- enable retpoline by default
- enable PIE by default.
- arm64 and riscv64 can now do --execute-only by default
- enable --exec-only as default on AMD64
- Make --execute-only the default on powerpc64.
- Permit the --exec-only option on i386 also.
- make --execute-only the default on powerpc
- default sparc64 ld.lld to --execute-only
- switch mips64 ld.lld to execute-only
- Implement support for PT_OPENBSD_NOBTCFI in lld(1).  This can be set using
  the -z nobtcfi option.

Index: lld/ELF/Driver.cpp
--- lld/ELF/Driver.cpp.orig
+++ lld/ELF/Driver.cpp
@@ -358,8 +358,19 @@ static void checkOptions() {
   }
 
   if (config->executeOnly) {
-    if (config->emachine != EM_AARCH64)
-      error("-execute-only is only supported on AArch64 targets");
+    switch (config->emachine) {
+    case EM_386:
+    case EM_AARCH64:
+    case EM_MIPS:
+    case EM_PPC:
+    case EM_PPC64:
+    case EM_RISCV:
+    case EM_SPARCV9:
+    case EM_X86_64:
+      break;
+    default:
+      error("-execute-only is not supported on this target");
+    }
 
     if (config->singleRoRx && !script->hasSectionsCommand)
       error("-execute-only and -no-rosegment cannot be used together");
@@ -451,10 +462,12 @@ static bool isKnownZFlag(StringRef s) {
          s == "initfirst" || s == "interpose" ||
          s == "keep-text-section-prefix" || s == "lazy" || s == "muldefs" ||
          s == "separate-code" || s == "separate-loadable-segments" ||
-         s == "start-stop-gc" || s == "nocombreloc" || s == "nocopyreloc" ||
+         s == "start-stop-gc" || s == "nobtcfi" ||
+         s == "nocombreloc" || s == "nocopyreloc" ||
          s == "nodefaultlib" || s == "nodelete" || s == "nodlopen" ||
          s == "noexecstack" || s == "nognustack" ||
          s == "nokeep-text-section-prefix" || s == "norelro" ||
+         s == "noretpolineplt" ||
          s == "noseparate-code" || s == "nostart-stop-gc" || s == "notext" ||
          s == "now" || s == "origin" || s == "pac-plt" || s == "rel" ||
          s == "rela" || s == "relro" || s == "retpolineplt" ||
@@ -1045,8 +1058,6 @@ static void readConfigs(opt::InputArgList &args) {
   errorHandler().errorHandlingScript =
       args.getLastArgValue(OPT_error_handling_script);
 
-  config->executeOnly =
-      args.hasFlag(OPT_execute_only, OPT_no_execute_only, false);
   config->exportDynamic =
       args.hasFlag(OPT_export_dynamic, OPT_no_export_dynamic, false);
   config->filterList = args::getStrings(args, OPT_filter);
@@ -1064,7 +1075,8 @@ static void readConfigs(opt::InputArgList &args) {
   config->ignoreDataAddressEquality =
       args.hasArg(OPT_ignore_data_address_equality);
   config->ignoreFunctionAddressEquality =
-      args.hasArg(OPT_ignore_function_address_equality);
+      args.hasFlag(OPT_ignore_function_address_equality,
+      OPT_no_ignore_function_address_equality, true);
   config->init = args.getLastArgValue(OPT_init, "_init");
   config->ltoAAPipeline = args.getLastArgValue(OPT_lto_aa_pipeline);
   config->ltoCSProfileGenerate = args.hasArg(OPT_lto_cs_profile_generate);
@@ -1118,7 +1130,12 @@ static void readConfigs(opt::InputArgList &args) {
   config->optimize = args::getInteger(args, OPT_O, 1);
   config->orphanHandling = getOrphanHandling(args);
   config->outputFile = args.getLastArgValue(OPT_o);
+#ifdef __OpenBSD__
+  config->pie = args.hasFlag(OPT_pie, OPT_no_pie,
+      !args.hasArg(OPT_shared) && !args.hasArg(OPT_relocatable));
+#else
   config->pie = args.hasFlag(OPT_pie, OPT_no_pie, false);
+#endif
   config->printIcfSections =
       args.hasFlag(OPT_print_icf_sections, OPT_no_print_icf_sections, false);
   config->printGcSections =
@@ -1181,6 +1198,7 @@ static void readConfigs(opt::InputArgList &args) {
   config->zInterpose = hasZOption(args, "interpose");
   config->zKeepTextSectionPrefix = getZFlag(
       args, "keep-text-section-prefix", "nokeep-text-section-prefix", false);
+  config->zNoBtCfi = hasZOption(args, "nobtcfi");
   config->zNodefaultlib = hasZOption(args, "nodefaultlib");
   config->zNodelete = hasZOption(args, "nodelete");
   config->zNodlopen = hasZOption(args, "nodlopen");
@@ -1188,7 +1206,11 @@ static void readConfigs(opt::InputArgList &args) {
   config->zOrigin = hasZOption(args, "origin");
   config->zPacPlt = hasZOption(args, "pac-plt");
   config->zRelro = getZFlag(args, "relro", "norelro", true);
-  config->zRetpolineplt = hasZOption(args, "retpolineplt");
+#ifndef __OpenBSD__
+  config->zRetpolineplt = getZFlag(args, "retpolineplt", "noretpolineplt", false);
+#else
+  config->zRetpolineplt = getZFlag(args, "retpolineplt", "noretpolineplt", true);
+#endif
   config->zRodynamic = hasZOption(args, "rodynamic");
   config->zSeparate = getZSeparate(args);
   config->zShstk = hasZOption(args, "shstk");
@@ -1459,6 +1481,23 @@ static void setConfigs(opt::InputArgList &args) {
       args.hasFlag(OPT_toc_optimize, OPT_no_toc_optimize, m == EM_PPC64);
   config->pcRelOptimize =
       args.hasFlag(OPT_pcrel_optimize, OPT_no_pcrel_optimize, m == EM_PPC64);
+
+  config->executeOnly = false;
+#ifdef __OpenBSD__
+  switch (m) {
+  case EM_AARCH64:
+  case EM_MIPS:
+  case EM_PPC:
+  case EM_PPC64:
+  case EM_RISCV:
+  case EM_SPARCV9:
+  case EM_X86_64:
+    config->executeOnly = true;
+    break;
+  }
+#endif
+  config->executeOnly =
+      args.hasFlag(OPT_execute_only, OPT_no_execute_only, config->executeOnly);
 }
 
 // Returns a value of "-format" option.
@@ -1596,7 +1635,7 @@ void LinkerDriver::inferMachineType() {
 }
 
 // Parse -z max-page-size=<value>. The default value is defined by
-// each target.
+// each target. Is set to 1 if given nmagic or omagic.
 static uint64_t getMaxPageSize(opt::InputArgList &args) {
   uint64_t val = args::getZOptionValue(args, OPT_z, "max-page-size",
                                        target->defaultMaxPageSize);
@@ -1611,7 +1650,7 @@ static uint64_t getMaxPageSize(opt::InputArgList &args
 }
 
 // Parse -z common-page-size=<value>. The default value is defined by
-// each target.
+// each target. Is set to 1 if given nmagic or omagic.
 static uint64_t getCommonPageSize(opt::InputArgList &args) {
   uint64_t val = args::getZOptionValue(args, OPT_z, "common-page-size",
                                        target->defaultCommonPageSize);
@@ -1628,6 +1667,16 @@ static uint64_t getCommonPageSize(opt::InputArgList &a
   return val;
 }
 
+// Parse -z max-page-size=<value>. The default value is defined by
+// each target.
+static uint64_t getRealMaxPageSize(opt::InputArgList &args) {
+  uint64_t val = args::getZOptionValue(args, OPT_z, "max-page-size",
+                                       target->defaultMaxPageSize);
+  if (!isPowerOf2_64(val))
+    error("max-page-size: value isn't a power of 2");
+  return val;
+}
+
 // Parses -image-base option.
 static Optional<uint64_t> getImageBase(opt::InputArgList &args) {
   // Because we are using "Config->maxPageSize" here, this function has to be
@@ -2414,6 +2463,11 @@ template <class ELFT> void LinkerDriver::link(opt::Inp
   // optimizations such as DATA_SEGMENT_ALIGN in linker scripts. LLD's use of it
   // is limited to writing trap instructions on the last executable segment.
   config->commonPageSize = getCommonPageSize(args);
+  // textAlignPageSize is the alignment page size to use when aligning PT_LOAD
+  // sections. This is the same as maxPageSize except under -omagic, where data
+  // sections are non-aligned (maxPageSize set to 1) but text sections are aligned
+  // to the target page size.
+  config->textAlignPageSize = config->omagic ? getRealMaxPageSize(args) : config->maxPageSize;
 
   config->imageBase = getImageBase(args);