[LLD][ELF] Fix problem with LA25 Thunks when OutputSection of caller and callee differ

[peter.smith]

Summary

This is a simple mistake when saving the target output section of the Thunk, for the Mips LA25 Thunk it needs to be the OutputSection of the callee and not the caller.

I've added a test case with sufficiently different section names that they get put in different OutputSections. In the existing test case the OutputSection of the caller and callee are the same so this problem doesn't show up.

[ruiu]

LGTM

lld/trunk/ELF/Relocations.cpp

void createThunks(ArrayRef<OutputSection *> OutputSections) {
 
   // Find or create a ThunkSection to be placed immediately before IS
   auto GetISThunkSec = [&](InputSection *IS, OutputSection *OS) {
     ThunkSection<ELFT> *TS = ThunkedSections.lookup(IS);
     if (TS)
       return TS;
     auto *TOS = cast<OutputSection>(IS->OutSec);
     TS = make<ThunkSection<ELFT>>(TOS, IS->OutSecOff);
-    ThunkSections[OS].push_back(TS);
+    ThunkSections[TOS].push_back(TS);
     ThunkedSections[IS] = TS;
     return TS;
   };
   // Find or create a ThunkSection to be placed as last executable section in
   // OS.
   auto GetOSThunkSec = [&](ThunkSection<ELFT> *&TS, OutputSection *OS) {
     if (TS == nullptr) {
       uint32_t Off = 0;

lld/trunk/test/ELF/mips-npic-call-pic-os.s

+# REQUIRES: mips
+# Check LA25 stubs creation with caller in different Output Section to callee.
+# This stub code is necessary when non-PIC code calls PIC function.
+
+# RUN: llvm-mc -filetype=obj -triple=mips-unknown-linux \
+# RUN:   %p/Inputs/mips-fpic.s -o %t-fpic.o
+# RUN: llvm-mc -filetype=obj -triple=mips-unknown-linux \
+# RUN:   %p/Inputs/mips-fnpic.s -o %t-fnpic.o
+# RUN: ld.lld -r %t-fpic.o %t-fnpic.o -o %t-sto-pic.o
+# RUN: llvm-mc -filetype=obj -triple=mips-unknown-linux \
+# RUN:   %p/Inputs/mips-pic.s -o %t-pic.o
+# RUN: llvm-mc -filetype=obj -triple=mips-unknown-linux %s -o %t-npic.o
+# RUN: ld.lld %t-npic.o %t-pic.o %t-sto-pic.o -o %t.exe
+# RUN: llvm-objdump -d %t.exe | FileCheck %s
+
+# CHECK: Disassembly of section .text:
+# CHECK-NEXT: __LA25Thunk_foo1a:
+# CHECK-NEXT:    20000:       3c 19 00 02     lui     $25, 2
+# CHECK-NEXT:    20004:       08 00 80 08     j       131104 <foo1a>
+# CHECK-NEXT:    20008:       27 39 00 20     addiu   $25, $25, 32
+# CHECK-NEXT:    2000c:       00 00 00 00     nop
+# CHECK: __LA25Thunk_foo1b:
+# CHECK-NEXT:    20010:       3c 19 00 02     lui     $25, 2
+# CHECK-NEXT:    20014:       08 00 80 09     j       131108 <foo1b>
+# CHECK-NEXT:    20018:       27 39 00 24     addiu   $25, $25, 36
+# CHECK-NEXT:    2001c:       00 00 00 00     nop
+# CHECK: foo1a:
+# CHECK-NEXT:    20020:       00 00 00 00     nop
+# CHECK: foo1b:
+# CHECK-NEXT:    20024:       00 00 00 00     nop
+# CHECK: __LA25Thunk_foo2:
+# CHECK-NEXT:    20028:       3c 19 00 02     lui     $25, 2
+# CHECK-NEXT:    2002c:       08 00 80 10     j       131136 <foo2>
+# CHECK-NEXT:    20030:       27 39 00 40     addiu   $25, $25, 64
+# CHECK-NEXT:    20034:       00 00 00 00     nop
+# CHECK-NEXT:    20038:       00 00 00 00     nop
+# CHECK-NEXT:    2003c:       00 00 00 00     nop
+# CHECK: foo2:
+# CHECK-NEXT:    20040:       00 00 00 00     nop
+# CHECK: __LA25Thunk_fpic:
+# CHECK-NEXT:    20044:       3c 19 00 02     lui     $25, 2
+# CHECK-NEXT:    20048:       08 00 80 18     j       131168 <fpic>
+# CHECK-NEXT:    2004c:       27 39 00 60     addiu   $25, $25, 96
+# CHECK-NEXT:    20050:       00 00 00 00     nop
+# CHECK-NEXT:    20054:       00 00 00 00     nop
+# CHECK-NEXT:    20058:       00 00 00 00     nop
+# CHECK-NEXT:    2005c:       00 00 00 00     nop
+# CHECK: fpic:
+# CHECK-NEXT:    20060:       00 00 00 00     nop
+# CHECK-NEXT:    20064:       00 00 00 00     nop
+# CHECK-NEXT:    20068:       00 00 00 00     nop
+# CHECK-NEXT:    2006c:       00 00 00 00     nop
+# CHECK: fnpic:
+# CHECK-NEXT:    20070:       00 00 00 00     nop
+# CHECK-NEXT: Disassembly of section differentos:
+# CHECK-NEXT: __start:
+# CHECK-NEXT:    20074:       0c 00 80 00     jal     131072 <__LA25Thunk_foo1a>
+# CHECK-NEXT:    20078:       00 00 00 00     nop
+# CHECK-NEXT:    2007c:       0c 00 80 0a     jal     131112 <__LA25Thunk_foo2>
+# CHECK-NEXT:    20080:       00 00 00 00     nop
+# CHECK-NEXT:    20084:       0c 00 80 04     jal     131088 <__LA25Thunk_foo1b>
+# CHECK-NEXT:    20088:       00 00 00 00     nop
+# CHECK-NEXT:    2008c:       0c 00 80 0a     jal     131112 <__LA25Thunk_foo2>
+# CHECK-NEXT:    20090:       00 00 00 00     nop
+# CHECK-NEXT:    20094:       0c 00 80 11     jal     131140 <__LA25Thunk_fpic>
+# CHECK-NEXT:    20098:       00 00 00 00     nop
+# CHECK-NEXT:    2009c:       0c 00 80 1c     jal     131184 <fnpic>
+# CHECK-NEXT:    200a0:       00 00 00 00     nop
+
+# Make sure the thunks are created properly no matter how
+# objects are laid out.
+#
+# RUN: ld.lld %t-pic.o %t-npic.o %t-sto-pic.o -o %t.exe
+# RUN: llvm-objdump -d %t.exe | FileCheck -check-prefix=REVERSE %s
+
+# REVERSE: Disassembly of section .text:
+# REVERSE-NEXT: __LA25Thunk_foo1a:
+# REVERSE-NEXT:    20000:       3c 19 00 02     lui     $25, 2
+# REVERSE-NEXT:    20004:       08 00 80 08     j       131104 <foo1a>
+# REVERSE-NEXT:    20008:       27 39 00 20     addiu   $25, $25, 32
+# REVERSE-NEXT:    2000c:       00 00 00 00     nop
+# REVERSE: __LA25Thunk_foo1b:
+# REVERSE-NEXT:    20010:       3c 19 00 02     lui     $25, 2
+# REVERSE-NEXT:    20014:       08 00 80 09     j       131108 <foo1b>
+# REVERSE-NEXT:    20018:       27 39 00 24     addiu   $25, $25, 36
+# REVERSE-NEXT:    2001c:       00 00 00 00     nop
+# REVERSE: foo1a:
+# REVERSE-NEXT:    20020:       00 00 00 00     nop
+# REVERSE: foo1b:
+# REVERSE-NEXT:    20024:       00 00 00 00     nop
+# REVERSE: __LA25Thunk_foo2:
+# REVERSE-NEXT:    20028:       3c 19 00 02     lui     $25, 2
+# REVERSE-NEXT:    2002c:       08 00 80 10     j       131136 <foo2>
+# REVERSE-NEXT:    20030:       27 39 00 40     addiu   $25, $25, 64
+# REVERSE-NEXT:    20034:       00 00 00 00     nop
+# REVERSE-NEXT:    20038:       00 00 00 00     nop
+# REVERSE-NEXT:    2003c:       00 00 00 00     nop
+# REVERSE: foo2:
+# REVERSE-NEXT:    20040:       00 00 00 00     nop
+# REVERSE-NEXT:    20044:       00 00 00 00     nop
+# REVERSE-NEXT:    20048:       00 00 00 00     nop
+# REVERSE-NEXT:    2004c:       00 00 00 00     nop
+# REVERSE: __LA25Thunk_fpic:
+# REVERSE-NEXT:    20050:       3c 19 00 02     lui     $25, 2
+# REVERSE-NEXT:    20054:       08 00 80 18     j       131168 <fpic>
+# REVERSE-NEXT:    20058:       27 39 00 60     addiu   $25, $25, 96
+# REVERSE-NEXT:    2005c:       00 00 00 00     nop
+# REVERSE: fpic:
+# REVERSE-NEXT:    20060:       00 00 00 00     nop
+# REVERSE-NEXT:    20064:       00 00 00 00     nop
+# REVERSE-NEXT:    20068:       00 00 00 00     nop
+# REVERSE-NEXT:    2006c:       00 00 00 00     nop
+# REVERSE: fnpic:
+# REVERSE-NEXT:    20070:       00 00 00 00     nop
+# REVERSE-NEXT: Disassembly of section differentos:
+# REVERSE-NEXT: __start:
+# REVERSE-NEXT:    20074:       0c 00 80 00     jal     131072 <__LA25Thunk_foo1a>
+# REVERSE-NEXT:    20078:       00 00 00 00     nop
+# REVERSE-NEXT:    2007c:       0c 00 80 0a     jal     131112 <__LA25Thunk_foo2>
+# REVERSE-NEXT:    20080:       00 00 00 00     nop
+# REVERSE-NEXT:    20084:       0c 00 80 04     jal     131088 <__LA25Thunk_foo1b>
+# REVERSE-NEXT:    20088:       00 00 00 00     nop
+# REVERSE-NEXT:    2008c:       0c 00 80 0a     jal     131112 <__LA25Thunk_foo2>
+# REVERSE-NEXT:    20090:       00 00 00 00     nop
+# REVERSE-NEXT:    20094:       0c 00 80 14     jal     131152 <__LA25Thunk_fpic>
+# REVERSE-NEXT:    20098:       00 00 00 00     nop
+# REVERSE-NEXT:    2009c:       0c 00 80 1c     jal     131184 <fnpic>
+# REVERSE-NEXT:    200a0:       00 00 00 00     nop
+
+  .section differentos, "ax", %progbits
+  .globl __start
+__start:
+  jal foo1a
+  jal foo2
+  jal foo1b
+  jal foo2
+  jal fpic
+  jal fnpic