From 2d077d6dfa7909a21293ebdac81488367628e0fa Mon Sep 17 00:00:00 2001
From: Fangrui Song <maskray@google.com>
Date: Thu, 9 Jan 2020 11:59:28 -0800
Subject: [PATCH] [ELF] Make TargetInfo::writeIgotPlt a no-op

RELA targets don't read initial .got.plt entries.
REL targets (ARM, x86-32) write the address of the IFUNC resolver to the
entry (`write32le(buf, s.getVA())`).

The default writeIgotPlt() is not meaningful. Make it a no-op. AArch64
and x86-64 will have 0 as initial .got.plt entries associated with
IFUNC.

Reviewed By: peter.smith

Differential Revision: https://reviews.llvm.org/D72474
---
 lld/ELF/Target.cpp                   | 4 ----
 lld/ELF/Target.h                     | 2 +-
 lld/test/ELF/aarch64-gnu-ifunc-plt.s | 4 ++--
 lld/test/ELF/gnu-ifunc-plt.s         | 4 ++--
 4 files changed, 5 insertions(+), 9 deletions(-)

diff --git a/lld/ELF/Target.cpp b/lld/ELF/Target.cpp
index aaae89b..70a68fd 100644
--- a/lld/ELF/Target.cpp
+++ b/lld/ELF/Target.cpp
@@ -150,10 +150,6 @@ bool TargetInfo::inBranchRange(RelType type, uint64_t src, uint64_t dst) const {
   return true;
 }
 
-void TargetInfo::writeIgotPlt(uint8_t *buf, const Symbol &s) const {
-  writeGotPlt(buf, s);
-}
-
 RelExpr TargetInfo::adjustRelaxExpr(RelType type, const uint8_t *data,
                                     RelExpr expr) const {
   return expr;
diff --git a/lld/ELF/Target.h b/lld/ELF/Target.h
index 7284bfd..7206736 100644
--- a/lld/ELF/Target.h
+++ b/lld/ELF/Target.h
@@ -32,7 +32,7 @@ public:
   virtual void writeGotPltHeader(uint8_t *buf) const {}
   virtual void writeGotHeader(uint8_t *buf) const {}
   virtual void writeGotPlt(uint8_t *buf, const Symbol &s) const {};
-  virtual void writeIgotPlt(uint8_t *buf, const Symbol &s) const;
+  virtual void writeIgotPlt(uint8_t *buf, const Symbol &s) const {}
   virtual int64_t getImplicitAddend(const uint8_t *buf, RelType type) const;
   virtual int getTlsGdRelaxSkip(RelType type) const { return 1; }
 
diff --git a/lld/test/ELF/aarch64-gnu-ifunc-plt.s b/lld/test/ELF/aarch64-gnu-ifunc-plt.s
index 08a6c49..91e8129 100644
--- a/lld/test/ELF/aarch64-gnu-ifunc-plt.s
+++ b/lld/test/ELF/aarch64-gnu-ifunc-plt.s
@@ -23,8 +23,8 @@
 // GOTPLT: Contents of section .got.plt:
 // GOTPLT-NEXT:  230440 00000000 00000000 00000000 00000000
 // GOTPLT-NEXT:  230450 00000000 00000000 f0022100 00000000
-// GOTPLT-NEXT:  230460 f0022100 00000000 f0022100 00000000
-// GOTPLT-NEXT:  230470 f0022100 00000000
+// GOTPLT-NEXT:  230460 f0022100 00000000 00000000 00000000
+// GOTPLT-NEXT:  230470 00000000 00000000
 
 // Check that the PLTRELSZ tag does not include the IRELATIVE relocations
 // CHECK: DynamicSection [
diff --git a/lld/test/ELF/gnu-ifunc-plt.s b/lld/test/ELF/gnu-ifunc-plt.s
index 2fad0b1..3d0cec0 100644
--- a/lld/test/ELF/gnu-ifunc-plt.s
+++ b/lld/test/ELF/gnu-ifunc-plt.s
@@ -25,8 +25,8 @@
 // GOTPLT: Contents of section .got.plt:
 // GOTPLT-NEXT:  203430 40232000 00000000 00000000 00000000
 // GOTPLT-NEXT:  203440 00000000 00000000 06132000 00000000
-// GOTPLT-NEXT:  203450 16132000 00000000 26132000 00000000
-// GOTPLT-NEXT:  203460 36132000 00000000
+// GOTPLT-NEXT:  203450 16132000 00000000 00000000 00000000
+// GOTPLT-NEXT:  203460 00000000 00000000
 
 // Check that the PLTRELSZ tag does not include the IRELATIVE relocations
 // CHECK: DynamicSection [
-- 
2.7.4