[lld-macho] Fix symbol relocs handling for LSDAs

[int3]

Summary

Similar to D113702, but for the LSDAs. Clang seems to emit all LSDA
relocs as section relocs, but ld -r can turn those relocs into symbol
ones.

[int3]

update

[oontvoo]

LG Thanks!!!

lld/MachO/UnwindInfoSection.cpp

442–443

Thank you!!! was wondering why our build was crashing at this line today.

assert.h assertion failed at llvm/include/llvm/ADT/PointerUnion.h:159 in T llvm::PointerUnion<lld::macho::Symbol *, lld::macho::InputSection *>::get() const [PTs = <lld::macho::Symbol *, lld::macho::InputSection *>, T = lld::macho::InputSection *]: is<T>() && "Invalid accessor called"

lld/test/MachO/compact-unwind-sym-relocs.s

246–250

dont need these?

[oontvoo]

P.S: build failures look real - PTAL

[int3]

fix

lld/MachO/UnwindInfoSection.cpp

while (++foldEnd < cuIndices.end() &&
       // to support it, but it seems unlikely to be used in practice.
       Reloc *lsda1 =
           findLsdaReloc(symbolsVec[*foldBegin].second->compactUnwind);
       Reloc *lsda2 = findLsdaReloc(symbolsVec[*foldEnd].second->compactUnwind);
       if (lsda1 == nullptr && lsda2 == nullptr)
         continue;
       if (lsda1 == nullptr || lsda2 == nullptr)
         break;
-      if (lsda1->referent.get<InputSection *>() !=
-          lsda2->referent.get<InputSection *>())
+      if (lsda1->referent != lsda2->referent)
         break;
       if (lsda1->addend != lsda2->addend)
         break;
     }
     *foldWrite++ = *foldBegin;
     foldBegin = foldEnd;
   }
   cuIndices.erase(foldWrite, cuIndices.end());
if (i < cuIndices.size() &&
                                  cuIndices.size() - page.entryIndex);
       i = page.entryIndex + page.entryCount;
     } else {
       page.kind = UNWIND_SECOND_LEVEL_COMPRESSED;
     }
   }
 
   for (size_t idx : cuIndices) {
-    const CompactUnwindEntry<Ptr> &cu = cuEntries[idx];
     lsdaIndex[idx] = entriesWithLsda.size();
-    if (cu.lsda != 0)
+    if (findLsdaReloc(symbolsVec[idx].second->compactUnwind))
       entriesWithLsda.push_back(idx);
   }
 
   // compute size of __TEXT,__unwind_info section
   level2PagesOffset = sizeof(unwind_info_section_header) +
                       commonEncodings.size() * sizeof(uint32_t) +
                       personalities.size() * sizeof(uint32_t) +
                       // The extra second-level-page entry is for the sentinel
void UnwindInfoSectionImpl<Ptr>::writeTo(uint8_t *buf) const {
 
   // LSDAs
   auto *lep =
       reinterpret_cast<unwind_info_section_header_lsda_index_entry *>(iep);
   for (size_t idx : entriesWithLsda) {
     const CompactUnwindEntry<Ptr> &cu = cuEntries[idx];
     const Defined *d = symbolsVec[idx].second;
     if (Reloc *r = findLsdaReloc(d->compactUnwind)) {
-      auto *isec = r->referent.get<InputSection *>();
-      lep->lsdaOffset = isec->getVA(r->addend) - in.header->addr;
+      uint64_t va;
+      if (auto *isec = r->referent.dyn_cast<InputSection *>()) {
+        va = isec->getVA(r->addend);
+      } else {
+        auto *sym = r->referent.get<Symbol *>();
+        va = sym->getVA() + r->addend;
+      }
+      lep->lsdaOffset = va - in.header->addr;
     }
     lep->functionOffset = cu.functionAddress - in.header->addr;
     lep++;
   }
 
   // Level-2 pages
   auto *pp = reinterpret_cast<uint32_t *>(lep);
   for (const SecondLevelPage &page : secondLevelPages) {

lld/test/MachO/compact-unwind-sym-relocs.s

 # REQUIRES: x86
 
 ## Test that we correctly handle symbol relocations in the compact unwind
 ## section.
 
 ## llvm-mc does not emit such relocations for compact unwind, but `ld -r` does.
 ## As such, these yaml files were from an object file produced with 'ld -r',
 ## specifically:
 ##
 ##  // foo.s
+## .globl _foo
 ## .text
-## .globl _main
-## _main:
+## .p2align 2
+## _foo:
 ##   .cfi_startproc
+##   .cfi_personality 155, ___gxx_personality_v0
+##   .cfi_lsda 16, _exception0
 ##   .cfi_def_cfa_offset 16
+##   ret
 ##   .cfi_endproc
-##   nop
+## 
+## .section __TEXT,__gcc_except_tab
+## _exception0:
+##   .space 0
 ##
 ## llvm-mc -filetype=obj -triple=x86_64-apple-macos10.15 -o foo1.o foo.s
 ## ld -r -o foo.o foo1.o
 
 # RUN: rm -rf %t; mkdir -p %t
 # RUN: yaml2obj %s -o %t/foo.o
-# RUN: %lld -o %t/a.out %t/foo.o
-# RUN: llvm-objdump --macho --section-headers %t/a.out | FileCheck %s
-# CHECK: __unwind_info {{.*}} DATA
+# RUN: %lld -dylib -lc++ %t/foo.o -o %t/foo
+# RUN: llvm-objdump --macho --syms --unwind-info %t/foo | FileCheck %s
+
+# CHECK:      SYMBOL TABLE:
+# CHECK-DAG:  [[#%x,MAIN:]]        g     F __TEXT,__text _foo
+# CHECK-DAG:  [[#%x,EXCEPT0:]]     l     O __TEXT,__gcc_except_tab _exception0
+
+# CHECK:      LSDA descriptors:
+# CHECK-NEXT:   [0]: function offset=0x[[#%.8x,MAIN]], LSDA offset=0x[[#%.8x,EXCEPT0]]
 
 --- !mach-o
 FileHeader:
   magic:           0xFEEDFACF
-  cputype:         0x01000007
-  cpusubtype:      0x00000003
-  filetype:        0x00000001
+  cputype:         0x1000007
+  cpusubtype:      0x3
+  filetype:        0x1
   ncmds:           2
-  sizeofcmds:      384
-  flags:           0x00000000
-  reserved:        0x00000000
+  sizeofcmds:      464
+  flags:           0x0
+  reserved:        0x0
 LoadCommands:
   - cmd:             LC_SEGMENT_64
-    cmdsize:         312
+    cmdsize:         392
     segname:         ''
     vmaddr:          0
-    vmsize:          64
-    fileoff:         448
-    filesize:        64
+    vmsize:          112
+    fileoff:         528
+    filesize:        112
     maxprot:         7
     initprot:        7
-    nsects:          2
+    nsects:          4
     flags:           0
     Sections:
       - sectname:        __text
         segname:         __TEXT
-        addr:            0x0000000000000000
+        addr:            0x0
         size:            1
-        offset:          0x000001C0
-        align:           0
-        reloff:          0x00000000
+        offset:          0x210
+        align:           2
+        reloff:          0x0
         nreloc:          0
         flags:           0x80000400
-        reserved1:       0x00000000
-        reserved2:       0x00000000
-        reserved3:       0x00000000
-        content:         '90'
+        reserved1:       0x0
+        reserved2:       0x0
+        reserved3:       0x0
+        content:         C3
+      - sectname:        __gcc_except_tab
+        segname:         __TEXT
+        addr:            0x1
+        size:            0
+        offset:          0x211
+        align:           0
+        reloff:          0x0
+        nreloc:          0
+        flags:           0x0
+        reserved1:       0x0
+        reserved2:       0x0
+        reserved3:       0x0
+        content:         ''
+      - sectname:        __eh_frame
+        segname:         __TEXT
+        addr:            0x8
+        size:            72
+        offset:          0x218
+        align:           3
+        reloff:          0x280
+        nreloc:          7
+        flags:           0x0
+        reserved1:       0x0
+        reserved2:       0x0
+        reserved3:       0x0
+        content:         1C00000000000000017A504C5200017810079B0400000010100C0708900100002400000004000000F8FFFFFFFFFFFFFF010000000000000008E7FFFFFFFFFFFFFF0E100000000000
+        relocations:
+          - address:         0x13
+            symbolnum:       4
+            pcrel:           true
+            length:          2
+            extern:          true
+            type:            4
+            scattered:       false
+            value:           0
+          - address:         0x24
+            symbolnum:       1
+            pcrel:           false
+            length:          2
+            extern:          true
+            type:            5
+            scattered:       false
+            value:           0
+          - address:         0x24
+            symbolnum:       2
+            pcrel:           false
+            length:          2
+            extern:          true
+            type:            0
+            scattered:       false
+            value:           0
+          - address:         0x28
+            symbolnum:       2
+            pcrel:           false
+            length:          3
+            extern:          true
+            type:            5
+            scattered:       false
+            value:           0
+          - address:         0x28
+            symbolnum:       3
+            pcrel:           false
+            length:          3
+            extern:          true
+            type:            0
+            scattered:       false
+            value:           0
+          - address:         0x39
+            symbolnum:       2
+            pcrel:           false
+            length:          3
+            extern:          true
+            type:            5
+            scattered:       false
+            value:           0
+          - address:         0x39
+            symbolnum:       0
+            pcrel:           false
+            length:          3
+            extern:          true
+            type:            0
+            scattered:       false
+            value:           0
       - sectname:        __compact_unwind
         segname:         __LD
-        addr:            0x0000000000000020
+        addr:            0x50
         size:            32
-        offset:          0x000001E0
+        offset:          0x260
         align:           3
-        reloff:          0x00000200
-        nreloc:          1
-        flags:           0x02000000
-        reserved1:       0x00000000
-        reserved2:       0x00000000
-        reserved3:       0x00000000
-        content:         '0000000000000000010000000000020200000000000000000000000000000000'
+        reloff:          0x2B8
+        nreloc:          4
+        flags:           0x2000000
+        reserved1:       0x0
+        reserved2:       0x0
+        reserved3:       0x0
+        content:         '0000000000000000010000000000024200000000000000000000000000000000'
         relocations:
-          - address:         0x00000000
+          - address:         0x0
+            symbolnum:       3
+            pcrel:           false
+            length:          3
+            extern:          true
+            type:            0
+            scattered:       false
+            value:           0
+          - address:         0x18
+            symbolnum:       0
+            pcrel:           false
+            length:          3
+            extern:          true
+            type:            0
+            scattered:       false
+            value:           0
+          - address:         0x10
+            symbolnum:       4
+            pcrel:           false
+            length:          3
+            extern:          true
+            type:            0
+            scattered:       false
+            value:           0
+          - address:         0x18
             symbolnum:       0
             pcrel:           false
             length:          3
             extern:          true
             type:            0
             scattered:       false
             value:           0
   - cmd:             LC_SYMTAB
     cmdsize:         24
-    symoff:          520
-    nsyms:           1
-    stroff:          552
-    strsize:         8
+    symoff:          728
+    nsyms:           5
+    stroff:          808
+    strsize:         64
 LinkEditData:
   NameList:
+    - n_strx:          29
+      n_type:          0xE
+      n_sect:          2
+      n_desc:          32
+      n_value:         1
+    - n_strx:          41
+      n_type:          0xE
+      n_sect:          3
+      n_desc:          0
+      n_value:         8
+    - n_strx:          51
+      n_type:          0xE
+      n_sect:          3
+      n_desc:          0
+      n_value:         40
     - n_strx:          2
-      n_type:          0x0F
+      n_type:          0xF
       n_sect:          1
       n_desc:          32
       n_value:         0
+    - n_strx:          7
+      n_type:          0x1
+      n_sect:          0
+      n_desc:          0
+      n_value:         0
   StringTable:
     - ' '
-    - _main
-
+    - _foo
+    - ___gxx_personality_v0
+    - _exception0
+    - EH_Frame1
+    - func.eh
+    - ''
+    - ''
+    - ''
+    - ''
+    - ''
 ...