[AArch64] Implement branch over stub section.

Ensure that injection of a stub section does not break a link where
there is an xpectation that flow of control can pass from one input
section to another simply by linking the input sections in series.

The solution here is to allow stub sections to be inserted after any
input section (existing behaviour), but inject an additional branch at
the start of each stub section such that control flow falling into the
stub section will branch over the stub section.

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 6642b4b..014e30d 100644 (file)
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,5 +1,13 @@
 2015-03-25  Marcus Shawcroft  <marcus.shawcroft@arm.com>
 
+       * elfnn-aarch64.c (_bfd_aarch64_resize_stubs): Adjust stub section
+       size for initial branch.
+       (elfNN_aarch64_build_stubs): Write initial branch.
+       _bfd_aarch64_decode_(elfNN_aarch64_output_arch_local_syms): Write
+       mapping symbol on initial branch.
+
+2015-03-25  Marcus Shawcroft  <marcus.shawcroft@arm.com>
+
        * elfnn-aarch64.c (_bfd_aarch64_erratum_835769_scan):
        Update erratum count.
 

diff --git a/bfd/elfnn-aarch64.c b/bfd/elfnn-aarch64.c
index 4ac4691..9b62a5e 100644 (file)
--- a/bfd/elfnn-aarch64.c
+++ b/bfd/elfnn-aarch64.c
@@ -3117,8 +3117,17 @@ _bfd_aarch64_resize_stubs (struct elf_aarch64_link_hash_table *htab)
     }
 
   bfd_hash_traverse (&htab->stub_hash_table, aarch64_size_one_stub, htab);
-}
 
+  for (section = htab->stub_bfd->sections;
+       section != NULL; section = section->next)
+    {
+      if (!strstr (section->name, STUB_SUFFIX))
+       continue;
+
+      if (section->size)
+       section->size += 4;
+    }
+}
 
 /* Determine and set the size of the stub section for a final link.
 
@@ -3482,6 +3491,9 @@ elfNN_aarch64_build_stubs (struct bfd_link_info *info)
       if (stub_sec->contents == NULL && size != 0)
        return FALSE;
       stub_sec->size = 0;
+
+      bfd_putl32 (0x14000000 | (size >> 2), stub_sec->contents);
+      stub_sec->size += 4;
     }
 
   /* Build the stubs as directed by the stub hash table.  */
@@ -6501,6 +6513,10 @@ elfNN_aarch64_output_arch_local_syms (bfd *output_bfd,
          osi.sec_shndx = _bfd_elf_section_from_bfd_section
            (output_bfd, osi.sec->output_section);
 
+         /* The first instruction in a stub is always a branch.  */
+         if (!elfNN_aarch64_output_map_sym (&osi, AARCH64_MAP_INSN, 0))
+           return FALSE;
+
          bfd_hash_traverse (&htab->stub_hash_table, aarch64_map_one_stub,
                             &osi);
        }

diff --git a/ld/testsuite/ChangeLog b/ld/testsuite/ChangeLog
index b29e53d..c4ce066 100644 (file)
--- a/ld/testsuite/ChangeLog
+++ b/ld/testsuite/ChangeLog
@@ -1,5 +1,13 @@
 2015-03-25  Marcus Shawcroft  <marcus.shawcroft@arm.com>
 
+       * ld-aarch64/erratum835769.d: Adjust for initial branch over stub
+       section.
+       * ld-aarch64/farcall-b.d: Likewise.
+       * ld-aarch64/farcall-bl.d: Likewise.
+       * ld-aarch64/farcall-back.d: Likewise.
+
+2015-03-25  Marcus Shawcroft  <marcus.shawcroft@arm.com>
+
        * ld-aarch64/erratum835769.d: Adjust for removal of padding before
        835769 workaround stubs.
 

diff --git a/ld/testsuite/ld-aarch64/erratum835769.d b/ld/testsuite/ld-aarch64/erratum835769.d
index 1ff8d05..f3b0ed4 100644 (file)
--- a/ld/testsuite/ld-aarch64/erratum835769.d
+++ b/ld/testsuite/ld-aarch64/erratum835769.d
@@ -33,6 +33,7 @@ Disassembly of section .text:
 [ \t0-9a-f]+:[ \t]+aa0503e0[ \t]+mov[ \t]+x0, x5
 [ \t0-9a-f]+:[ \t]+d65f03c0[ \t]+ret
 
+[ \t0-9a-f]+:[ \t]+14000007[ \t]+b[ \t]+[0-9a-f]+ <__erratum_835769_veneer_0\+0x8>
 [0-9a-f]+ <__erratum_835769_veneer_2>:
 [ \t0-9a-f]+:[ \t]+9b031885[ \t]+madd[ \t]+x5, x4, x3, x6
 [ \t0-9a-f]+:[ \t0-9a-z]+[ \t]+b[ \t]+[0-9a-f]+ <a7str\+0x[0-9a-f]+>

diff --git a/ld/testsuite/ld-aarch64/farcall-b.d b/ld/testsuite/ld-aarch64/farcall-b.d
index f3cb5ef..c1a0c6f 100644 (file)
--- a/ld/testsuite/ld-aarch64/farcall-b.d
+++ b/ld/testsuite/ld-aarch64/farcall-b.d
@@ -8,12 +8,13 @@
 Disassembly of section .text:
 
 0000000000001000 <_start>:
- +1000:        14000002        b       1008 <__bar_veneer>
+ +1000:        14000003        b       100c <__bar_veneer>
  +1004:        d65f03c0        ret
-0000000000001008 <__bar_veneer>:
-    1008:      90040010        adrp    x16, 8001000 <bar>
-    100c:      91000210        add     x16, x16, #0x0
-    1010:      d61f0200        br      x16
+[ \t]+1008:[ \t]+14000007[ \t]+b[ \t]+1024 <__bar_veneer\+0x18>
+000000000000100c <__bar_veneer>:
+    100c:      90040010        adrp    x16, 8001000 <bar>
+    1010:      91000210        add     x16, x16, #0x0
+    1014:      d61f0200        br      x16
        ...
 
 Disassembly of section .foo:

diff --git a/ld/testsuite/ld-aarch64/farcall-back.d b/ld/testsuite/ld-aarch64/farcall-back.d
index 9ff43b3..8b22360 100644 (file)
--- a/ld/testsuite/ld-aarch64/farcall-back.d
+++ b/ld/testsuite/ld-aarch64/farcall-back.d
@@ -9,64 +9,66 @@
 Disassembly of section .text:
 
 0000000000001000 <_start>:
-    1000:      14000412        b       2048 <__bar1_veneer>
-    1004:      94000411        bl      2048 <__bar1_veneer>
-    1008:      14000406        b       2020 <__bar2_veneer>
-    100c:      94000405        bl      2020 <__bar2_veneer>
-    1010:      14000408        b       2030 <__bar3_veneer>
-    1014:      94000407        bl      2030 <__bar3_veneer>
+    1000:      14000413        b       204c <__bar1_veneer>
+    1004:      94000412        bl      204c <__bar1_veneer>
+    1008:      14000407        b       2024 <__bar2_veneer>
+    100c:      94000406        bl      2024 <__bar2_veneer>
+    1010:      14000409        b       2034 <__bar3_veneer>
+    1014:      94000408        bl      2034 <__bar3_veneer>
     1018:      d65f03c0        ret
        ...
 
 000000000000201c <_back>:
     201c:      d65f03c0        ret
 
-0000000000002020 <__bar2_veneer>:
-    2020:      f07ffff0        adrp    x16, 100001000 <bar1\+0x1000>
-    2024:      91002210        add     x16, x16, #0x8
-    2028:      d61f0200        br      x16
-    202c:      00000000        .inst   0x00000000 ; undefined
+[ \t]+2020:[ \t]+14000013[ \t]+b[ \t]+206c <__bar1_veneer\+0x20>
+0000000000002024 <__bar2_veneer>:
+    2024:      f07ffff0        adrp    x16, 100001000 <bar1\+0x1000>
+    2028:      91002210        add     x16, x16, #0x8
+    202c:      d61f0200        br      x16
+    2030:      00000000        .inst   0x00000000 ; undefined
 
-0000000000002030 <__bar3_veneer>:
-    2030:      58000090        ldr     x16, 2040 <__bar3_veneer\+0x10>
-    2034:      10000011        adr     x17, 2034 <__bar3_veneer\+0x4>
-    2038:      8b110210        add     x16, x16, x17
-    203c:      d61f0200        br      x16
-    2040:      ffffffdc        .word   0xffffffdc
-    2044:      00000000        .word   0x00000000
+0000000000002034 <__bar3_veneer>:
+    2034:      58000090        ldr     x16, 2044 <__bar3_veneer\+0x10>
+    2038:      10000011        adr     x17, 2038 <__bar3_veneer\+0x4>
+    203c:      8b110210        add     x16, x16, x17
+    2040:      d61f0200        br      x16
+    2044:      ffffffd8        .word   0xffffffd8
+    2048:      00000000        .word   0x00000000
 
-0000000000002048 <__bar1_veneer>:
-    2048:      d07ffff0        adrp    x16, 100000000 <bar1>
-    204c:      91000210        add     x16, x16, #0x0
-    2050:      d61f0200        br      x16
+000000000000204c <__bar1_veneer>:
+    204c:      d07ffff0        adrp    x16, 100000000 <bar1>
+    2050:      91000210        add     x16, x16, #0x0
+    2054:      d61f0200        br      x16
        ...
 
 Disassembly of section .foo:
 
 0000000100000000 <bar1>:
    100000000:  d65f03c0        ret
-   100000004:  14000805        b       100002018 <___start_veneer>
+   100000004:  14000806        b       10000201c <___start_veneer>
        ...
 
 0000000100001008 <bar2>:
    100001008:  d65f03c0        ret
-   10000100c:  14000403        b       100002018 <___start_veneer>
+   10000100c:  14000404        b       10000201c <___start_veneer>
        ...
 
 0000000100002010 <bar3>:
    100002010:  d65f03c0        ret
-   100002014:  14000007        b       100002030 <___back_veneer>
+   100002014:  14000008        b       100002034 <___back_veneer>
 
-0000000100002018 <___start_veneer>:
-   100002018:  58000090        ldr     x16, 100002028 <___start_veneer\+0x10>
-   10000201c:  10000011        adr     x17, 10000201c <___start_veneer\+0x4>
-   100002020:  8b110210        add     x16, x16, x17
-   100002024:  d61f0200        br      x16
-   100002028:  ffffefe4        .word   0xffffefe4
-   10000202c:  fffffffe        .word   0xfffffffe
+[ \t]+100002018:[ \t]+1400000d[ \t]+b[ \t]+10000204c <___back_veneer\+0x18>
+000000010000201c <___start_veneer>:
+   10000201c:  58000090        ldr     x16, 10000202c <___start_veneer\+0x10>
+   100002020:  10000011        adr     x17, 100002020 <___start_veneer\+0x4>
+   100002024:  8b110210        add     x16, x16, x17
+   100002028:  d61f0200        br      x16
+   10000202c:  ffffefe0        .word   0xffffefe0
+   100002030:  fffffffe        .word   0xfffffffe
 
-0000000100002030 <___back_veneer>:
-   100002030:  90800010        adrp    x16, 2000 <_start\+0x1000>
-   100002034:  91007210        add     x16, x16, #0x1c
-   100002038:  d61f0200        br      x16
+0000000100002034 <___back_veneer>:
+   100002034:  90800010        adrp    x16, 2000 <_start\+0x1000>
+   100002038:  91007210        add     x16, x16, #0x1c
+   10000203c:  d61f0200        br      x16
        ...

diff --git a/ld/testsuite/ld-aarch64/farcall-bl.d b/ld/testsuite/ld-aarch64/farcall-bl.d
index 2bdd2c4..78e94dc 100644 (file)
--- a/ld/testsuite/ld-aarch64/farcall-bl.d
+++ b/ld/testsuite/ld-aarch64/farcall-bl.d
@@ -8,13 +8,13 @@
 Disassembly of section .text:
 
 0000000000001000 <_start>:
- +1000:        94000002        bl      1008 <__bar_veneer>
+ +1000:        94000003        bl      100c <__bar_veneer>
  +1004:        d65f03c0        ret
-
-0000000000001008 <__bar_veneer>:
-    1008:      90040010        adrp    x16, 8001000 <bar>
-    100c:      91000210        add     x16, x16, #0x0
-    1010:      d61f0200        br      x16
+[ \t]+1008:[ \t]+14000007[ \t]+b[ \t]+1024 <__bar_veneer\+0x18>
+000000000000100c <__bar_veneer>:
+    100c:      90040010        adrp    x16, 8001000 <bar>
+    1010:      91000210        add     x16, x16, #0x0
+    1014:      d61f0200        br      x16
        ...
 
 Disassembly of section .foo: