Fix problems with bss handling in linker scripts.

PR 16711 noted that gold allocates file space for BSS sections when using
a linker script. I've fixed that by rewriting set_section_addresses and
set_section_list_addresses to track the file offset separate from the
current virtual address, so that BSS sections do not move the file offset.
Now, if a series of BSS sections come at the end of a segment, we do not
allocate file space; but if a script forces them into the middle of a
segment, we will still allocate file space (matching Gnu ld behavior).
I've also added a warning when that happens.

That exposed another problem where orphan .bss sections were sometimes
placed in the middle of a segment. For example, if the script mentions
the .got section, but both .data and .bss are orphans, gold would put
both .data and .bss in front of .got. I've fixed that by ensuring that
orphan BSS sections are always placed after all other allocated sections.

It also exposed a problem where the SUBALIGN property is not handled
properly. The ld manual clearly states that it should override input section
alignment, whether greater or less than the given alignment, but gold would
only increase an input section's alignment. Gold would also place the output
section based on its original alignment before the SUBALIGN property took
effect, leading to a misaligned output section (where the input section
was properly aligned in memory, but was not aligned relative to the start
of the section), in violation of the ELF/gABI spec. I've fixed that by
making sure that the SUBALIGN property overrides the internal alignment of
the input sections as well as the external alignment of the output section.
This affected the behavior of script_test_2, which was written to expect
a misaligned section.

The net effect is, I think, improved compatibility with the BFD linker.
There are still cases where orphan placement differs, but the differences
should be rarer and less important. ALIGN and SUBALIGN behavior is closer,
but still not an exact match -- I still found cases where ld would create
a misaligned output section, and where gold will properly align it.

gold/
	PR gold/16711
	* output.cc (Output_section::set_final_data_size): Calculate data size
	based on relative offset rather than file offset.
	(Output_segment::set_section_addresses): Track file offset separately
	from address offset.
	(Output_segment::set_section_list_addresses): Add pfoff parameter.
	Track file offset separately.  Don't move file offset for BSS
	sections.
	* output.h (Output_segment::set_section_list_addresses): Add pfoff
	parameter.
	* script-sections.cc (Orphan_section_placement): Add PLACE_LAST_ALLOC.
	(Orphan_section_placement::Orphan_section_placement): Initialize it.
	(Orphan_section_placement::output_section_init): Track last allocated
	section.
	(Orphan_section_placement::find_place): Place BSS after last allocated
	section.
	(Output_section_element_input::set_section_addresses): Always override
	input section alignment when SUBALIGN is specified.
	(Output_section_definition::set_section_addresses): Override alignment
	of output section when SUBALIGN is specified.

	* testsuite/Makefile.am (script_test_15a, script_test_15b)
	(script_test_15c): New test cases.
	* testsuite/Makefile.in: Regenerate.
	* testsuite/script_test_2.cc: Adjust expected layout.
	* testsuite/script_test_15.c: New source file.
	* testsuite/script_test_15a.sh: New shell script.
	* testsuite/script_test_15a.t: New linker script.
	* testsuite/script_test_15b.sh: New shell script.
	* testsuite/script_test_15b.t: New linker script.
	* testsuite/script_test_15c.sh: New shell script.
	* testsuite/script_test_15c.t: New linker script.

1 files changed, 35 insertions, 3 deletions

diff --git a/gold/testsuite/Makefile.in b/gold/testsuite/Makefile.in
index 5fef3cf..a1d8b39 100644
--- a/gold/testsuite/Makefile.in
+++ b/gold/testsuite/Makefile.in
@@ -365,9 +365,11 @@ check_PROGRAMS = $(am__EXEEXT_1) $(am__EXEEXT_2) $(am__EXEEXT_3) \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	script_test_4 script_test_5 \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	script_test_6 script_test_7 \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	script_test_8 script_test_9 \
-@GCC_TRUE@@NATIVE_LINKER_TRUE@	script_test_14 dynamic_list \
-@GCC_TRUE@@NATIVE_LINKER_TRUE@	dynamic_list.stdout libthin1.a \
-@GCC_TRUE@@NATIVE_LINKER_TRUE@	libthin3.a libthinall.a \
+@GCC_TRUE@@NATIVE_LINKER_TRUE@	script_test_14 script_test_15a \
+@GCC_TRUE@@NATIVE_LINKER_TRUE@	script_test_15b script_test_15c \
+@GCC_TRUE@@NATIVE_LINKER_TRUE@	dynamic_list dynamic_list.stdout \
+@GCC_TRUE@@NATIVE_LINKER_TRUE@	libthin1.a libthin3.a \
+@GCC_TRUE@@NATIVE_LINKER_TRUE@	libthinall.a \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	alt/thin_archive_test_2.o \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	alt/thin_archive_test_4.o \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	alt/libthin2.a alt/libthin4.a
@@ -391,6 +393,12 @@ check_PROGRAMS = $(am__EXEEXT_1) $(am__EXEEXT_2) $(am__EXEEXT_3) \
 
 # Test for SORT_BY_INIT_PRIORITY.
 
+# Test BSS section placement at end of segment.
+
+# Test BSS section placement in middle of segment.
+
+# Test orphan BSS section placement.
+
 # Test --dynamic-list, --dynamic-list-data, --dynamic-list-cpp-new,
 # and --dynamic-list-cpp-typeinfo
 @GCC_TRUE@@NATIVE_LINKER_TRUE@am__append_42 =  \
@@ -410,6 +418,9 @@ check_PROGRAMS = $(am__EXEEXT_1) $(am__EXEEXT_2) $(am__EXEEXT_3) \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	script_test_8.sh \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	script_test_9.sh \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	script_test_14.sh \
+@GCC_TRUE@@NATIVE_LINKER_TRUE@	script_test_15a.sh \
+@GCC_TRUE@@NATIVE_LINKER_TRUE@	script_test_15b.sh \
+@GCC_TRUE@@NATIVE_LINKER_TRUE@	script_test_15c.sh \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	dynamic_list.sh
 
 # Create the data files that debug_msg.sh analyzes.
@@ -459,6 +470,9 @@ check_PROGRAMS = $(am__EXEEXT_1) $(am__EXEEXT_2) $(am__EXEEXT_3) \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	script_test_8.stdout \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	script_test_9.stdout \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	script_test_14.stdout \
+@GCC_TRUE@@NATIVE_LINKER_TRUE@	script_test_15a.stdout \
+@GCC_TRUE@@NATIVE_LINKER_TRUE@	script_test_15b.stdout \
+@GCC_TRUE@@NATIVE_LINKER_TRUE@	script_test_15c.stdout \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	dynamic_list.stdout
 @GCC_FALSE@initpri1_DEPENDENCIES =
 @NATIVE_LINKER_FALSE@initpri1_DEPENDENCIES =
@@ -5101,6 +5115,12 @@ script_test_9.sh.log: script_test_9.sh
 	@p='script_test_9.sh'; $(am__check_pre) $(LOG_COMPILE) "$$tst" $(am__check_post)
 script_test_14.sh.log: script_test_14.sh
 	@p='script_test_14.sh'; $(am__check_pre) $(LOG_COMPILE) "$$tst" $(am__check_post)
+script_test_15a.sh.log: script_test_15a.sh
+	@p='script_test_15a.sh'; $(am__check_pre) $(LOG_COMPILE) "$$tst" $(am__check_post)
+script_test_15b.sh.log: script_test_15b.sh
+	@p='script_test_15b.sh'; $(am__check_pre) $(LOG_COMPILE) "$$tst" $(am__check_post)
+script_test_15c.sh.log: script_test_15c.sh
+	@p='script_test_15c.sh'; $(am__check_pre) $(LOG_COMPILE) "$$tst" $(am__check_post)
 dynamic_list.sh.log: dynamic_list.sh
 	@p='dynamic_list.sh'; $(am__check_pre) $(LOG_COMPILE) "$$tst" $(am__check_post)
 plugin_test_1.sh.log: plugin_test_1.sh
@@ -6642,6 +6662,18 @@ uninstall-am:
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	gcctestdir/ld -o $@ script_test_14.o -T $(srcdir)/script_test_14.t
 @GCC_TRUE@@NATIVE_LINKER_TRUE@script_test_14.stdout: script_test_14
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	$(TEST_OBJDUMP) -s script_test_14 > $@
+@GCC_TRUE@@NATIVE_LINKER_TRUE@script_test_15a: $(srcdir)/script_test_15a.t script_test_15.o gcctestdir/ld
+@GCC_TRUE@@NATIVE_LINKER_TRUE@	gcctestdir/ld -o $@ script_test_15.o -T $(srcdir)/script_test_15a.t
+@GCC_TRUE@@NATIVE_LINKER_TRUE@script_test_15a.stdout: script_test_15a
+@GCC_TRUE@@NATIVE_LINKER_TRUE@	$(TEST_READELF) -lSW script_test_15a > $@
+@GCC_TRUE@@NATIVE_LINKER_TRUE@script_test_15b: $(srcdir)/script_test_15b.t script_test_15.o gcctestdir/ld
+@GCC_TRUE@@NATIVE_LINKER_TRUE@	gcctestdir/ld -o $@ script_test_15.o -T $(srcdir)/script_test_15b.t
+@GCC_TRUE@@NATIVE_LINKER_TRUE@script_test_15b.stdout: script_test_15b
+@GCC_TRUE@@NATIVE_LINKER_TRUE@	$(TEST_READELF) -lSW script_test_15b > $@
+@GCC_TRUE@@NATIVE_LINKER_TRUE@script_test_15c: $(srcdir)/script_test_15c.t script_test_15.o gcctestdir/ld
+@GCC_TRUE@@NATIVE_LINKER_TRUE@	gcctestdir/ld -o $@ script_test_15.o -T $(srcdir)/script_test_15c.t
+@GCC_TRUE@@NATIVE_LINKER_TRUE@script_test_15c.stdout: script_test_15c
+@GCC_TRUE@@NATIVE_LINKER_TRUE@	$(TEST_READELF) -lSW script_test_15c > $@
 @GCC_TRUE@@NATIVE_LINKER_TRUE@dynamic_list: basic_test.o gcctestdir/ld $(srcdir)/dynamic_list.t
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	$(CXXLINK) -Bgcctestdir/ basic_test.o \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	  -Wl,--dynamic-list $(srcdir)/dynamic_list.t \