ppc476 icache bug workaround

This implements a work-around for an icache bug on 476 that can cause
execution of stale instructions when control falls through from one
page to the next.  The idea is to prevent such fall-through by
replacing the last instruction on a page with a branch to a patch
area containing the instruction, then branch to the next page.

The patch also fixes a number of bugs in the existing support for long
branch trampolines.

bfd/
	* elf32-ppc.c (struct ppc_elf_link_hash_table): Add params.
	Delete emit_stub_syms, no_tls_get_addr_opt.  Update all uses.
	(ppc_elf_link_params): New function.
	(ppc_elf_create_glink): Align .glink to 64 bytes for ppc476
	workaround.
	(ppc_elf_select_plt_layout): Remove plt_style and emit_stub_syms
	parameters.  Use htab->params instead.
	(ppc_elf_tls_setup): Remove no_tls_get_addr_opt parameter.
	(ppc_elf_size_dynamic_sections): Align __glink_PLTresolve to
	64 bytes for ppc476 workaround.
	(struct ppc_elf_relax_info): New.
	(ppc_elf_relax_section): Exclude linker created sections and
	those too small to hold one instruction.  Don't add another
	branch 	around trampolines on later relax passes.  Don't
	generate trampolines for undefined symbols when !relocatable,
	nor for plugin symbols.  Allocate space for ppc476 workaround
	patch area.  Free fixups on error return path.
	(ppc_elf_relocate_section): Handle ppc476 workaround patching.
	* elf32-ppc.h (struct ppc_elf_params): New.
	(ppc_elf_select_plt_layout, ppc_elf_tls_setup): Update prototype.
	(ppc_elf_link_params): Declare.
	* section.c (SEC_INFO_TYPE_TARGET): Define.
	* bfd-in2.h: Regenerate.
ld/
	* emultempl/ppc32elf.em (no_tls_get_addr_opt, emit_stub_syms)
	plt_style): Delete.  Adjust all refs to instead use..
	(params): ..this.  New variable.
	(ppc_after_open_output): New function.  Tweak params and pass to
	ppc_elf_link_params.
	(ppc_after_open): Adjust ppc_elf_select_plt_layout call.
	(ppc_before_allocation): Adjust ppc_elf_tls_setup call.  Enable
	relaxation for ppc476 workaround.
	(PARSE_AND_LIST_*): Add --{no-,}ppc476-workaround support.
	(LDEMUL_CREATE_OUTPUT_SECTION_STATEMENTS): Define.
Enable ppc476 workaround for ld -r.

The Linux kernel builds modules using ld -r.  These might need the
ppc476 workaround, so enable it for ld -r if sections have sufficient
alignment to tell location within a page.

bfd/
	* elf32-ppc.c (ppc_elf_relax_section): Enable ppc476 workaround
	for ld -r, when code sections are sufficiently aligned.
	* elf32-ppc.h (struct ppc_elf_params): Delete pagesize.  Add
	pagesize_p2.
ld/
	* emultempl/ppc32elf.em (pagesize): New static var.
	(ppc_after_open_output): Set params.pagesize_p2 from pagesize.
	(PARSE_AND_LIST_ARGS_CASES): Adjust to use pagesize.
ppc476 workaround for ld -r fixes

This fixes the glaring error that the ppc476 workaround wasn't
actually enabled for ld -r, and adjusts relocations to match moved
code.

bfd/
	* elf32-ppc.c (ppc_elf_relocate_section): Move relocs on insns
	patched for ppc476 workaround.  Reapply branch taken/not taken
	relocs.
ld/
	* emultempl/ppc32elf.em (ppc_after_open_output): Really enable
	ppc476 workaround for ld -r.
Add ppc476 workaround bootstrap test

I was running this by hand to test out --ppc476-workaround.  Another
bootstrap test doesn't take all that long, so let's add it to the
testsuite.

	* ld-bootstrap/bootstrap.exp: Add ppc476 workaround test.
	* ld-bootstrap/ppc476.t: New file.
Fix ELF ppc32 targets that don't use ppc32elf.em

5446cbdf82892a800ed7eef563a795e75223ec52 broke powerpc-lynxos,
powerpc-netware, powerpc-windiss and powerpc-vxworks.

bfd/
	* elf32-ppc.c (ppc_elf_link_hash_table_create): Provide default
	params for targets that don't use ppc32elf.em.
ld/
	* emulparams/elf32ppcvxworks.sh: Source plt_unwind.sh and
	use ppc32elf.em.
	* emultempl/ppc32elf.em (ppc_after_open): Don't compile for
	vxworks.
	(LDEMUL_AFTER_OPEN): Don't set for vxworks.
	(PARSE_AND_LIST_LONGOPTS, PARSE_AND_LIST_OPTIONS): Exclude
	-secure-plt, -bss-plt and -sdata-got when vxworks.
ppc476 icache workaround fix for bctr

I got the ppc476 workaround wrong.  bctr (and bctrl) as the last
instruction in a page can hit the icache bug if the preceding mtctr
insn is close by, and the destination is in the first few instructions
on the next page.  This scenario can occur with code generated by gcc
to implement switch statements, or in code generated to call by
function pointer.

To prevent the bctr problem it is also necessary to remove other
instructions that otherwise would be safe.

bfd/
	* elf32-ppc.c (ppc_elf_relocate_section): Remove bctr from list
	of safe ppc476 insns at end of page.  Also remove non-branch insns.
	Expand comments.
ld/
	* emultempl/ppc32elf.em (no_zero_padding, ppc_finish): New functions.
	(LDEMUL_FINISH): Define.
ppc476 gas warn on data in code sections

    	* config/tc-ppc.c (warn_476, last_insn, last_seg, last_subseg):
    	New static vars.
    	(md_longopts, md_parse_option, md_show_usage): Add --ppc476-workaround.
    	(ppc_elf_cons_fix_check): New function.
    	(md_assemble): Set last_insn, last_seg, last_subseg.
    	(ppc_elf_cons, ppc_byte, md_apply_fix): Handle warn_476.
    	* config/tc-ppc.h (TC_CONS_FIX_CHECK): Define.
    	(ppc_elf_cons_fix_check): Declare.
    	* read.c (cons_worker): Invoke TC_CONS_FIX_CHECK.
ppc476 plt call stubs

Fuss over bctr in call stubs.

	* elf32-ppc.c (BA): Define
	(ppc_elf_link_hash_table_create): Correct default_params.
	(write_glink_stub): Pad small plt call stub with "ba 0" rather
	than "nop" for ppc476_workaround.
	(ppc_elf_finish_dynamic_sections): Likewise for branch table
	and __glink_PLTresolve.  Ensure plt call stub at end of page
	doesn't allow fall-thru prefetch.
fill ppc476 fixup area

Stops false positive warnings from scanner.

	* elf32-ppc.c (ppc_elf_relocate_section): Fill 476 fixup area
	with "ba 0" rather than zeros.
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