[ELF] Add --rosegment and --no-rosegment

Fixes https://github.com/rui314/mold/issues/514

elf/cmdline.cc

@@ -113,6 +113,8 @@ Options:
   --require-defined SYMBOL    Require SYMBOL be defined in the final output
   --retain-symbols-file FILE  Keep only symbols listed in FILE
   --reverse-sections          Reverses input sections in the output file
+  --rosegment                 Put read-only non-executable sections in their own segment (default)
+    --no-rosegment            Put read-only non-executable sections in an executable segment
   --rpath DIR                 Add DIR to runtime search path
   --rpath-link DIR            Ignored
   --run COMMAND ARG...        Run COMMAND with mold as /usr/bin/ld
@@ -537,6 +539,10 @@ std::vector<std::string> parse_nonpositional_args(Context<E> &ctx) {
       ctx.arg.shuffle_sections_seed = parse_number(ctx, "shuffle-sections", arg);
     } else if (read_flag("reverse-sections")) {
       ctx.arg.shuffle_sections = SHUFFLE_SECTIONS_REVERSE;
+    } else if (read_flag("rosegment")) {
+      ctx.arg.rosegment = true;
+    } else if (read_flag("no-rosegment")) {
+      ctx.arg.rosegment = false;
     } else if (read_arg("y") || read_arg("trace-symbol")) {
       ctx.arg.trace_symbol.push_back(arg);
     } else if (read_arg("filler")) {

elf/mold.h

@@ -1593,6 +1593,7 @@ struct Context {
     bool relax = true;
     bool relocatable = false;
     bool repro = false;
+    bool rosegment = true;
     bool shared = false;
     bool stats = false;
     bool strip_all = false;

elf/output-chunks.cc

@@ -116,10 +116,12 @@ static i64 to_phdr_flags(Context<E> &ctx, Chunk<E> *chunk) {
     return PF_R | PF_W | PF_X;
 
   i64 ret = PF_R;
-  if (chunk->shdr.sh_flags & SHF_WRITE)
+  bool write = (chunk->shdr.sh_flags & SHF_WRITE);
+  if (write)
     ret |= PF_W;
-  if ((chunk->shdr.sh_flags & SHF_EXECINSTR) ||
-      (ctx.arg.z_separate_code == NOSEPARATE_CODE))
+  if ((ctx.arg.z_separate_code == NOSEPARATE_CODE) ||
+      (!ctx.arg.rosegment && !write) ||
+      (chunk->shdr.sh_flags & SHF_EXECINSTR))
     ret |= PF_X;
   return ret;
 }

test/elf/rosegment.sh

@@ -0,0 +1,33 @@
+#!/bin/bash
+export LC_ALL=C
+set -e
+CC="${TEST_CC:-cc}"
+CXX="${TEST_CXX:-c++}"
+GCC="${TEST_GCC:-gcc}"
+GXX="${TEST_GXX:-g++}"
+OBJDUMP="${OBJDUMP:-objdump}"
+MACHINE="${MACHINE:-$(uname -m)}"
+testname=$(basename "$0" .sh)
+echo -n "Testing $testname ... "
+cd "$(dirname "$0")"/../..
+t=out/test/elf/$testname
+mkdir -p $t
+
+cat <<EOF | $CC -o $t/a.o -c -xc -
+#include <stdio.h>
+int main() { printf("Hello world\n"); }
+EOF
+
+$CC -B. -o $t/exe1 $t/a.o
+readelf -W --segments $t/exe1 > $t/log1
+! grep -q '\.interp .* \.text' $t/log1 || false
+
+$CC -B. -o $t/exe2 $t/a.o -Wl,--rosegment
+readelf -W --segments $t/exe2 > $t/log2
+! grep -q '\.interp .* \.text' $t/log2 || false
+
+$CC -B. -o $t/exe3 $t/a.o -Wl,--no-rosegment
+readelf -W --segments $t/exe3 > $t/log3
+grep -q '\.interp .* \.text' $t/log3
+
+echo OK