[ELF] Support --[no-]undefined-version

Fixes #921
rui314 · Dec 21, 2022 · e2d7353 · justanotheranonymoususer · Dec 21, 2022 · e2d7353
1 parent 864f9a0
commit e2d7353
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Showing 10 changed files with 57 additions and 21 deletions.
diff --git a/docs/mold.1 b/docs/mold.1
@@ -950,6 +950,15 @@ Set target system root directory to
 .It Fl -trace
 Print name of each input file.
 .Pp
+.It Fl -undefined-version
+.It Fl -no-undefined-version
+By default,
+.Nm
+warns on a symbol specified by a version script or by
+.Fl -export-dynamic-symbol
+if it is not defined. You can silence the warning by
+.Fl -undefined-version .
+.Pp
 .It Fl -unique Ns = Ns Ar pattern
 Don't merge input sections that match
 .Ar pattern .
@@ -1197,7 +1206,6 @@ Mark object to interpose all DSOs but executable.
 .It Fl -no-allow-shlib-undefined
 .It Fl -no-copy-dt-needed-entries
 .It Fl -no-fatal-warnings
-.It Fl -no-undefined-version
 .It Fl -nostdlib
 .It Fl -rpath-link Ns = Ns Ar dir
 .It Fl -sort-common

diff --git a/elf/cmdline.cc b/elf/cmdline.cc
@@ -149,6 +149,8 @@ inline const char helpmsg[] = R"(
   --threads                   Use multiple threads (default)
     --no-threads
   --trace                     Print name of each input file
+  --undefined-version         Report version scripts that refer undefined symbols (default)
+    --no-undefined-version
   --unique PATTERN            Don't merge input sections that match a given pattern
   --unresolved-symbols [report-all,ignore-all,ignore-in-object-files,ignore-in-shared-libs]
                               How to handle unresolved symbols
@@ -990,6 +992,10 @@ std::vector<std::string> parse_nonpositional_args(Context<E> &ctx) {
         Fatal(ctx) << "-R" << arg
                    << ": -R as an alias for --just-symbols is not supported";
       add_rpath(arg);
+    } else if (read_flag("undefined-version")) {
+      ctx.arg.undefined_version = true;
+    } else if (read_flag("no-undefined-version")) {
+      ctx.arg.undefined_version = false;
     } else if (read_flag("build-id")) {
       ctx.arg.build_id.kind = BuildId::HASH;
       ctx.arg.build_id.hash_size = 20;
@@ -1046,7 +1052,6 @@ std::vector<std::string> parse_nonpositional_args(Context<E> &ctx) {
     } else if (read_flag("no-add-needed")) {
     } else if (read_flag("no-call-graph-profile-sort")) {
     } else if (read_flag("no-copy-dt-needed-entries")) {
-    } else if (read_flag("no-undefined-version")) {
     } else if (read_arg("sort-section")) {
     } else if (read_flag("sort-common")) {
     } else if (read_flag("dc")) {

diff --git a/elf/linker-script.cc b/elf/linker-script.cc
@@ -278,7 +278,7 @@ static bool read_label(std::span<std::string_view> &tok,
 template <typename E>
 static void
 read_version_script_commands(Context<E> &ctx, std::span<std::string_view> &tok,
-                             u16 ver_idx, bool is_cpp) {
+                             std::string_view ver_str, u16 ver_idx, bool is_cpp) {
   bool is_global = true;
 
   while (!tok.empty() && tok[0] != "}") {
@@ -298,11 +298,11 @@ read_version_script_commands(Context<E> &ctx, std::span<std::string_view> &tok,
       if (!tok.empty() && tok[0] == "\"C\"") {
         tok = tok.subspan(1);
         tok = skip(ctx, tok, "{");
-        read_version_script_commands( ctx, tok, ver_idx, false);
+        read_version_script_commands( ctx, tok, ver_str, ver_idx, false);
       } else {
         tok = skip(ctx, tok, "\"C++\"");
         tok = skip(ctx, tok, "{");
-        read_version_script_commands(ctx, tok, ver_idx, true);
+        read_version_script_commands(ctx, tok, ver_str, ver_idx, true);
       }
 
       tok = skip(ctx, tok, "}");
@@ -314,9 +314,11 @@ read_version_script_commands(Context<E> &ctx, std::span<std::string_view> &tok,
       ctx.default_version = (is_global ? ver_idx : VER_NDX_LOCAL);
       ctx.default_version_from_version_script = true;
     } else if (is_global) {
-      ctx.version_patterns.push_back({unquote(tok[0]), ver_idx, is_cpp});
+      ctx.version_patterns.push_back({unquote(tok[0]), current_file<E>->name,
+                                      ver_str, ver_idx, is_cpp});
     } else {
-      ctx.version_patterns.push_back({unquote(tok[0]), VER_NDX_LOCAL, is_cpp});
+      ctx.version_patterns.push_back({unquote(tok[0]), current_file<E>->name,
+                                      ver_str, VER_NDX_LOCAL, is_cpp});
     }
 
     tok = tok.subspan(1);
@@ -332,17 +334,21 @@ void read_version_script(Context<E> &ctx, std::span<std::string_view> &tok) {
   u16 next_ver = VER_NDX_LAST_RESERVED + ctx.arg.version_definitions.size() + 1;
 
   while (!tok.empty() && tok[0] != "}") {
+    std::string_view ver_str;
     u16 ver_idx;
+
     if (tok[0] == "{") {
+      ver_str = "global";
       ver_idx = VER_NDX_GLOBAL;
     } else {
+      ver_str = tok[0];
       ver_idx = next_ver++;
       ctx.arg.version_definitions.push_back(std::string(tok[0]));
       tok = tok.subspan(1);
     }
 
     tok = skip(ctx, tok, "{");
-    read_version_script_commands(ctx, tok, ver_idx, false);
+    read_version_script_commands(ctx, tok, ver_str, ver_idx, false);
     tok = skip(ctx, tok, "}");
     if (!tok.empty() && tok[0] != ";")
       tok = tok.subspan(1);
@@ -385,7 +391,8 @@ void read_dynamic_list_commands(Context<E> &ctx, std::span<std::string_view> &to
     if (tok[0] == "*")
       ctx.default_version = VER_NDX_GLOBAL;
     else
-      ctx.version_patterns.push_back({unquote(tok[0]), VER_NDX_GLOBAL, is_cpp});
+      ctx.version_patterns.push_back({unquote(tok[0]), current_file<E>->name,
+                                      "global", VER_NDX_GLOBAL, is_cpp});
 
     tok = skip(ctx, tok.subspan(1), ";");
   }

diff --git a/elf/main.cc b/elf/main.cc
@@ -295,7 +295,8 @@ static void read_input_files(Context<E> &ctx, std::span<std::string> args) {
       if (arg == "*")
         ctx.default_version = VER_NDX_GLOBAL;
       else
-        ctx.version_patterns.push_back({arg, VER_NDX_GLOBAL, false});
+        ctx.version_patterns.push_back({arg, "--export-dynamic-symbol",
+                                        "global", VER_NDX_GLOBAL, false});
     } else if (remove_prefix(arg, "--export-dynamic-symbol-list=")) {
       MappedFile<Context<E>> *mf = find_from_search_paths(ctx, std::string(arg));
       if (!mf)

diff --git a/elf/mold.h b/elf/mold.h
@@ -1560,6 +1560,8 @@ typedef enum {
 
 struct VersionPattern {
   std::string_view pattern;
+  std::string_view source;
+  std::string_view ver_str;
   u16 ver_idx = -1;
   bool is_cpp = false;
 };
@@ -1641,6 +1643,7 @@ struct Context {
     bool strip_all = false;
     bool strip_debug = false;
     bool trace = false;
+    bool undefined_version = false;
     bool warn_common = false;
     bool warn_once = false;
     bool warn_textrel = false;

diff --git a/elf/passes.cc b/elf/passes.cc
@@ -1375,10 +1375,16 @@ void apply_version_script(Context<E> &ctx) {
   };
 
   if (is_simple()) {
-    for (VersionPattern &v : ctx.version_patterns)
-      if (Symbol<E> *sym = get_symbol(ctx, v.pattern);
-          sym->file && !sym->file->is_dso)
+    for (VersionPattern &v : ctx.version_patterns) {
+      Symbol<E> *sym = get_symbol(ctx, v.pattern);
+
+      if (!sym->file && !ctx.arg.undefined_version)
+        Warn(ctx) << v.source << ": cannot assign version `" << v.ver_str
+                  << "` to symbol `" << *sym << "`: symbol not found";
+
+      if (sym->file && !sym->file->is_dso)
         sym->ver_idx = v.ver_idx;
+    }
     return;
   }
 

diff --git a/test/elf/no-undefined-version.sh b/test/elf/no-undefined-version.sh
@@ -0,0 +1,11 @@
+#!/bin/bash
+. $(dirname $0)/common.inc
+
+echo 'ver_x { global: foo; };' > $t/a.ver
+
+cat <<EOF | $CC -o $t/b.o -c -xc -
+int main() {}
+EOF
+
+$CC -B. -o $t/exe -Wl,--version-script,$t/a.ver $t/b.o 2> $t/log
+grep -Fq 'a.ver: cannot assign version `ver_x` to symbol `foo`: symbol not found' $t/log
diff --git a/test/elf/symbol-version2.sh b/test/elf/symbol-version2.sh
@@ -10,11 +10,7 @@ __asm__(".symver bar1, bar@TEST");
 EOF
 
 cat <<EOF > $t/b.version
-TEST {
-global:
-  foo;
-  bar;
-};
+TEST { global: foo; };
 EOF
 
 $CC -B. -o $t/c.so -shared $t/a.o -Wl,--version-script=$t/b.version

diff --git a/test/elf/version-script17.sh b/test/elf/version-script17.sh
@@ -19,7 +19,7 @@ cat <<'EOF' > $t/c.ver
 { local: *; global: xyz; };
 EOF
 
-$CC -B. -o $t/exe2 $t/a.o $t/b.so -Wl,--version-script=$t/c.ver
+$CC -B. -o $t/exe2 $t/a.o $t/b.so -Wl,--version-script=$t/c.ver -Wl,--undefined-version
 nm -g $t/exe2 > $t/log2
 ! grep -q foo $t/log2 || false
 

diff --git a/test/elf/version-script6.sh b/test/elf/version-script6.sh
@@ -26,8 +26,7 @@ extern int bar;
 int baz() { return foo + bar; }
 EOF
 
-$CC -B. -shared -Wl,-version-script,$t/d.ver \
-  -o $t/f.so $t/e.o $t/c.so
+$CC -B. -shared -Wl,-version-script,$t/d.ver -o $t/f.so $t/e.o $t/c.so -Wl,--undefined-version
 
 readelf --dyn-syms $t/f.so > $t/log
 grep -q 'foo@VER_X1' $t/log