RFC: ld: Add --text-section-ordering-file (version 2)
H.J. Lu
hjl.tools@gmail.com
Mon May 6 18:27:40 GMT 2024
On Sun, Apr 28, 2024 at 5:12 PM Alan Modra <amodra@gmail.com> wrote:
>
> On Fri, Apr 26, 2024 at 10:13:48PM +0930, Alan Modra wrote:
> > On Fri, Apr 26, 2024 at 10:59:00AM +0100, Nick Clifton wrote:
> > > It could be done, but I like keeping things simple.
> >
> > Here's a completely untested implementation of the idea I'm proposing,
> > written just to show that the linker modifications are relatively
> > small. (There is a very good chance I've messed up list handling..)
> > What appears inside the --section-ordering-file output sections is
> > spliced in to corresponding output sections in the default script,
> > before the first input wild statement.
> >
> > I like keeping things simple too. This should work without modifying
> > default linker scripts (and user scripts!), and allows all the usual
> > ways of specifying input sections. That means you can use constructs
> > like EXCLUDE_FILE, SORT, KEEP, *(.text .rdata) vs. *(.text) *(.rdata)
> > and so on.
>
> The patch wasn't too far wrong. I had some compile issues when plugin
> support was disabled, and it is probably a bad idea to allow creation
> of new output sections via --section-ordering-file, so that is now
> disallowed.
>
> I'm not putting forward this patch as a finished work, it's just a
> demonstrator.
>
> What I'd like to see is:
> 1) Lose that horrible "INCLUDE section-ordering-file" requirement for
> existing scripts. Do you really want that put into every output
> section in every script in scripttempl/?
> 2) Parse the section ordering file in ldgram.y. An entry under file:
> would be appropriate, like we do for version scripts. That would
> at least lose the SECTIONS clause required by my demonstrator
> patch. You wouldn't necessarily need to follow existing
> specification of output and input sections, or to support other
> things allowed in output sections, but I do think a syntax with an
> explicit output section is a good idea. ie. not one where the
> output .text is deduced from the input .text.mumble.
>
>
> diff --git a/ld/ld.h b/ld/ld.h
> index fcdd9a2c083..15d9dc262b6 100644
> --- a/ld/ld.h
> +++ b/ld/ld.h
> @@ -196,6 +196,8 @@ typedef struct
>
> /* Default linker script. */
> char *default_script;
> +
> + char *section_ordering_file;
> } args_type;
>
> extern args_type command_line;
> @@ -325,6 +327,7 @@ extern ld_config_type config;
>
> extern FILE * saved_script_handle;
> extern bool force_make_executable;
> +extern bool in_section_ordering;
>
> extern int yyparse (void);
> extern void add_cref (const char *, bfd *, asection *, bfd_vma);
> diff --git a/ld/ldlang.c b/ld/ldlang.c
> index 54d1af62ebe..6424d4764d1 100644
> --- a/ld/ldlang.c
> +++ b/ld/ldlang.c
> @@ -1299,6 +1299,7 @@ output_section_statement_newfunc (struct bfd_hash_entry *entry,
> ret->s.output_section_statement.section_alignment = NULL;
> ret->s.output_section_statement.block_value = 1;
> lang_list_init (&ret->s.output_section_statement.children);
> + lang_list_init (&ret->s.output_section_statement.sort_children);
> lang_statement_append (stat_ptr, &ret->s, &ret->s.header.next);
>
> /* For every output section statement added to the list, except the
> @@ -7613,13 +7614,21 @@ lang_enter_output_section_statement (const char *output_section_statement_name,
> lang_output_section_statement_type *os;
>
> os = lang_output_section_statement_lookup (output_section_statement_name,
> - constraint, 2);
> + constraint,
> + in_section_ordering ? 0 : 2);
> + if (os == NULL)
> + einfo (_("%F%P:%pS: error: output section must already exist\n"), NULL);
> current_section = os;
>
> + /* Make next things chain into subchain of this. */
> + push_stat_ptr (in_section_ordering ? &os->sort_children : &os->children);
> +
> + if (in_section_ordering)
> + return os;
> +
> if (os->addr_tree == NULL)
> - {
> - os->addr_tree = address_exp;
> - }
> + os->addr_tree = address_exp;
> +
> os->sectype = sectype;
> if (sectype == type_section || sectype == typed_readonly_section)
> os->sectype_value = sectype_value;
> @@ -7629,9 +7638,6 @@ lang_enter_output_section_statement (const char *output_section_statement_name,
> os->flags = SEC_NO_FLAGS;
> os->block_value = 1;
>
> - /* Make next things chain into subchain of this. */
> - push_stat_ptr (&os->children);
> -
> os->align_lma_with_input = align_with_input == ALIGN_WITH_INPUT;
> if (os->align_lma_with_input && align != NULL)
> einfo (_("%F%P:%pS: error: align with input and explicit align specified\n"),
> @@ -7971,21 +7977,6 @@ find_rescan_insertion (lang_input_statement_type *add)
> return iter;
> }
>
> -/* Insert SRCLIST into DESTLIST after given element by chaining
> - on FIELD as the next-pointer. (Counterintuitively does not need
> - a pointer to the actual after-node itself, just its chain field.) */
> -
> -static void
> -lang_list_insert_after (lang_statement_list_type *destlist,
> - lang_statement_list_type *srclist,
> - lang_statement_union_type **field)
> -{
> - *(srclist->tail) = *field;
> - *field = srclist->head;
> - if (destlist->tail == field)
> - destlist->tail = srclist->tail;
> -}
> -
> /* Detach new nodes added to DESTLIST since the time ORIGLIST
> was taken as a copy of it and leave them in ORIGLIST. */
>
> @@ -8033,6 +8024,21 @@ find_next_input_statement (lang_statement_union_type **s)
> }
> #endif /* BFD_SUPPORTS_PLUGINS */
>
> +/* Insert SRCLIST into DESTLIST after given element by chaining
> + on FIELD as the next-pointer. (Counterintuitively does not need
> + a pointer to the actual after-node itself, just its chain field.) */
> +
> +static void
> +lang_list_insert_after (lang_statement_list_type *destlist,
> + lang_statement_list_type *srclist,
> + lang_statement_union_type **field)
> +{
> + *(srclist->tail) = *field;
> + *field = srclist->head;
> + if (destlist->tail == field)
> + destlist->tail = srclist->tail;
> +}
> +
> /* Add NAME to the list of garbage collection entry points. */
>
> void
> @@ -8127,9 +8133,34 @@ reset_resolved_wilds (void)
> lang_for_each_statement (reset_one_wild);
> }
>
> +/* For each output section statement, splice any entries on the
> + sort_children list before the first wild statement on the children
> + list. */
> +
> +static void
> +lang_os_merge_sort_children (void)
> +{
> + lang_output_section_statement_type *os;
> + for (os = (void *) lang_os_list.head; os != NULL; os = os->next)
> + {
> + if (os->sort_children.head != NULL)
> + {
> + lang_statement_union_type **where;
> + for (where = &os->children.head;
> + *where != NULL;
> + where = &(*where)->header.next)
> + if ((*where)->header.type == lang_wild_statement_enum)
> + break;
> + lang_list_insert_after (&os->children, &os->sort_children, where);
> + }
> + }
> +}
> +
> void
> lang_process (void)
> {
> + lang_os_merge_sort_children ();
> +
> /* Finalize dynamic list. */
> if (link_info.dynamic_list)
> lang_finalize_version_expr_head (&link_info.dynamic_list->head);
> @@ -8817,6 +8848,10 @@ lang_leave_output_section_statement (fill_type *fill, const char *memspec,
> lang_output_section_phdr_list *phdrs,
> const char *lma_memspec)
> {
> + pop_stat_ptr ();
> + if (in_section_ordering)
> + return;
> +
> lang_get_regions (¤t_section->region,
> ¤t_section->lma_region,
> memspec, lma_memspec,
> @@ -8825,7 +8860,6 @@ lang_leave_output_section_statement (fill_type *fill, const char *memspec,
>
> current_section->fill = fill;
> current_section->phdrs = phdrs;
> - pop_stat_ptr ();
> }
>
> /* Set the output format type. -oformat overrides scripts. */
> diff --git a/ld/ldlang.h b/ld/ldlang.h
> index ea1c26d00f3..91947c56fda 100644
> --- a/ld/ldlang.h
> +++ b/ld/ldlang.h
> @@ -162,6 +162,8 @@ typedef struct lang_output_section_statement_struct
>
> lang_output_section_phdr_list *phdrs;
>
> + lang_statement_list_type sort_children;
> +
> /* Used by ELF SHF_LINK_ORDER sorting. */
> void *data;
>
> diff --git a/ld/ldlex.h b/ld/ldlex.h
> index d575562a357..5708e6f5e34 100644
> --- a/ld/ldlex.h
> +++ b/ld/ldlex.h
> @@ -62,6 +62,7 @@ enum option_values
> OPTION_SONAME,
> OPTION_SORT_COMMON,
> OPTION_SORT_SECTION,
> + OPTION_SECTION_ORDERING_FILE,
> OPTION_STATS,
> OPTION_SYMBOLIC,
> OPTION_SYMBOLIC_FUNCTIONS,
> diff --git a/ld/ldmain.c b/ld/ldmain.c
> index fe389681bd3..77b57a9fd32 100644
> --- a/ld/ldmain.c
> +++ b/ld/ldmain.c
> @@ -90,6 +90,8 @@ bool version_printed;
> /* TRUE if we should demangle symbol names. */
> bool demangling;
>
> +bool in_section_ordering;
> +
> args_type command_line;
>
> ld_config_type config;
> @@ -446,6 +448,19 @@ main (int argc, char **argv)
> info_msg ("\n==================================================\n");
> }
>
> + if (command_line.section_ordering_file)
> + {
> + FILE *hold_script_handle;
> +
> + hold_script_handle = saved_script_handle;
> + ldfile_open_command_file (command_line.section_ordering_file);
> + saved_script_handle = hold_script_handle;
> + in_section_ordering = true;
> + parser_input = input_script;
> + yyparse ();
> + in_section_ordering = false;
> + }
> +
> if (command_line.force_group_allocation
> || !bfd_link_relocatable (&link_info))
> link_info.resolve_section_groups = true;
> diff --git a/ld/lexsup.c b/ld/lexsup.c
> index dad3b6059ed..0c337a4d170 100644
> --- a/ld/lexsup.c
> +++ b/ld/lexsup.c
> @@ -487,6 +487,9 @@ static const struct ld_option ld_options[] =
> { {"sort-section", required_argument, NULL, OPTION_SORT_SECTION},
> '\0', N_("name|alignment"),
> N_("Sort sections by name or maximum alignment"), TWO_DASHES },
> + { {"section-ordering-file", required_argument, NULL, OPTION_SECTION_ORDERING_FILE},
> + '\0', N_("FILE"),
> + N_("Sort sections by statements in FILE"), TWO_DASHES },
> { {"spare-dynamic-tags", required_argument, NULL, OPTION_SPARE_DYNAMIC_TAGS},
> '\0', N_("COUNT"), N_("How many tags to reserve in .dynamic section"),
> TWO_DASHES },
> @@ -1400,6 +1403,9 @@ parse_args (unsigned argc, char **argv)
> einfo (_("%F%P: invalid section sorting option: %s\n"),
> optarg);
> break;
> + case OPTION_SECTION_ORDERING_FILE:
> + command_line.section_ordering_file = optarg;
> + break;
> case OPTION_STATS:
> config.stats = true;
> break;
> diff --git a/ld/testsuite/ld-scripts/section-order-1a.d b/ld/testsuite/ld-scripts/section-order-1a.d
> new file mode 100644
> index 00000000000..03d848b83ea
> --- /dev/null
> +++ b/ld/testsuite/ld-scripts/section-order-1a.d
> @@ -0,0 +1,17 @@
> +#source: section-order-1b.s
> +#source: section-order-1a.s
> +#source: start.s
> +#ld: --section-ordering-file section-order-1a.t
> +#nm: -n
> +
> +#...
> +[0-9a-f]+ T yyy
> +#...
> +[0-9a-f]+ T bar
> +#...
> +[0-9a-f]+ T [_]+start
> +#...
> +[0-9a-f]+ T xxx
> +#...
> +[0-9a-f]+ T foo
> +#pass
> diff --git a/ld/testsuite/ld-scripts/section-order-1a.s b/ld/testsuite/ld-scripts/section-order-1a.s
> new file mode 100644
> index 00000000000..17d311fd58f
> --- /dev/null
> +++ b/ld/testsuite/ld-scripts/section-order-1a.s
> @@ -0,0 +1,19 @@
> + .section .text.foo
> + .globl foo
> +foo:
> + .dc.a 0
> +
> + .section .text.bar
> + .globl bar
> +bar:
> + .dc.a 0
> +
> + .section .data.small
> + .globl small
> +small:
> + .dc.a 0
> +
> + .section .bar
> + .global bar
> +bart:
> + .dc.a 0
> diff --git a/ld/testsuite/ld-scripts/section-order-1a.t b/ld/testsuite/ld-scripts/section-order-1a.t
> new file mode 100644
> index 00000000000..e3786818fea
> --- /dev/null
> +++ b/ld/testsuite/ld-scripts/section-order-1a.t
> @@ -0,0 +1,15 @@
> +SECTIONS
> +{
> + .text : {
> + *(.text.yyy)
> + *(.text.b?r)
> + *(.text)
> + *(.text.xxx .text.foo)
> + }
> +
> + .data : {
> + *(.data.small)
> + *(.big*)
> + *(.bar .baz*)
> + }
> +}
> diff --git a/ld/testsuite/ld-scripts/section-order-1b.d b/ld/testsuite/ld-scripts/section-order-1b.d
> new file mode 100644
> index 00000000000..41b4d16097e
> --- /dev/null
> +++ b/ld/testsuite/ld-scripts/section-order-1b.d
> @@ -0,0 +1,17 @@
> +#source: section-order-1a.s
> +#source: section-order-1b.s
> +#source: start.s
> +#ld: --section-ordering-file section-order-1b.t
> +#nm: -n
> +
> +#...
> +[0-9a-f]+ T yyy
> +#...
> +[0-9a-f]+ T bar
> +#...
> +[0-9a-f]+ T [_]+start
> +#...
> +[0-9a-f]+ T xxx
> +#...
> +[0-9a-f]+ T foo
> +#pass
> diff --git a/ld/testsuite/ld-scripts/section-order-1b.s b/ld/testsuite/ld-scripts/section-order-1b.s
> new file mode 100644
> index 00000000000..7fe103d0ea6
> --- /dev/null
> +++ b/ld/testsuite/ld-scripts/section-order-1b.s
> @@ -0,0 +1,19 @@
> + .section .text.xxx
> + .globl xxx
> +xxx:
> + .dc.a 0
> +
> + .section .text.yyy
> + .globl yyy
> +yyy:
> + .dc.a 0
> +
> + .section .big
> + .global big
> +big:
> + .dc.a 0
> +
> + .section .baz
> + .global baz
> +baz:
> + .dc.a 0
> diff --git a/ld/testsuite/ld-scripts/section-order-1b.t b/ld/testsuite/ld-scripts/section-order-1b.t
> new file mode 100644
> index 00000000000..896653b2608
> --- /dev/null
> +++ b/ld/testsuite/ld-scripts/section-order-1b.t
> @@ -0,0 +1,9 @@
> +SECTIONS {
> + .text : {
> + *(.text.yyy)
> + *(.text.b?r)
> + *(*t)
> + *(.text.xxx)
> + *(.text.foo)
> + }
> +}
> diff --git a/ld/testsuite/ld-scripts/section-order-1c.d b/ld/testsuite/ld-scripts/section-order-1c.d
> new file mode 100644
> index 00000000000..65819cbcb63
> --- /dev/null
> +++ b/ld/testsuite/ld-scripts/section-order-1c.d
> @@ -0,0 +1,13 @@
> +#source: section-order-1b.s
> +#source: section-order-1a.s
> +#source: start.s
> +#ld: --section-ordering-file section-order-1a.t
> +#nm: -n
> +
> +#...
> +[0-9a-f]+ D small
> +#...
> +[0-9a-f]+ D big
> +#...
> +[0-9a-f]+ D ba.*
> +#pass
> diff --git a/ld/testsuite/ld-scripts/section-order.exp b/ld/testsuite/ld-scripts/section-order.exp
> new file mode 100644
> index 00000000000..9b87e746cd1
> --- /dev/null
> +++ b/ld/testsuite/ld-scripts/section-order.exp
> @@ -0,0 +1,45 @@
> +# Test for --section-ordering-file FILE.
> +# Copyright (C) 2024 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.
> +
> +# The --section-ordering-file option is only supported by ELF and
> +# PE COFF linkers, which allow for arbitrarily named sections, eg:
> +# .text.*
> +if { !([is_elf_format] || [is_pecoff_format]) } {
> + return
> +}
> +
> +set old_ldflags $LDFLAGS
> +if { [istarget spu*-*-*] } then {
> + set LDFLAGS "$LDFLAGS --local-store 0:0 --no-overlays"
> +} elseif { [is_pecoff_format] } then {
> + set LDFLAGS "$LDFLAGS --image-base 0"
> +} elseif { [is_xcoff_format] } then {
> + set LDFLAGS "$LDFLAGS -bnogc"
> +}
> +
> +set test_list [lsort [glob -nocomplain $srcdir/$subdir/section-order*.d]]
> +foreach test_file $test_list {
> + set test_name [file rootname $test_file]
> + set map_file "tmpdir/[file tail $test_name].map"
> + verbose $test_name
> + run_dump_test $test_name
> +}
> +
> +set LDFLAGS $old_ldflags
> diff --git a/ld/testsuite/ld-scripts/start.s b/ld/testsuite/ld-scripts/start.s
> new file mode 100644
> index 00000000000..3f646267716
> --- /dev/null
> +++ b/ld/testsuite/ld-scripts/start.s
> @@ -0,0 +1,14 @@
> + .text
> + .global start /* Used by SH targets. */
> +start:
> + .global _start
> +_start:
> + .global __start
> +__start:
> + .global _mainCRTStartup /* Used by PE targets. */
> +_mainCRTStartup:
> + .global main /* Used by HPPA targets. */
> +main:
> + .globl _main /* Used by LynxOS targets. */
> +_main:
> + .dc.a 0
>
> --
> Alan Modra
Noah is also working on something similar.
--
H.J.
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