Index: ELF/LinkerScript.cpp =================================================================== --- ELF/LinkerScript.cpp +++ ELF/LinkerScript.cpp @@ -825,12 +825,18 @@ if (!Sec.Phdrs.empty()) return false; - // We do not want to remove sections that reference symbols in address and - // other expressions. We add script symbols as undefined, and want to ensure - // all of them are defined in the output, hence have to keep them. + // We do not want to remove OutputSections with expressions that reference + // symbols even if the OutputSection is empty. We want to ensure that the + // expressions can be evaluated and report an error if they cannot. if (Sec.ExpressionsUseSymbols) return false; + // OutputSections may be referenced by name in ADDR and LOADADDR expressions, + // as an empty Section can has a valid VMA and LMA we keep the OutputSection + // to maintain the integrity of the other Expression. + if (Sec.UsedInExpression) + return false; + for (BaseCommand *Base : Sec.SectionCommands) { if (auto Cmd = dyn_cast(Base)) // Don't create empty output sections just for unreferenced PROVIDE Index: ELF/OutputSections.h =================================================================== --- ELF/OutputSections.h +++ ELF/OutputSections.h @@ -90,6 +90,7 @@ bool NonAlloc = false; bool Noload = false; bool ExpressionsUseSymbols = false; + bool UsedInExpression = false; bool InOverlay = false; void finalize(); Index: ELF/ScriptParser.cpp =================================================================== --- ELF/ScriptParser.cpp +++ ELF/ScriptParser.cpp @@ -1155,6 +1155,7 @@ if (Tok == "ADDR") { StringRef Name = readParenLiteral(); OutputSection *Sec = Script->getOrCreateOutputSection(Name); + Sec->UsedInExpression = true; return [=]() -> ExprValue { checkIfExists(Sec, Location); return {Sec, false, 0, Location}; @@ -1231,6 +1232,7 @@ if (Tok == "LOADADDR") { StringRef Name = readParenLiteral(); OutputSection *Cmd = Script->getOrCreateOutputSection(Name); + Cmd->UsedInExpression = true; return [=] { checkIfExists(Cmd, Location); return Cmd->getLMA(); Index: test/ELF/linkerscript/empty-sections-expressions.test =================================================================== --- /dev/null +++ test/ELF/linkerscript/empty-sections-expressions.test @@ -0,0 +1,24 @@ +# REQUIRES: x86 +# RUN: echo ".text; nop; .data; .byte 0" \ +# RUN: | llvm-mc -filetype=obj -triple=x86_64-pc-linux - -o %t.o +# RUN: ld.lld -o %t --script %s %t.o +# RUN: llvm-readelf -program-headers %t | FileCheck %s + +## Check we do not remove the empty output sections used in LOADADDR/ADDR +## expressions and hence can evaluate the correct addresses. + +# CHECK: Program Headers: +# CHECK-NEXT: Type Offset VirtAddr PhysAddr +# CHECK-NEXT: LOAD 0x001000 0x0000000000080000 0x0000000000080000 +# CHECK-NEXT: LOAD 0x001001 0x0000000000080001 0x0000000000082000 + +# CHECK: Section to Segment mapping: +# CHECK: 00 .empty .text +# CHECK-NEXT: 01 .data + +SECTIONS { + . = 0x00080000; + .empty : { *(.empty ) } + .text : AT(LOADADDR(.empty) + SIZEOF(.empty)) { *(.text) } + .data : AT(ADDR(.empty) + 0x2000) { *(.data) } +}