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Index: head/contrib/llvm/tools/lld/ELF/Config.h
===================================================================
--- head/contrib/llvm/tools/lld/ELF/Config.h
+++ head/contrib/llvm/tools/lld/ELF/Config.h
@@ -155,6 +155,7 @@
bool ZCombreloc;
bool ZExecstack;
bool ZHazardplt;
+ bool ZIfuncnoplt;
bool ZNocopyreloc;
bool ZNodelete;
bool ZNodlopen;
Index: head/contrib/llvm/tools/lld/ELF/Driver.cpp
===================================================================
--- head/contrib/llvm/tools/lld/ELF/Driver.cpp
+++ head/contrib/llvm/tools/lld/ELF/Driver.cpp
@@ -669,6 +669,7 @@
Config->ZCombreloc = !hasZOption(Args, "nocombreloc");
Config->ZExecstack = hasZOption(Args, "execstack");
Config->ZHazardplt = hasZOption(Args, "hazardplt");
+ Config->ZIfuncnoplt = hasZOption(Args, "ifunc-noplt");
Config->ZNocopyreloc = hasZOption(Args, "nocopyreloc");
Config->ZNodelete = hasZOption(Args, "nodelete");
Config->ZNodlopen = hasZOption(Args, "nodlopen");
Index: head/contrib/llvm/tools/lld/ELF/Relocations.cpp
===================================================================
--- head/contrib/llvm/tools/lld/ELF/Relocations.cpp
+++ head/contrib/llvm/tools/lld/ELF/Relocations.cpp
@@ -374,6 +374,9 @@
R_PPC_PLT_OPD, R_TLSDESC_CALL, R_TLSDESC_PAGE, R_HINT>(E))
return true;
+ if (Sym.isGnuIFunc() && Config->ZIfuncnoplt)
+ return false;
+
// These never do, except if the entire file is position dependent or if
// only the low bits are used.
if (E == R_GOT || E == R_PLT || E == R_TLSDESC)
@@ -921,7 +924,9 @@
// Strenghten or relax a PLT access.
//
// GNU ifunc symbols must be accessed via PLT because their addresses
- // are determined by runtime.
+ // are determined by runtime. If the -z ifunc-noplt option is specified,
+ // we permit the optimization of ifunc calls by omitting the PLT entry
+ // and preserving relocations at ifunc call sites.
//
// On the other hand, if we know that a PLT entry will be resolved within
// the same ELF module, we can skip PLT access and directly jump to the
@@ -929,7 +934,7 @@
// 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() && !Config->ZIfuncnoplt)
Expr = toPlt(Expr);
else if (!Preemptible && Expr == R_GOT_PC && !isAbsoluteValue(Sym))
Expr =
@@ -1031,6 +1036,16 @@
// uses Elf_Rel, since in that case the written value is the addend.
if (IsConstant) {
Sec.Relocations.push_back({Expr, Type, Offset, Addend, &Sym});
+ continue;
+ }
+
+ // Preserve relocations against ifuncs if we were asked to do so.
+ if (Sym.isGnuIFunc() && Config->ZIfuncnoplt) {
+ if (Config->IsRela)
+ InX::RelaDyn->addReloc({Type, &Sec, Offset, false, &Sym, Addend});
+ else
+ // Preserve the existing addend.
+ InX::RelaDyn->addReloc({Type, &Sec, Offset, false, &Sym, 0});
continue;
}
Index: head/contrib/llvm/tools/lld/ELF/Writer.cpp
===================================================================
--- head/contrib/llvm/tools/lld/ELF/Writer.cpp
+++ head/contrib/llvm/tools/lld/ELF/Writer.cpp
@@ -1400,8 +1400,11 @@
applySynthetic({InX::EhFrame},
[](SyntheticSection *SS) { SS->finalizeContents(); });
- for (Symbol *S : Symtab->getSymbols())
+ for (Symbol *S : Symtab->getSymbols()) {
S->IsPreemptible |= computeIsPreemptible(*S);
+ if (S->isGnuIFunc() && Config->ZIfuncnoplt)
+ S->ExportDynamic = true;
+ }
// Scan relocations. This must be done after every symbol is declared so that
// we can correctly decide if a dynamic relocation is needed.
Index: head/usr.bin/clang/lld/ld.lld.1
===================================================================
--- head/usr.bin/clang/lld/ld.lld.1
+++ head/usr.bin/clang/lld/ld.lld.1
@@ -25,7 +25,7 @@
.\"
.\" $FreeBSD$
.\"
-.Dd February 7, 2018
+.Dd August 22, 2018
.Dt LD.LLD 1
.Os
.Sh NAME
@@ -443,6 +443,13 @@
Stack permissions are recorded in the
.Dv PT_GNU_STACK
segment.
+.It Cm ifunc-noplt
+Do not emit PLT entries for GNU ifuncs.
+Instead, preserve relocations for ifunc call sites so that they may
+be applied by a run-time loader.
+Note that this feature requires special loader support and will
+generally result in application crashes when used outside of freestanding
+environments.
.It Cm muldefs
Do not error if a symbol is defined multiple times.
The first definition will be used.

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