From ef01e7d7eef09fd289d78ccfbe9be19b854e87c8 Mon Sep 17 00:00:00 2001
From: Rui Ueyama <ruiu@cs.stanford.edu>
Date: Sat, 10 Apr 2021 18:16:01 +0900
Subject: [PATCH] Add `-z initfirst`

---
 cmdline.cc        |  2 ++
 elf.h             |  1 +
 mold.h            |  1 +
 output_chunks.cc  |  2 ++
 test/initfirst.sh | 19 +++++++++++++++++++
 5 files changed, 25 insertions(+)
 create mode 100755 test/initfirst.sh

diff --git a/cmdline.cc b/cmdline.cc
index a836cf0b..d9454916 100644
--- a/cmdline.cc
+++ b/cmdline.cc
@@ -372,6 +372,8 @@ void parse_nonpositional_args(Context<E> &ctx,
       ctx.arg.z_delete = false;
     } else if (read_z_flag(args, "nocopyreloc")) {
       ctx.arg.z_copyreloc = false;
+    } else if (read_z_flag(args, "initfirst")) {
+      ctx.arg.z_initfirst = true;
     } else if (read_flag(args, "no-undefined")) {
       ctx.arg.z_defs = true;
     } else if (read_flag(args, "fatal-warnings")) {
diff --git a/elf.h b/elf.h
index 664359c3..5f63ef9e 100644
--- a/elf.h
+++ b/elf.h
@@ -182,6 +182,7 @@ static constexpr u32 DF_STATIC_TLS = 0x10;
 
 static constexpr u32 DF_1_NOW = 0x00000001;
 static constexpr u32 DF_1_NODELETE = 0x00000008;
+static constexpr u32 DF_1_INITFIRST = 0x00000020;
 static constexpr u32 DF_1_NOOPEN = 0x00000040;
 static constexpr u32 DF_1_PIE = 0x08000000;
 
diff --git a/mold.h b/mold.h
index 790e6b93..74b02fbc 100644
--- a/mold.h
+++ b/mold.h
@@ -1273,6 +1273,7 @@ struct Context {
     bool z_delete = true;
     bool z_dlopen = true;
     bool z_execstack = false;
+    bool z_initfirst = false;
     bool z_now = false;
     bool z_relro = true;
     i16 default_version = VER_NDX_GLOBAL;
diff --git a/output_chunks.cc b/output_chunks.cc
index 803c8718..2a5528ef 100644
--- a/output_chunks.cc
+++ b/output_chunks.cc
@@ -480,6 +480,8 @@ static std::vector<typename E::WordTy> create_dynamic_section(Context<E> &ctx) {
     flags1 |= DF_1_NOOPEN;
   if (!ctx.arg.z_delete)
     flags1 |= DF_1_NODELETE;
+  if (ctx.arg.z_initfirst)
+    flags1 |= DF_1_INITFIRST;
 
   if (ctx.has_gottp_rel)
     flags |= DF_STATIC_TLS;
diff --git a/test/initfirst.sh b/test/initfirst.sh
new file mode 100755
index 00000000..ce63a394
--- /dev/null
+++ b/test/initfirst.sh
@@ -0,0 +1,19 @@
+#!/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 -fPIC -o $t/a.o -xc -
+#include <stdio.h>
+
+void foo() {
+  printf("Hello world\n");
+}
+EOF
+
+clang -fuse-ld=`pwd`/../mold -shared -o $t/b.so $t/a.o -Wl,-z,initfirst
+readelf --dynamic $t/b.so | grep -q 'Flags: INITFIRST'
+
+echo OK