Index: ELF/Config.h =================================================================== --- ELF/Config.h +++ ELF/Config.h @@ -175,6 +175,7 @@ bool UseAndroidRelrTags = false; bool WarnBackrefs; bool WarnCommon; + bool WarnIfuncTextrel; bool WarnMissingEntry; bool WarnSymbolOrdering; bool WriteAddends; Index: ELF/Driver.cpp =================================================================== --- ELF/Driver.cpp +++ ELF/Driver.cpp @@ -829,6 +829,8 @@ Config->WarnBackrefs = Args.hasFlag(OPT_warn_backrefs, OPT_no_warn_backrefs, false); Config->WarnCommon = Args.hasFlag(OPT_warn_common, OPT_no_warn_common, false); + Config->WarnIfuncTextrel = + Args.hasFlag(OPT_warn_ifunc_textrel, OPT_no_warn_ifunc_textrel, false); Config->WarnSymbolOrdering = Args.hasFlag(OPT_warn_symbol_ordering, OPT_no_warn_symbol_ordering, true); Config->ZCombreloc = getZFlag(Args, "combreloc", "nocombreloc", true); Index: ELF/Options.td =================================================================== --- ELF/Options.td +++ ELF/Options.td @@ -348,6 +348,10 @@ "Warn about duplicate common symbols", "Do not warn about duplicate common symbols (default)">; +defm warn_ifunc_textrel: B<"warn-ifunc-textrel", + "Warn about using IFUNC symbols with text relocations", + "Do not warn about using IFUNC symbols with text relocations (default)">; + defm warn_symbol_ordering: B<"warn-symbol-ordering", "Warn about problems with the symbol ordering file (default)", "Do not warn about problems with the symbol ordering file">; Index: ELF/Relocations.cpp =================================================================== --- ELF/Relocations.cpp +++ ELF/Relocations.cpp @@ -50,6 +50,7 @@ #include "SyntheticSections.h" #include "Target.h" #include "Thunks.h" +#include "lld/Common/ErrorHandler.h" #include "lld/Common/Memory.h" #include "lld/Common/Strings.h" #include "llvm/ADT/SmallSet.h" @@ -980,12 +981,22 @@ // all dynamic symbols that can be resolved within the executable will // actually be resolved that way at runtime, because the main exectuable // is always at the beginning of a search list. We can leverage that fact. - if (Sym.isGnuIFunc()) + if (Sym.isGnuIFunc()) { + if (!Config->ZText && Config->WarnIfuncTextrel) { + warn("using IFUNC symbols when text relocations are allowed may produce " + "a binary that will segfault, if the object file is linked with " + "old version of glibc (The issue is fixed with version 2.29). " + "If this applies to you, consider recompiling the object files " + "without -fPIC and without '-Wl,-z,notext' option. " + "Use -no-warn-ifunc-textrel to turn off this warning." + + getLocation(Sec, Sym, Offset)); + } Expr = toPlt(Expr); - else if (!Sym.IsPreemptible && Expr == R_GOT_PC && !isAbsoluteValue(Sym)) + } else if (!Sym.IsPreemptible && Expr == R_GOT_PC && !isAbsoluteValue(Sym)) { Expr = Target->adjustRelaxExpr(Type, RelocatedAddr, Expr); - else if (!Sym.IsPreemptible) + } else if (!Sym.IsPreemptible) { Expr = fromPlt(Expr); + } // This relocation does not require got entry, but it is relative to got and // needs it to be created. Here we request for that. Index: docs/ld.lld.1 =================================================================== --- docs/ld.lld.1 +++ docs/ld.lld.1 @@ -428,6 +428,9 @@ traditional Unix-like linkers. .It Fl -warn-common Warn about duplicate common symbols. +.It Fl -warn-ifunc-textrel +Warn about usinc ifunc symbols in conjunction with text relocations. +This will cause segment faults if linked with glibc version 2.28 and before. .It Fl -warn-unresolved-symbols Report unresolved symbols as warnings. .It Fl -whole-archive Index: test/ELF/textrel.s =================================================================== --- /dev/null +++ test/ELF/textrel.s @@ -0,0 +1,40 @@ +# REQUIRES: x86 +# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux-gnu %s -o %t.o + +# Without --warn-text-ifunc, lld should run fine: +# RUN: ld.lld -z notext %t.o -o %t2 + +# With --warn-text-ifunc, lld should run with warnings: +# RUN: ld.lld --warn-ifunc-textrel -z notext %t.o -o /dev/null 2>&1 | FileCheck %s +# CHECK: using IFUNC symbols when text relocations are allowed may produce +# CHECK-SAME: a binary that will segfault, if the object file is linked with +# CHECK-SAME: old version of glibc (The issue is fixed with version 2.29). +# CHECK-SAME: If this applies to you, consider recompiling the object files +# CHECK-SAME: without -fPIC and without '-Wl,-z,notext' option. +# CHECK-SAME: Use -no-warn-ifunc-textrel to turn off this warning. +# CHECK: >>> defined in {{.*}} +# CHECK: >>> referenced by {{.*}}:(.text+0x8) + +# Without text relocations, lld should run fine: +# RUN: ld.lld --fatal-warnings %t.o -o /dev/null + +.text +.globl a_func_impl +a_func_impl: + nop + +.globl selector +.type selector,@function +selector: + movl $a_func_impl, %eax + retq + +.globl a_func +.type a_func,@gnu_indirect_function +.set a_func, selector + +.globl _start +.type _start,@function +main: + callq a_func + retq