ld/aarch64elf: add support for DT_AARCH64_MEMTAG_STACK dynamic tag
Add new command line option -z memtag-stack for aarch64 elf. This
option instructs the linker to generate the necessary dynamic tag
DT_AARCH64_MEMTAG_STACK, which the dynamic loader can then use to
protect the stack memory with PROT_MTE. Linker issues an 'unrecognized
option' error when -z memtag-stack is specified for non-aarch64 based
emulations.
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
... ... ...
0x000000007000000c (AARCH64_MEMTAG_STACK) 0x1
... ... ...
TBD:
1. Error/Warn if user says -z memtag-stack but does not select a
mode ?
2. Should ld check that all input ELF components were compiled with
-fsanitize=memtag-stack ? If yes, we likely need something like
GNU_PROPERTY_AARCH64_FEATURE_1_MEMTAG_STACK specified in the ABI.
Should we then allow the user to select the desirable action like we
do in other cases, via say memtag-report[=none|warning|error] ?
ChangeLog:
* bfd/elfnn-aarch64.c (elfNN_aarch64_late_size_sections): Emit
DT_AARCH64_MEMTAG_STACK dynamic tag.
* bfd/elfxx-aarch64.h (struct aarch64_memtag_opts): Add new
member for tracking whether stack access uses MTE insns.
* binutils/readelf.c (get_aarch64_dynamic_type): Handle
DT_AARCH64_MEMTAG_STACK.
* ld/emultempl/aarch64elf.em: Add new command line option.
* ld/ld.texi: Add documentation for -z memtag-stack.
* ld/testsuite/ld-aarch64/aarch64-elf.exp: Add new test.
* ld/testsuite/ld-aarch64/dt-memtag-stack.d: New test.
include/ChangeLog:
* elf/aarch64.h (DT_AARCH64_MEMTAG_STACK): New definition.