[PATCH] D73532: [ELF][PPC32] Support relocatable link of R_PPC_PLTREL24

[Fangrui Song via Phabricator via llvm-commits]

MaskRay created this revision.
MaskRay added a reviewer: Bdragon28.
Herald added subscribers: llvm-commits, jsji, atanasyan, kbarton, arichardson, nemanjai, sdardis, emaste.
Herald added a reviewer: espindola.
Herald added a project: LLVM.

Similar to R_MIPS_GPREL16 and R_MIPS_GPREL32 (D45972 <https://reviews.llvm.org/D45972>), R_PPC_PLTREL24 requires addend adjustment.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D73532

Files:
  lld/ELF/InputSection.cpp
  lld/test/ELF/ppc32-relocatable-pltrel24.s


Index: lld/test/ELF/ppc32-relocatable-pltrel24.s
===================================================================
--- /dev/null
+++ lld/test/ELF/ppc32-relocatable-pltrel24.s
@@ -0,0 +1,45 @@
+# REQUIRES: ppc
+## Test addend adjustment of R_PPC_PLTREL24 in -r mode. If r_addend indicates
+## .got2, adjust it by the local .got2's output section offset.
+
+# RUN: llvm-mc -filetype=obj -triple=powerpc %s -o %t.o
+# RUN: ld.lld -r %t.o %t.o %t.o -o %t
+# RUN: llvm-readobj -r %t | FileCheck %s
+
+# RUN: ld.lld -shared --emit-relocs %t.o %t.o %t.o -o %t.so
+# RUN: llvm-readobj -r %t.so | FileCheck --check-prefix=DSO %s
+
+# CHECK:      .rela.adjust {
+# CHECK-NEXT:   0x0 R_PPC_PLTREL24 foo 0x8000
+# CHECK-NEXT:   0x4 R_PPC_PLTREL24 bar 0x8000
+# CHECK-NEXT:   0x8 R_PPC_PLTREL24 foo 0x8004
+# CHECK-NEXT:   0xC R_PPC_PLTREL24 bar 0x8004
+# CHECK-NEXT:   0x10 R_PPC_PLTREL24 foo 0x8008
+# CHECK-NEXT:   0x14 R_PPC_PLTREL24 bar 0x8008
+# CHECK-NEXT: }
+# CHECK-NEXT: .rela.no_adjust {
+# CHECK-NEXT:   0x0 R_PPC_PLTREL24 foo 0x0
+# CHECK-NEXT:   0x4 R_PPC_PLTREL24 foo 0x0
+# CHECK-NEXT:   0x8 R_PPC_PLTREL24 foo 0x0
+# CHECK-NEXT: }
+
+## No adjustment in non -r mode.
+# DSO:      .rela.adjust {
+# DSO-NEXT:   R_PPC_PLTREL24 foo 0x8000
+# DSO-NEXT:   R_PPC_PLTREL24 bar 0x8000
+# DSO-NEXT:   R_PPC_PLTREL24 foo 0x8000
+# DSO-NEXT:   R_PPC_PLTREL24 bar 0x8000
+# DSO-NEXT:   R_PPC_PLTREL24 foo 0x8000
+# DSO-NEXT:   R_PPC_PLTREL24 bar 0x8000
+# DSO-NEXT: }
+.section .got2,"aw"
+.long 0
+
+.section .adjust,"ax"
+## Refers to .got2+addend, adjust.
+bl foo+0x8000 at plt
+bl bar+0x8000 at plt
+
+.section .no_adjust,"ax"
+## Refers to .got, no adjustment.
+bl foo at plt
Index: lld/ELF/InputSection.cpp
===================================================================
--- lld/ELF/InputSection.cpp
+++ lld/ELF/InputSection.cpp
@@ -465,7 +465,7 @@
       if (!RelTy::IsRela)
         addend = target->getImplicitAddend(bufLoc, type);
 
-      if (config->emachine == EM_MIPS && config->relocatable &&
+      if (config->relocatable && config->emachine == EM_MIPS &&
           target->getRelExpr(type, sym, bufLoc) == R_MIPS_GOTREL) {
         // Some MIPS relocations depend on "gp" value. By default,
         // this value has 0x7ff0 offset from a .got section. But
@@ -485,6 +485,13 @@
         p->r_addend = sym.getVA(addend) - section->getOutputSection()->addr;
       else if (config->relocatable && type != target->noneRel)
         sec->relocations.push_back({R_ABS, type, rel.r_offset, addend, &sym});
+    } else if (config->relocatable && config->emachine == EM_PPC &&
+               type == R_PPC_PLTREL24 && p->r_addend >= 0x8000) {
+      // Similar to R_MIPS_GOTREL{16,32}, if r_addend indicates .got2
+      // (>=0x8000), adjust it by the local .got2's output section offset. If
+      // r_addend=0, don't adjust. The PLT call stub is relative to .got.
+      // Because .got should not exist as an input section, the adjustment is 0.
+      p->r_addend += sec->file->ppc32Got2OutSecOff;
     }
   }
 }


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