V3 [PATCH] ld: Add --export-dynamic-symbol and --export-dynamic-symbol-list
H.J. Lu
hjl.tools@gmail.com
Sat May 23 19:50:34 GMT 2020
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.
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