[LinkerScript] Implement `MEMORY` command

As specified here:

* https://sourceware.org/binutils/docs/ld/MEMORY.html#MEMORY

There are two deviations from what is specified for GNU ld:

  1. Only integer constants and *not* constant expressions
     are allowed in `LENGTH` and `ORIGIN` initializations.

  2. The `I` and `L` attributes are *not* implemented.

With (1) there is currently no easy way to evaluate integer
only constant expressions.  This can be enhanced in the
future.

With (2) it isn't clear how these flags map to the `SHF_*`
flags or if they even make sense for an ELF linker.

Differential Revision: https://reviews.llvm.org/D28911

llvm-svn: 292875

1 files changed, 21 insertions, 0 deletions

diff --git a/lld/ELF/LinkerScript.h b/lld/ELF/LinkerScript.h
index 505162f0ab4..8dd60405433 100644
--- a/lld/ELF/LinkerScript.h
+++ b/lld/ELF/LinkerScript.h
@@ -15,6 +15,7 @@
 #include "Writer.h"
 #include "lld/Core/LLVM.h"
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/MemoryBuffer.h"
@@ -127,6 +128,7 @@ struct OutputSectionCommand : BaseCommand {
   uint32_t Filler = 0;
   ConstraintKind Constraint = ConstraintKind::NoConstraint;
   std::string Location;
+  std::string MemoryRegionName;
 };
 
 // This struct represents one section match pattern in SECTIONS() command.
@@ -187,6 +189,18 @@ struct PhdrsCommand {
   Expr LMAExpr;
 };
 
+// This struct is used to represent the location and size of regions of
+// target memory. Instances of the struct are created by parsing the
+// MEMORY command.
+struct MemoryRegion {
+  std::string Name;
+  uint64_t Origin;
+  uint64_t Length;
+  uint64_t Offset;
+  uint32_t Flags;
+  uint32_t NotFlags;
+};
+
 class LinkerScriptBase {
 protected:
   ~LinkerScriptBase() = default;
@@ -215,6 +229,9 @@ struct ScriptConfiguration {
   // List of section patterns specified with KEEP commands. They will
   // be kept even if they are unused and --gc-sections is specified.
   std::vector<InputSectionDescription *> KeptSections;
+
+  // A map from memory region name to a memory region descriptor.
+  llvm::DenseMap<llvm::StringRef, MemoryRegion> MemoryRegions;
 };
 
 extern ScriptConfiguration *ScriptConfig;
@@ -273,9 +290,13 @@ private:
   std::vector<size_t> getPhdrIndices(StringRef SectionName);
   size_t getPhdrIndex(const Twine &Loc, StringRef PhdrName);
 
+  MemoryRegion *findMemoryRegion(OutputSectionCommand *Cmd,
+                                 OutputSectionBase *Sec);
+
   uintX_t Dot;
   uintX_t LMAOffset = 0;
   OutputSectionBase *CurOutSec = nullptr;
+  MemoryRegion *CurMemRegion = nullptr;
   uintX_t ThreadBssOffset = 0;
   void switchTo(OutputSectionBase *Sec);
   void flush();