[AArch64] Fix resolution of R_PLT_PAGE RelExpr

smithp35 · smithp35 · commit ad51cee866f4 · 2018-11-14T13:53:47.000Z
The R_AARCH64_ADR_PREL_PG_HI21 relocation type is given the R_PAGE_PC RelExpr. This can be transformed to R_PLT_PAGE_PC via toPlt(). Unfortunately the resolution is identical to R_PAGE_PC so instead of getting the address of the PLT entry we get the address of the symbol which may not be correct in the case of static ifuncs. The fix is to handle the cases separately and use getPltVA() + A with R_PLT_PAGE_PC. Differential Revision: https://reviews.llvm.org/D54474 llvm-svn: 346863
diff --git a/lld/ELF/InputSection.cpp b/lld/ELF/InputSection.cpp
@@ -668,14 +668,13 @@ static uint64_t getRelocTargetVA(const InputFile *File, RelType Type, int64_t A,
   case R_MIPS_TLSLD:
     return In.MipsGot->getVA() + In.MipsGot->getTlsIndexOffset(File) -
            In.MipsGot->getGp(File);
-  case R_PAGE_PC:
+  case R_PAGE_PC: {
+    uint64_t Val = Sym.isUndefWeak() ? A : Sym.getVA(A);
+    return getAArch64Page(Val) - getAArch64Page(P);
+  }
   case R_PLT_PAGE_PC: {
-    uint64_t Dest;
-    if (Sym.isUndefWeak())
-      Dest = getAArch64Page(A);
-    else
-      Dest = getAArch64Page(Sym.getVA(A));
-    return Dest - getAArch64Page(P);
+    uint64_t Val = Sym.isUndefWeak() ? A : Sym.getPltVA() + A;
+    return getAArch64Page(Val) - getAArch64Page(P);
   }
   case R_RISCV_PC_INDIRECT: {
     const Relocation *HiRel = getRISCVPCRelHi20(&Sym, A);
diff --git a/lld/test/ELF/aarch64-gnu-ifunc3.s b/lld/test/ELF/aarch64-gnu-ifunc3.s
@@ -0,0 +1,49 @@
+# REQUIRES: aarch64
+# RUN: llvm-mc -filetype=obj -triple=aarch64-none-linux-gnu %s -o %t.o
+# RUN: ld.lld -static %t.o -o %tout
+# RUN: llvm-objdump -D %tout | FileCheck %s
+# RUN: llvm-readobj -r %tout | FileCheck %s --check-prefix=RELOC
+
+# The address of myfunc is the address of the PLT entry for myfunc.
+# The adrp to myfunc should generate a PLT entry and a got entry with an
+# irelative relocation.
+.text
+.globl myfunc
+.type myfunc,@gnu_indirect_function
+myfunc:
+ ret
+
+.text
+.globl _start
+.type _start,@function
+_start:
+ adrp x8, myfunc
+ add  x8, x8, :lo12:myfunc
+ ret
+
+# CHECK: Disassembly of section .text:
+# CHECK-NEXT: myfunc:
+# CHECK-NEXT:   210000:	c0 03 5f d6 	ret
+# CHECK: _start:
+# adrp x8, 0x210000 + 0x10 from add == .plt entry
+# CHECK-NEXT:   210004:	08 00 00 90 	adrp	x8, #0
+# CHECK-NEXT:   210008:	08 41 00 91 	add	x8, x8, #16
+# CHECK-NEXT:   21000c:	c0 03 5f d6 	ret
+# CHECK-NEXT: Disassembly of section .plt:
+# CHECK-NEXT: .plt:
+# adrp x16, 0x220000, 0x220000 == address in .got.plt
+# CHECK-NEXT:   210010:	90 00 00 90 	adrp	x16, #65536
+# CHECK-NEXT:   210014:	11 02 40 f9 	ldr	x17, [x16]
+# CHECK-NEXT:   210018:	10 02 00 91 	add	x16, x16, #0
+# CHECK-NEXT:   21001c:	20 02 1f d6 	br	x17
+# CHECK-NEXT: Disassembly of section .got.plt:
+# CHECK-NEXT: .got.plt:
+# 0x210010 == address in .plt
+# CHECK-NEXT:   220000:	10 00 21 00
+# CHECK-NEXT:   220004:	00 00 00 00
+
+# RELOC: Relocations [
+# RELOC-NEXT:  Section (1) .rela.plt {
+# RELOC-NEXT:    0x220000 R_AARCH64_IRELATIVE - 0x210000
+# RELOC-NEXT:  }
+# RELOC-NEXT: ]
