if (ABI_64_P (abfd))
@@ -798,6 +807,7 @@ _bfd_x86_elf_link_hash_table_create (bfd *abfd)
          ret->dt_reloc_ent = DT_RELENT;
          ret->sizeof_reloc = sizeof (Elf32_External_Rel);
          ret->got_entry_size = 4;
+         ret->pcrel_plt = FALSE;
          ret->pointer_r_type = R_386_32;
          ret->dynamic_interpreter = ELF32_DYNAMIC_INTERPRETER;
          ret->dynamic_interpreter_size
index 0162a90c6d38c4f2c813dfa240d125170d8d8bbb..f84fe01630bf7c50f3e182bde658cc2542acd9db 100644 (file)
    into the shared library.  However, if we are linking with -Bsymbolic,
    we do not need to copy a reloc against a global symbol which is
    defined in an object we are including in the link (i.e., DEF_REGULAR
-   is set).  At this point we have not seen all the input files, so it
-   is possible that DEF_REGULAR is not set now but will be set later (it
-   is never cleared).  In case of a weak definition, DEF_REGULAR may be
-   cleared later by a strong definition in a shared library.  We account
-   for that possibility below by storing information in the relocs_copied
-   field of the hash table entry.  A similar situation occurs when
-   creating shared libraries and symbol visibility changes render the
-   symbol local.
+   is set).
+
+   If PCREL_PLT is true, don't generate dynamic relocation in PIE for
+   PC-relative relocation against a dynamic function definition in data
+   section when PLT address can be used.
 
    If on the other hand, we are creating an executable, we may need to
    keep relocations for symbols satisfied by a dynamic library if we
 
    We also need to generate dynamic pointer relocation against
    STT_GNU_IFUNC symbol in the non-code section.  */
-#define NEED_DYNAMIC_RELOCATION_P(INFO, H, SEC, R_TYPE, POINTER_TYPE) \
+#define NEED_DYNAMIC_RELOCATION_P(INFO, PCREL_PLT, H, SEC, R_TYPE, \
+                                 POINTER_TYPE) \
   ((bfd_link_pic (INFO) \
     && (! X86_PCREL_TYPE_P (R_TYPE) \
        || ((H) != NULL \
            && (! (bfd_link_pie (INFO) \
                   || SYMBOLIC_BIND ((INFO), (H))) \
                || (H)->root.type == bfd_link_hash_defweak \
-               || !(H)->def_regular)))) \
-               || ((H) != NULL \
-                   && (H)->type == STT_GNU_IFUNC \
-                   && (R_TYPE) == POINTER_TYPE \
-                   && ((SEC)->flags & SEC_CODE) == 0) \
-                   || (ELIMINATE_COPY_RELOCS \
-                       && !bfd_link_pic (INFO) \
-                       && (H) != NULL \
-                       && ((H)->root.type == bfd_link_hash_defweak \
-                           || !(H)->def_regular)))
+               || (!(bfd_link_pie (INFO) \
+                     && (PCREL_PLT) \
+                     && (H)->plt.refcount > 0 \
+                     && ((SEC)->flags & SEC_CODE) == 0 \
+                     && (H)->type == STT_FUNC \
+                     && (H)->def_dynamic) \
+                   && !(H)->def_regular))))) \
+   || ((H) != NULL \
+       && (H)->type == STT_GNU_IFUNC \
+       && (R_TYPE) == POINTER_TYPE \
+       && ((SEC)->flags & SEC_CODE) == 0) \
+   || (ELIMINATE_COPY_RELOCS \
+       && !bfd_link_pic (INFO) \
+       && (H) != NULL \
+       && ((H)->root.type == bfd_link_hash_defweak \
+          || !(H)->def_regular)))
 
 /* TRUE if dynamic relocation should be generated.  Don't copy a
    pc-relative relocation into the output file if the symbol needs
@@ -482,6 +486,14 @@ struct elf_x86_link_hash_table
   /* TRUE if GOT is referenced.  */
   unsigned int got_referenced : 1;
 
+  /* TRUE if PLT is PC-relative.  PLT in PDE and PC-relative PLT in PIE
+     can be used as function address.
+
+     NB: i386 has non-PIC PLT and PIC PLT.  Only non-PIC PLT in PDE can
+     be used as function address.  PIC PLT in PIE can't be used as
+     function address.  */
+  unsigned int pcrel_plt : 1;
+
   bfd_vma (*r_info) (bfd_vma, bfd_vma);
   bfd_vma (*r_sym) (bfd_vma);
   bfd_boolean (*is_reloc_section) (const char *);
index 42ddf8bf0049d50263489916c488e1b49cfab765..c8a967ab145e9449f76ad66bdd24d58353ce0938 100644 (file)
@@ -1,3 +1,15 @@
+2018-02-14  H.J. Lu  <hongjiu.lu@intel.com>
+
+       PR ld/22842
+       * testsuite/ld-i386/i386.exp: Run PR ld/22842 tests.
+       * testsuite/ld-x86-64/x86-64.exp: Likewise.
+       * testsuite/ld-i386/pr22842a.c: New file.
+       * testsuite/ld-i386/pr22842b.S: Likewise.
+       * testsuite/ld-x86-64/pr22842a.c: Likewise.
+       * testsuite/ld-x86-64/pr22842a.rd: Likewise.
+       * testsuite/ld-x86-64/pr22842b.S: Likewise.
+       * testsuite/ld-x86-64/pr22842b.rd: Likewise.
+
 2018-02-14  Maciej W. Rozycki  <macro@mips.com>
 
        * ldlex.h (ldlex_command): Remove prototype.
index e4ec07d0e97712c68bfa837ae38350c413f42aba..ba2cce87ecec29deb7de830dc1dcc36fc358f9a0 100644 (file)
@@ -1273,6 +1273,14 @@ if { [isnative]
            {} \
            "pr21997-1.so" \
        ] \
+       [list \
+           "Build pr22842.so" \
+           "-shared" \
+           "-fPIC" \
+           { pr22842a.c } \
+           {} \
+           "pr22842.so" \
+       ] \
     ]
 
     run_ld_link_exec_tests [list \
@@ -1371,6 +1379,14 @@ if { [isnative]
            "pr21997-1-pie-2" \
            "pass.out" \
        ] \
+       [list \
+           "Build pr22842" \
+           "-pie -Wl,--no-as-needed tmpdir/pr22842.so" \
+           "" \
+           { pr22842b.S } \
+           "pr22842" \
+           "pass.out" \
+       ] \
     ]
 
     if { [at_least_gcc_version 5 0] } {
diff --git a/ld/testsuite/ld-i386/pr22842a.c b/ld/testsuite/ld-i386/pr22842a.c
new file mode 100644 (file)
index 0000000..52489bb
--- /dev/null
@@ -0,0 +1,20 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+void
+test (void)
+{
+  static int count;
+  if (count)
+    printf("PASS\n");
+  count++;
+}
+
+void
+foo (void (*bar) (void))
+{
+  if (bar != test)
+    abort ();
+  bar ();
+  test ();
+}
diff --git a/ld/testsuite/ld-i386/pr22842b.S b/ld/testsuite/ld-i386/pr22842b.S
new file mode 100644 (file)
index 0000000..d959a5f
--- /dev/null
@@ -0,0 +1,41 @@
+       .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
+       movl    bar@GOT(%ebx), %eax
+       addl    (%eax), %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
+       .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
+
+       .data
+       .p2align 2
+bar:
+       .long   test - .
+
+       .section        .note.GNU-stack,"",@progbits
diff --git a/ld/testsuite/ld-x86-64/pr22842a.c b/ld/testsuite/ld-x86-64/pr22842a.c
new file mode 100644 (file)
index 0000000..52489bb
--- /dev/null
@@ -0,0 +1,20 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+void
+test (void)
+{
+  static int count;
+  if (count)
+    printf("PASS\n");
+  count++;
+}
+
+void
+foo (void (*bar) (void))
+{
+  if (bar != test)
+    abort ();
+  bar ();
+  test ();
+}
diff --git a/ld/testsuite/ld-x86-64/pr22842a.rd b/ld/testsuite/ld-x86-64/pr22842a.rd
new file mode 100644 (file)
index 0000000..d78ea2f
--- /dev/null
@@ -0,0 +1,4 @@
+#failif
+#...
+[0-9a-f ]+R_X86_64_NONE.*
+#...
diff --git a/ld/testsuite/ld-x86-64/pr22842b.S b/ld/testsuite/ld-x86-64/pr22842b.S
new file mode 100644 (file)
index 0000000..f0659cd
--- /dev/null
@@ -0,0 +1,20 @@
+       .text
+       .globl  main
+       .type   main,@function
+main:
+       pushq   %rax
+        movslq  bar(%rip), %rax
+        leaq    bar(%rip), %rdi
+       addq    %rax, %rdi
+
+       callq   foo
+       xorl    %eax, %eax
+       popq    %rcx
+       retq
+
+       .data
+       .p2align 2
+bar:
+       .long   test - .
+
+       .section        .note.GNU-stack,"",@progbits
diff --git a/ld/testsuite/ld-x86-64/pr22842b.rd b/ld/testsuite/ld-x86-64/pr22842b.rd
new file mode 100644 (file)
index 0000000..f1036d5
--- /dev/null
@@ -0,0 +1,4 @@
+#failif
+#...
+[0-9a-f ]+R_X86_64_PC32 +[0-9a-f]+ +test \+ 0
+#...
index 8442663af176a9b0c505becebeaa411bb57c30ac..2a46266e0dd7783c50a997be18ffd7905097c319 100644 (file)
@@ -1190,6 +1190,23 @@ if { [isnative] && [which $CC] != 0 } {
            {{readelf -drW pr22791-2.rd}} \
            "pr22791-2" \
        ] \
+       [list \
+           "Build pr22842.so" \
+           "-shared" \
+           "-fPIC" \
+           { pr22842a.c } \
+           {} \
+           "pr22842.so" \
+       ] \
+       [list \
+           "Build pr22842" \
+           "-pie -Wl,--no-as-needed tmpdir/pr22842.so" \
+           "" \
+           { pr22842b.S } \
+           {{readelf -rW pr22842a.rd} \
+            {readelf -rW pr22842b.rd}} \
+           "pr22842" \
+       ] \
     ]
 
     if  {[istarget "x86_64-*-linux*-gnux32"]} {
@@ -1524,6 +1541,14 @@ if { [isnative] && [which $CC] != 0 } {
            "pass.out" \
            "$NOPIE_CFLAGS" \
        ] \
+       [list \
+           "Build pr22842" \
+           "-pie -Wl,--no-as-needed tmpdir/pr22842.so" \
+           "" \
+           { pr22842b.S } \
+           "pr22842" \
+           "pass.out" \
+       ] \
     ]
 
     # Run-time tests which require working ifunc attribute support.