[BOLT] Fix .relr section addend patching

The new relocation offset in .relr section patching was calculated
wrong previously. Pass the new file offset to lambda instead of
re-calculating it in it. Test removes relocation from mytext section,
so in case of wrong offset calculation we won't emit right addend value
in expected place, i.e. on the new relocation offset.

Differential Revision: https://reviews.llvm.org/D159543

Author: yota9

bolt/lib/Rewrite/RewriteInstance.cpp

@@ -4720,9 +4720,11 @@ void RewriteInstance::patchELFAllocatableRelrSection(
   const uint8_t PSize = BC->AsmInfo->getCodePointerSize();
   const uint64_t MaxDelta = ((CHAR_BIT * DynamicRelrEntrySize) - 1) * PSize;
 
-  auto FixAddend = [&](const BinarySection &Section, const Relocation &Rel) {
+  auto FixAddend = [&](const BinarySection &Section, const Relocation &Rel,
+                       uint64_t FileOffset) {
     // Fix relocation symbol value in place if no static relocation found
-    // on the same address
+    // on the same address. We won't check the BF relocations here since it
+    // is rare case and no optimization is required.
     if (Section.getRelocationAt(Rel.Offset))
       return;
 
@@ -4731,11 +4733,6 @@ void RewriteInstance::patchELFAllocatableRelrSection(
     if (!Addend)
       return;
 
-    uint64_t FileOffset = Section.getOutputFileOffset();
-    if (!FileOffset)
-      FileOffset = Section.getInputFileOffset();
-
-    FileOffset += Rel.Offset;
     OS.pwrite(reinterpret_cast<const char *>(&Addend), PSize, FileOffset);
   };
 
@@ -4757,7 +4754,7 @@ void RewriteInstance::patchELFAllocatableRelrSection(
       RelOffset = RelOffset == 0 ? SectionAddress + Rel.Offset : RelOffset;
       assert((RelOffset & 1) == 0 && "Wrong relocation offset");
       RelOffsets.emplace(RelOffset);
-      FixAddend(Section, Rel);
+      FixAddend(Section, Rel, RelOffset);
     }
   }
 

bolt/test/AArch64/constant_island_pie_update.s

@@ -13,8 +13,11 @@
 // .relr.dyn
 # RUN: %clang %cflags -fPIC -pie %t.o -o %t.relr.exe -nostdlib \
 # RUN:   -Wl,-q -Wl,-z,notext -Wl,--pack-dyn-relocs=relr
+# RUN: llvm-objcopy --remove-section .rela.mytext %t.relr.exe
 # RUN: llvm-bolt %t.relr.exe -o %t.relr.bolt --use-old-text=0 --lite=0
 # RUN: llvm-objdump -j .text -d --show-all-symbols %t.relr.bolt | FileCheck %s
+# RUN: llvm-objdump -j .text -d %t.relr.bolt | \
+# RUN:   FileCheck %s --check-prefix=ADDENDCHECK
 # RUN: llvm-readelf -rsW %t.relr.bolt | FileCheck --check-prefix=ELFCHECK %s
 # RUN: llvm-readelf -SW %t.relr.bolt | FileCheck --check-prefix=RELRSZCHECK %s
 
@@ -30,6 +33,11 @@
 # CHECK-NEXT: {{.*}} .word 0x{{[0]+}}[[#ADDR]]
 # CHECK-NEXT: {{.*}} .word 0x00000000
 
+// Check that addend was properly patched in mytextP with stripped relocations
+# ADDENDCHECK: [[#%x,ADDR:]] <exitLocal>:
+# ADDENDCHECK: {{.*}} <mytextP>:
+# ADDENDCHECK-NEXT: {{.*}} .word 0x{{[0]+}}[[#ADDR]]
+# ADDENDCHECK-NEXT: {{.*}} .word 0x00000000
 
 // Check that we've relaxed adr to adrp + add to refer external CI
 # CHECK: <addressDynCi>:
@@ -40,9 +48,10 @@
 # ELFCHECK: [[#%x,OFF:]] [[#%x,INFO_DYN:]] R_AARCH64_RELATIVE
 # ELFCHECK-NEXT: [[#OFF + 8]] {{0*}}[[#INFO_DYN]] R_AARCH64_RELATIVE
 # ELFCHECK-NEXT: [[#OFF + 24]] {{0*}}[[#INFO_DYN]] R_AARCH64_RELATIVE
+# ELFCHECK-NEXT: {{.*}} R_AARCH64_RELATIVE
 # ELFCHECK: {{.*}}[[#OFF]] {{.*}} $d
 
-// Check that .relr.dyn size is 2 bytes to ensure that last 2 relocations were
+// Check that .relr.dyn size is 2 bytes to ensure that last 3 relocations were
 // encoded as a bitmap so the total section size for 3 relocations is 2 bytes.
 # RELRSZCHECK: .relr.dyn RELR [[#%x,ADDR:]] [[#%x,OFF:]] {{0*}}10
 
@@ -81,3 +90,17 @@ addressDynCi:
   adr x1, .Lci
   bl _start
 .size addressDynCi, .-addressDynCi
+
+  .section ".mytext", "ax"
+  .balign 8
+  .global dummy
+  .type dummy, %function
+dummy:
+  nop
+  .word 0
+  .size dummy, .-dummy
+
+  .global mytextP
+mytextP:
+  .xword exitLocal
+  .size mytextP, .-mytextP