Add an AArch64-specific test and a more generic memory tagging test that
other architectures can run.
Even though architectures not supporting memory tagging can run the memory
tagging tests, the runtime check will make the tests bail out early, as it
would make no sense to proceed without proper support.
It is also tricky to do any further runtime tests for memory tagging, given
we'd need to deal with tags, and those are arch-specific. Therefore the
test in gdb.base is more of a smoke test.
If an architecture wants to implement memory tagging, then it makes sense to
have tests within gdb.arch instead.
gdb/testsuite/ChangeLog:
YYYY-MM-DD Luis Machado <email address hidden>
* gdb.arch/aarch64-mte.c: New file.
* gdb.arch/aarch64-mte.exp: New test.
* gdb.base/memtag.c: New file.
* gdb.base/memtag.exp: New test.
* lib/gdb.exp (supports_memtag): New function.
Document new "x" and "print" memory tagging extensions
Document the changes to the "print" and "x" commands to support memory
tagging.
gdb/doc/ChangeLog:
YYYY-MM-DD Luis Machado <email address hidden>
* gdb.texinfo (Data): Document memory tagging changes to the "print"
command.
(Examining Memory): Document memory tagging changes to the "x"
command.
(Memory Tagging): Update with more information on changes to the "x"
and "print" commands.
Extend "x" and "print" commands to support memory tagging
Extend the "x" and "print" commands to make use of memory tagging
functionality, if supported by the architecture.
The "print" command will point out any possible tag mismatches it finds
when dealing with pointers, in case such a pointer is tagged. No additional
modifiers are needed.
Suppose we have a pointer "p" with value 0x1234 (logical tag 0x0) and that we
have an allocation tag of 0x1 for that particular area of memory. This is the
expected output:
(gdb) p/x p
Logical tag (0x0) does not match the allocation tag (0x1).
$1 = 0x1234
The "x" command has a new 'm' modifier that will enable displaying of
allocation tags alongside the data dump. It will display one allocation
tag per line.
AArch64 has a tag granule of 16 bytes, which means we can have one tag for
every 16 bytes of memory. In this case, this is what the "x" command will
display with the new 'm' modifier:
(gdb) x/32bxm p
<Allocation Tag 0x1 for range [0x1230,0x1240)>
0x1234: 0x01 0x02 0x00 0x00 0x00 0x00 0x00 0x00
0x123c: 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
<Allocation Tag 0x1 for range [0x1240,0x1250)>
0x1244: 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x124c: 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
(gdb) x/4gxm a
<Allocation Tag 0x1 for range [0x1230,0x1240)>
0x1234: 0x0000000000000201 0x0000000000000000
<Allocation Tag 0x1 for range [0x1240,0x1250)>
0x1244: 0x0000000000000000 0x0000000000000000
gdb/ChangeLog:
YYYY-MM-DD Luis Machado <email address hidden>
* printcmd.c (decode_format): Handle the 'm' modifier.
(do_examine): Display allocation tags when required/supported.
(should_validate_memtags): New function.
(print_command_1): Display memory tag mismatches.
* valprint.h (struct format_data) <print_tags>: New field.
Add new commands under the "mtag" prefix to allow users to inspect, modify and
check memory tags in different ways.
The available subcommands are the following:
- mtag showltag <expression>: Shows the logical tag for a particular address.
- mtag setltag <expression> <tag>: Prints the address tagged with the logical
tag <tag>.
- mtag showatag <expression>: Shows the allocation tag for a particular address.
- mtag setatag <expression> <length> <tags>: Sets one or more allocation tags to
the specified tags.
- mtag check <expression>: Check if the logical tag in <address> matches its
allocation tag.
These commands make use of the memory tagging gdbarch methods, and are still
available, but disabled, when memory tagging is not supported by the
architecture.
I've pondered about a way to make these commands invisible when memory tagging
is not available, but given the check is at runtime (and support may come and go
based on a process' configuration), that is a bit too late in the process to
either not include the commands or get rid of them.
Ideas are welcome.
gdb/ChangeLog:
YYYY-MM-DD Luis Machado <email address hidden>
* printcmd.c: Include gdbsupport/rsp-low.h.
(mtaglist): New static global.
(process_print_command_args): Factored out of
print_command_1.
(print_command_1): Use process_print_command_args.
(show_addr_not_tagged, show_memtag_unsupported, mtag_command)
(mtag_showtag_command, mtag_showltag_command, mtag_showatag_command)
(parse_setltag_input, mtag_setltag_command, parse_setatag_input)
(mtag_setatag_command, mtag_check_command): New functions.
(_initialize_printcmd): Add "mtag" prefix and subcommands.
gdbsupport/ChangeLog:
YYYY-MM-DD Luis Machado <email address hidden>
* rsp-low.cc (fromhex): Change error message text to not be
RSP-specific.
Whenever a memory tag violation occurs, we get a SIGSEGV. Additional
information can be obtained through the siginfo data structure.
For AArch64 the Linux kernel may expose the fault address and tag
information, if we have a synchronous event. Otherwise there is
no fault address available.
gdb/ChangeLog:
YYYY-MM-DD Luis Machado <email address hidden>
* aarch64-linux-tdep.c
(aarch64_linux_handle_segmentation_fault): New function.
(aarch64_linux_init_abi): Register
aarch64_linux_handle_segmentation_fault as segmentation fault hook.
* arch/aarch64-linux.h (SEGV_MTEAERR): Define.
(SEGV_MTESERR): Define.
AArch64: Add unit testing for logical tag set/get operations
Add some unit testing to exercise setting/getting logical tags in the
AArch64 implementation.
gdb/ChangeLog:
YYYY-MM-DD Luis Machado <email address hidden>
* aarch64-linux-tdep.c: Include gdbsupport/selftest.h.
(aarch64_linux_ltag_tests): New function.
(_initialize_aarch64_linux_tdep): Register aarch64_linux_ltag_tests.
