[PATCH] ld: Add --export-dynamic-symbol
Fangrui Song
maskray@google.com
Mon May 4 17:48:51 GMT 2020
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?)
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