Add -z execstack and -z noexecstack

commandline.cc

@@ -277,6 +277,10 @@ void parse_nonpositional_args(std::span<std::string_view> args,
       config.print_stats = true;
     } else if (read_z_flag(args, "now")) {
       config.z_now = true;
+    } else if (read_z_flag(args, "execstack")) {
+      config.z_execstack = true;
+    } else if (read_z_flag(args, "noexecstack")) {
+      config.z_execstack = false;
     } else if (read_flag(args, "fork")) {
       config.fork = true;
     } else if (read_flag(args, "no-fork")) {

mold.h

@@ -86,6 +86,7 @@ struct Config {
   bool shared = false;
   bool strip_all = false;
   bool trace = false;
+  bool z_execstack = false;
   bool z_now = false;
   i16 default_version = VER_NDX_GLOBAL;
   std::vector<std::string_view> version_definitions;

output_chunks.cc

@@ -151,11 +151,13 @@ std::vector<ElfPhdr> create_phdr() {
     define(PT_GNU_EH_FRAME, PF_R, 1, out::eh_frame_hdr);
 
   // Add PT_GNU_STACK, which is a marker segment that doesn't really
-  // contain any segments. If exists, the runtime turn on the No Exeecute
-  // bit for stack pages.
+  // contain any segments. It controls executable bit of stack area.
   vec.push_back({});
   vec.back().p_type = PT_GNU_STACK;
-  vec.back().p_flags = PF_R | PF_W;
+  if (config.z_execstack)
+    vec.back().p_flags = PF_R | PF_W | PF_X;
+  else
+    vec.back().p_flags = PF_R | PF_W;
 
   return vec;
 }

test/execstack.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+set -e
+cd $(dirname $0)
+echo -n "Testing $(basename -s .sh $0) ... "
+t=$(pwd)/tmp/$(basename -s .sh $0)
+mkdir -p $t
+
+cat <<EOF | clang -c -xc -o $t/a.o -
+int main() {}
+EOF
+
+clang -fuse-ld=`pwd`/../mold -o $t/exe $t/a.o -Wl,-z,execstack
+readelf --segments -W $t/exe > $t/log
+grep -q 'GNU_STACK.* RWE ' $t/log
+
+clang -fuse-ld=`pwd`/../mold -o $t/exe $t/a.o -Wl,-z,execstack \
+  -Wl,-z,noexecstack
+readelf --segments -W $t/exe > $t/log
+grep -q 'GNU_STACK.* RW ' $t/log
+
+clang -fuse-ld=`pwd`/../mold -o $t/exe $t/a.o
+readelf --segments -W $t/exe > $t/log
+grep -q 'GNU_STACK.* RW ' $t/log
+
+echo OK