[PATCH] D43347: [ELF][MIPS] Support linking of PIE for MIPS

[Simon Atanasyan via Phabricator via llvm-commits]

atanasyan updated this revision to Diff 139888.
atanasyan added a comment.

Rebased against the trunk.


Repository:
  rLLD LLVM Linker

https://reviews.llvm.org/D43347

Files:
  ELF/SyntheticSections.cpp
  ELF/SyntheticSections.h
  test/ELF/mips-dynamic.s


Index: test/ELF/mips-dynamic.s
===================================================================
--- test/ELF/mips-dynamic.s
+++ test/ELF/mips-dynamic.s
@@ -6,7 +6,11 @@
 
 # RUN: ld.lld %t.o %td.so -o %t.exe
 # RUN: llvm-readobj -sections -dynamic-table %t.exe \
-# RUN:   | FileCheck -check-prefix=EXE %s
+# RUN:   | FileCheck -check-prefixes=EXE,NOPIE %s
+
+# RUN: ld.lld -pie %t.o %td.so -o %t.so
+# RUN: llvm-readobj -sections -dyn-symbols -dynamic-table %t.so \
+# RUN:   | FileCheck -check-prefixes=EXE,PIE %s
 
 # RUN: ld.lld %t.o --image-base=0x123000 %td.so -o %t.exe
 # RUN: llvm-readobj -sections -dynamic-table %t.exe \
@@ -49,11 +53,13 @@
 # EXE-DAG:    0x00000003 PLTGOT               [[GOTADDR]]
 # EXE-DAG:    0x70000001 MIPS_RLD_VERSION     1
 # EXE-DAG:    0x70000005 MIPS_FLAGS           NOTPOT
-# EXE-DAG:    0x70000006 MIPS_BASE_ADDRESS    0x10000
+# NOPIE-DAG:  0x70000006 MIPS_BASE_ADDRESS    0x10000
+# PIE-DAG:    0x70000006 MIPS_BASE_ADDRESS    0x0
 # EXE-DAG:    0x7000000A MIPS_LOCAL_GOTNO     2
 # EXE-DAG:    0x70000011 MIPS_SYMTABNO        2
 # EXE-DAG:    0x70000013 MIPS_GOTSYM          0x2
-# EXE-DAG:    0x70000016 MIPS_RLD_MAP         [[RLDMAPADDR]]
+# NOPIE-DAG:  0x70000016 MIPS_RLD_MAP         [[RLDMAPADDR]]
+# EXE-DAG:    0x70000035 MIPS_RLD_MAP_REL     0x{{[0-9A-F]+}}
 # EXE:      ]
 
 # IMAGE_BASE: 0x70000006 MIPS_BASE_ADDRESS    0x123000
Index: ELF/SyntheticSections.h
===================================================================
--- ELF/SyntheticSections.h
+++ ELF/SyntheticSections.h
@@ -359,6 +359,7 @@
   void add(int32_t Tag, std::function<uint64_t()> Fn);
   void addInt(int32_t Tag, uint64_t Val);
   void addInSec(int32_t Tag, InputSection *Sec);
+  void addInSecRelative(int32_t Tag, InputSection *Sec);
   void addOutSec(int32_t Tag, OutputSection *Sec);
   void addSize(int32_t Tag, OutputSection *Sec);
   void addSym(int32_t Tag, Symbol *Sym);
Index: ELF/SyntheticSections.cpp
===================================================================
--- ELF/SyntheticSections.cpp
+++ ELF/SyntheticSections.cpp
@@ -1028,6 +1028,13 @@
 }
 
 template <class ELFT>
+void DynamicSection<ELFT>::addInSecRelative(int32_t Tag, InputSection *Sec) {
+  size_t TagOffset = Entries.size() * Entsize;
+  Entries.push_back(
+      {Tag, [=] { return Sec->getVA(0) - (getVA() + TagOffset); }});
+}
+
+template <class ELFT>
 void DynamicSection<ELFT>::addOutSec(int32_t Tag, OutputSection *Sec) {
   Entries.push_back({Tag, [=] { return Sec->Addr; }});
 }
@@ -1180,8 +1187,13 @@
     else
       addInt(DT_MIPS_GOTSYM, InX::DynSymTab->getNumSymbols());
     addInSec(DT_PLTGOT, InX::MipsGot);
-    if (InX::MipsRldMap)
-      addInSec(DT_MIPS_RLD_MAP, InX::MipsRldMap);
+    if (InX::MipsRldMap) {
+      if (!Config->Pie)
+        addInSec(DT_MIPS_RLD_MAP, InX::MipsRldMap);
+      // Store the offset to the .rld_map section
+      // relative to the address of the tag.
+      addInSecRelative(DT_MIPS_RLD_MAP_REL, InX::MipsRldMap);
+    }
   }
 
   addInt(DT_NULL, 0);


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