V3 [PATCH] ld: Add --export-dynamic-symbol and --export-dynamic-symbol-list

Message ID CAMe9rOrs+shaYZPEHGm1CsoBvkGMymmw0kFctL91nzxKj1SReA@mail.gmail.com
State Superseded
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  • V3 [PATCH] ld: Add --export-dynamic-symbol and --export-dynamic-symbol-list
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Commit Message

On Sat, May 23, 2020 at 11:29 AM Fangrui Song <maskray@google.com> wrote:
>

> On 2020-05-23, H.J. Lu wrote:

> >From: Fangrui Song <maskray@google.com>

> >

> >--export-dynamic-symbol-list is like a dynamic list, but without

> >the symbolic property for unspecified symbols.

> >

> >When creating an executable, --export-dynamic-symbol-list is treated

> >like --dynamic-list.

> >

> >When creating a shared library, it is treated like --dynamic-list if

> >-Bsymbolic or --dynamic-list are used,  otherwise, it is ignored, so

> >that references to matched symbols will not be bound to the definitions

> >within the shared library.

> >

> >2020-05-XX  Fangrui Song  <maskray@google.com>

> >           H.J. Lu  <hongjiu.lu@intel.com>

> >

> >       PR ld/25910

> >       * NEWS: Mention --export-dynamic-symbol[-list].

> >       * ld.texi: Document --export-dynamic-symbol[-list].

> >       * ldgram.y: Pass current_dynamic_list_p to

> >       lang_append_dynamic_list.

> >       * ldlang.c (current_dynamic_list_p): New.

> >       (ang_append_dynamic_list): Updated to take a pointer to

> >       struct bfd_elf_dynamic_list * argument instead of using

> >       link_info.dynamic_list.

> >       (lang_append_dynamic_list_cpp_typeinfo): Pass

> >       &link_info.dynamic_list to ang_append_dynamic_list.

> >       (lang_append_dynamic_list_cpp_new): Likewise.

> >       * ldlang.h (current_dynamic_list_p): New.

> >       (lang_append_dynamic_list): Add a pointer to

> >       struct bfd_elf_dynamic_list * argument.

> >       * ldlex.h (option_values): Add OPTION_EXPORT_DYNAMIC_SYMBOL and

> >       OPTION_EXPORT_DYNAMIC_SYMBOL_LIST.

> >       * lexsup.c (ld_options): Add entries for

> >       OPTION_EXPORT_DYNAMIC_SYMBOL and

> >       OPTION_EXPORT_DYNAMIC_SYMBOL_LIST.

> >       (parse_args): Handle --export-dynamic-symbol and

> >       --export-dynamic-symbol-list.

> >       * testsuite/ld-dynamic/export-dynamic-symbol-1.d: New.

> >       * testsuite/ld-dynamic/export-dynamic-symbol-2.d: New.

> >       * testsuite/ld-dynamic/export-dynamic-symbol-glob.d: New.

> >       * testsuite/ld-dynamic/export-dynamic-symbol-list-1.d: New.

> >       * testsuite/ld-dynamic/export-dynamic-symbol-list-2.d: New.

> >       * testsuite/ld-dynamic/export-dynamic-symbol-list-glob.d: New.

> >       * testsuite/ld-dynamic/export-dynamic-symbol.exp: New.

> >       * testsuite/ld-dynamic/export-dynamic-symbol.s: New.

> >       * testsuite/ld-dynamic/foo-bar.list: New.

> >       * testsuite/ld-dynamic/foo.list: New.

> >       * testsuite/ld-dynamic/foo.s: New.

> >       * testsuite/ld-dynamic/fstar.list: New.

> >       * testsuite/ld-elf/dlempty.list: New.

> >       * testsuite/ld-elf/shared.exp: Add tests for

> >       --export-dynamic-symbol and --export-dynamic-symbol-list.

> >---

> > ld/NEWS                                       |  3 +

> > ld/ld.texi                                    | 18 +++++

> > ld/ldgram.y                                   |  2 +-

> > ld/ldlang.c                                   | 16 ++--

> > ld/ldlang.h                                   |  5 +-

> > ld/ldlex.h                                    |  2 +

> > ld/lexsup.c                                   | 75 +++++++++++++++++++

> > .../ld-dynamic/export-dynamic-symbol-1.d      |  9 +++

> > .../ld-dynamic/export-dynamic-symbol-2.d      |  9 +++

> > .../ld-dynamic/export-dynamic-symbol-glob.d   |  8 ++

> > .../ld-dynamic/export-dynamic-symbol-list-1.d |  9 +++

> > .../ld-dynamic/export-dynamic-symbol-list-2.d |  9 +++

> > .../export-dynamic-symbol-list-glob.d         |  8 ++

> > .../ld-dynamic/export-dynamic-symbol.exp      | 39 ++++++++++

> > .../ld-dynamic/export-dynamic-symbol.s        |  9 +++

> > ld/testsuite/ld-dynamic/foo-bar.list          |  1 +

> > ld/testsuite/ld-dynamic/foo.list              |  1 +

> > ld/testsuite/ld-dynamic/foo.s                 |  4 +

> > ld/testsuite/ld-dynamic/fstar.list            |  1 +

> > ld/testsuite/ld-elf/dlempty.list              |  3 +

> > ld/testsuite/ld-elf/shared.exp                | 36 +++++++++

> > 21 files changed, 258 insertions(+), 9 deletions(-)

> > create mode 100644 ld/testsuite/ld-dynamic/export-dynamic-symbol-1.d

> > create mode 100644 ld/testsuite/ld-dynamic/export-dynamic-symbol-2.d

> > create mode 100644 ld/testsuite/ld-dynamic/export-dynamic-symbol-glob.d

> > create mode 100644 ld/testsuite/ld-dynamic/export-dynamic-symbol-list-1.d

> > create mode 100644 ld/testsuite/ld-dynamic/export-dynamic-symbol-list-2.d

> > create mode 100644 ld/testsuite/ld-dynamic/export-dynamic-symbol-list-glob.d

> > create mode 100644 ld/testsuite/ld-dynamic/export-dynamic-symbol.exp

> > create mode 100644 ld/testsuite/ld-dynamic/export-dynamic-symbol.s

> > create mode 100644 ld/testsuite/ld-dynamic/foo-bar.list

> > create mode 100644 ld/testsuite/ld-dynamic/foo.list

> > create mode 100644 ld/testsuite/ld-dynamic/foo.s

> > create mode 100644 ld/testsuite/ld-dynamic/fstar.list

> > create mode 100644 ld/testsuite/ld-elf/dlempty.list

> >

> >diff --git a/ld/NEWS b/ld/NEWS

> >index 9f5bbe51cf..870c480bde 100644

> >--- a/ld/NEWS

> >+++ b/ld/NEWS

> >@@ -1,5 +1,8 @@

> > -*- text -*-

> >

> >+* Add ELF linker command-line options, --export-dynamic-symbol and

> >+  --export-dynamic-symbol-list, to make symbols dynamic.

> >+

> > * Add command-line options --enable-non-contiguous-regions and

> >   --enable-non-contiguous-regions-warnings.

> >

> >diff --git a/ld/ld.texi b/ld/ld.texi

> >index 4dc78e65fa..92e47c6324 100644

> >--- a/ld/ld.texi

> >+++ b/ld/ld.texi

> >@@ -569,6 +569,24 @@ Note that this option is specific to ELF targeted ports.  PE targets

> > support a similar function to export all symbols from a DLL or EXE; see

> > the description of @samp{--export-all-symbols} below.

> >

> >+@kindex --export-dynamic-symbol=@var{glob}

> >+@cindex export dynamic symbol

> >+@item --export-dynamic-symbol=@var{glob}

> >+When creating a dynamically linked executable, symbols matching

> >+@var{glob} will be added to the dynamic symbol table. When creating a

> >+shared library, references to symbols matching @var{glob} will not be

> >+bound to the definitions within the shared library. This option is a

> >+no-op when creating a shared library and @samp{-Bsymbolic} or

> >+@samp{--dynamic-list} are not specified. This option is only meaningful

> >+on ELF platforms which support shared libraries.

>

> Is --export-dynamic-symbol still effective for -shared?

> I think either way is ok.


Yes.

> >+@kindex --export-dynamic-symbol-list=@var{file}

> >+@cindex export dynamic symbol list

> >+@item --export-dynamic-symbol-list=@var{file}

> >+Specify a @samp{--export-dynamic-symbol} for each pattern in the file.

> >+The format of the file is the same as the version node without

> >+scope and node name.  See @ref{VERSION} for more information.

> >+

> > @ifclear SingleFormat

> > @cindex big-endian objects

> > @cindex endianness

> >diff --git a/ld/ldgram.y b/ld/ldgram.y

> >index df5c035c03..36845c4c30 100644

> >--- a/ld/ldgram.y

> >+++ b/ld/ldgram.y

> >@@ -1313,7 +1313,7 @@ dynamic_list_node:

> > dynamic_list_tag:

> >               vers_defns ';'

> >               {

> >-                lang_append_dynamic_list ($1);

> >+                lang_append_dynamic_list (current_dynamic_list_p, $1);

> >               }

> >       ;

> >

> >diff --git a/ld/ldlang.c b/ld/ldlang.c

> >index 3d653d460d..14a6a577d2 100644

> >--- a/ld/ldlang.c

> >+++ b/ld/ldlang.c

> >@@ -118,6 +118,7 @@ lang_statement_list_type file_chain = { NULL, NULL };

> >    lang_statement_union).  */

> > lang_statement_list_type input_file_chain;

> > static const char *current_input_file;

> >+struct bfd_elf_dynamic_list **current_dynamic_list_p;

> > struct bfd_sym_chain entry_symbol = { NULL, NULL };

> > const char *entry_section = ".text";

> > struct lang_input_statement_flags input_flags;

> >@@ -9324,15 +9325,16 @@ lang_add_unique (const char *name)

> > /* Append the list of dynamic symbols to the existing one.  */

> >

> > void

> >-lang_append_dynamic_list (struct bfd_elf_version_expr *dynamic)

> >+lang_append_dynamic_list (struct bfd_elf_dynamic_list **list_p,

> >+                        struct bfd_elf_version_expr *dynamic)

> > {

> >-  if (link_info.dynamic_list)

> >+  if (*list_p)

> >     {

> >       struct bfd_elf_version_expr *tail;

> >       for (tail = dynamic; tail->next != NULL; tail = tail->next)

> >       ;

> >-      tail->next = link_info.dynamic_list->head.list;

> >-      link_info.dynamic_list->head.list = dynamic;

> >+      tail->next = (*list_p)->head.list;

> >+      (*list_p)->head.list = dynamic;

> >     }

> >   else

> >     {

> >@@ -9341,7 +9343,7 @@ lang_append_dynamic_list (struct bfd_elf_version_expr *dynamic)

> >       d = (struct bfd_elf_dynamic_list *) xcalloc (1, sizeof *d);

> >       d->head.list = dynamic;

> >       d->match = lang_vers_match;

> >-      link_info.dynamic_list = d;

> >+      *list_p = d;

> >     }

> > }

> >

> >@@ -9363,7 +9365,7 @@ lang_append_dynamic_list_cpp_typeinfo (void)

> >     dynamic = lang_new_vers_pattern (dynamic, symbols [i], "C++",

> >                                    FALSE);

> >

> >-  lang_append_dynamic_list (dynamic);

> >+  lang_append_dynamic_list (&link_info.dynamic_list, dynamic);

> > }

> >

> > /* Append the list of C++ operator new and delete dynamic symbols to the

> >@@ -9384,7 +9386,7 @@ lang_append_dynamic_list_cpp_new (void)

> >     dynamic = lang_new_vers_pattern (dynamic, symbols [i], "C++",

> >                                    FALSE);

> >

> >-  lang_append_dynamic_list (dynamic);

> >+  lang_append_dynamic_list (&link_info.dynamic_list, dynamic);

> > }

> >

> > /* Scan a space and/or comma separated string of features.  */

> >diff --git a/ld/ldlang.h b/ld/ldlang.h

> >index 3018c3e2ba..529ccd1585 100644

> >--- a/ld/ldlang.h

> >+++ b/ld/ldlang.h

> >@@ -513,6 +513,8 @@ extern bfd_boolean entry_from_cmdline;

> > extern lang_statement_list_type file_chain;

> > extern lang_statement_list_type input_file_chain;

> >

> >+extern struct bfd_elf_dynamic_list **current_dynamic_list_p;

> >+

> > extern int lang_statement_iteration;

> > extern struct asneeded_minfo **asneeded_list_tail;

> >

> >@@ -673,7 +675,8 @@ extern struct bfd_elf_version_deps *lang_add_vers_depend

> >   (struct bfd_elf_version_deps *, const char *);

> > extern void lang_register_vers_node

> >   (const char *, struct bfd_elf_version_tree *, struct bfd_elf_version_deps *);

> >-extern void lang_append_dynamic_list (struct bfd_elf_version_expr *);

> >+extern void lang_append_dynamic_list (struct bfd_elf_dynamic_list **,

> >+                                    struct bfd_elf_version_expr *);

> > extern void lang_append_dynamic_list_cpp_typeinfo (void);

> > extern void lang_append_dynamic_list_cpp_new (void);

> > extern void lang_add_unique

> >diff --git a/ld/ldlex.h b/ld/ldlex.h

> >index 22b928d2d9..2c8d043a09 100644

> >--- a/ld/ldlex.h

> >+++ b/ld/ldlex.h

> >@@ -81,6 +81,8 @@ enum option_values

> >   OPTION_DYNAMIC_LIST_CPP_NEW,

> >   OPTION_DYNAMIC_LIST_CPP_TYPEINFO,

> >   OPTION_DYNAMIC_LIST_DATA,

> >+  OPTION_EXPORT_DYNAMIC_SYMBOL,

> >+  OPTION_EXPORT_DYNAMIC_SYMBOL_LIST,

> >   OPTION_WARN_COMMON,

> >   OPTION_WARN_CONSTRUCTORS,

> >   OPTION_WARN_FATAL,

> >diff --git a/ld/lexsup.c b/ld/lexsup.c

> >index fe9526b527..2bac1631d6 100644

> >--- a/ld/lexsup.c

> >+++ b/ld/lexsup.c

> >@@ -504,6 +504,10 @@ static const struct ld_option ld_options[] =

> >     '\0', NULL, N_("Use C++ typeinfo dynamic list"), TWO_DASHES },

> >   { {"dynamic-list", required_argument, NULL, OPTION_DYNAMIC_LIST},

> >     '\0', N_("FILE"), N_("Read dynamic list"), TWO_DASHES },

> >+  { {"export-dynamic-symbol", required_argument, NULL, OPTION_EXPORT_DYNAMIC_SYMBOL},

> >+    '\0', N_("SYMBOL"), N_("Export the specified symbol"), EXACTLY_TWO_DASHES },

> >+  { {"export-dynamic-symbol-list", required_argument, NULL, OPTION_EXPORT_DYNAMIC_SYMBOL_LIST},

> >+    '\0', N_("FILE"), N_("Read export dynamic symbol list"), EXACTLY_TWO_DASHES },

> >   { {"warn-common", no_argument, NULL, OPTION_WARN_COMMON},

> >     '\0', NULL, N_("Warn about duplicate common symbols"), TWO_DASHES },

> >   { {"warn-constructors", no_argument, NULL, OPTION_WARN_CONSTRUCTORS},

> >@@ -581,6 +585,7 @@ parse_args (unsigned argc, char **argv)

> >     dynamic_list_data,

> >     dynamic_list

> >   } opt_dynamic_list = dynamic_list_unset;

> >+  struct bfd_elf_dynamic_list *export_list = NULL;

> >

> >   shortopts = (char *) xmalloc (OPTION_COUNT * 3 + 2);

> >   longopts = (struct option *)

> >@@ -1418,6 +1423,7 @@ parse_args (unsigned argc, char **argv)

> >           ldfile_open_command_file (optarg);

> >           saved_script_handle = hold_script_handle;

> >           parser_input = input_dynamic_list;

> >+          current_dynamic_list_p = &link_info.dynamic_list;

> >           yyparse ();

> >         }

> >         if (opt_dynamic_list != dynamic_list_data)

> >@@ -1425,6 +1431,29 @@ parse_args (unsigned argc, char **argv)

> >         if (opt_symbolic == symbolic)

> >           opt_symbolic = symbolic_unset;

> >         break;

> >+      case OPTION_EXPORT_DYNAMIC_SYMBOL:

> >+        {

> >+          struct bfd_elf_version_expr *expr

> >+            = lang_new_vers_pattern (NULL, xstrdup (optarg), NULL,

> >+                                     FALSE);

> >+          lang_append_dynamic_list (&export_list, expr);

> >+          }

> >+        break;

> >+      case OPTION_EXPORT_DYNAMIC_SYMBOL_LIST:

> >+        /* This option indicates a small script that only specifies

> >+           an export list.  Read it, but don't assume that we've

> >+           seen a linker script.  */

> >+        {

> >+          FILE *hold_script_handle;

> >+

> >+          hold_script_handle = saved_script_handle;

> >+          ldfile_open_command_file (optarg);

> >+          saved_script_handle = hold_script_handle;

> >+          parser_input = input_dynamic_list;

> >+          current_dynamic_list_p = &export_list;

> >+          yyparse ();

> >+        }

> >+        break;

> >       case OPTION_WARN_COMMON:

> >         config.warn_common = TRUE;

> >         break;

> >@@ -1632,6 +1661,52 @@ parse_args (unsigned argc, char **argv)

> >       && command_line.check_section_addresses < 0)

> >     command_line.check_section_addresses = 0;

> >

> >+  if (export_list && !bfd_link_relocatable (&link_info))

> >+    {

> >+      struct bfd_elf_version_expr *head = export_list->head.list;

> >+      struct bfd_elf_version_expr *next;

> >+

> >+      /* For --export-dynamic-symbol[-list]:

> >+       1. When building executable, treat like --dynamic-list.

> >+       2. When building shared object:

> >+          a. If -Bsymbolic or --dynamic-list are used, treat like

> >+             --dynamic-list.

> >+          b. Otherwise, ignored.

> >+       */

> >+      bfd_boolean kept = (bfd_link_executable (&link_info)

> >+                        || opt_symbolic != symbolic_unset

> >+                        || opt_dynamic_list != dynamic_list_unset);

> >+

> >+      if (kept)

> >+      {

> >+        /* Append the export list to link_info.dynamic_list.  */

> >+        if (link_info.dynamic_list)

> >+          {

> >+            for (next = head; next->next != NULL; next = next->next)

> >+              ;

> >+            next->next = link_info.dynamic_list->head.list;

> >+            link_info.dynamic_list->head.list = head;

> >+          }

> >+        else

> >+          link_info.dynamic_list = export_list;

> >+

> >+        if (opt_dynamic_list != dynamic_list_data)

> >+          opt_dynamic_list = dynamic_list;

> >+        if (opt_symbolic == symbolic)

> >+          opt_symbolic = symbolic_unset;

>

> The interaction with -Bsymbolic appears to be more complex now.

> I think users will pretty much avoid the combination of -Bsymbolic and

> (--dynamic-list or --export-dynamic-symbol or --export-dynamic-symbol-list).

>

> So I beg for a re-consideration of

> https://sourceware.org/bugzilla/show_bug.cgi?id=26018

> https://sourceware.org/pipermail/binutils/2020-May/111223.html

>


Here is the updated patch on top of

https://sourceware.org/pipermail/binutils/2020-May/111228.html

-- 
H.J.

Comments

On 2020-05-23, H.J. Lu wrote:
>On Sat, May 23, 2020 at 11:29 AM Fangrui Song <maskray@google.com> wrote:

>>

>> On 2020-05-23, H.J. Lu wrote:

>> >From: Fangrui Song <maskray@google.com>

>> >

>> >--export-dynamic-symbol-list is like a dynamic list, but without

>> >the symbolic property for unspecified symbols.

>> >

>> >When creating an executable, --export-dynamic-symbol-list is treated

>> >like --dynamic-list.

>> >

>> >When creating a shared library, it is treated like --dynamic-list if

>> >-Bsymbolic or --dynamic-list are used,  otherwise, it is ignored, so

>> >that references to matched symbols will not be bound to the definitions

>> >within the shared library.

>> >

>> >2020-05-XX  Fangrui Song  <maskray@google.com>

>> >           H.J. Lu  <hongjiu.lu@intel.com>

>> >

>> >       PR ld/25910

>> >       * NEWS: Mention --export-dynamic-symbol[-list].

>> >       * ld.texi: Document --export-dynamic-symbol[-list].

>> >       * ldgram.y: Pass current_dynamic_list_p to

>> >       lang_append_dynamic_list.

>> >       * ldlang.c (current_dynamic_list_p): New.

>> >       (ang_append_dynamic_list): Updated to take a pointer to

>> >       struct bfd_elf_dynamic_list * argument instead of using

>> >       link_info.dynamic_list.

>> >       (lang_append_dynamic_list_cpp_typeinfo): Pass

>> >       &link_info.dynamic_list to ang_append_dynamic_list.

>> >       (lang_append_dynamic_list_cpp_new): Likewise.

>> >       * ldlang.h (current_dynamic_list_p): New.

>> >       (lang_append_dynamic_list): Add a pointer to

>> >       struct bfd_elf_dynamic_list * argument.

>> >       * ldlex.h (option_values): Add OPTION_EXPORT_DYNAMIC_SYMBOL and

>> >       OPTION_EXPORT_DYNAMIC_SYMBOL_LIST.

>> >       * lexsup.c (ld_options): Add entries for

>> >       OPTION_EXPORT_DYNAMIC_SYMBOL and

>> >       OPTION_EXPORT_DYNAMIC_SYMBOL_LIST.

>> >       (parse_args): Handle --export-dynamic-symbol and

>> >       --export-dynamic-symbol-list.

>> >       * testsuite/ld-dynamic/export-dynamic-symbol-1.d: New.

>> >       * testsuite/ld-dynamic/export-dynamic-symbol-2.d: New.

>> >       * testsuite/ld-dynamic/export-dynamic-symbol-glob.d: New.

>> >       * testsuite/ld-dynamic/export-dynamic-symbol-list-1.d: New.

>> >       * testsuite/ld-dynamic/export-dynamic-symbol-list-2.d: New.

>> >       * testsuite/ld-dynamic/export-dynamic-symbol-list-glob.d: New.

>> >       * testsuite/ld-dynamic/export-dynamic-symbol.exp: New.

>> >       * testsuite/ld-dynamic/export-dynamic-symbol.s: New.

>> >       * testsuite/ld-dynamic/foo-bar.list: New.

>> >       * testsuite/ld-dynamic/foo.list: New.

>> >       * testsuite/ld-dynamic/foo.s: New.

>> >       * testsuite/ld-dynamic/fstar.list: New.

>> >       * testsuite/ld-elf/dlempty.list: New.

>> >       * testsuite/ld-elf/shared.exp: Add tests for

>> >       --export-dynamic-symbol and --export-dynamic-symbol-list.

>> >---

>> > ld/NEWS                                       |  3 +

>> > ld/ld.texi                                    | 18 +++++

>> > ld/ldgram.y                                   |  2 +-

>> > ld/ldlang.c                                   | 16 ++--

>> > ld/ldlang.h                                   |  5 +-

>> > ld/ldlex.h                                    |  2 +

>> > ld/lexsup.c                                   | 75 +++++++++++++++++++

>> > .../ld-dynamic/export-dynamic-symbol-1.d      |  9 +++

>> > .../ld-dynamic/export-dynamic-symbol-2.d      |  9 +++

>> > .../ld-dynamic/export-dynamic-symbol-glob.d   |  8 ++

>> > .../ld-dynamic/export-dynamic-symbol-list-1.d |  9 +++

>> > .../ld-dynamic/export-dynamic-symbol-list-2.d |  9 +++

>> > .../export-dynamic-symbol-list-glob.d         |  8 ++

>> > .../ld-dynamic/export-dynamic-symbol.exp      | 39 ++++++++++

>> > .../ld-dynamic/export-dynamic-symbol.s        |  9 +++

>> > ld/testsuite/ld-dynamic/foo-bar.list          |  1 +

>> > ld/testsuite/ld-dynamic/foo.list              |  1 +

>> > ld/testsuite/ld-dynamic/foo.s                 |  4 +

>> > ld/testsuite/ld-dynamic/fstar.list            |  1 +

>> > ld/testsuite/ld-elf/dlempty.list              |  3 +

>> > ld/testsuite/ld-elf/shared.exp                | 36 +++++++++

>> > 21 files changed, 258 insertions(+), 9 deletions(-)

>> > create mode 100644 ld/testsuite/ld-dynamic/export-dynamic-symbol-1.d

>> > create mode 100644 ld/testsuite/ld-dynamic/export-dynamic-symbol-2.d

>> > create mode 100644 ld/testsuite/ld-dynamic/export-dynamic-symbol-glob.d

>> > create mode 100644 ld/testsuite/ld-dynamic/export-dynamic-symbol-list-1.d

>> > create mode 100644 ld/testsuite/ld-dynamic/export-dynamic-symbol-list-2.d

>> > create mode 100644 ld/testsuite/ld-dynamic/export-dynamic-symbol-list-glob.d

>> > create mode 100644 ld/testsuite/ld-dynamic/export-dynamic-symbol.exp

>> > create mode 100644 ld/testsuite/ld-dynamic/export-dynamic-symbol.s

>> > create mode 100644 ld/testsuite/ld-dynamic/foo-bar.list

>> > create mode 100644 ld/testsuite/ld-dynamic/foo.list

>> > create mode 100644 ld/testsuite/ld-dynamic/foo.s

>> > create mode 100644 ld/testsuite/ld-dynamic/fstar.list

>> > create mode 100644 ld/testsuite/ld-elf/dlempty.list

>> >

>> >diff --git a/ld/NEWS b/ld/NEWS

>> >index 9f5bbe51cf..870c480bde 100644

>> >--- a/ld/NEWS

>> >+++ b/ld/NEWS

>> >@@ -1,5 +1,8 @@

>> > -*- text -*-

>> >

>> >+* Add ELF linker command-line options, --export-dynamic-symbol and

>> >+  --export-dynamic-symbol-list, to make symbols dynamic.

>> >+

>> > * Add command-line options --enable-non-contiguous-regions and

>> >   --enable-non-contiguous-regions-warnings.

>> >

>> >diff --git a/ld/ld.texi b/ld/ld.texi

>> >index 4dc78e65fa..92e47c6324 100644

>> >--- a/ld/ld.texi

>> >+++ b/ld/ld.texi

>> >@@ -569,6 +569,24 @@ Note that this option is specific to ELF targeted ports.  PE targets

>> > support a similar function to export all symbols from a DLL or EXE; see

>> > the description of @samp{--export-all-symbols} below.

>> >

>> >+@kindex --export-dynamic-symbol=@var{glob}

>> >+@cindex export dynamic symbol

>> >+@item --export-dynamic-symbol=@var{glob}

>> >+When creating a dynamically linked executable, symbols matching

>> >+@var{glob} will be added to the dynamic symbol table. When creating a

>> >+shared library, references to symbols matching @var{glob} will not be

>> >+bound to the definitions within the shared library. This option is a

>> >+no-op when creating a shared library and @samp{-Bsymbolic} or

>> >+@samp{--dynamic-list} are not specified. This option is only meaningful

>> >+on ELF platforms which support shared libraries.

>>

>> Is --export-dynamic-symbol still effective for -shared?

>> I think either way is ok.

>

>Yes.

>

>> >+@kindex --export-dynamic-symbol-list=@var{file}

>> >+@cindex export dynamic symbol list

>> >+@item --export-dynamic-symbol-list=@var{file}

>> >+Specify a @samp{--export-dynamic-symbol} for each pattern in the file.

>> >+The format of the file is the same as the version node without

>> >+scope and node name.  See @ref{VERSION} for more information.

>> >+

>> > @ifclear SingleFormat

>> > @cindex big-endian objects

>> > @cindex endianness

>> >diff --git a/ld/ldgram.y b/ld/ldgram.y

>> >index df5c035c03..36845c4c30 100644

>> >--- a/ld/ldgram.y

>> >+++ b/ld/ldgram.y

>> >@@ -1313,7 +1313,7 @@ dynamic_list_node:

>> > dynamic_list_tag:

>> >               vers_defns ';'

>> >               {

>> >-                lang_append_dynamic_list ($1);

>> >+                lang_append_dynamic_list (current_dynamic_list_p, $1);

>> >               }

>> >       ;

>> >

>> >diff --git a/ld/ldlang.c b/ld/ldlang.c

>> >index 3d653d460d..14a6a577d2 100644

>> >--- a/ld/ldlang.c

>> >+++ b/ld/ldlang.c

>> >@@ -118,6 +118,7 @@ lang_statement_list_type file_chain = { NULL, NULL };

>> >    lang_statement_union).  */

>> > lang_statement_list_type input_file_chain;

>> > static const char *current_input_file;

>> >+struct bfd_elf_dynamic_list **current_dynamic_list_p;

>> > struct bfd_sym_chain entry_symbol = { NULL, NULL };

>> > const char *entry_section = ".text";

>> > struct lang_input_statement_flags input_flags;

>> >@@ -9324,15 +9325,16 @@ lang_add_unique (const char *name)

>> > /* Append the list of dynamic symbols to the existing one.  */

>> >

>> > void

>> >-lang_append_dynamic_list (struct bfd_elf_version_expr *dynamic)

>> >+lang_append_dynamic_list (struct bfd_elf_dynamic_list **list_p,

>> >+                        struct bfd_elf_version_expr *dynamic)

>> > {

>> >-  if (link_info.dynamic_list)

>> >+  if (*list_p)

>> >     {

>> >       struct bfd_elf_version_expr *tail;

>> >       for (tail = dynamic; tail->next != NULL; tail = tail->next)

>> >       ;

>> >-      tail->next = link_info.dynamic_list->head.list;

>> >-      link_info.dynamic_list->head.list = dynamic;

>> >+      tail->next = (*list_p)->head.list;

>> >+      (*list_p)->head.list = dynamic;

>> >     }

>> >   else

>> >     {

>> >@@ -9341,7 +9343,7 @@ lang_append_dynamic_list (struct bfd_elf_version_expr *dynamic)

>> >       d = (struct bfd_elf_dynamic_list *) xcalloc (1, sizeof *d);

>> >       d->head.list = dynamic;

>> >       d->match = lang_vers_match;

>> >-      link_info.dynamic_list = d;

>> >+      *list_p = d;

>> >     }

>> > }

>> >

>> >@@ -9363,7 +9365,7 @@ lang_append_dynamic_list_cpp_typeinfo (void)

>> >     dynamic = lang_new_vers_pattern (dynamic, symbols [i], "C++",

>> >                                    FALSE);

>> >

>> >-  lang_append_dynamic_list (dynamic);

>> >+  lang_append_dynamic_list (&link_info.dynamic_list, dynamic);

>> > }

>> >

>> > /* Append the list of C++ operator new and delete dynamic symbols to the

>> >@@ -9384,7 +9386,7 @@ lang_append_dynamic_list_cpp_new (void)

>> >     dynamic = lang_new_vers_pattern (dynamic, symbols [i], "C++",

>> >                                    FALSE);

>> >

>> >-  lang_append_dynamic_list (dynamic);

>> >+  lang_append_dynamic_list (&link_info.dynamic_list, dynamic);

>> > }

>> >

>> > /* Scan a space and/or comma separated string of features.  */

>> >diff --git a/ld/ldlang.h b/ld/ldlang.h

>> >index 3018c3e2ba..529ccd1585 100644

>> >--- a/ld/ldlang.h

>> >+++ b/ld/ldlang.h

>> >@@ -513,6 +513,8 @@ extern bfd_boolean entry_from_cmdline;

>> > extern lang_statement_list_type file_chain;

>> > extern lang_statement_list_type input_file_chain;

>> >

>> >+extern struct bfd_elf_dynamic_list **current_dynamic_list_p;

>> >+

>> > extern int lang_statement_iteration;

>> > extern struct asneeded_minfo **asneeded_list_tail;

>> >

>> >@@ -673,7 +675,8 @@ extern struct bfd_elf_version_deps *lang_add_vers_depend

>> >   (struct bfd_elf_version_deps *, const char *);

>> > extern void lang_register_vers_node

>> >   (const char *, struct bfd_elf_version_tree *, struct bfd_elf_version_deps *);

>> >-extern void lang_append_dynamic_list (struct bfd_elf_version_expr *);

>> >+extern void lang_append_dynamic_list (struct bfd_elf_dynamic_list **,

>> >+                                    struct bfd_elf_version_expr *);

>> > extern void lang_append_dynamic_list_cpp_typeinfo (void);

>> > extern void lang_append_dynamic_list_cpp_new (void);

>> > extern void lang_add_unique

>> >diff --git a/ld/ldlex.h b/ld/ldlex.h

>> >index 22b928d2d9..2c8d043a09 100644

>> >--- a/ld/ldlex.h

>> >+++ b/ld/ldlex.h

>> >@@ -81,6 +81,8 @@ enum option_values

>> >   OPTION_DYNAMIC_LIST_CPP_NEW,

>> >   OPTION_DYNAMIC_LIST_CPP_TYPEINFO,

>> >   OPTION_DYNAMIC_LIST_DATA,

>> >+  OPTION_EXPORT_DYNAMIC_SYMBOL,

>> >+  OPTION_EXPORT_DYNAMIC_SYMBOL_LIST,

>> >   OPTION_WARN_COMMON,

>> >   OPTION_WARN_CONSTRUCTORS,

>> >   OPTION_WARN_FATAL,

>> >diff --git a/ld/lexsup.c b/ld/lexsup.c

>> >index fe9526b527..2bac1631d6 100644

>> >--- a/ld/lexsup.c

>> >+++ b/ld/lexsup.c

>> >@@ -504,6 +504,10 @@ static const struct ld_option ld_options[] =

>> >     '\0', NULL, N_("Use C++ typeinfo dynamic list"), TWO_DASHES },

>> >   { {"dynamic-list", required_argument, NULL, OPTION_DYNAMIC_LIST},

>> >     '\0', N_("FILE"), N_("Read dynamic list"), TWO_DASHES },

>> >+  { {"export-dynamic-symbol", required_argument, NULL, OPTION_EXPORT_DYNAMIC_SYMBOL},

>> >+    '\0', N_("SYMBOL"), N_("Export the specified symbol"), EXACTLY_TWO_DASHES },

>> >+  { {"export-dynamic-symbol-list", required_argument, NULL, OPTION_EXPORT_DYNAMIC_SYMBOL_LIST},

>> >+    '\0', N_("FILE"), N_("Read export dynamic symbol list"), EXACTLY_TWO_DASHES },

>> >   { {"warn-common", no_argument, NULL, OPTION_WARN_COMMON},

>> >     '\0', NULL, N_("Warn about duplicate common symbols"), TWO_DASHES },

>> >   { {"warn-constructors", no_argument, NULL, OPTION_WARN_CONSTRUCTORS},

>> >@@ -581,6 +585,7 @@ parse_args (unsigned argc, char **argv)

>> >     dynamic_list_data,

>> >     dynamic_list

>> >   } opt_dynamic_list = dynamic_list_unset;

>> >+  struct bfd_elf_dynamic_list *export_list = NULL;

>> >

>> >   shortopts = (char *) xmalloc (OPTION_COUNT * 3 + 2);

>> >   longopts = (struct option *)

>> >@@ -1418,6 +1423,7 @@ parse_args (unsigned argc, char **argv)

>> >           ldfile_open_command_file (optarg);

>> >           saved_script_handle = hold_script_handle;

>> >           parser_input = input_dynamic_list;

>> >+          current_dynamic_list_p = &link_info.dynamic_list;

>> >           yyparse ();

>> >         }

>> >         if (opt_dynamic_list != dynamic_list_data)

>> >@@ -1425,6 +1431,29 @@ parse_args (unsigned argc, char **argv)

>> >         if (opt_symbolic == symbolic)

>> >           opt_symbolic = symbolic_unset;

>> >         break;

>> >+      case OPTION_EXPORT_DYNAMIC_SYMBOL:

>> >+        {

>> >+          struct bfd_elf_version_expr *expr

>> >+            = lang_new_vers_pattern (NULL, xstrdup (optarg), NULL,

>> >+                                     FALSE);

>> >+          lang_append_dynamic_list (&export_list, expr);

>> >+          }

>> >+        break;

>> >+      case OPTION_EXPORT_DYNAMIC_SYMBOL_LIST:

>> >+        /* This option indicates a small script that only specifies

>> >+           an export list.  Read it, but don't assume that we've

>> >+           seen a linker script.  */

>> >+        {

>> >+          FILE *hold_script_handle;

>> >+

>> >+          hold_script_handle = saved_script_handle;

>> >+          ldfile_open_command_file (optarg);

>> >+          saved_script_handle = hold_script_handle;

>> >+          parser_input = input_dynamic_list;

>> >+          current_dynamic_list_p = &export_list;

>> >+          yyparse ();

>> >+        }

>> >+        break;

>> >       case OPTION_WARN_COMMON:

>> >         config.warn_common = TRUE;

>> >         break;

>> >@@ -1632,6 +1661,52 @@ parse_args (unsigned argc, char **argv)

>> >       && command_line.check_section_addresses < 0)

>> >     command_line.check_section_addresses = 0;

>> >

>> >+  if (export_list && !bfd_link_relocatable (&link_info))

>> >+    {

>> >+      struct bfd_elf_version_expr *head = export_list->head.list;

>> >+      struct bfd_elf_version_expr *next;

>> >+

>> >+      /* For --export-dynamic-symbol[-list]:

>> >+       1. When building executable, treat like --dynamic-list.

>> >+       2. When building shared object:

>> >+          a. If -Bsymbolic or --dynamic-list are used, treat like

>> >+             --dynamic-list.

>> >+          b. Otherwise, ignored.

>> >+       */

>> >+      bfd_boolean kept = (bfd_link_executable (&link_info)

>> >+                        || opt_symbolic != symbolic_unset

>> >+                        || opt_dynamic_list != dynamic_list_unset);

>> >+

>> >+      if (kept)

>> >+      {

>> >+        /* Append the export list to link_info.dynamic_list.  */

>> >+        if (link_info.dynamic_list)

>> >+          {

>> >+            for (next = head; next->next != NULL; next = next->next)

>> >+              ;

>> >+            next->next = link_info.dynamic_list->head.list;

>> >+            link_info.dynamic_list->head.list = head;

>> >+          }

>> >+        else

>> >+          link_info.dynamic_list = export_list;

>> >+

>> >+        if (opt_dynamic_list != dynamic_list_data)

>> >+          opt_dynamic_list = dynamic_list;

>> >+        if (opt_symbolic == symbolic)

>> >+          opt_symbolic = symbolic_unset;

>>

>> The interaction with -Bsymbolic appears to be more complex now.

>> I think users will pretty much avoid the combination of -Bsymbolic and

>> (--dynamic-list or --export-dynamic-symbol or --export-dynamic-symbol-list).

>>

>> So I beg for a re-consideration of

>> https://sourceware.org/bugzilla/show_bug.cgi?id=26018

>> https://sourceware.org/pipermail/binutils/2020-May/111223.html

>>

>

>Here is the updated patch on top of

>

>https://sourceware.org/pipermail/binutils/2020-May/111228.html


Thanks for PATCH v3. LGTM.

I have verified the semantics of new tests dl2d ~ dl2k.

Patch

From a7722abb6a524efdf30e19490e24246bca305900 Mon Sep 17 00:00:00 2001
From: Fangrui Song <maskray@google.com>
Date: Wed, 22 Apr 2020 22:12:42 -0700
Subject: [PATCH] ld: Add --export-dynamic-symbol and
 --export-dynamic-symbol-list

--export-dynamic-symbol-list is like a dynamic list, but without
the symbolic property for unspecified symbols.

When creating an executable, --export-dynamic-symbol-list is treated
like --dynamic-list.

When creating a shared library, it is treated like --dynamic-list if
-Bsymbolic or --dynamic-list are used,  otherwise, it is ignored, so
that references to matched symbols will not be bound to the definitions
within the shared library.

2020-05-XX  Fangrui Song  <maskray@google.com>
	    H.J. Lu  <hongjiu.lu@intel.com>

	PR ld/25910
	* NEWS: Mention --export-dynamic-symbol[-list].
	* ld.texi: Document --export-dynamic-symbol[-list].
	* ldgram.y: Pass current_dynamic_list_p to
	lang_append_dynamic_list.
	* ldlang.c (current_dynamic_list_p): New.
	(ang_append_dynamic_list): Updated to take a pointer to
	struct bfd_elf_dynamic_list * argument instead of using
	link_info.dynamic_list.
	(lang_append_dynamic_list_cpp_typeinfo): Pass
	&link_info.dynamic_list to ang_append_dynamic_list.
	(lang_append_dynamic_list_cpp_new): Likewise.
	* ldlang.h (current_dynamic_list_p): New.
	(lang_append_dynamic_list): Add a pointer to
	struct bfd_elf_dynamic_list * argument.
	* ldlex.h (option_values): Add OPTION_EXPORT_DYNAMIC_SYMBOL and
	OPTION_EXPORT_DYNAMIC_SYMBOL_LIST.
	* lexsup.c (ld_options): Add entries for
	OPTION_EXPORT_DYNAMIC_SYMBOL and
	OPTION_EXPORT_DYNAMIC_SYMBOL_LIST.
	(parse_args): Handle --export-dynamic-symbol and
	--export-dynamic-symbol-list.
	* testsuite/ld-dynamic/export-dynamic-symbol-1.d: New.
	* testsuite/ld-dynamic/export-dynamic-symbol-2.d: New.
	* testsuite/ld-dynamic/export-dynamic-symbol-glob.d: New.
	* testsuite/ld-dynamic/export-dynamic-symbol-list-1.d: New.
	* testsuite/ld-dynamic/export-dynamic-symbol-list-2.d: New.
	* testsuite/ld-dynamic/export-dynamic-symbol-list-glob.d: New.
	* testsuite/ld-dynamic/export-dynamic-symbol.exp: New.
	* testsuite/ld-dynamic/export-dynamic-symbol.s: New.
	* testsuite/ld-dynamic/foo-bar.list: New.
	* testsuite/ld-dynamic/foo.list: New.
	* testsuite/ld-dynamic/foo.s: New.
	* testsuite/ld-dynamic/fstar.list: New.
	* testsuite/ld-elf/dlempty.list: New.
	* testsuite/ld-elf/shared.exp: Add tests for
	--export-dynamic-symbol and --export-dynamic-symbol-list.
---
 ld/NEWS                                       |  3 +
 ld/ld.texi                                    | 18 +++++
 ld/ldgram.y                                   |  2 +-
 ld/ldlang.c                                   | 16 +++--
 ld/ldlang.h                                   |  5 +-
 ld/ldlex.h                                    |  2 +
 ld/lexsup.c                                   | 72 +++++++++++++++++++
 .../ld-dynamic/export-dynamic-symbol-1.d      |  9 +++
 .../ld-dynamic/export-dynamic-symbol-2.d      |  9 +++
 .../ld-dynamic/export-dynamic-symbol-glob.d   |  8 +++
 .../ld-dynamic/export-dynamic-symbol-list-1.d |  9 +++
 .../ld-dynamic/export-dynamic-symbol-list-2.d |  9 +++
 .../export-dynamic-symbol-list-glob.d         |  8 +++
 .../ld-dynamic/export-dynamic-symbol.exp      | 39 ++++++++++
 .../ld-dynamic/export-dynamic-symbol.s        |  9 +++
 ld/testsuite/ld-dynamic/foo-bar.list          |  1 +
 ld/testsuite/ld-dynamic/foo.list              |  1 +
 ld/testsuite/ld-dynamic/foo.s                 |  4 ++
 ld/testsuite/ld-dynamic/fstar.list            |  1 +
 ld/testsuite/ld-elf/dlempty.list              |  3 +
 ld/testsuite/ld-elf/shared.exp                | 42 +++++++++++
 21 files changed, 261 insertions(+), 9 deletions(-)
 create mode 100644 ld/testsuite/ld-dynamic/export-dynamic-symbol-1.d
 create mode 100644 ld/testsuite/ld-dynamic/export-dynamic-symbol-2.d
 create mode 100644 ld/testsuite/ld-dynamic/export-dynamic-symbol-glob.d
 create mode 100644 ld/testsuite/ld-dynamic/export-dynamic-symbol-list-1.d
 create mode 100644 ld/testsuite/ld-dynamic/export-dynamic-symbol-list-2.d
 create mode 100644 ld/testsuite/ld-dynamic/export-dynamic-symbol-list-glob.d
 create mode 100644 ld/testsuite/ld-dynamic/export-dynamic-symbol.exp
 create mode 100644 ld/testsuite/ld-dynamic/export-dynamic-symbol.s
 create mode 100644 ld/testsuite/ld-dynamic/foo-bar.list
 create mode 100644 ld/testsuite/ld-dynamic/foo.list
 create mode 100644 ld/testsuite/ld-dynamic/foo.s
 create mode 100644 ld/testsuite/ld-dynamic/fstar.list
 create mode 100644 ld/testsuite/ld-elf/dlempty.list

diff --git a/ld/NEWS b/ld/NEWS
index 9f5bbe51cf..870c480bde 100644
--- a/ld/NEWS
+++ b/ld/NEWS
@@ -1,5 +1,8 @@ 
 -*- text -*-
 
+* Add ELF linker command-line options, --export-dynamic-symbol and
+  --export-dynamic-symbol-list, to make symbols dynamic.
+
 * Add command-line options --enable-non-contiguous-regions and
   --enable-non-contiguous-regions-warnings.
 
diff --git a/ld/ld.texi b/ld/ld.texi
index 4dc78e65fa..92e47c6324 100644
--- a/ld/ld.texi
+++ b/ld/ld.texi
@@ -569,6 +569,24 @@  Note that this option is specific to ELF targeted ports.  PE targets
 support a similar function to export all symbols from a DLL or EXE; see
 the description of @samp{--export-all-symbols} below.
 
+@kindex --export-dynamic-symbol=@var{glob}
+@cindex export dynamic symbol
+@item --export-dynamic-symbol=@var{glob}
+When creating a dynamically linked executable, symbols matching
+@var{glob} will be added to the dynamic symbol table. When creating a
+shared library, references to symbols matching @var{glob} will not be
+bound to the definitions within the shared library. This option is a
+no-op when creating a shared library and @samp{-Bsymbolic} or
+@samp{--dynamic-list} are not specified. This option is only meaningful
+on ELF platforms which support shared libraries.
+
+@kindex --export-dynamic-symbol-list=@var{file}
+@cindex export dynamic symbol list
+@item --export-dynamic-symbol-list=@var{file}
+Specify a @samp{--export-dynamic-symbol} for each pattern in the file.
+The format of the file is the same as the version node without
+scope and node name.  See @ref{VERSION} for more information.
+
 @ifclear SingleFormat
 @cindex big-endian objects
 @cindex endianness
diff --git a/ld/ldgram.y b/ld/ldgram.y
index df5c035c03..36845c4c30 100644
--- a/ld/ldgram.y
+++ b/ld/ldgram.y
@@ -1313,7 +1313,7 @@  dynamic_list_node:
 dynamic_list_tag:
 		vers_defns ';'
 		{
-		  lang_append_dynamic_list ($1);
+		  lang_append_dynamic_list (current_dynamic_list_p, $1);
 		}
 	;
 
diff --git a/ld/ldlang.c b/ld/ldlang.c
index 3d653d460d..14a6a577d2 100644
--- a/ld/ldlang.c
+++ b/ld/ldlang.c
@@ -118,6 +118,7 @@  lang_statement_list_type file_chain = { NULL, NULL };
    lang_statement_union).  */
 lang_statement_list_type input_file_chain;
 static const char *current_input_file;
+struct bfd_elf_dynamic_list **current_dynamic_list_p;
 struct bfd_sym_chain entry_symbol = { NULL, NULL };
 const char *entry_section = ".text";
 struct lang_input_statement_flags input_flags;
@@ -9324,15 +9325,16 @@  lang_add_unique (const char *name)
 /* Append the list of dynamic symbols to the existing one.  */
 
 void
-lang_append_dynamic_list (struct bfd_elf_version_expr *dynamic)
+lang_append_dynamic_list (struct bfd_elf_dynamic_list **list_p,
+			  struct bfd_elf_version_expr *dynamic)
 {
-  if (link_info.dynamic_list)
+  if (*list_p)
     {
       struct bfd_elf_version_expr *tail;
       for (tail = dynamic; tail->next != NULL; tail = tail->next)
 	;
-      tail->next = link_info.dynamic_list->head.list;
-      link_info.dynamic_list->head.list = dynamic;
+      tail->next = (*list_p)->head.list;
+      (*list_p)->head.list = dynamic;
     }
   else
     {
@@ -9341,7 +9343,7 @@  lang_append_dynamic_list (struct bfd_elf_version_expr *dynamic)
       d = (struct bfd_elf_dynamic_list *) xcalloc (1, sizeof *d);
       d->head.list = dynamic;
       d->match = lang_vers_match;
-      link_info.dynamic_list = d;
+      *list_p = d;
     }
 }
 
@@ -9363,7 +9365,7 @@  lang_append_dynamic_list_cpp_typeinfo (void)
     dynamic = lang_new_vers_pattern (dynamic, symbols [i], "C++",
 				     FALSE);
 
-  lang_append_dynamic_list (dynamic);
+  lang_append_dynamic_list (&link_info.dynamic_list, dynamic);
 }
 
 /* Append the list of C++ operator new and delete dynamic symbols to the
@@ -9384,7 +9386,7 @@  lang_append_dynamic_list_cpp_new (void)
     dynamic = lang_new_vers_pattern (dynamic, symbols [i], "C++",
 				     FALSE);
 
-  lang_append_dynamic_list (dynamic);
+  lang_append_dynamic_list (&link_info.dynamic_list, dynamic);
 }
 
 /* Scan a space and/or comma separated string of features.  */
diff --git a/ld/ldlang.h b/ld/ldlang.h
index 3018c3e2ba..529ccd1585 100644
--- a/ld/ldlang.h
+++ b/ld/ldlang.h
@@ -513,6 +513,8 @@  extern bfd_boolean entry_from_cmdline;
 extern lang_statement_list_type file_chain;
 extern lang_statement_list_type input_file_chain;
 
+extern struct bfd_elf_dynamic_list **current_dynamic_list_p;
+
 extern int lang_statement_iteration;
 extern struct asneeded_minfo **asneeded_list_tail;
 
@@ -673,7 +675,8 @@  extern struct bfd_elf_version_deps *lang_add_vers_depend
   (struct bfd_elf_version_deps *, const char *);
 extern void lang_register_vers_node
   (const char *, struct bfd_elf_version_tree *, struct bfd_elf_version_deps *);
-extern void lang_append_dynamic_list (struct bfd_elf_version_expr *);
+extern void lang_append_dynamic_list (struct bfd_elf_dynamic_list **,
+				      struct bfd_elf_version_expr *);
 extern void lang_append_dynamic_list_cpp_typeinfo (void);
 extern void lang_append_dynamic_list_cpp_new (void);
 extern void lang_add_unique
diff --git a/ld/ldlex.h b/ld/ldlex.h
index 22b928d2d9..2c8d043a09 100644
--- a/ld/ldlex.h
+++ b/ld/ldlex.h
@@ -81,6 +81,8 @@  enum option_values
   OPTION_DYNAMIC_LIST_CPP_NEW,
   OPTION_DYNAMIC_LIST_CPP_TYPEINFO,
   OPTION_DYNAMIC_LIST_DATA,
+  OPTION_EXPORT_DYNAMIC_SYMBOL,
+  OPTION_EXPORT_DYNAMIC_SYMBOL_LIST,
   OPTION_WARN_COMMON,
   OPTION_WARN_CONSTRUCTORS,
   OPTION_WARN_FATAL,
diff --git a/ld/lexsup.c b/ld/lexsup.c
index 49e013b5bd..7a00621ae6 100644
--- a/ld/lexsup.c
+++ b/ld/lexsup.c
@@ -504,6 +504,10 @@  static const struct ld_option ld_options[] =
     '\0', NULL, N_("Use C++ typeinfo dynamic list"), TWO_DASHES },
   { {"dynamic-list", required_argument, NULL, OPTION_DYNAMIC_LIST},
     '\0', N_("FILE"), N_("Read dynamic list"), TWO_DASHES },
+  { {"export-dynamic-symbol", required_argument, NULL, OPTION_EXPORT_DYNAMIC_SYMBOL},
+    '\0', N_("SYMBOL"), N_("Export the specified symbol"), EXACTLY_TWO_DASHES },
+  { {"export-dynamic-symbol-list", required_argument, NULL, OPTION_EXPORT_DYNAMIC_SYMBOL_LIST},
+    '\0', N_("FILE"), N_("Read export dynamic symbol list"), EXACTLY_TWO_DASHES },
   { {"warn-common", no_argument, NULL, OPTION_WARN_COMMON},
     '\0', NULL, N_("Warn about duplicate common symbols"), TWO_DASHES },
   { {"warn-constructors", no_argument, NULL, OPTION_WARN_CONSTRUCTORS},
@@ -581,6 +585,7 @@  parse_args (unsigned argc, char **argv)
     dynamic_list_data,
     dynamic_list
   } opt_dynamic_list = dynamic_list_unset;
+  struct bfd_elf_dynamic_list *export_list = NULL;
 
   shortopts = (char *) xmalloc (OPTION_COUNT * 3 + 2);
   longopts = (struct option *)
@@ -1412,11 +1417,35 @@  parse_args (unsigned argc, char **argv)
 	    ldfile_open_command_file (optarg);
 	    saved_script_handle = hold_script_handle;
 	    parser_input = input_dynamic_list;
+	    current_dynamic_list_p = &link_info.dynamic_list;
 	    yyparse ();
 	  }
 	  if (opt_dynamic_list != dynamic_list_data)
 	    opt_dynamic_list = dynamic_list;
 	  break;
+	case OPTION_EXPORT_DYNAMIC_SYMBOL:
+	  {
+	    struct bfd_elf_version_expr *expr
+	      = lang_new_vers_pattern (NULL, xstrdup (optarg), NULL,
+				       FALSE);
+	    lang_append_dynamic_list (&export_list, expr);
+          }
+	  break;
+	case OPTION_EXPORT_DYNAMIC_SYMBOL_LIST:
+	  /* This option indicates a small script that only specifies
+	     an export list.  Read it, but don't assume that we've
+	     seen a linker script.  */
+	  {
+	    FILE *hold_script_handle;
+
+	    hold_script_handle = saved_script_handle;
+	    ldfile_open_command_file (optarg);
+	    saved_script_handle = hold_script_handle;
+	    parser_input = input_dynamic_list;
+	    current_dynamic_list_p = &export_list;
+	    yyparse ();
+	  }
+	  break;
 	case OPTION_WARN_COMMON:
 	  config.warn_common = TRUE;
 	  break;
@@ -1624,6 +1653,49 @@  parse_args (unsigned argc, char **argv)
       && command_line.check_section_addresses < 0)
     command_line.check_section_addresses = 0;
 
+  if (export_list)
+    {
+      struct bfd_elf_version_expr *head = export_list->head.list;
+      struct bfd_elf_version_expr *next;
+
+      /* For --export-dynamic-symbol[-list]:
+	 1. When building executable, treat like --dynamic-list.
+	 2. When building shared object:
+	    a. If -Bsymbolic or --dynamic-list are used, treat like
+	       --dynamic-list.
+	    b. Otherwise, ignored.
+       */
+      if (!bfd_link_relocatable (&link_info)
+	  && (bfd_link_executable (&link_info)
+	      || opt_symbolic != symbolic_unset
+	      || opt_dynamic_list != dynamic_list_unset))
+	{
+	  /* Append the export list to link_info.dynamic_list.  */
+	  if (link_info.dynamic_list)
+	    {
+	      for (next = head; next->next != NULL; next = next->next)
+		;
+	      next->next = link_info.dynamic_list->head.list;
+	      link_info.dynamic_list->head.list = head;
+	    }
+	  else
+	    link_info.dynamic_list = export_list;
+
+	  if (opt_dynamic_list != dynamic_list_data)
+	    opt_dynamic_list = dynamic_list;
+	}
+      else
+	{
+	  /* Free the export list.  */
+	  for (; head->next != NULL; head = next)
+	    {
+	      next = head->next;
+	      free (head);
+	    }
+	  free (export_list);
+	}
+    }
+
   switch (opt_dynamic_list)
     {
     case dynamic_list_unset:
diff --git a/ld/testsuite/ld-dynamic/export-dynamic-symbol-1.d b/ld/testsuite/ld-dynamic/export-dynamic-symbol-1.d
new file mode 100644
index 0000000000..c1dd4e2f55
--- /dev/null
+++ b/ld/testsuite/ld-dynamic/export-dynamic-symbol-1.d
@@ -0,0 +1,9 @@ 
+#name: --export-dynamic-symbol foo archive
+#source: export-dynamic-symbol.s
+#ld: -pie --export-dynamic-symbol foo tmpdir/libfoo.a
+#nm: -n
+
+#failif
+#...
+[0-9a-f]+ T +foo
+#...
diff --git a/ld/testsuite/ld-dynamic/export-dynamic-symbol-2.d b/ld/testsuite/ld-dynamic/export-dynamic-symbol-2.d
new file mode 100644
index 0000000000..7ec4eed3ed
--- /dev/null
+++ b/ld/testsuite/ld-dynamic/export-dynamic-symbol-2.d
@@ -0,0 +1,9 @@ 
+#name: -u --export-dynamic-symbol foo archive
+#source: export-dynamic-symbol.s
+#ld: -pie -u foo --export-dynamic-symbol foo --export-dynamic-symbol=bar tmpdir/libfoo.a
+#nm: -D
+
+#...
+[0-9a-f]+ T +bar
+[0-9a-f]+ T +foo
+#...
diff --git a/ld/testsuite/ld-dynamic/export-dynamic-symbol-glob.d b/ld/testsuite/ld-dynamic/export-dynamic-symbol-glob.d
new file mode 100644
index 0000000000..05a6e15b3b
--- /dev/null
+++ b/ld/testsuite/ld-dynamic/export-dynamic-symbol-glob.d
@@ -0,0 +1,8 @@ 
+#name: -u --export-dynamic-symbol f* archive
+#source: export-dynamic-symbol.s
+#ld: -pie -u foo --export-dynamic-symbol f* tmpdir/libfoo.a
+#nm: -D
+
+#...
+[0-9a-f]+ T +foo
+#...
diff --git a/ld/testsuite/ld-dynamic/export-dynamic-symbol-list-1.d b/ld/testsuite/ld-dynamic/export-dynamic-symbol-list-1.d
new file mode 100644
index 0000000000..aa1b8839e6
--- /dev/null
+++ b/ld/testsuite/ld-dynamic/export-dynamic-symbol-list-1.d
@@ -0,0 +1,9 @@ 
+#name: --export-dynamic-symbol-list foo archive
+#source: export-dynamic-symbol.s
+#ld: -pie --export-dynamic-symbol-list foo.list tmpdir/libfoo.a
+#nm: -n
+
+#failif
+#...
+[0-9a-f]+ T +foo
+#...
diff --git a/ld/testsuite/ld-dynamic/export-dynamic-symbol-list-2.d b/ld/testsuite/ld-dynamic/export-dynamic-symbol-list-2.d
new file mode 100644
index 0000000000..367a07c1bb
--- /dev/null
+++ b/ld/testsuite/ld-dynamic/export-dynamic-symbol-list-2.d
@@ -0,0 +1,9 @@ 
+#name: -u --export-dynamic-symbol-list foo bar archive
+#source: export-dynamic-symbol.s
+#ld: -pie -u foo --export-dynamic-symbol-list foo-bar.list tmpdir/libfoo.a
+#nm: -D
+
+#...
+[0-9a-f]+ T +bar
+[0-9a-f]+ T +foo
+#...
diff --git a/ld/testsuite/ld-dynamic/export-dynamic-symbol-list-glob.d b/ld/testsuite/ld-dynamic/export-dynamic-symbol-list-glob.d
new file mode 100644
index 0000000000..f0e3427306
--- /dev/null
+++ b/ld/testsuite/ld-dynamic/export-dynamic-symbol-list-glob.d
@@ -0,0 +1,8 @@ 
+#name: -u --export-dynamic-symbol-list fstar archive
+#source: export-dynamic-symbol.s
+#ld: -pie -u foo --export-dynamic-symbol-list fstar.list tmpdir/libfoo.a
+#nm: -D
+
+#...
+[0-9a-f]+ T +foo
+#...
diff --git a/ld/testsuite/ld-dynamic/export-dynamic-symbol.exp b/ld/testsuite/ld-dynamic/export-dynamic-symbol.exp
new file mode 100644
index 0000000000..d0b4bc4eb0
--- /dev/null
+++ b/ld/testsuite/ld-dynamic/export-dynamic-symbol.exp
@@ -0,0 +1,39 @@ 
+# Expect script for ld --export-dynamic-symbol tests
+#   Copyright (C) 2020 Free Software Foundation, Inc.
+#
+# This file is part of the GNU Binutils.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
+# MA 02110-1301, USA.
+#
+
+if ![is_elf_format] {
+    return
+}
+
+set build_tests {
+  {"Build libfoo.a"
+   "" "" ""
+   {foo.s} {} "libfoo.a"}
+}
+
+run_ld_link_tests $build_tests
+
+set test_list [lsort [glob -nocomplain $srcdir/$subdir/export-dynamic-symbol-*.d]]
+foreach test_file $test_list {
+    set test_name [file rootname $test_file]
+    verbose $test_name
+    run_dump_test $test_name
+}
diff --git a/ld/testsuite/ld-dynamic/export-dynamic-symbol.s b/ld/testsuite/ld-dynamic/export-dynamic-symbol.s
new file mode 100644
index 0000000000..4b1b8ebd5c
--- /dev/null
+++ b/ld/testsuite/ld-dynamic/export-dynamic-symbol.s
@@ -0,0 +1,9 @@ 
+	.text
+	.global _start
+_start:
+	.word 0
+
+	.section .text.1, "ax"
+	.global bar
+bar:
+	.word 0
diff --git a/ld/testsuite/ld-dynamic/foo-bar.list b/ld/testsuite/ld-dynamic/foo-bar.list
new file mode 100644
index 0000000000..87732e1de4
--- /dev/null
+++ b/ld/testsuite/ld-dynamic/foo-bar.list
@@ -0,0 +1 @@ 
+{ foo; bar; };
diff --git a/ld/testsuite/ld-dynamic/foo.list b/ld/testsuite/ld-dynamic/foo.list
new file mode 100644
index 0000000000..f89f569438
--- /dev/null
+++ b/ld/testsuite/ld-dynamic/foo.list
@@ -0,0 +1 @@ 
+{ foo; };
diff --git a/ld/testsuite/ld-dynamic/foo.s b/ld/testsuite/ld-dynamic/foo.s
new file mode 100644
index 0000000000..4a70181776
--- /dev/null
+++ b/ld/testsuite/ld-dynamic/foo.s
@@ -0,0 +1,4 @@ 
+	.text
+	.globl foo
+foo:
+	.byte 0
diff --git a/ld/testsuite/ld-dynamic/fstar.list b/ld/testsuite/ld-dynamic/fstar.list
new file mode 100644
index 0000000000..330d1dd2b8
--- /dev/null
+++ b/ld/testsuite/ld-dynamic/fstar.list
@@ -0,0 +1 @@ 
+{ f*; };
diff --git a/ld/testsuite/ld-elf/dlempty.list b/ld/testsuite/ld-elf/dlempty.list
new file mode 100644
index 0000000000..9b3884b10e
--- /dev/null
+++ b/ld/testsuite/ld-elf/dlempty.list
@@ -0,0 +1,3 @@ 
+{
+  empty;
+};
diff --git a/ld/testsuite/ld-elf/shared.exp b/ld/testsuite/ld-elf/shared.exp
index 7d35f3f379..5606c9937f 100644
--- a/ld/testsuite/ld-elf/shared.exp
+++ b/ld/testsuite/ld-elf/shared.exp
@@ -601,6 +601,27 @@  set build_tests {
   {"Build libdl2d.so with --dynamic-list-data -Bsymbolic"
    "-shared -Wl,-Bsymbolic,--dynamic-list-data" "-fPIC"
    {dl2.c dl2xxx.c} {} "libdl2d.so"}
+  {"Build libdl2e.so with --export-dynamic-symbol=foo"
+   "-shared -Wl,--export-dynamic-symbol=foo" "-fPIC"
+   {dl2.c dl2xxx.c} {} "libdl2e.so"}
+  {"Build libdl2f.so with --dynamic-list=dlempty.list and --export-dynamic-symbol=foo"
+   "-shared -Wl,--dynamic-list=dlempty.list,--export-dynamic-symbol=foo" "-fPIC"
+   {dl2.c dl2xxx.c} {} "libdl2f.so"}
+  {"Build libdl2g.so with --export-dynamic-symbol-list=dl2.list"
+   "-shared -Wl,--export-dynamic-symbol-list=dl2.list" "-fPIC"
+   {dl2.c dl2xxx.c} {} "libdl2g.so"}
+  {"Build libdl2h.so with --dynamic-list=dlempty.list and --export-dynamic-symbol-list=dl2.list"
+   "-shared -Wl,--dynamic-list=dlempty.list,--export-dynamic-symbol-list=dl2.list" "-fPIC"
+   {dl2.c dl2xxx.c} {} "libdl2h.so"}
+  {"Build libdl2i.so with -Bsymbolic and --export-dynamic-symbol=foo"
+   "-shared -Wl,-Bsymbolic,--export-dynamic-symbol=foo" "-fPIC"
+   {dl2.c dl2xxx.c} {} "libdl2i.so"}
+  {"Build libdl2j.so with -Bsymbolic and --export-dynamic-symbol-list=dl2.list"
+   "-shared -Wl,-Bsymbolic,--export-dynamic-symbol-list=dl2.list" "-fPIC"
+   {dl2.c dl2xxx.c} {} "libdl2j.so"}
+  {"Build libdl2k.so with --export-dynamic-symbol-list=dl2.list and -Bsymbolic"
+   "-shared -Wl,--export-dynamic-symbol-list=dl2.list,-Bsymbolic" "-fPIC"
+   {dl2.c dl2xxx.c} {} "libdl2k.so"}
   {"Build libdl4a.so with --dynamic-list=dl4.list"
    "-shared -Wl,--dynamic-list=dl4.list" "-fPIC"
    {dl4.c dl4xxx.c} {} "libdl4a.so"}
@@ -880,6 +901,27 @@  set run_tests [list \
     [list "Run with libdl2d.so" \
      "-Wl,--no-as-needed tmpdir/libdl2d.so" "" \
      {dl2main.c} "dl2d" "dl2a.out" ] \
+    [list "Run with libdl2e.so" \
+     "-Wl,--no-as-needed tmpdir/libdl2e.so" "" \
+     {dl2main.c} "dl2e" "dl2b.out" ] \
+    [list "Run with libdl2f.so" \
+     "-Wl,--no-as-needed tmpdir/libdl2f.so" "" \
+     {dl2main.c} "dl2f" "dl2a.out" ] \
+    [list "Run with libdl2g.so" \
+     "-Wl,--no-as-needed tmpdir/libdl2g.so" "" \
+     {dl2main.c} "dl2g" "dl2b.out" ] \
+    [list "Run with libdl2h.so" \
+     "-Wl,--no-as-needed tmpdir/libdl2h.so" "" \
+     {dl2main.c} "dl2h" "dl2a.out" ] \
+    [list "Run with libdl2i.so" \
+     "-Wl,--no-as-needed tmpdir/libdl2i.so" "" \
+     {dl2main.c} "dl2i" "dl2a.out" ] \
+    [list "Run with libdl2j.so" \
+     "-Wl,--no-as-needed tmpdir/libdl2j.so" "" \
+     {dl2main.c} "dl2j" "dl2a.out" ] \
+    [list "Run with libdl2k.so" \
+     "-Wl,--no-as-needed tmpdir/libdl2k.so" "" \
+     {dl2main.c} "dl2k" "dl2a.out" ] \
     [list "Run with libdl4a.so" \
      "-Wl,--no-as-needed tmpdir/libdl4a.so" "" \
      {dl4main.c} "dl4a" "dl4a.out" ] \
-- 
2.26.2