Set max segment protection level.

The initial segment protection was also being used to set the maximum
segment protection level.  Instead, the maximum should be set according
to the architecture we are linking.  For example on Mac OS it should be
RWX on most pages, but on iOS is often on R_X.

rdar://problem/24515136

llvm-svn: 259966

1 files changed, 36 insertions, 7 deletions

diff --git a/lld/lib/ReaderWriter/MachO/MachONormalizedFileFromAtoms.cpp b/lld/lib/ReaderWriter/MachO/MachONormalizedFileFromAtoms.cpp
index 684c535a913..73f4e146906 100644
--- a/lld/lib/ReaderWriter/MachO/MachONormalizedFileFromAtoms.cpp
+++ b/lld/lib/ReaderWriter/MachO/MachONormalizedFileFromAtoms.cpp
@@ -92,13 +92,15 @@ struct SegmentInfo {
   StringRef                  name;
   uint64_t                   address;
   uint64_t                   size;
-  uint32_t                   access;
+  uint32_t                   init_access;
+  uint32_t                   max_access;
   std::vector<SectionInfo*>  sections;
   uint32_t                   normalizedSegmentIndex;
 };
 
 SegmentInfo::SegmentInfo(StringRef n)
- : name(n), address(0), size(0), access(0), normalizedSegmentIndex(0) {
+ : name(n), address(0), size(0), init_access(0), max_access(0),
+   normalizedSegmentIndex(0) {
 }
 
 class Util {
@@ -432,12 +434,38 @@ SegmentInfo *Util::segmentForName(StringRef segName) {
       return si;
   }
   auto *info = new (_allocator) SegmentInfo(segName);
+
+  // Set the initial segment protection.
   if (segName.equals("__TEXT"))
-    info->access = VM_PROT_READ | VM_PROT_EXECUTE;
-  else if (segName.equals("__DATA"))
-    info->access = VM_PROT_READ | VM_PROT_WRITE;
+    info->init_access = VM_PROT_READ | VM_PROT_EXECUTE;
   else if (segName.equals("__PAGEZERO"))
-    info->access = 0;
+    info->init_access = 0;
+  else if (segName.equals("__LINKEDIT"))
+    info->init_access = VM_PROT_READ;
+  else {
+    // All others default to read-write
+    info->init_access = VM_PROT_READ | VM_PROT_WRITE;
+  }
+
+  // Set max segment protection
+  // Note, its overkill to use a switch statement here, but makes it so much
+  // easier to use switch coverage to catch new cases.
+  switch (_ctx.os()) {
+    case lld::MachOLinkingContext::OS::unknown:
+    case lld::MachOLinkingContext::OS::macOSX:
+    case lld::MachOLinkingContext::OS::iOS_simulator:
+      if (segName.equals("__PAGEZERO")) {
+        info->max_access = 0;
+        break;
+      }
+      // All others default to all
+      info->max_access = VM_PROT_READ | VM_PROT_WRITE | VM_PROT_EXECUTE;
+      break;
+    case lld::MachOLinkingContext::OS::iOS:
+      // iPhoneOS always uses same protection for max and initial
+      info->max_access = info->init_access;
+      break;
+  }
   _segmentInfos.push_back(info);
   return info;
 }
@@ -589,7 +617,8 @@ void Util::copySegmentInfo(NormalizedFile &file) {
     seg.name    = sgi->name;
     seg.address = sgi->address;
     seg.size    = sgi->size;
-    seg.access  = sgi->access;
+    seg.init_access  = sgi->init_access;
+    seg.max_access  = sgi->max_access;
     file.segments.push_back(seg);
   }
 }