MachO: align segment virtual addresses to page size.

Segments must occupy a multiple of the page size in memory (4096 currently). We
check for this when emitting files, but the placement algorithm broke down for
the second non-__TEXT segment encountered: the offset wasn't aligned up to 4096
before starting its layout.

llvm-svn: 212031

lld/lib/ReaderWriter/MachO/MachONormalizedFileFromAtoms.cpp

@@ -278,11 +278,12 @@ SectionInfo *Util::sectionForAtom(const DefinedAtom *atom) {
     // Not found, so need to create a new custom section.
     size_t seperatorIndex = customName.find('/');
     assert(seperatorIndex != StringRef::npos);
-    StringRef segName = customName.slice(0, seperatorIndex-1);
-    StringRef sectName = customName.drop_front(seperatorIndex);
+    StringRef segName = customName.slice(0, seperatorIndex);
+    StringRef sectName = customName.drop_front(seperatorIndex + 1);
     SectionInfo *sect = new (_allocator) SectionInfo(segName, sectName,
                                                      S_REGULAR);
     _customSections.push_back(sect);
+    _sectionInfos.push_back(sect);
     return sect;
   }
 }
@@ -452,6 +453,8 @@ void Util::assignAddressesToSections() {
         layoutSectionsInTextSegment(seg, address);
       else
         layoutSectionsInSegment(seg, address);
+
+      address = llvm::RoundUpToAlignment(address, _context.pageSize());
     }
     DEBUG_WITH_TYPE("WriterMachO-norm",
       llvm::dbgs() << "assignAddressesToSections()\n";

lld/test/mach-o/exe-segment-overlap.yaml

@@ -0,0 +1,44 @@
+# RUN: lld -flavor darwin -arch x86_64 %s -o %t
+# RUN: llvm-readobj -sections -section-data %t | FileCheck %s
+
+--- !native
+defined-atoms:
+   - name:            start
+     scope:           global
+     content:         [ 90 ]
+
+   - name:            _s2
+     type:            data
+     content:         [ 31, 32, 33, 34 ]
+
+   - name:            _kustom
+     scope:           global
+     type:            unknown
+     content:         [ 01, 02, 03, 04, 05, 06, 07, 08 ]
+     section-choice:  custom-required
+     section-name:    __CUST/__custom
+
+
+# CHECK-LABEL: Section {
+# CHECK:     Name: __text
+# CHECK:     Segment: __TEXT
+# CHECK:     Size: 0x1
+# CHECK:     Offset: 4095
+
+# CHECK-LABEL: Section {
+# CHECK:     Name: __data
+# CHECK:     Segment: __DATA
+# CHECK:     Size: 0x4
+# CHECK:     Offset: 4096
+# CHECK:     SectionData (
+# CHECK-NEXT: 0000: 31323334
+# CHECK-NEXT: )
+
+# CHECK-LABEL: Section {
+# CHECK:     Name: __custom{{ }}
+# CHECK:     Segment: __CUST{{ }}
+# CHECK:     Size: 0x8
+# CHECK:     Offset: 8192
+# CHECK:     SectionData (
+# CHECK-NEXT: 0000: 01020304 05060708
+# CHECK-NEXT: )