[PATCH] D54782: [ELF] Write IPLT header in -static -z retpolineplt mode

[Fangrui Song via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL347404: [ELF] Write IPLT header in -static -z retpolineplt mode (authored by MaskRay, committed by ).

Repository:
  rL LLVM

https://reviews.llvm.org/D54782

Files:
  lld/trunk/ELF/Symbols.cpp
  lld/trunk/ELF/SyntheticSections.cpp
  lld/trunk/test/ELF/x86-64-retpoline-znow-static-iplt.s


Index: lld/trunk/test/ELF/x86-64-retpoline-znow-static-iplt.s
===================================================================
--- lld/trunk/test/ELF/x86-64-retpoline-znow-static-iplt.s
+++ lld/trunk/test/ELF/x86-64-retpoline-znow-static-iplt.s
@@ -0,0 +1,26 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
+# RUN: ld.lld -z retpolineplt -z now %t.o -o %t
+# RUN: llvm-objdump -d -no-show-raw-insn %t | FileCheck %s
+
+#0x201001+5 + 42 = 0x201030 (foo at plt)
+# CHECK:      _start:
+# CHECK-NEXT:  201001:       callq   42
+
+#Static IPLT header due to -z retpolineplt
+# CHECK:      {{^}}.plt:
+# CHECK-NEXT:  201010:       callq   11 <.plt+0x10>
+# CHECK-NEXT:  201015:       pause
+# CHECK-NEXT:  201017:       lfence
+#foo at plt
+# CHECK:       201030:       movq    4041(%rip), %r11
+# CHECK-NEXT:  201037:       jmp     -44 <.plt>
+
+.type foo STT_GNU_IFUNC
+.globl foo
+foo:
+  ret
+
+.globl _start
+_start:
+  call foo
Index: lld/trunk/ELF/Symbols.cpp
===================================================================
--- lld/trunk/ELF/Symbols.cpp
+++ lld/trunk/ELF/Symbols.cpp
@@ -144,8 +144,11 @@
 }
 
 uint64_t Symbol::getPltVA() const {
-  if (this->IsInIplt)
+  if (this->IsInIplt) {
+    if (Config->ZRetpolineplt)
+      return In.Iplt->getVA() + Target->getPltEntryOffset(PltIndex);
     return In.Iplt->getVA() + PltIndex * Target->PltEntrySize;
+  }
   return In.Plt->getVA() + Target->getPltEntryOffset(PltIndex);
 }
 
Index: lld/trunk/ELF/SyntheticSections.cpp
===================================================================
--- lld/trunk/ELF/SyntheticSections.cpp
+++ lld/trunk/ELF/SyntheticSections.cpp
@@ -2280,17 +2280,18 @@
 PltSection::PltSection(bool IsIplt)
     : SyntheticSection(SHF_ALLOC | SHF_EXECINSTR, SHT_PROGBITS, 16,
                        Config->EMachine == EM_PPC64 ? ".glink" : ".plt"),
-      HeaderSize(IsIplt ? 0 : Target->PltHeaderSize), IsIplt(IsIplt) {
+      HeaderSize(!IsIplt || Config->ZRetpolineplt ? Target->PltHeaderSize : 0),
+      IsIplt(IsIplt) {
   // The PLT needs to be writable on SPARC as the dynamic linker will
   // modify the instructions in the PLT entries.
   if (Config->EMachine == EM_SPARCV9)
     this->Flags |= SHF_WRITE;
 }
 
 void PltSection::writeTo(uint8_t *Buf) {
-  // At beginning of PLT but not the IPLT, we have code to call the dynamic
+  // At beginning of PLT or retpoline IPLT, we have code to call the dynamic
   // linker to resolve dynsyms at runtime. Write such code.
-  if (!IsIplt)
+  if (HeaderSize > 0)
     Target->writePltHeader(Buf);
   size_t Off = HeaderSize;
   // The IPlt is immediately after the Plt, account for this in RelOff


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