[binutils-gdb][ld][AArch64] Fix group_sections algorithm
authorWilco Dijkstra <wdijkstr@arm.com>
Mon, 4 May 2020 14:51:56 +0000 (15:51 +0100)
committerNick Clifton <nickc@redhat.com>
Mon, 4 May 2020 14:51:56 +0000 (15:51 +0100)
PR ld/25665
* bfd/elfnn-aarch64.c (group_sections): Copy implementation
from elf32-arm.c.
* testsuite/ld-aarch64/aarch64-elf.exp: Add new test.
* testsuite/ld-aarch64/farcall-group.s: New large group test.
* testsuite/ld-aarch64/farcall-group.d: Likewise.

bfd/ChangeLog
bfd/elfnn-aarch64.c
ld/ChangeLog
ld/testsuite/ld-aarch64/aarch64-elf.exp
ld/testsuite/ld-aarch64/farcall-group.d [new file with mode: 0644]
ld/testsuite/ld-aarch64/farcall-group.s [new file with mode: 0644]

index a2b0771db27d8db4bae12d73eeca8f6404e3bc91..be1c985615c7292594338e139daaed831e3a94fa 100644 (file)
@@ -1,3 +1,9 @@
+2020-05-01  Wilco Dijkstra  <wdijkstr@arm.com>
+
+       PR ld/25665
+       * elfnn-aarch64.c (group_sections): Copy implementation from
+       elf32-arm.c.
+
 2020-05-01  Alan Modra  <amodra@gmail.com>
 
        PR 25900
index 02688ccee10c145a5578e2ee8158d69373a8fd9b..4bb5707d2f453c4b0fc32eeba5d58f0e2ba30d75 100644 (file)
@@ -3546,7 +3546,7 @@ elfNN_aarch64_next_input_section (struct bfd_link_info *info, asection *isec)
     {
       asection **list = htab->input_list + isec->output_section->index;
 
-      if (*list != bfd_abs_section_ptr)
+      if (*list != bfd_abs_section_ptr && (isec->flags & SEC_CODE) != 0)
        {
          /* Steal the link_sec pointer for our list.  */
          /* This happens to make the list in reverse order,
@@ -3567,67 +3567,96 @@ elfNN_aarch64_next_input_section (struct bfd_link_info *info, asection *isec)
 static void
 group_sections (struct elf_aarch64_link_hash_table *htab,
                bfd_size_type stub_group_size,
-               bfd_boolean stubs_always_before_branch)
+               bfd_boolean stubs_always_after_branch)
 {
-  asection **list = htab->input_list + htab->top_index;
+  asection **list = htab->input_list;
 
   do
     {
       asection *tail = *list;
+      asection *head;
 
       if (tail == bfd_abs_section_ptr)
        continue;
 
+      /* Reverse the list: we must avoid placing stubs at the
+        beginning of the section because the beginning of the text
+        section may be required for an interrupt vector in bare metal
+        code.  */
+#define NEXT_SEC PREV_SEC
+      head = NULL;
       while (tail != NULL)
+       {
+         /* Pop from tail.  */
+         asection *item = tail;
+         tail = PREV_SEC (item);
+
+         /* Push on head.  */
+         NEXT_SEC (item) = head;
+         head = item;
+       }
+
+      while (head != NULL)
        {
          asection *curr;
-         asection *prev;
-         bfd_size_type total;
+         asection *next;
+         bfd_vma stub_group_start = head->output_offset;
+         bfd_vma end_of_next;
 
-         curr = tail;
-         total = tail->size;
-         while ((prev = PREV_SEC (curr)) != NULL
-                && ((total += curr->output_offset - prev->output_offset)
-                    < stub_group_size))
-           curr = prev;
+         curr = head;
+         while (NEXT_SEC (curr) != NULL)
+           {
+             next = NEXT_SEC (curr);
+             end_of_next = next->output_offset + next->size;
+             if (end_of_next - stub_group_start >= stub_group_size)
+               /* End of NEXT is too far from start, so stop.  */
+               break;
+             /* Add NEXT to the group.  */
+             curr = next;
+           }
 
-         /* OK, the size from the start of CURR to the end is less
+         /* OK, the size from the start to the start of CURR is less
             than stub_group_size and thus can be handled by one stub
-            section.  (Or the tail section is itself larger than
+            section.  (Or the head section is itself larger than
             stub_group_size, in which case we may be toast.)
             We should really be keeping track of the total size of
             stubs added here, as stubs contribute to the final output
             section size.  */
          do
            {
-             prev = PREV_SEC (tail);
+             next = NEXT_SEC (head);
              /* Set up this stub group.  */
-             htab->stub_group[tail->id].link_sec = curr;
+             htab->stub_group[head->id].link_sec = curr;
            }
-         while (tail != curr && (tail = prev) != NULL);
+         while (head != curr && (head = next) != NULL);
 
          /* But wait, there's more!  Input sections up to stub_group_size
-            bytes before the stub section can be handled by it too.  */
-         if (!stubs_always_before_branch)
+            bytes after the stub section can be handled by it too.  */
+         if (!stubs_always_after_branch)
            {
-             total = 0;
-             while (prev != NULL
-                    && ((total += tail->output_offset - prev->output_offset)
-                        < stub_group_size))
+             stub_group_start = curr->output_offset + curr->size;
+
+             while (next != NULL)
                {
-                 tail = prev;
-                 prev = PREV_SEC (tail);
-                 htab->stub_group[tail->id].link_sec = curr;
+                 end_of_next = next->output_offset + next->size;
+                 if (end_of_next - stub_group_start >= stub_group_size)
+                   /* End of NEXT is too far from stubs, so stop.  */
+                   break;
+                 /* Add NEXT to the stub group.  */
+                 head = next;
+                 next = NEXT_SEC (head);
+                 htab->stub_group[head->id].link_sec = curr;
                }
            }
-         tail = prev;
+         head = next;
        }
     }
-  while (list-- != htab->input_list);
+  while (list++ != htab->input_list + htab->top_index);
 
   free (htab->input_list);
 }
 
+#undef PREV_SEC
 #undef PREV_SEC
 
 #define AARCH64_BITS(x, pos, n) (((x) >> (pos)) & ((1 << (n)) - 1))
index 323a956c65a157eeaf294bd8e5dcadb41d6f865f..63b0b769a87155cb4c75ef7e67dbf36f3c5b8fc7 100644 (file)
@@ -1,3 +1,10 @@
+2020-05-01  Wilco Dijkstra  <wdijkstr@arm.com>
+
+       PR ld/25665
+       * testsuite/ld-aarch64/farcall-group.s: New large group test.
+       * testsuite/ld-aarch64/farcall-group.d: New test driver.
+       * testsuite/ld-aarch64/aarch64-elf.exp: Run the new test.
+
 2020-05-01  Alan Modra  <amodra@gmail.com>
 
        PR 25882
index fefc751b0fe2da935b88bf3d7827e628449c5443..297a3e96db95b70d92c7249ab52d3a136ef5e3f8 100644 (file)
@@ -262,6 +262,7 @@ run_dump_test "farcall-b-none-function"
 run_dump_test "farcall-bl-none-function"
 run_dump_test "farcall-b-section"
 run_dump_test "farcall-bl-section"
+run_dump_test "farcall-group"
 
 run_dump_test "tls-relax-all"
 run_dump_test "tls-relax-all-ilp32"
diff --git a/ld/testsuite/ld-aarch64/farcall-group.d b/ld/testsuite/ld-aarch64/farcall-group.d
new file mode 100644 (file)
index 0000000..365b6b9
--- /dev/null
@@ -0,0 +1,30 @@
+#name: aarch64-farcall-group
+#source: farcall-group.s
+#as:
+#ld: -Ttext=0x400078
+#objdump: -dr
+#...
+
+Disassembly of section .text:
+
+0000000000400078 <_start>:
+  400078:      95000008        bl      4400098 <__end_veneer>
+       ...
+ 440007c:      (d503201f|1f2003d5)     .word   0x(d503201f|1f2003d5)
+ 4400080:      1400000e        b       44000b8 <__end_veneer\+0x20>
+ 4400084:      d503201f        nop
+
+0000000004400088 <___start_veneer>:
+ 4400088:      90fe0010        adrp    x16, 400000 <.*>
+ 440008c:      9101e210        add     x16, x16, #0x78
+ 4400090:      d61f0200        br      x16
+ 4400094:      00000000        udf     #0
+
+0000000004400098 <__end_veneer>:
+ 4400098:      90020010        adrp    x16, 8400000 <__end_veneer\+0x3ffff68>
+ 440009c:      9102e210        add     x16, x16, #0xb8
+ 44000a0:      d61f0200        br      x16
+       ...
+
+00000000084000b8 <end>:
+ 84000b8:      96fffff4        bl      4400088 <___start_veneer>
diff --git a/ld/testsuite/ld-aarch64/farcall-group.s b/ld/testsuite/ld-aarch64/farcall-group.s
new file mode 100644 (file)
index 0000000..7fe8f94
--- /dev/null
@@ -0,0 +1,15 @@
+       .section .text.t1
+       .global _start
+       .global end
+_start:
+       bl      end
+
+       .section .text.t2
+       .zero 64 * 1024 * 1024
+
+       .section .text.t3
+       .zero 64 * 1024 * 1024
+
+       .section .text.t4
+end:
+       bl _start
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