Don't bypass the GOT for delta32toGOT references

[pete]

Summary

Hi all

In arm64, the relocation from gcc_except_table to a global in the data section was using a delta32toGOT reference. However, lld was turning this in to a direct reference from the gcc_except_table to the global it points at.

This was ultimately crashing in libunwind as the gcc_except_table had encoded the DW_EH_PE_indirect flag to tell us that the data requires an extra level of indirection, i.e., is in the GOT.

[kledzik]

LGTM

test/mach-o/gcc_except_tab-got-arm64.yaml

5–12

Some spurious comments here.

[pete]

Thanks Nick. Committed with a fix to that comment in the test. r255085.

test/mach-o/gcc_except_tab-got-arm64.yaml

5–12

Oops. That was left over from the test I copied. Thanks for catching it.

lib/ReaderWriter/MachO/ArchHandler_arm64.cpp

     case gotOffset12:
       canBypassGOT = true;
       return true;
+    case delta32ToGOT:
+      canBypassGOT = false;
+      return true;
     case imageOffsetGot:
       canBypassGOT = false;
       return true;

       const_cast<Reference *>(ref)->setKindValue(targetNowGOT ?
                                                  offset12scale8 : addOffset12);
       break;
+    case delta32ToGOT:
+      const_cast<Reference *>(ref)->setKindValue(delta32);
+      break;
     case imageOffsetGot:
       const_cast<Reference *>(ref)->setKindValue(imageOffset);
       break;

test/mach-o/gcc_except_tab-got-arm64.yaml

+# RUN: lld -flavor darwin -arch arm64 %s \
+# RUN: -dylib %p/Inputs/libSystem.yaml -o %t
+# RUN: llvm-objdump -section-headers %t | FileCheck %s
+#
+# Test parsing and writing of arm64 data relocations.
+#
+# The first step tests if the supplied mach-o file is parsed into the correct
+# set of references.  The second step verifies relocations can be round-tripped
+# by writing to a new .o file, then parsing that file which should result in
+# the same references.
+#
+#_test:
+
+
+--- !native
+defined-atoms:   
+  - name:            _main
+    scope:           global
+    content:         [ FD, 7B, BF, A9, FD, 03, 00, 91, FF, 43, 00, D1, 
+                       BF, C3, 1F, B8, 00, 00, 00, 94, BF, 03, 00, 91, 
+                       FD, 7B, C1, A8, C0, 03, 5F, D6 ]
+    alignment:       4
+  - name:            __ZTSP1A
+    scope:           hidden
+    type:            constant
+    content:         [ 50, 31, 41, 00 ]
+    merge:           as-weak
+  - name:            GCC_except_table0
+    type:            unwind-lsda
+    content:         [ FF, 9B, E7, 80, 00, 03, 5B, 00, 00, 00, 00, 1C, 
+                       00, 00, 00, 00, 00, 00, 00, 00, 1C, 00, 00, 00, 
+                       18, 00, 00, 00, 84, 00, 00, 00, 03, 40, 00, 00, 
+                       00, 10, 00, 00, 00, 94, 00, 00, 00, 03, 60, 00, 
+                       00, 00, 20, 00, 00, 00, B4, 00, 00, 00, 05, 80, 
+                       00, 00, 00, 68, 00, 00, 00, 00, 00, 00, 00, 00, 
+                       E8, 00, 00, 00, 08, 00, 00, 00, 28, 01, 00, 00, 
+                       00, F0, 00, 00, 00, 74, 00, 00, 00, 00, 00, 00, 
+                       00, 00, 00, 00, 01, 7D, 01, 00, A8, FF, FF, FF ]
+    alignment:       4
+    references:      
+      - kind:            delta32ToGOT
+        offset:          104
+        target:          __ZTIP1A
+  - name:            __ZTIP1A
+    scope:           hidden
+    type:            data
+    content:         [ 10, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 
+                       00, 00, 00, 80, 00, 00, 00, 00, 00, 00, 00, 00, 
+                       00, 00, 00, 00, 00, 00, 00, 00 ]
+    merge:           as-weak
+    alignment:       16
+shared-library-atoms:
+  - name:            dyld_stub_binder
+    load-name:       /usr/lib/libSystem.B.dylib
+    type:            unknown
+...
+
+# Make sure we have a GOT relocation.
+# This could only have come from __gcc_except_tab to __ZTIP1A
+# CHECK: __got
 No newline at end of file

test/mach-o/unwind-info-simple-arm64.yaml

 # CHECK:   Number of indices in array:                0x2
 # CHECK:   Common encodings: (count = 0)
 # CHECK:   Personality functions: (count = 1)
-# CHECK:     personality[1]: 0x00004018
+# CHECK:     personality[1]: 0x00004020
 # CHECK:   Top level indices: (count = 2)
 # CHECK:     [0]: function offset=0x00003e68, 2nd level page offset=0x00000040, LSDA offset=0x00000038
 # CHECK:     [1]: function offset=0x00003edc, 2nd level page offset=0x00000000, LSDA offset=0x00000040