[PATCH] ld: Add --export-dynamic-symbol and --export-dynamic-symbol-list
H.J. Lu
hjl.tools@gmail.com
Wed May 13 12:08:19 GMT 2020
On Tue, May 12, 2020 at 9:38 PM Fangrui Song <maskray@google.com> wrote:
>
> On 2020-05-11, H.J. Lu wrote:
> >On Sun, May 10, 2020 at 11:46 PM Fangrui Song <maskray@google.com> wrote:
> >>
> >> On 2020-05-08, H.J. Lu wrote:
> >> >On Fri, May 8, 2020 at 8:12 AM Fangrui Song <maskray@google.com> wrote:
> >> >>
> >> >>
> >> >> On 2020-05-08, H.J. Lu wrote:
> >> >> >On Fri, May 8, 2020 at 7:54 AM Fangrui Song <maskray@google.com> wrote:
> >> >> >>
> >> >> >> On 2020-05-08, H.J. Lu wrote:
> >> >> >> >On Wed, May 6, 2020 at 11:42 AM Fangrui Song <maskray@google.com> wrote:
> >> >> >> >>
> >> >> >> >> On 2020-05-05, H.J. Lu wrote:
> >> >> >> >> >On Tue, May 5, 2020 at 9:55 AM Fangrui Song <maskray@google.com> wrote:
> >> >> >> >> >>
> >> >> >> >> >>
> >> >> >> >> >> On 2020-05-05, H.J. Lu wrote:
> >> >> >> >> >> >On Tue, May 5, 2020 at 8:30 AM Fangrui Song <maskray@google.com> wrote:
> >> >> >> >> >> >>
> >> >> >> >> >> >> On 2020-05-05, H.J. Lu wrote:
> >> >> >> >> >> >> >On Mon, May 4, 2020 at 7:10 PM Fangrui Song <maskray@google.com> wrote:
> >> >> >> >> >> >> >>
> >> >> >> >> >> >> >> On 2020-05-04, H.J. Lu wrote:
> >> >> >> >> >> >> >> >On Mon, May 4, 2020 at 10:48 AM Fangrui Song <maskray@google.com> wrote:
> >> >> >> >> >> >> >> >>
> >> >> >> >> >> >> >> >> On 2020-05-03, H.J. Lu wrote:
> >> >> >> >> >> >> >> >> >On Sat, May 2, 2020 at 11:15 PM Fangrui Song via Binutils
> >> >> >> >> >> >> >> >> ><binutils@sourceware.org> wrote:
> >> >> >> >> >> >> >> >> >>
> >> >> >> >> >> >> >> >> >> PR ld/25910
> >> >> >> >> >> >> >> >> >> * ldlang.c (export_dynamic_symbol_list): New.
> >> >> >> >> >> >> >> >> >> (ldlang_add_export_dynamic_symbol): New.
> >> >> >> >> >> >> >> >> >> (lang_place_export_dynamic_symbols): New.
> >> >> >> >> >> >> >> >> >> (lang_process): Handle export_dynamic_symbol_list.
> >> >> >> >> >> >> >> >> >> * ldlang.h (ldlang_add_export_dynamic_symbol): New.
> >> >> >> >> >> >> >> >> >> * ldlex.h (option_values): Add OPTION_EXPORT_DYNAMIC_SYMBOL.
> >> >> >> >> >> >> >> >> >> * lexsup.c (ld_options): Add entry for OPTION_EXPORT_DYNAMIC_SYMBOL.
> >> >> >> >> >> >> >> >> >> (parse_args): Handle it.
> >> >> >> >> >> >> >> >> >> * ld.texi: Add --export-dynamic-symbol documentation.
> >> >> >> >> >> >> >> >> >> * testsuite/ld-undefined/export-dynamic-symbol.exp: Run new test.
> >> >> >> >> >> >> >> >> >> * testsuite/ld-undefined/export-dynamic-symbol-1.d: New.
> >> >> >> >> >> >> >> >> >> ---
> >> >> >> >> >> >> >> >> >> ld/ld.texi | 8 +++++
> >> >> >> >> >> >> >> >> >> ld/ldlang.c | 26 ++++++++++++++
> >> >> >> >> >> >> >> >> >> ld/ldlang.h | 2 ++
> >> >> >> >> >> >> >> >> >> ld/ldlex.h | 1 +
> >> >> >> >> >> >> >> >> >> ld/lexsup.c | 7 ++++
> >> >> >> >> >> >> >> >> >> .../ld-undefined/export-dynamic-symbol-1.d | 8 +++++
> >> >> >> >> >> >> >> >> >> .../ld-undefined/export-dynamic-symbol.exp | 35 +++++++++++++++++++
> >> >> >> >> >> >> >> >> >> 7 files changed, 87 insertions(+)
> >> >> >> >> >> >> >> >> >> create mode 100644 ld/testsuite/ld-undefined/export-dynamic-symbol-1.d
> >> >> >> >> >> >> >> >> >> create mode 100644 ld/testsuite/ld-undefined/export-dynamic-symbol.exp
> >> >> >> >> >> >> >> >> >>
> >> >> >> >> >> >> >> >> >> diff --git a/ld/ld.texi b/ld/ld.texi
> >> >> >> >> >> >> >> >> >> index 4dc78e65fa..b3dc95f314 100644
> >> >> >> >> >> >> >> >> >> --- a/ld/ld.texi
> >> >> >> >> >> >> >> >> >> +++ b/ld/ld.texi
> >> >> >> >> >> >> >> >> >> @@ -569,6 +569,14 @@ 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{symbol}
> >> >> >> >> >> >> >> >> >> +@cindex export dynamic symbol
> >> >> >> >> >> >> >> >> >> +@item --export-dynamic-symbol=@var{symbol}
> >> >> >> >> >> >> >> >> >> +Specify a symbol that should be added to the dynamic symbol table.
> >> >> >> >> >> >> >> >> >> +Additionally, force @var{symbol} to be entered in the output file as an
> >> >> >> >> >> >> >> >> >> +undefined symbol. Doing this may, for example, trigger linking of additional
> >> >> >> >> >> >> >> >> >> +modules from archives.
> >> >> >> >> >> >> >> >> >> +
> >> >> >> >> >> >> >> >> >> @ifclear SingleFormat
> >> >> >> >> >> >> >> >> >> @cindex big-endian objects
> >> >> >> >> >> >> >> >> >> @cindex endianness
> >> >> >> >> >> >> >> >> >> diff --git a/ld/ldlang.c b/ld/ldlang.c
> >> >> >> >> >> >> >> >> >> index b2cdb3603a..e7ecdfeaf0 100644
> >> >> >> >> >> >> >> >> >> --- a/ld/ldlang.c
> >> >> >> >> >> >> >> >> >> +++ b/ld/ldlang.c
> >> >> >> >> >> >> >> >> >> @@ -3910,6 +3910,26 @@ lang_place_undefineds (void)
> >> >> >> >> >> >> >> >> >> insert_undefined (ptr->name);
> >> >> >> >> >> >> >> >> >> }
> >> >> >> >> >> >> >> >> >>
> >> >> >> >> >> >> >> >> >> +static struct bfd_sym_chain export_dynamic_symbol_list = { NULL, NULL };
> >> >> >> >> >> >> >> >> >> +
> >> >> >> >> >> >> >> >> >> +void
> >> >> >> >> >> >> >> >> >> +ldlang_add_export_dynamic_symbol (const char *const name)
> >> >> >> >> >> >> >> >> >> +{
> >> >> >> >> >> >> >> >> >> + struct bfd_sym_chain *sym;
> >> >> >> >> >> >> >> >> >> + sym = stat_alloc (sizeof (*sym));
> >> >> >> >> >> >> >> >> >> + sym->name = xstrdup (name);
> >> >> >> >> >> >> >> >> >> + sym->next = export_dynamic_symbol_list.next;
> >> >> >> >> >> >> >> >> >> + export_dynamic_symbol_list.next = sym;
> >> >> >> >> >> >> >> >> >> +}
> >> >> >> >> >> >> >> >> >> +
> >> >> >> >> >> >> >> >> >> +static void
> >> >> >> >> >> >> >> >> >> +lang_place_export_dynamic_symbols (void)
> >> >> >> >> >> >> >> >> >> +{
> >> >> >> >> >> >> >> >> >> + struct bfd_sym_chain *sym;
> >> >> >> >> >> >> >> >> >> + for (sym = export_dynamic_symbol_list.next; sym != NULL; sym = sym->next)
> >> >> >> >> >> >> >> >> >> + insert_undefined (sym->name);
> >> >> >> >> >> >> >> >> >> +}
> >> >> >> >> >> >> >> >> >> +
> >> >> >> >> >> >> >> >> >> /* Structure used to build the list of symbols that the user has required
> >> >> >> >> >> >> >> >> >> be defined. */
> >> >> >> >> >> >> >> >> >>
> >> >> >> >> >> >> >> >> >> @@ -7795,6 +7815,10 @@ void
> >> >> >> >> >> >> >> >> >> lang_process (void)
> >> >> >> >> >> >> >> >> >> {
> >> >> >> >> >> >> >> >> >> /* Finalize dynamic list. */
> >> >> >> >> >> >> >> >> >> + struct bfd_sym_chain *sym;
> >> >> >> >> >> >> >> >> >> + for (sym = export_dynamic_symbol_list.next; sym != NULL; sym = sym->next)
> >> >> >> >> >> >> >> >> >> + lang_append_dynamic_list (
> >> >> >> >> >> >> >> >> >> + lang_new_vers_pattern (NULL, sym->name, NULL, FALSE));
> >> >> >> >> >> >> >> >> >> if (link_info.dynamic_list)
> >> >> >> >> >> >> >> >> >> lang_finalize_version_expr_head (&link_info.dynamic_list->head);
> >> >> >> >> >> >> >> >> >>
> >> >> >> >> >> >> >> >> >> @@ -7808,6 +7832,8 @@ lang_process (void)
> >> >> >> >> >> >> >> >> >>
> >> >> >> >> >> >> >> >> >> /* Add to the hash table all undefineds on the command line. */
> >> >> >> >> >> >> >> >> >> lang_place_undefineds ();
> >> >> >> >> >> >> >> >> >> + /* Add --export-dynamic-symbol symbols to the hash table. */
> >> >> >> >> >> >> >> >> >> + lang_place_export_dynamic_symbols ();
> >> >> >> >> >> >> >> >> >>
> >> >> >> >> >> >> >> >> >> if (!bfd_section_already_linked_table_init ())
> >> >> >> >> >> >> >> >> >> einfo (_("%F%P: can not create hash table: %E\n"));
> >> >> >> >> >> >> >> >> >> diff --git a/ld/ldlang.h b/ld/ldlang.h
> >> >> >> >> >> >> >> >> >> index 2aa3930f95..8c004b173c 100644
> >> >> >> >> >> >> >> >> >> --- a/ld/ldlang.h
> >> >> >> >> >> >> >> >> >> +++ b/ld/ldlang.h
> >> >> >> >> >> >> >> >> >> @@ -606,6 +606,8 @@ extern lang_output_section_statement_type *next_matching_output_section_statemen
> >> >> >> >> >> >> >> >> >> (lang_output_section_statement_type *, int);
> >> >> >> >> >> >> >> >> >> extern void ldlang_add_undef
> >> >> >> >> >> >> >> >> >> (const char *const, bfd_boolean);
> >> >> >> >> >> >> >> >> >> +extern void ldlang_add_export_dynamic_symbol
> >> >> >> >> >> >> >> >> >> + (const char *const);
> >> >> >> >> >> >> >> >> >> extern void ldlang_add_require_defined
> >> >> >> >> >> >> >> >> >> (const char *const);
> >> >> >> >> >> >> >> >> >> extern void lang_add_output_format
> >> >> >> >> >> >> >> >> >> diff --git a/ld/ldlex.h b/ld/ldlex.h
> >> >> >> >> >> >> >> >> >> index 22b928d2d9..70f2da5636 100644
> >> >> >> >> >> >> >> >> >> --- a/ld/ldlex.h
> >> >> >> >> >> >> >> >> >> +++ b/ld/ldlex.h
> >> >> >> >> >> >> >> >> >> @@ -81,6 +81,7 @@ enum option_values
> >> >> >> >> >> >> >> >> >> OPTION_DYNAMIC_LIST_CPP_NEW,
> >> >> >> >> >> >> >> >> >> OPTION_DYNAMIC_LIST_CPP_TYPEINFO,
> >> >> >> >> >> >> >> >> >> OPTION_DYNAMIC_LIST_DATA,
> >> >> >> >> >> >> >> >> >> + OPTION_EXPORT_DYNAMIC_SYMBOL,
> >> >> >> >> >> >> >> >> >> OPTION_WARN_COMMON,
> >> >> >> >> >> >> >> >> >> OPTION_WARN_CONSTRUCTORS,
> >> >> >> >> >> >> >> >> >> OPTION_WARN_FATAL,
> >> >> >> >> >> >> >> >> >> diff --git a/ld/lexsup.c b/ld/lexsup.c
> >> >> >> >> >> >> >> >> >> index d1955b9afa..0a0c2f2873 100644
> >> >> >> >> >> >> >> >> >> --- a/ld/lexsup.c
> >> >> >> >> >> >> >> >> >> +++ b/ld/lexsup.c
> >> >> >> >> >> >> >> >> >> @@ -504,6 +504,8 @@ 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_("Read dynamic list"), 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},
> >> >> >> >> >> >> >> >> >> @@ -1425,6 +1427,11 @@ parse_args (unsigned argc, char **argv)
> >> >> >> >> >> >> >> >> >> if (opt_symbolic == symbolic)
> >> >> >> >> >> >> >> >> >> opt_symbolic = symbolic_unset;
> >> >> >> >> >> >> >> >> >> break;
> >> >> >> >> >> >> >> >> >> + case OPTION_EXPORT_DYNAMIC_SYMBOL:
> >> >> >> >> >> >> >> >> >> + ldlang_add_export_dynamic_symbol (optarg);
> >> >> >> >> >> >> >> >> >> + if (opt_dynamic_list != dynamic_list_data)
> >> >> >> >> >> >> >> >> >> + opt_dynamic_list = dynamic_list;
> >> >> >> >> >> >> >> >> >> + break;
> >> >> >> >> >> >> >> >> >> case OPTION_WARN_COMMON:
> >> >> >> >> >> >> >> >> >> config.warn_common = TRUE;
> >> >> >> >> >> >> >> >> >> break;
> >> >> >> >> >> >> >> >> >> diff --git a/ld/testsuite/ld-undefined/export-dynamic-symbol-1.d b/ld/testsuite/ld-undefined/export-dynamic-symbol-1.d
> >> >> >> >> >> >> >> >> >> new file mode 100644
> >> >> >> >> >> >> >> >> >> index 0000000000..768bf0abd6
> >> >> >> >> >> >> >> >> >> --- /dev/null
> >> >> >> >> >> >> >> >> >> +++ b/ld/testsuite/ld-undefined/export-dynamic-symbol-1.d
> >> >> >> >> >> >> >> >> >> @@ -0,0 +1,8 @@
> >> >> >> >> >> >> >> >> >> +#name: --export-dynamic-symbol foo archive
> >> >> >> >> >> >> >> >> >> +#source: require-defined.s
> >> >> >> >> >> >> >> >> >> +#ld: -pie --export-dynamic-symbol foo tmpdir/libentry.a
> >> >> >> >> >> >> >> >> >
> >> >> >> >> >> >> >> >> >I assume that it supports
> >> >> >> >> >> >> >> >> >
> >> >> >> >> >> >> >> >> >$ ld -pie --export-dynamic-symbol foo --export-dynamic-symbol bar ...
> >> >> >> >> >> >> >> >> >
> >> >> >> >> >> >> >> >> >Please add another --export-dynamic-symbol to your test.
> >> >> >> >> >> >> >> >> >
> >> >> >> >> >> >> >> >> >--
> >> >> >> >> >> >> >> >> >H.J.
> >> >> >> >> >> >> >> >>
> >> >> >> >> >> >> >> >> I face a test difficulty. If I add another `#nm:`, runtest complains:
> >> >> >> >> >> >> >> >>
> >> >> >> >> >> >> >> >> % cd Debug/ld
> >> >> >> >> >> >> >> >> % runtest --tool ld --srcdir ../../ld/testsuite/ export-dynamic-symbol.exp
> >> >> >> >> >> >> >> >> ...
> >> >> >> >> >> >> >> >> ERROR: option nm multiply set in ../../ld/testsuite/ld-undefined/export-dynamic-symbol-1.d
> >> >> >> >> >> >> >> >>
> >> >> >> >> >> >> >> >> There may also be a problem of symbol table order determinism. I don't
> >> >> >> >> >> >> >> >> know whether another symbol may be ordered before foo in some ports and
> >> >> >> >> >> >> >> >> after foo in other ports.
> >> >> >> >> >> >> >> >>
> >> >> >> >> >> >> >> >> Honestly, I think for a number of tests, even if they test generic
> >> >> >> >> >> >> >> >> behavior, it might be fine to restrict them to run on certain hosts,
> >> >> >> >> >> >> >> >> e.g. Linux x86. What I know about testing is lacking, though, I don't
> >> >> >> >> >> >> >> >> know what can be tested.
> >> >> >> >> >> >> >> >>
> >> >> >> >> >> >> >> >> Ideally `#nm:` should just be free-form shell scripts but unfortunately
> >> >> >> >> >> >> >> >> it seems to support very limited features (undocumented?)
> >> >> >> >> >> >> >> >
> >> >> >> >> >> >> >> >You can't add another #nm. But you can pass additional options to nm.
> >> >> >> >> >> >> >> >
> >> >> >> >> >> >> >> >--
> >> >> >> >> >> >> >> >H.J.
> >> >> >> >> >> >> >>
> >> >> >> >> >> >> >> Attached PATCH v2.
> >> >> >> >> >> >> >>
> >> >> >> >> >> >> >> Added export-dynamic-symbol-2.d
> >> >> >> >> >> >> >
> >> >> >> >> >> >> >There is
> >> >> >> >> >> >> >
> >> >> >> >> >> >> >'--dynamic-list=DYNAMIC-LIST-FILE'
> >> >> >> >> >> >> > Specify the name of a dynamic list file to the linker. This is
> >> >> >> >> >> >> > typically used when creating shared libraries to specify a list of
> >> >> >> >> >> >> > global symbols whose references shouldn't be bound to the
> >> >> >> >> >> >> > definition within the shared library, or creating dynamically
> >> >> >> >> >> >> > linked executables to specify a list of symbols which should be
> >> >> >> >> >> >> > added to the symbol table in the executable. This option is only
> >> >> >> >> >> >> > meaningful on ELF platforms which support shared libraries.
> >> >> >> >> >> >> >
> >> >> >> >> >> >> >The new --export-dynamic-symbol option puts it on command-line
> >> >> >> >> >> >> >and implicitly adds -u. This makes the new option different from
> >> >> >> >> >> >> >--dynamic-list. I don't think -u should be added implicitly. If needed,
> >> >> >> >> >> >> >you should add another option to add -u for all symbols on dynamic
> >> >> >> >> >> >> >list.
> >> >> >> >> >> >> >
> >> >> >> >> >> >> >--
> >> >> >> >> >> >> >H.J.
> >> >> >> >> >> >>
> >> >> >> >> >> >> I would also hope gold did not add -u. I don't particularly like it (see
> >> >> >> >> >> >> also https://reviews.llvm.org/D43103)
> >> >> >> >> >> >
> >> >> >> >> >> >Please drop implicit -u.
> >> >> >> >> >>
> >> >> >> >> >> Done. Attached PATCH v3.
> >> >> >> >> >> Improved tests to check a glob pattern and multiple --export-dynamic-symbol.
> >> >> >> >> >>
> >> >> >> >> >> Moved ld-undefined/ to ld-dynamic/ since the feature is decoupled from -u now.
> >> >> >> >> >>
> >> >> >> >> >> >> If you think we can correct this, I think it should be fine.
> >> >> >> >> >> >
> >> >> >> >> >> >Please open a gold bug for this.
> >> >> >> >> >> >
> >> >> >> >> >> >Thanks.
> >> >> >> >> >> >
> >> >> >> >> >> >--
> >> >> >> >> >> >H.J.
> >> >> >> >> >>
> >> >> >> >> >> Filed https://sourceware.org/bugzilla/show_bug.cgi?id=25925 (--export-dynamic-symbol should drop implicit -u)
> >> >> >> >> >>
> >> >> >> >> >>
> >> >> >> >> >> I may have to migrate some internal projects if they rely on the
> >> >> >> >> >> --export-dynamic-symbol semantics, but hopefully there will not be much
> >> >> >> >> >> work. I am glad that --export-dynamic-symbol semantic will be orthogonal!
> >> >> >> >> >
> >> >> >> >> >+ case OPTION_EXPORT_DYNAMIC_SYMBOL:
> >> >> >> >> >+ ldlang_add_export_dynamic_symbol (optarg);
> >> >> >> >> >
> >> >> >> >> >Can you simply call
> >> >> >> >> >
> >> >> >> >> >lang_append_dynamic_list (lang_new_vers_pattern (NULL, optarg, NULL, FALSE));
> >> >> >> >> >
> >> >> >> >> >here?
> >> >> >> >> >
> >> >> >> >> >--
> >> >> >> >> >H.J.
> >> >> >> >>
> >> >> >> >> Attached PATCH v4, which also handles -shared. The previous patches do not handle -shared.
> >> >> >> >> Added two tests to ld-elf/shared.exp
> >> >> >> >>
> >> >> >> >> The updated semantics:
> >> >> >> >>
> >> >> >> >> + @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{--dynamic-list} is not
> >> >> >> >> + specified. This option is only meaningful on ELF platforms which
> >> >> >> >> + support shared libraries.
> >> >> >> >>
> >> >> >> >> i.e. --export-dynamic-symbol is like addition to --dynamic-list,
> >> >> >> >> except: -shared --export-dynamic-symbol without --dynamic-list will not
> >> >> >> >> act as -Bsymbolic.
> >> >> >> >>
> >> >> >> >> In the option processing loop, we cannot call lang_append_dynamic_list
> >> >> >> >> because when -shared is specified but --dynamic-list is not specified,
> >> >> >> >> --export-dynamic-symbol should be a no-op.
> >> >> >> >
> >> >> >> >--dynamic-list implies -Bsymbolic. If we add --export-dynamic-symbol,
> >> >> >> >we should also add --export-dynamic-symbol-list, which is similar to
> >> >> >> >--dynamic-list, but without -Bsymbolic.
> >> >> >>
> >> >> >> --export-dynamic-symbol-list a.list where a.list is a plain text like:
> >> >> >> foo
> >> >> >> bar
> >> >> >> ?
> >> >> >
> >> >> >I prefer to use the same format as --dynamic-list.
> >> >> >
> >> >> >> The feature can be provided by a response file @a.rsp
> >> >> >> --export-dynamic-symbol foo
> >> >> >> --export-dynamic-symbol bar
> >> >>
> >> >> Adding --export-dynamic-symbol-list is fine. We can implement that separately.
> >> >
> >> >Since implement --export-dynamic-symbol-list at the same time may impact how
> >> >--export-dynamic-symbol is implemented, they should be added together.
> >>
> >> OK. Added --export-dynamic-symbol-list as well.
> >>
> >> Retitled.
> >
> >A couple comments:
>
> Thanks for the review!
>
> >1. Please add an entry to ld/NEWS.
> >2. Please a note to ld.texi for the difference between --dynamic-list and
> >--export-dynamic-symbol.
>
> >3. What happens when there are both --dynamic-list and and
> >--export-dynamic-symbol, with and without -Bsymbolic?
>
> --export-symbol-symbol adds additional entries to --dynamic-list.
I don't think so. See below.
>
> I'd expect --dynamic-list to override -Bsymbolic (i.e. --dynamic-list is a
> refined -Bsymbolic).
> gold and
> LLD (https://github.com/llvm/llvm-project/blob/master/lld/ELF/Symbols.cpp#L368)
> behave this way.
> GNU ld seems to make every symbol symbolic.
Ld manual says
'--dynamic-list=DYNAMIC-LIST-FILE'
Specify the name of a dynamic list file to the linker. This is
typically used when creating shared libraries to specify a list of
global symbols whose references shouldn't be bound to the
definition within the shared library, or creating dynamically
linked executables to specify a list of symbols which should be
added to the symbol table in the executable. This option is only
meaningful on ELF platforms which support shared libraries.
The format of the dynamic list is the same as the version node
without scope and node name. See *note VERSION:: for more
information.
When producing a shared library, --dynamic-list implies -Bsymbolic
with exception for the symbols on the dynamic list.
> This can be tested with:
>
> .globl main, foo, bar
> main: call foo
> foo: call bar
> bar: ret
>
> // a.list
> { foo; };
>
> It is also fine if you think -Bsymbolic should override --dynamic-list.
> (Please add a test for that so that I know how to test --export-dynamic-list)
> We can then file a gold bug.
>
> >4. Can you reuse lang_append_dynamic_list to implement
> >--export-dynamic-symbol?
>
> This is difficult. It seems that another global variable needs to be introduced.
> yacc code duplication may not be that bad compared with the alternative.
Since --export-dynamic-symbol is a NOP for -shared and identical with
--dynamic-list otherwise, let's only consider the -shared case:
1. Without -Bsymbolic nor --dynamic-list, --export-dynamic-symbol should
be dropped.
2. With -Bsymbolic or --dynamic-list, --export-dynamic-symbol should also
be dropped since --export-dynamic-symbol doesn't change symbol binding.
I think we should add a bit field to bfd_elf_version_expr to indicate if symbol
binding should be symbolic (-Bsymbolic) and use lang_append_dynamic_list
for both --dynamic-list and --export-dynamic-symbol. The only
difference is that
symbols from --export-dynamic-symbol aren't symbolic and can be dropped for
-shared.
--
H.J.
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