[lldb] Refactor DataBuffer so we can map files as read-only

Currently, all data buffers are assumed to be writable. This is a
problem on macOS where it's not allowed to load unsigned binaries in
memory as writable. To be more precise, MAP_RESILIENT_CODESIGN and
MAP_RESILIENT_MEDIA need to be set for mapped (unsigned) binaries on our
platform.

Binaries are mapped through FileSystem::CreateDataBuffer which returns a
DataBufferLLVM. The latter is backed by a llvm::WritableMemoryBuffer
because every DataBuffer in LLDB is considered to be writable. In order
to use a read-only llvm::MemoryBuffer I had to split our abstraction
around it.

This patch distinguishes between a DataBuffer (read-only) and
WritableDataBuffer (read-write) and updates LLDB to use the appropriate
one.

rdar://74890607

Differential revision: https://reviews.llvm.org/D122856

1 files changed, 2 insertions, 1 deletions

diff --git a/lldb/source/Expression/IRExecutionUnit.cpp b/lldb/source/Expression/IRExecutionUnit.cpp
index 91b92f1ba300..49fa72f7112d 100644
--- a/lldb/source/Expression/IRExecutionUnit.cpp
+++ b/lldb/source/Expression/IRExecutionUnit.cpp
@@ -151,7 +151,8 @@ Status IRExecutionUnit::DisassembleFunction(Stream &stream,
     return ret;
   }
 
-  lldb::DataBufferSP buffer_sp(new DataBufferHeap(func_range.second, 0));
+  lldb::WritableDataBufferSP buffer_sp(
+      new DataBufferHeap(func_range.second, 0));
 
   Process *process = exe_ctx.GetProcessPtr();
   Status err;