[ExecutionEngine] Correct the size of a write in a COFF i386 relocation

[xiaobai]

Summary

We want to be writing a 32bit value, so we should be writing 4 bytes
instead of 2.

[smeenai]

Looks like a pretty simple and obvious fix.

[xiaobai]

Thanks for the review @smeenai! I don't have commit access, would you mind committing this for me?

[smeenai]

I can commit it for you, but I remembered that this should probably include a test case, assuming that there are tests set up for this functionality (and I hope there are).

[xiaobai]

Updated the test to ensure that this functionality is tested.

[xiaobai]

Replacing uses of space with tab where appropriate.

[xiaobai]

Thanks to @compnerd for the help with the test case. :)

lib/ExecutionEngine/RuntimeDyld/Targets/RuntimeDyldCOFFI386.h

case COFF::IMAGE_REL_I386_SECREL:
       // 32-bit offset of the target from the beginning of its section.
       assert(static_cast<int32_t>(RE.Addend) <= INT32_MAX &&
              "relocation overflow");
       assert(static_cast<int32_t>(RE.Addend) >= INT32_MIN &&
              "relocation underflow");
       DEBUG(dbgs() << "\t\tOffset: " << RE.Offset
                    << " RelType: IMAGE_REL_I386_SECREL Value: " << RE.Addend
                    << '\n');
-      writeBytesUnaligned(RE.Addend, Target, 2);
+      writeBytesUnaligned(RE.Addend, Target, 4);
       break;
     default:
       llvm_unreachable("unsupported relocation type");
     }
   }
 
   void registerEHFrames() override {}
 };
 
 }
 
 #endif
 

test/ExecutionEngine/RuntimeDyld/X86/COFF_i386.s

 # rtdyld-check: *{4}__imp__OutputDebugStringA = 0xfffffffe
 
   .global __imp__ExitProcess
   .align 4
 __imp__ExitProcess:
   .long "_ExitProcess@4"      // IMAGE_REL_I386_DIR32
 # rtdyld-check: *{4}__imp__ExitProcess = 0xffffffff
 
-  .global string
-  .align 1
-string:
-  .asciz "Hello World!\n"
-
   .global relocations
 relocations:
 rel5:
   .long _function@imgrel      // IMAGE_REL_I386_DIR32NB
 # rtdyld-check: *{4}rel5 = _function - section_addr(COFF_i386.s.tmp.obj, .text)
 rel6:
 # rtdyld-check: *{2}rel6 = 1
   .secidx __imp__OutputDebugStringA // IMAGE_REL_I386_SECTION
 rel7:
-# rtdyld-check: *{4}rel7 = relocations - section_addr(COFF_i386.s.tmp.obj, .data)
-  .secrel32 relocations     // IMAGE_REL_I386_SECREL
+# rtdyld-check: *{4}rel7 = string - section_addr(COFF_i386.s.tmp.obj, .data)
+  .secrel32 string                        // IMAGE_REL_I386_SECREL
 
 # Test that addends work.
 rel8:
 # rtdyld-check: *{4}rel8 = string
   .long string        // IMAGE_REL_I386_DIR32
 rel9:
 # rtdyld-check: *{4}rel9 = string+1
   .long string+1        // IMAGE_REL_I386_DIR32
 rel10:
 # rtdyld-check: *{4}rel10 = string - section_addr(COFF_i386.s.tmp.obj, .text) + 1
   .long string@imgrel+1     // IMAGE_REL_I386_DIR32NB
 rel11:
 # rtdyld-check: *{4}rel11 = string - section_addr(COFF_i386.s.tmp.obj, .data) + 1
   .long string@SECREL32+1     // IMAGE_REL_I386_SECREL
+
+# We explicitly add padding to put string outside of the 16bit address space
+# (absolute and as an offset from .data), so that relocations involving
+# 32bit addresses / offsets are not accidentally truncated to 16 bits.
+        .space 65536
+        .global string
+        .align 1
+string:
+        .asciz "Hello World!\n"