[PATCH] D27303: [ELF] - Implemented R_386_16 and R_386PC16 relocations

[George Rimar via Phabricator via llvm-commits]

grimar updated this revision to Diff 79922.
grimar added a comment.

- Uploaded correct testcase.


https://reviews.llvm.org/D27303

Files:
  ELF/Target.cpp
  test/ELF/Inputs/i386-pc16.s
  test/ELF/i386-pc16.s


Index: test/ELF/i386-pc16.s
===================================================================
--- test/ELF/i386-pc16.s
+++ test/ELF/i386-pc16.s
@@ -0,0 +1,20 @@
+# REQUIRES: x86
+
+# RUN: llvm-mc -filetype=obj -triple=i386-pc-linux %s -o %t.o
+# RUN: llvm-mc -filetype=obj -triple=i386-pc-linux %S/Inputs/i386-pc16.s -o %t2.o
+# RUN: ld.lld %t.o %t2.o -o %t.exe
+# RUN: llvm-objdump -s -section=.text %t.exe | FileCheck %s
+
+# CHECK: Contents of section .text:
+# CHECK:  11000 be07100f 85090001 00000000 00000000
+# CHECK:  11010 02000000 00000000
+
+.global _start
+.code16
+_start:
+ movw $foo,%si #R_386_16
+ jne bar       #R_386_PC16
+
+foo:
+ .quad 1
+
Index: test/ELF/Inputs/i386-pc16.s
===================================================================
--- test/ELF/Inputs/i386-pc16.s
+++ test/ELF/Inputs/i386-pc16.s
@@ -0,0 +1,3 @@
+.global bar
+bar:
+ .quad 2
Index: ELF/Target.cpp
===================================================================
--- ELF/Target.cpp
+++ ELF/Target.cpp
@@ -329,6 +329,7 @@
     return R_TLSLD;
   case R_386_PLT32:
     return R_PLT_PC;
+  case R_386_PC16:
   case R_386_PC32:
     return R_PC;
   case R_386_GOTPC:
@@ -437,11 +438,13 @@
   switch (Type) {
   default:
     return 0;
+  case R_386_16:
   case R_386_32:
   case R_386_GOT32:
   case R_386_GOT32X:
   case R_386_GOTOFF:
   case R_386_GOTPC:
+  case R_386_PC16:
   case R_386_PC32:
   case R_386_PLT32:
   case R_386_TLS_LE:
@@ -451,6 +454,16 @@
 
 void X86TargetInfo::relocateOne(uint8_t *Loc, uint32_t Type,
                                 uint64_t Val) const {
+  // A program or object file using R_386_8, R_386_16, R_386_PC16 or R_386_PC8
+  // relocations is not conformant to latest ABI. The R_386_16, and R_386_8
+  // relocations truncate the computed value to 16 - bits and 8 - bits
+  // respectively. Unfortunately R_386_PC16 and R_386_16 are used by some
+  // applications, for example by FreeBSD loaders.
+  if (Type == R_386_16 || Type == R_386_PC16) {
+    write16le(Loc, Val);
+    return;
+  }
+
   checkInt<32>(Loc, Val, Type);
   write32le(Loc, Val);
 }


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