[ELF][i386] Sort .ctors and .dtors sections

rui314 · Apr 3, 2022 · 392781a · 392781a
1 parent 4e10ee7
commit 392781a
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Showing 8 changed files with 47 additions and 10 deletions.
diff --git a/elf/main.cc b/elf/main.cc
@@ -549,6 +549,10 @@ static int elf_main(int argc, char **argv) {
   // a special rule. Sort them.
   sort_init_fini(ctx);
 
+  // Likewise, .ctors and .dtors have to be sorted. They are rare
+  // because they are superceded by .init_array/.fini_array, though.
+  sort_ctor_dtor(ctx);
+
   // Handle --shuffle-sections
   if (ctx.arg.shuffle_sections != SHUFFLE_SECTIONS_NONE)
     shuffle_sections(ctx);

diff --git a/elf/mold.h b/elf/mold.h
@@ -1277,6 +1277,7 @@ template <typename E> void print_dependencies_full(Context<E> &);
 template <typename E> void write_repro_file(Context<E> &);
 template <typename E> void check_duplicate_symbols(Context<E> &);
 template <typename E> void sort_init_fini(Context<E> &);
+template <typename E> void sort_ctor_dtor(Context<E> &);
 template <typename E> void shuffle_sections(Context<E> &);
 template <typename E> std::vector<Chunk<E> *>
 collect_output_sections(Context<E> &);

diff --git a/elf/output-chunks.cc b/elf/output-chunks.cc
@@ -768,6 +768,7 @@ static std::string_view get_output_name(Context<E> &ctx, std::string_view name)
   static std::string_view prefixes[] = {
     ".text.", ".data.rel.ro.", ".data.", ".rodata.", ".bss.rel.ro.", ".bss.",
     ".init_array.", ".fini_array.", ".tbss.", ".tdata.", ".gcc_except_table.",
+    ".ctors.", ".dtors.",
   };
 
   for (std::string_view prefix : prefixes) {

diff --git a/elf/passes.cc b/elf/passes.cc
@@ -634,7 +634,7 @@ void sort_init_fini(Context<E> &ctx) {
   Timer t(ctx, "sort_init_fini");
 
   auto get_priority = [](InputSection<E> *isec) {
-    static std::regex re(R"(_array\.(\d+)$)", std::regex_constants::optimize);
+    static std::regex re(R"(\.(\d+)$)", std::regex_constants::optimize);
     std::string name = isec->name().begin();
     std::smatch m;
     if (std::regex_search(name, m, re))
@@ -654,6 +654,43 @@ void sort_init_fini(Context<E> &ctx) {
   }
 }
 
+template <typename E>
+void sort_ctor_dtor(Context<E> &ctx) {
+  Timer t(ctx, "sort_ctor_dtor");
+
+  auto get_priority = [](InputSection<E> *isec) {
+    auto opts = std::regex_constants::optimize | std::regex_constants::ECMAScript;
+    static std::regex re1(R"((?:clang_rt\.)?crtbegin)", opts);
+    static std::regex re2(R"((?:clang_rt\.)?crtend)", opts);
+    static std::regex re3(R"(\.(\d+)$)", opts);
+
+    // crtbegin.o and crtend.o contain marker symbols such as
+    // __CTOR_LIST__ or __DTOR_LIST__. So they have to be at the
+    // beginning or end of the section.
+    std::smatch m;
+    if (std::regex_search(isec->file.filename, m, re1))
+      return -2;
+    if (std::regex_search(isec->file.filename, m, re2))
+      return 65536;
+
+    std::string name(isec->name());
+    if (std::regex_search(name, m, re3))
+      return std::stoi(m[1]);
+    return -1;
+  };
+
+  for (std::unique_ptr<OutputSection<E>> &osec : ctx.output_sections) {
+    if (osec->name == ".ctors" || osec->name == ".dtors") {
+      if (ctx.arg.shuffle_sections != SHUFFLE_SECTIONS_REVERSE)
+        std::reverse(osec->members.begin(), osec->members.end());
+
+      sort(osec->members, [&](InputSection<E> *a, InputSection<E> *b) {
+        return get_priority(a) < get_priority(b);
+      });
+    }
+  }
+}
+
 template <typename T>
 static void shuffle(std::vector<T> &vec, u64 seed) {
   if (vec.empty())
@@ -686,7 +723,8 @@ void shuffle_sections(Context<E> &ctx) {
 
   auto is_eligible = [](OutputSection<E> &osec) {
     return osec.name != ".init" && osec.name != ".fini" &&
-           osec.name != ".init_array" && osec.name != ".fini_array";
+           osec.name != ".init_array" && osec.name != ".fini_array" &&
+           osec.name != ".ctors" && osec.name != ".dtors";
   };
 
   switch (ctx.arg.shuffle_sections) {
@@ -1485,6 +1523,7 @@ void write_dependency_file(Context<E> &ctx) {
   template void write_repro_file(Context<E> &);                         \
   template void check_duplicate_symbols(Context<E> &);                  \
   template void sort_init_fini(Context<E> &);                           \
+  template void sort_ctor_dtor(Context<E> &);                           \
   template void shuffle_sections(Context<E> &);                         \
   template std::vector<Chunk<E> *> collect_output_sections(Context<E> &); \
   template void compute_section_sizes(Context<E> &);                    \

diff --git a/test/elf/init-array-priorities.sh b/test/elf/init-array-priorities.sh
@@ -14,8 +14,6 @@ mold="$(pwd)/mold"
 t=out/test/elf/$testname
 mkdir -p $t
 
-[ $MACHINE = i386 ] && { echo skipped; exit; }
-
 # musl does not support GNU-style init/fini priorities
 echo 'int main() {}' | $CC -o $t/exe -xc -
 readelf --dynamic $t/exe | grep -q ld-musl && { echo skipped; exit; }

diff --git a/test/elf/reverse-sections.sh b/test/elf/reverse-sections.sh
@@ -14,8 +14,6 @@ mold="$(pwd)/mold"
 t=out/test/elf/$testname
 mkdir -p $t
 
-[ $MACHINE = i386 ] && { echo skipped; exit; }
-
 cat <<EOF | $CC -o $t/a.o -c -xc++ -
 #include <iostream>
 static struct Foo1 {

diff --git a/test/elf/shuffle-sections-seed.sh b/test/elf/shuffle-sections-seed.sh
@@ -14,8 +14,6 @@ mold="$(pwd)/mold"
 t=out/test/elf/$testname
 mkdir -p $t
 
-[ $MACHINE = i386 ] && { echo skipped; exit; }
-
 cat <<EOF | $CC -o $t/a.o -ffunction-sections -c -xc -
 #include <stdio.h>
 int main() {

diff --git a/test/elf/shuffle-sections.sh b/test/elf/shuffle-sections.sh
@@ -14,8 +14,6 @@ mold="$(pwd)/mold"
 t=out/test/elf/$testname
 mkdir -p $t
 
-[ $MACHINE = i386 ] && { echo skipped; exit; }
-
 cat <<EOF | $CC -o $t/a.o -ffunction-sections -c -xc -
 #include <stdio.h>
 int main() {