[llvm] a3e975d - Fixes handling logic for i386/ELF GOTPC relocation

[Kshitij Jain via llvm-commits]

Author: Kshitij Jain
Date: 2023-01-14T05:01:49Z
New Revision: a3e975d42efa2ec1349c1a3ce203d78bbd7ee10d

URL: https://github.com/llvm/llvm-project/commit/a3e975d42efa2ec1349c1a3ce203d78bbd7ee10d
DIFF: https://github.com/llvm/llvm-project/commit/a3e975d42efa2ec1349c1a3ce203d78bbd7ee10d.diff

LOG: Fixes handling logic for i386/ELF GOTPC relocation

The i386/ELF JITLink backend was not correctly handling the GOTPC relocation
by skipping the in-built addend, which was manifesting itself in the form of
a segmentation fault in the `LF_external_to_absolute_conversion.s` test. This
CR has fixed that issue.

Reviewed By: lhames

Differential Revision: https://reviews.llvm.org/D141746

Added: 
    

Modified: 
    llvm/lib/ExecutionEngine/JITLink/ELF_i386.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/ExecutionEngine/JITLink/ELF_i386.cpp b/llvm/lib/ExecutionEngine/JITLink/ELF_i386.cpp
index 07f5ecc789428..dec59e4137a38 100644
--- a/llvm/lib/ExecutionEngine/JITLink/ELF_i386.cpp
+++ b/llvm/lib/ExecutionEngine/JITLink/ELF_i386.cpp
@@ -11,14 +11,13 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ExecutionEngine/JITLink/ELF_i386.h"
+#include "DefineExternalSectionStartAndEndSymbols.h"
 #include "ELFLinkGraphBuilder.h"
 #include "JITLinkGeneric.h"
 #include "llvm/BinaryFormat/ELF.h"
 #include "llvm/ExecutionEngine/JITLink/i386.h"
 #include "llvm/Object/ELFObjectFile.h"
 
-#include "DefineExternalSectionStartAndEndSymbols.h"
-
 #define DEBUG_TYPE "jitlink"
 
 using namespace llvm;
@@ -180,9 +179,18 @@ class ELFLinkGraphBuilder_i386 : public ELFLinkGraphBuilder<ELFT> {
     if (!Kind)
       return Kind.takeError();
 
+    auto FixupAddress = orc::ExecutorAddr(FixupSection.sh_addr) + Rel.r_offset;
     int64_t Addend = 0;
 
-    auto FixupAddress = orc::ExecutorAddr(FixupSection.sh_addr) + Rel.r_offset;
+    switch (*Kind) {
+    case i386::EdgeKind_i386::Delta32: {
+      const char *FixupContent = BlockToFix.getContent().data() +
+                                 (FixupAddress - BlockToFix.getAddress());
+      Addend = *(const support::ulittle32_t *)FixupContent;
+      break;
+    }
+    }
+
     Edge::OffsetT Offset = FixupAddress - BlockToFix.getAddress();
     Edge GE(*Kind, Offset, *GraphSymbol, Addend);
     LLVM_DEBUG({