ld/aarch64elf: add support for DT_AARCH64_MEMTAG_MODE dynamic tag
Add new command line option -z memtag-mode=<mode> to aarch64 elf,
where <mode> can be one of none, sync, or async. For mode of sync or
async, a DT_AARCH64_MEMTAG_MODE dynamic tag with a value of 0 or 1
respectively is emitted.
readelf displays the dynamic tag when present:
$ readelf -d <exectutable>
Dynamic section at offset 0xfdd8 contains XX entries:
Tag Type Name/Value
0x0000000000000001 (NEEDED) Shared library: [libc.so.6]
0x000000000000000c (INIT) 0x400520
0x000000000000000d (FINI) 0x400b64
0x0000000000000019 (INIT_ARRAY) 0x41fdc8
... ... ...
0x0000000070000009 (AARCH64_MEMTAG_MODE) 0x1
... ... ...
[Note/FIXME: Asymm is an Armv8.7 extension to MTE; it is a mode of
operation that provides synchronous checking on memory reads, and
asynchronous checking of memory writes. Its not clear if and how the
toolchain (likely the compiler?) can do some sanity checking of whether
asymm is allowed. E.g., asymm should be disallowed with Armv8.5a ?
Further the MemtagABI does not yet define a constant for the asymm mode
value for DT_AARCH64_MEMTAG_MODE.]
TBD:
1. test cases and testing
2. Why does the ABI doc not define a constant for asymm ? The patch
skips adding support for asymm altogether ATM.
ChangeLog:
* bfd/elfnn-aarch64.c (struct elf_aarch64_link_hash_table): Add
new member for memtag properties.
(bfd_elfNN_aarch64_set_options): New argument to pass memtag
properties.
(elfNN_aarch64_late_size_sections): Emit DT_AARCH64_MEMTAG_MODE
dynamic tag.
* bfd/elfxx-aarch64.h: New definition for the various memtag
properties.
* binutils/readelf.c (get_aarch64_dynamic_type): Handle
DT_AARCH64_MEMTAG_MODE.
* ld/emultempl/aarch64elf.em: Likewise.
* ld/ld.texi: Add documentation for the new option
-z memtag-mode.
* ld/testsuite/ld-aarch64/aarch64-elf.exp: New test.
* ld/testsuite/ld-aarch64/dt-memtag.d: New test.
* ld/testsuite/ld-aarch64/dt-memtag-mode.s: New test.
include/ChangeLog:
* elf/aarch64.h (DT_AARCH64_MEMTAG_MODE): New definition.
9 files changed
