asan: memtag-stack add support for MTE instructions

asan: memtag-stack add support for MTE instructions

Memory tagging is used for detecting memory safety bugs.  On AArch64, the
memory tagging extension (MTE) helps in reducing the overheads of memory
tagging:
 - CPU: MTE instructions for efficiently tagging and untagging memory.
 - Memory: New memory type, Normal Tagged Memory, added to the Arm
   Architecture.

The MEMory TAGging (MEMTAG) sanitizer uses the same infrastructure as
HWASAN.  MEMTAG and HWASAN are both hardware-assisted solutions, and
rely on the same sanitizer machinery in parts.  So, define new
constructs that allow MEMTAG and HWASAN to share the infrastructure:

  - hwassist_sanitize_p () is true when either SANITIZE_MEMTAG or
    SANITIZE_HWASAN is true.
  - hwassist_sanitize_stack_p () is when hwassist_sanitize_p () and
    stack variables are to be sanitized.

MEMTAG and HWASAN do have differences, however, and hence, the need to
conditionalize using memtag_sanitize_p () in the relevant places. E.g.,

  - Instead of generating the libcall __hwasan_tag_memory, MEMTAG needs
    to invoke the target-specific hook TARGET_MEMTAG_TAG_MEMORY to tag
    memory.  Similar approach can be seen for handling
    handle_builtin_alloca, where instead of doing the gimple
    transformations, target hooks are used.

  - Add a new internal function HWASAN_ALLOCA_POISON to handle
    dynamically allocated stack when MEMTAG sanitizer is enabled. At
    expansion, this allows to, in turn, invoke target-hooks to increment
    tag, and use the generated tag to finally tag the dynamically allocated
    memory.

    The usual pattern:
        irg     x0, x0, x0
        subg    x0, x0, #16, #0
    creates a tag in x0 and so on.  For alloca, we need to apply the
    generated tag to the new sp.  In absense of an extract tag insn, the
    implemenation in expand_HWASAN_ALLOCA_POISON resorts to invoking irg
    again.

gcc/
	* asan.cc (handle_builtin_stack_restore): Accommodate MEMTAG
	sanitizer.
	(handle_builtin_alloca): Expand differently if MEMTAG sanitizer.
	(get_mem_refs_of_builtin_call): Include MEMTAG along with
	HWASAN.
	(memtag_sanitize_stack_p): New definition.
	(memtag_sanitize_allocas_p): Likewise.
	(memtag_memintrin): Likewise.
	(hwassist_sanitize_p): Likewise.
	(hwassist_sanitize_stack_p): Likewise.
	(report_error_func): Include MEMTAG along with HWASAN.
	(build_check_stmt): Likewise.
	(instrument_derefs): MEMTAG too does not deal with globals yet.
	(instrument_builtin_call): Include MEMTAG along with HWASAN.
	(maybe_instrument_call): Likewise.
	(asan_expand_mark_ifn): Likewise.
	(asan_expand_check_ifn): Likewise.
	(asan_expand_poison_ifn): Expand differently if MEMTAG sanitizer.
	(asan_instrument): Include MEMTAG along with HWASAN.
	(hwasan_emit_prologue): Expand differently if MEMTAG sanitizer.
	(hwasan_emit_untag_frame): Likewise.
	* asan.h (memtag_sanitize_stack_p): New declaration.
	(memtag_sanitize_allocas_p): Likewise.
	(hwassist_sanitize_p): Likewise.
	(hwassist_sanitize_stack_p): Likewise.
	(asan_sanitize_use_after_scope): Include MEMTAG along with
	HWASAN.
	* cfgexpand.cc (align_local_variable): Likewise.
	(expand_one_stack_var_at): Likewise.
	(expand_stack_vars): Likewise.
	(expand_one_stack_var_1): Likewise.
	(init_vars_expansion): Likewise.
	(expand_used_vars): Likewise.
	(pass_expand::execute): Likewise.
	* gimplify.cc (asan_poison_variable): Likewise.
	* internal-fn.cc (expand_HWASAN_ALLOCA_POISON): New definition.
	(expand_HWASAN_ALLOCA_UNPOISON): Expand differently if MEMTAG
	sanitizer.
	(expand_HWASAN_MARK): Likewise.
	* internal-fn.def (HWASAN_ALLOCA_POISON): Define new.
	* params.opt: Document new param.
	* sanopt.cc (pass_sanopt::execute): Include MEMTAG along with
	HWASAN.
	* gcc.cc (sanitize_spec_function): Add check for memtag-stack.
	* doc/tm.texi: Regenerate.
	* target.def (extract_tag): Update documentation.
	(add_tag): Likewise.
	(insert_random_tag): Likewise.

Co-authored-by: Indu Bhagat <indu.bhagat@oracle.com>
Signed-off-by: Claudiu Zissulescu <claudiu.zissulescu-ianculescu@oracle.com>