Handle relocations to thumb functions when dynamic linking COFF modules

Summary:
This adds the necessary logic to support relocations to thumb functions in the COFF dynamic linker.
The jumps to function addresses are mostly blx, which requires the ISA selection bit when jumping to a thumb function.

Note: I'm determining if the relocation requires the ISA bit when creating the relocation entries and not when resolving the relocation. I have to do that because I need the ObjectFile and the actual Symbol, which are available only when creating the entries. It would require a gross refactor if I do it otherwise, but I'm okay with doing it if you think it's better.

Reviewers: peter.smith, compnerd

Subscribers: rengolin, sas

Differential Revision: https://reviews.llvm.org/D25151

llvm-svn: 284410

diff --git a/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h b/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h
index ebc0f87..8944435 100644 (file)
--- a/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h
+++ b/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h
@@ -149,26 +149,41 @@ public:
   /// The size of this relocation (MachO specific).
   unsigned Size;
 
+  // COFF specific.
+  bool IsTargetThumbFunc;
+
   RelocationEntry(unsigned id, uint64_t offset, uint32_t type, int64_t addend)
       : SectionID(id), Offset(offset), RelType(type), Addend(addend),
-        SymOffset(0), IsPCRel(false), Size(0) {}
+        SymOffset(0), IsPCRel(false), Size(0), IsTargetThumbFunc(false) {}
 
   RelocationEntry(unsigned id, uint64_t offset, uint32_t type, int64_t addend,
                   uint64_t symoffset)
       : SectionID(id), Offset(offset), RelType(type), Addend(addend),
-        SymOffset(symoffset), IsPCRel(false), Size(0) {}
+        SymOffset(symoffset), IsPCRel(false), Size(0),
+        IsTargetThumbFunc(false) {}
 
   RelocationEntry(unsigned id, uint64_t offset, uint32_t type, int64_t addend,
                   bool IsPCRel, unsigned Size)
       : SectionID(id), Offset(offset), RelType(type), Addend(addend),
-        SymOffset(0), IsPCRel(IsPCRel), Size(Size) {}
+        SymOffset(0), IsPCRel(IsPCRel), Size(Size), IsTargetThumbFunc(false) {}
 
   RelocationEntry(unsigned id, uint64_t offset, uint32_t type, int64_t addend,
                   unsigned SectionA, uint64_t SectionAOffset, unsigned SectionB,
                   uint64_t SectionBOffset, bool IsPCRel, unsigned Size)
       : SectionID(id), Offset(offset), RelType(type),
         Addend(SectionAOffset - SectionBOffset + addend), IsPCRel(IsPCRel),
-        Size(Size) {
+        Size(Size), IsTargetThumbFunc(false) {
+    Sections.SectionA = SectionA;
+    Sections.SectionB = SectionB;
+  }
+
+  RelocationEntry(unsigned id, uint64_t offset, uint32_t type, int64_t addend,
+                  unsigned SectionA, uint64_t SectionAOffset, unsigned SectionB,
+                  uint64_t SectionBOffset, bool IsPCRel, unsigned Size,
+                  bool IsTargetThumbFunc)
+      : SectionID(id), Offset(offset), RelType(type),
+        Addend(SectionAOffset - SectionBOffset + addend), IsPCRel(IsPCRel),
+        Size(Size), IsTargetThumbFunc(IsTargetThumbFunc) {
     Sections.SectionA = SectionA;
     Sections.SectionB = SectionB;
   }

diff --git a/llvm/lib/ExecutionEngine/RuntimeDyld/Targets/RuntimeDyldCOFFThumb.h b/llvm/lib/ExecutionEngine/RuntimeDyld/Targets/RuntimeDyldCOFFThumb.h
index 570c928..8c6af0b 100644 (file)
--- a/llvm/lib/ExecutionEngine/RuntimeDyld/Targets/RuntimeDyldCOFFThumb.h
+++ b/llvm/lib/ExecutionEngine/RuntimeDyld/Targets/RuntimeDyldCOFFThumb.h
@@ -22,6 +22,26 @@
 
 namespace llvm {
 
+static bool isThumbFunc(symbol_iterator Symbol, const ObjectFile &Obj,
+                        section_iterator Section) {
+  Expected<SymbolRef::Type> SymTypeOrErr = Symbol->getType();
+  if (!SymTypeOrErr) {
+    std::string Buf;
+    raw_string_ostream OS(Buf);
+    logAllUnhandledErrors(SymTypeOrErr.takeError(), OS, "");
+    OS.flush();
+    report_fatal_error(Buf);
+  }
+
+  if (*SymTypeOrErr != SymbolRef::ST_Function)
+    return false;
+
+  // We check the IMAGE_SCN_MEM_16BIT flag in the section of the symbol to tell
+  // if it's thumb or not
+  return cast<COFFObjectFile>(Obj).getCOFFSection(*Section)->Characteristics &
+         COFF::IMAGE_SCN_MEM_16BIT;
+}
+
 class RuntimeDyldCOFFThumb : public RuntimeDyldCOFF {
 public:
   RuntimeDyldCOFFThumb(RuntimeDyld::MemoryManager &MM,
@@ -92,12 +112,22 @@ public:
       else
         return TargetSectionIDOrErr.takeError();
 
+      // We need to find out if the relocation is relative to a thumb function
+      // so that we include the ISA selection bit when resolve the relocation
+      bool IsTargetThumbFunc = isThumbFunc(Symbol, Obj, Section);
+
       switch (RelType) {
       default: llvm_unreachable("unsupported relocation type");
       case COFF::IMAGE_REL_ARM_ABSOLUTE:
         // This relocation is ignored.
         break;
-      case COFF::IMAGE_REL_ARM_ADDR32:
+      case COFF::IMAGE_REL_ARM_ADDR32: {
+        RelocationEntry RE = RelocationEntry(
+            SectionID, Offset, RelType, Addend, TargetSectionID,
+            getSymbolOffset(*Symbol), 0, 0, false, 0, IsTargetThumbFunc);
+        addRelocationForSection(RE, TargetSectionID);
+        break;
+      }
       case COFF::IMAGE_REL_ARM_ADDR32NB: {
         RelocationEntry RE =
             RelocationEntry(SectionID, Offset, RelType, Addend, TargetSectionID,
@@ -118,9 +148,9 @@ public:
         break;
       }
       case COFF::IMAGE_REL_ARM_MOV32T: {
-        RelocationEntry RE =
-            RelocationEntry(SectionID, Offset, RelType, Addend, TargetSectionID,
-                            getSymbolOffset(*Symbol), 0, 0, false, 0);
+        RelocationEntry RE = RelocationEntry(
+            SectionID, Offset, RelType, Addend, TargetSectionID,
+            getSymbolOffset(*Symbol), 0, 0, false, 0, IsTargetThumbFunc);
         addRelocationForSection(RE, TargetSectionID);
         break;
       }
@@ -142,6 +172,7 @@ public:
   void resolveRelocation(const RelocationEntry &RE, uint64_t Value) override {
     const auto Section = Sections[RE.SectionID];
     uint8_t *Target = Section.getAddressWithOffset(RE.Offset);
+    int ISASelectionBit = RE.IsTargetThumbFunc ? 1 : 0;
 
     switch (RE.RelType) {
     default: llvm_unreachable("unsupported relocation type");
@@ -154,6 +185,7 @@ public:
           RE.Sections.SectionA == static_cast<uint32_t>(-1)
               ? Value
               : Sections[RE.Sections.SectionA].getLoadAddressWithOffset(RE.Addend);
+      Result |= ISASelectionBit;
       assert(static_cast<int32_t>(Result) <= INT32_MAX &&
              "relocation overflow");
       assert(static_cast<int32_t>(Result) >= INT32_MIN &&
@@ -178,6 +210,7 @@ public:
                    << " RelType: IMAGE_REL_ARM_ADDR32NB"
                    << " TargetSection: " << RE.Sections.SectionA
                    << " Value: " << format("0x%08" PRIx32, Result) << '\n');
+      Result |= ISASelectionBit;
       writeBytesUnaligned(Result, Target, 4);
       break;
     }
@@ -228,7 +261,8 @@ public:
         Bytes[3] |= (((Immediate & 0x0700) >>  8) << 4);
       };
 
-      EncodeImmediate(&Target[0], static_cast<uint32_t>(Result) >> 00);
+      EncodeImmediate(&Target[0],
+                      (static_cast<uint32_t>(Result) >> 00) | ISASelectionBit);
       EncodeImmediate(&Target[4], static_cast<uint32_t>(Result) >> 16);
 
       break;

diff --git a/llvm/test/ExecutionEngine/RuntimeDyld/ARM/COFF_Thumb.s b/llvm/test/ExecutionEngine/RuntimeDyld/ARM/COFF_Thumb.s
index 14e74cb..991e88d 100644 (file)
--- a/llvm/test/ExecutionEngine/RuntimeDyld/ARM/COFF_Thumb.s
+++ b/llvm/test/ExecutionEngine/RuntimeDyld/ARM/COFF_Thumb.s
@@ -1,5 +1,5 @@
 // RUN: llvm-mc -triple thumbv7-windows-itanium -filetype obj -o %t.obj %s
-// RUN: llvm-rtdyld -triple thumbv7-windows -dummy-extern OutputDebugStringW=0x01310060 -dummy-extern OutputDebugStringA=0x78563412 -dummy-extern ExitProcess=0x54769890 -dummy-extern unnamed_addr=0x00001024 -verify -check %s %t.obj
+// RUN: llvm-rtdyld -triple thumbv7-windows -dummy-extern OutputDebugStringW=0x01310061 -dummy-extern OutputDebugStringA=0x78563413 -dummy-extern ExitProcess=0x54769891 -dummy-extern unnamed_addr=0x00001024 -verify -check %s %t.obj
 
        .text
        .syntax unified
@@ -82,13 +82,13 @@ string:
 __imp_OutputDebugStringA:
 @ rel6:
        .long OutputDebugStringA                        @ IMAGE_REL_ARM_ADDR32
-# rtdyld-check: *{4}__imp_OutputDebugStringA = 0x78563412
+# rtdyld-check: *{4}__imp_OutputDebugStringA = 0x78563413
 
        .p2align 2
 __imp_ExitProcess:
 @ rel7:
        .long ExitProcess                               @ IMAGE_REL_ARM_ADDR32
-# rtdyld-check: *{4}__imp_ExitProcess = 0x54769890
+# rtdyld-check: *{4}__imp_ExitProcess = 0x54769891
 
        .global relocations
 relocations:
@@ -118,6 +118,32 @@ rel12:                                                     @ IMAGE_REL_ARM_MOV32T
 __imp_OutputDebugStringW:
 @ rel13:
        .long OutputDebugStringW                        @ IMAGE_REL_ARM_ADDR32
-# rtdyld-check: *{4}__imp_OutputDebugStringW = 0x01310060
+# rtdyld-check: *{4}__imp_OutputDebugStringW = 0x01310061
 
        .p2align 2
+
+branch_to_thumb_func:
+@ rel14:                                                @ IMAGE_REL_ARM_MOV32T
+        movw r0, :lower16:function
+# rtdyld-check: decode_operand(branch_to_thumb_func, 1) = (function&0x0000ffff|1)
+        movt r0, :upper16:function
+# TODO rtdyld-check: decode_operand(branch_to_thumb_func, 1) = (function&0xffff0000>>16)
+        bx r0
+        trap
+
+        .data
+
+        .p2align 2
+a_data_symbol:
+        .long 1073741822
+
+        .p2align 2
+
+        .text
+
+ref_to_data_symbol_addr:
+@ rel15:                                                @ IMAGE_REL_ARM_MOV32T
+        movw r0, :lower16:a_data_symbol
+# rtdyld-check: decode_operand(ref_to_data_symbol_addr, 1) = (a_data_symbol&0x0000ffff)
+        movt r0, :upper16:a_data_symbol
+# TODO rtdyld-check: decode_operand(ref_to_data_symbol_addr, 1) = (a_data_symbol&0xffff0000>>16)