Support NEXT_SECTION in ALIGNOF and SIZEOF

This patch is aimed at making __bss_start properly aligned with the
first of any bss-style sections following.  Most of the work here
involves keeping track of the last output section seen when processing
the linker script.

You can almost align __bss_start properly by using
${RELOCATING+. = ALIGN(${DATA_SDATA-${NO_SMALL_DATA-ALIGNOF(.${SBSS_NAME}) != 0 ? ALIGNOF(.${SBSS_NAME}) : }}${BSS_PLT+ALIGNOF(.plt) != 0 ? ALIGNOF(.plt) : }ALIGNOF(.${BSS_NAME}));}
and changing every place that defines NO_SMALL_DATA to use " ", but
having two .plt sections (marked SPECIAL) on some backends foils that
idea.  The problem is that you only want to pick up the following
.plt, not the one preceeding __bss_start in the data segment if the
backend decides that is the proper .plt section.

Perhaps that could be fixed too, but I decided instead to extend the
linker script a little.  THIS_SECTION and PREV_SECTION could easily be
added too.

	* ld.texi (ALIGNOF, SIZEOF): Update and mention NEXT_SECTION.
	* ldexp.c (output_section_find): New function.
	(fold_name <ALIGNOF, SIZEOF>): Use output_section_find.
	(exp_fold_tree): Add os parameter.  Adjust all calls.
	(exp_fold_tree_no_dot, exp_get_vma, exp_get_power): Likewise.
	* ldexp.h (struct ldexp_control): Add last_os.
	(exp_fold_tree, exp_fold_tree_no_dot): Update prototypes.
	(exp_get_vma, exp_get_power): Likewise.
	* ldlang.c: Pass last output section to expression folder
	calls throughout file.
	(open_input_bfds): Add os parameter to track last os seen.
	(lang_size_sections_1): Rename output_section_statement param
	to current_os.  Track last os.
	(lang_do_assignments_1): Track last os.
	* scripttempl/arclinux.sc: Align to ALIGNOF NEXT_SECTION
	before defining __bss_start.
	* scripttempl/elf.sc: Likewise.
	* scripttempl/elf64bpf.sc: Likewise.
	* scripttempl/elf64hppa.sc: Likewise.
	* scripttempl/elf_chaos.sc: Likewise.
	* scripttempl/elfarc.sc: Likewise.
	* scripttempl/elfd10v.sc: Likewise.
	* scripttempl/elfxtensa.sc: Likewise.
	* scripttempl/epiphany_4x4.sc: Likewise.
	* scripttempl/iq2000.sc: Likewise.
	* scripttempl/mep.sc: Likewise.
	* scripttempl/nds32elf.sc: Likewise.
	* scripttempl/xstormy16.sc: Likewise.
	* testsuite/ld-x86-64/pe-x86-64-5.od: Update expected __bss_start.
	* testsuite/ld-x86-64/pe-x86-64-5.rd: Likewise.

1 files changed, 14 insertions, 7 deletions

diff --git a/ld/ld.texi b/ld/ld.texi
index 40d388a..406e87e 100644
--- a/ld/ld.texi
+++ b/ld/ld.texi
@@ -7114,10 +7114,13 @@ The builtin function @code{NEXT} is closely related to @code{ALIGN}.
 @kindex ALIGNOF(@var{section})
 @cindex section alignment
 Return the alignment in bytes of the named @var{section}, if that section has
-been allocated.  If the section has not been allocated when this is
-evaluated, the linker will report an error. In the following example,
-the alignment of the @code{.output} section is stored as the first
-value in that section.
+been allocated, or zero if the section has not been allocated.  If the
+section does not exist in the linker script the linker will report an
+error.  If @var{section} is @code{NEXT_SECTION} then @code{ALIGNOF} will
+return the alignment of the next allocated section specified in the
+linker script, or zero if there is no such section.  In the following
+example, the alignment of the @code{.output} section is stored as the
+first value in that section.
 @smallexample
 @group
 SECTIONS@{ @dots{}
@@ -7266,9 +7269,13 @@ name.
 @kindex SIZEOF(@var{section})
 @cindex section size
 Return the size in bytes of the named @var{section}, if that section has
-been allocated.  If the section has not been allocated when this is
-evaluated, the linker will report an error.  In the following example,
-@code{symbol_1} and @code{symbol_2} are assigned identical values:
+been allocated, or zero if the section has not been allocated.  If the
+section does not exist in the linker script the linker will report an
+error.  If @var{section} is @code{NEXT_SECTION} then @code{SIZEOF} will
+return the alignment of the next allocated section specified in the
+linker script, or zero if there is no such section.  In the following
+example, @code{symbol_1} and @code{symbol_2} are assigned identical
+values:
 @smallexample
 @group
 SECTIONS@{ @dots{}