[lld] r365049 - [ELF][RISCV] Error on R_RISCV_PCREL_LO12_[IS] that point to absolute symbols

[Fangrui Song via llvm-commits]

Author: maskray
Date: Wed Jul  3 08:38:59 2019
New Revision: 365049

URL: http://llvm.org/viewvc/llvm-project?rev=365049&view=rev
Log:
[ELF][RISCV] Error on R_RISCV_PCREL_LO12_[IS] that point to absolute symbols

The referenced symbol is expected to point to an R_RISCV_*_HI20
relocation. An absolute symbol has no associated section, therefore
there cannot be a matching R_RISCV_*_HI20.

This fixes the crash reported by PR42038. For reference, ld.bfd errors:

    (.init+0x4): dangerous relocation: %pcrel_lo missing matching %pcrel_hi

Differential Revision: https://reviews.llvm.org/D63273

Added:
    lld/trunk/test/ELF/riscv-pcrel-hilo-error.s
Modified:
    lld/trunk/ELF/InputSection.cpp

Modified: lld/trunk/ELF/InputSection.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/InputSection.cpp?rev=365049&r1=365048&r2=365049&view=diff
==============================================================================
--- lld/trunk/ELF/InputSection.cpp (original)
+++ lld/trunk/ELF/InputSection.cpp Wed Jul  3 08:38:59 2019
@@ -570,6 +570,11 @@ static uint64_t getARMStaticBase(const S
 // R_RISCV_PCREL_LO12's symbol and addend.
 static Relocation *getRISCVPCRelHi20(const Symbol *Sym, uint64_t Addend) {
   const Defined *D = cast<Defined>(Sym);
+  if (!D->Section) {
+    error("R_RISCV_PCREL_LO12 relocation points to an absolute symbol: " +
+          Sym->getName());
+    return nullptr;
+  }
   InputSection *IS = cast<InputSection>(D->Section);
 
   if (Addend != 0)

Added: lld/trunk/test/ELF/riscv-pcrel-hilo-error.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/riscv-pcrel-hilo-error.s?rev=365049&view=auto
==============================================================================
--- lld/trunk/test/ELF/riscv-pcrel-hilo-error.s (added)
+++ lld/trunk/test/ELF/riscv-pcrel-hilo-error.s Wed Jul  3 08:38:59 2019
@@ -0,0 +1,7 @@
+# REQUIRES: riscv
+# RUN: llvm-mc -filetype=obj -triple=riscv64 %s -o %t.o
+# RUN: not ld.lld %t.o --defsym external=0 2>&1 | FileCheck %s
+
+# CHECK: error: R_RISCV_PCREL_LO12 relocation points to an absolute symbol: external
+
+addi sp,sp,%pcrel_lo(external)