[PATCH, ARM] Work around Cortex-A8 erratum in linker

[Julian Brown]

Hi,

This patch contains a workaround for an erratum in ARM Cortex-A8
processors. The (position-dependent) nature of the erratum is such that
it is necessary to interoperate with the relaxation pass performed at
the end of linking which inserts long branch/interworking stubs.

The erratum (657417: A 32-bit branch instruction that spans two 4K
regions can result in an incorrect operation) affects only Thumb-2
code.  The method used to work around the problem is to insert a stub
(in a different page) and branch to that, then have the stub jump back
to the original destination.

The workaround is enabled by default if the link targets the ARMv7 (-A
or unspecified) architecture. It can be enabled otherwise by passing
--fix-cortex-a8 to the linker, or disabled unconditionally by passing
--no-fix-cortex-a8.

Tested with cross to arm-linux-gnueabi, with new test cases. OK to
apply?

Thanks,

Julian

ChangeLog

    ld/
    * emultempl/armelf.em (fix_cortex_a8): New.
    (arm_elf_before_allocation): Call bfd_elf32_arm_set_cortex_a8_fix.
    (arm_elf_create_output_section_statements): Add fix_cortex_a8 to
    bfd_elf32_arm_set_target_relocs.
    (OPTION_FIX_CORTEX_A8, OPTION_NO_FIX_CORTEX_A8): New.
    (PARSE_AND_LIST_LONGOPTS): Add [no-]fix-cortex-a8 options.
    (PARSE_AND_LIST_OPTIONS): Add [no-]fix-cortex-a8 options.
    (PARSE_AND_LIST_ARGS_CASES): Handle OPTION_[NO_]FIX_CORTEX_A8.
    * ld.texinfo (--[no-]fix-cortex-a8): Briefly document new options.

    bfd/
    * elf32-arm.c (THUMB16_BCOND_INSN, THUMB32_INSN, THUMB32_B_INSN):
    New macros.
    (elf32_arm_stub_a8_veneer_b_cond, elf32_arm_stub_a8_veneer_b)
    (elf32_arm_stub_a8_veneer_blx): New stub sequences.
    (elf32_arm_stub_type): Add arm_stub_a8_veneer_b_cond,
    arm_stub_a8_veneer_b and arm_stub_a8_veneer_blx.
    (elf32_arm_stub_hash_entry): Add target_addend, orig_insn fields.
    (a8_erratum_fix, a8_erratum_reloc): New structs.
    (elf32_arm_link_hash_table): Add a8_erratum_fixes,
    num_a8_erratum_fixes, fix_cortex_a8 fields.
    (elf32_arm_link_hash_table_create): Zero fix_cortex_a8.
    (elf32_arm_add_stub): Split into two parts, creating...
    (elf32_arm_create_or_find_stub_sec): New function.
    (elf32_arm_final_link_relocate): Add forward declaration.
    (arm_build_one_stub): Add support for THUMB32_TYPE, Thumb-2
    relocations, multiple relocations per stub.
    (find_stub_size_and_template): New (using parts of
    arm_size_one_stub).
    (arm_size_one_stub): Use find_stub_size_and_template.
    (a8_reloc_compare): New.
    (find_thumb_glue): Add forward declaration.
    (cortex_a8_erratum_scan): New.
    (elf32_arm_size_stubs): Add Cortex-A8 erratum workaround support.
    (bfd_elf32_arm_set_cortex_a8_fix): New.
    (bfd_elf32_arm_set_target_relocs): Add fix_cortex_a8 argument.
    (arm_map_one_stub): Add THUMB32_TYPE support.
    (a8_branch_to_stub_data): New.
    (make_branch_to_a8_stub): New.
    (elf32_arm_write_section): Add Cortex-A8 erratum workaround support.
    * bfd-in.h (bfd_elf32_arm_set_cortex_a8_fix): New.
    (bfd_elf32_arm_set_target_relocs): Add argument for controlling
    Cortex-A8 erratum workaround.
    * bfd-in2.h: Regenerate.

    ld/testsuite/
    * ld-arm/cortex-a8-arm-target.s: New.
    * ld-arm/cortex-a8-thumb-target.s: New.
    * ld-arm/cortex-a8-fix-b-rel.s: New.
    * ld-arm/cortex-a8-fix-b-rel-arm.d: New.
    * ld-arm/cortex-a8-fix-b-rel-thumb.d: New.
    * ld-arm/cortex-a8-fix-b.s: New.
    * ld-arm/cortex-a8-fix-b.d: New.
    * ld-arm/cortex-a8-fix-bl-rel.s: New.
    * ld-arm/cortex-a8-fix-bl-rel-arm.d: New.
    * ld-arm/cortex-a8-fix-bl-rel-thumb.d: New.
    * ld-arm/cortex-a8-fix-bl.s: New.
    * ld-arm/cortex-a8-fix-bl.d: New.
    * ld-arm/cortex-a8-fix-bcc-rel.s: New.
    * ld-arm/cortex-a8-fix-bcc-rel-thumb.d: New.
    * ld-arm/cortex-a8-fix-bcc.s: New.
    * ld-arm/cortex-a8-fix-bcc.d: New.
    * ld-arm/cortex-a8-fix-blx-rel.s: New.
    * ld-arm/cortex-a8-fix-blx-rel-arm.d: New.
    * ld-arm/cortex-a8-fix-blx-rel-thumb.d: New.
    * ld-arm/cortex-a8-fix-blx.s: New.
    * ld-arm/cortex-a8-fix-blx.d: New.
    * ld-arm/arm-elf.exp: Add new tests.
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