Discard section

src/cmdline.cc

@@ -92,6 +92,8 @@ static const char helpmsg[] = R"(
     --no-demangle
   --detach                    Create separate debug info file in the background (default)
     --no-detach
+  --discard-section SECTION   Discard an input section
+    --no-discard-section SECTION
   --enable-new-dtags          Emit DT_RUNPATH for --rpath (default)
     --disable-new-dtags       Emit DT_RPATH for --rpath
   --execute-only              Make executable segments unreadable
@@ -1128,6 +1130,10 @@ std::vector<std::string> parse_nonpositional_args(Context<E> &ctx) {
       ctx.arg.print_gc_sections = true;
     } else if (read_flag("no-print-gc-sections")) {
       ctx.arg.print_gc_sections = false;
+    } else if (read_arg("discard-section")) {
+      ctx.arg.discard_section.insert(arg);
+    } else if (read_arg("no-discard-section")) {
+      ctx.arg.discard_section.erase(arg);
     } else if (read_arg("icf")) {
       if (arg == "all") {
         ctx.arg.icf = true;

src/input-files.cc

@@ -353,6 +353,10 @@ void ObjectFile<E>::initialize_sections(Context<E> &ctx) {
           is_debug_section(shdr, name))
         continue;
 
+      // Ignore section is specified by --discard-section.
+      if (ctx.arg.discard_section.contains(name))
+        continue;
+
       if (name == ".comment" &&
           this->get_string(ctx, shdr).starts_with("rustc "))
         this->is_rust_obj = true;

src/mold.h

@@ -2049,6 +2049,7 @@ struct Context {
     std::optional<std::vector<Symbol<E> *>> retain_symbols_file;
     std::unordered_map<std::string_view, u64> section_align;
     std::unordered_map<std::string_view, u64> section_start;
+    std::unordered_set<std::string_view> discard_section;
     std::unordered_set<std::string_view> ignore_ir_file;
     std::unordered_set<std::string_view> wrap;
     std::vector<SectionOrder> section_order;

test/discard-section.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+. $(dirname $0)/common.inc
+
+cat <<'EOF' | $CC -x assembler -c -o $t/a.o -x assembler -
+
+.section .foo,"a"
+.ascii "foo\0"
+.section .bar,"a"
+.ascii "bar\0"
+.section .text
+.globl _start
+_start:
+EOF
+
+./mold -o $t/exe0 $t/a.o
+readelf -S $t/exe0 | grep '.foo'
+readelf -S $t/exe0 | grep '.bar'
+
+./mold -o $t/exe1 $t/a.o --discard-section='.foo'
+readelf -S $t/exe1 | grep -v '.foo'
+readelf -S $t/exe1 | grep '.bar'
+
+./mold -o $t/exe2 $t/a.o --discard-section='foo' --discard-section='boo' --no-discard-section='foo'
+readelf -S $t/exe2 | grep '.foo'
+readelf -S $t/exe2 | grep -v '.bar'