Re: [PATCH] gdbstub: add support to Xfer:auxv:read: packet

[Alex Bennée]

Lirong Yuan <yuanzi@google.com> writes:

> On Tue, Mar 31, 2020 at 12:20 AM Alex Bennée <alex.bennee@linaro.org> wrote:
>>
>>
>> Lirong Yuan <yuanzi@google.com> writes:
>>
>> > On Mon, Mar 30, 2020 at 12:47 PM Alex Bennée <alex.bennee@linaro.org> 
>> > wrote:
>> >
>> >>
>> >> Lirong Yuan <yuanzi@google.com> writes:
>> >>
>> >> > On Sat, Mar 21, 2020 at 6:56 AM Alex Bennée <alex.bennee@linaro.org>
>> >> wrote:
>> >> >
>> >> >>
>> >> >> Lirong Yuan <yuanzi@google.com> writes:
>> >> >>
>> >> >> > On Fri, Mar 20, 2020 at 2:17 AM Alex Bennée <alex.bennee@linaro.org>
>> >> >> wrote:
>> >> >> <snip>
>> >> >> >>
>> >> >> >> Sorry I missed this on my radar. There was a minor re-factor of
>> >> gdbstub
>> >> >> >> that was just merged which will mean this patch needs a re-base to
>> >> use
>> >> >> >> g_string_* functions to expand stings.
>> >> >> >>
>> >> >> >> Also we have some simple gdbstub tests now - could we come up with a
>> >> >> >> multiarch gdbstub test to verify this is working properly?
>> >> >> >>
>> >> >> <snip>
>> >> >> > For sure, I will re-base this patch to use g_string_* functions.
>> >> >> >
>> >> >> > Currently we are using qemu aarch64. I am not sure how to do this 
>> >> >> > yet,
>> >> >> but
>> >> >> > I could try to add something to
>> >> >> > https://github.com/qemu/qemu/tree/master/tests/tcg/aarch64/gdbstub
>> >> >>
>> >> >> If the auxv support is appropriate to all linux-user targets you can
>> >> >> plumb it into the multiarch tests - you can even use the existing
>> >> >> binaries.
>> >> >>
>> >> >> So you need:
>> >> >>
>> >> >>   - a stanza in the makefiles to launch the test (see
>> >> >>     tests/tcg/aarch64/Makefile.target)
>> >> >>
>> >> >>   - a .py test script that manipulates gdbstub to check things are
>> >> working
>> >> >>
>> >> >> So something like:
>> >> >>
>> >> >> .PHONY: gdbstub-foo-binary
>> >> >> run-gdbstub-foo-binary: foo-binary
>> >> >>         $(call run-test, $@, $(GDB_SCRIPT) \
>> >> >>                 --gdb $(HAVE_GDB_BIN) \
>> >> >>                 --qemu $(QEMU) --qargs "$(QEMU_OPTS)" \
>> >> >>                 --bin $< --test $(MULTIARCH_SRC)/gdbstub/test-foo.py, \
>> >> >>         "basic gdbstub FOO support")
>> >> >>
>> >> >>
>> >> >> >
>> >> >> > Does this sound good?
>> >> >>
>> >> >> Hope that helps.
>> >> >>
>> >> >> >
>> >> >> > Thanks!
>> >> >> > Lirong
>> >> >>
>> >> >>
>> >> >> --
>> >> >> Alex Bennée
>> >> >>
>> >> >
>> >> > Hi Alex,
>> >> >
>> >> > Thanks for the instructions, very helpful!
>> >> >
>> >> > I rebased this patch to use g_string_* functions, and the link to
>> >> patchwork
>> >> > is:
>> >> > http://patchwork.ozlabs.org/patch/1264125/
>> >> > Could you help take another look?
>> >> >
>> >> > Regarding testing, I looked at some instructions for running tests, e.g.
>> >> > https://github.com/qemu/qemu/blob/master/docs/devel/testing.rst
>> >> > https://wiki.qemu.org/Testing
>> >> > However I still could not get the tests for aarch64 to run. Do you know
>> >> how
>> >> > to run the aarch64 or multi-arch tests?
>> >>
>> >> The aarch64 ones run with "make run-tcg-tests-aarch64-linux-user" add
>> >> V=1 to see the details.
>> >>
>> >> > Also there aren't any existing gdb stub tests that try to read
>> >> > uninterpreted bytes from the target’s special data area identified by a
>> >> > keyword:
>> >> >
>> >> https://sourceware.org/gdb/current/onlinedocs/gdb/General-Query-Packets.html#qXfer-auxiliary-vector-read
>> >> > I looked at some other gdb stub tests, but they did not seem to send any
>> >> > queries:
>> >> > https://github.com/qemu/qemu/tree/master/tests/tcg/aarch64/gdbstub
>> >> > So I am not sure how to set up one for "Xfer:auxv:read:" packets...
>> >> > Are there plans to add more tests for other packets like
>> >> > "Xfer:features:read:"?
>> >> > I'd be happy to add a test if there is an example of how to do it. :)
>> >>
>> >> What would you do from a normal gdb command line. At the very least you
>> >> run the same command with gdb.execute(), e.g.:
>> >>
>> >>   gdb.execute("set confirm off")
>> >>
>> >> is the same as typing
>> >>
>> >>   set confirm off
>> >>
>> >> at the gdb command prompt.
>> >>
>> >> >
>> >> > Thanks,
>> >> > Lirong
>> >>
>> >>
>> >> --
>> >> Alex Bennée
>> >>
>> >
>> > Hey Alex,
>> >
>> > I tried to run the test but they were skipped. Do you know if there's any
>> > other flag that needs to be set?
>> >
>> > $ make run-tcg-tests-aarch64-linux-user
>> > make[1]: Entering directory '/usr/local/google/home/yuanzi/qemu/slirp'
>> > make[1]: Nothing to be done for 'all'.
>> > make[1]: Leaving directory '/usr/local/google/home/yuanzi/qemu/slirp'
>> >   BUILD   TCG tests for aarch64-linux-user
>> >   BUILD   aarch64-linux-user guest-tests SKIPPED
>> >   RUN     TCG tests for aarch64-linux-user
>> >   RUN     tests for aarch64-linux-user SKIPPED
>>
>> Ahh you either need to have docker enabled or the aarch64 compilers in
>> your path when you run configure so the test programs can be built. The
>> details are in docs/devel/testing.rst
>>
>> > I don't think any command needs to be run. It should just send the query
>> > automatically.
>> > Could we assume that it will work the same in the test?
>>
>> If that is enough to exercise the code. Can we not validate the data somehow?
>>
>>
>> --
>> Alex Bennée
>
> Hi Alex,
>
> Thanks for the suggestions! I just installed docker and ran the tests,
> but got the following error messages for gdbstub tests:
> $ make run-tcg-tests-aarch64-linux-user
> ...
> TEST    basic gdbstub support
> warning: while parsing target description (at line 1): Target
> description specified unknown architecture "aarch64"
> warning: Could not load XML target description; ignoring
> Truncated register 37 in remote 'g' packet
> Traceback (most recent call last):
>   File 
> "/usr/local/google/home/yuanzi/Documents/gdbstub-patch/qemu/tests/tcg/multiarch/gdbstub/sha1.py",
> line 68, in <module>
>     if gdb.parse_and_eval('$pc') == 0:
> gdb.error: No registers.
>   TEST    basic gdbstub SVE support
> warning: while parsing target description (at line 1): Target
> description specified unknown architecture "aarch64"
> warning: Could not load XML target description; ignoring
> Truncated register 37 in remote 'g' packet
>
> I'm not sure if there is any additional setup needed to make those
> tests pass. Do you know how to fix those errors?

The error is because the gdb you have installed doesn't understand
foreign architectures. The test should have skipped in this case so I',
not sure why it causes it to fail.

You can either ensure you have multiarch capable gdb (this is
binutils-multiarch on debian for example) or build your own gdb and
point at it with --gdb in configure.

>
> Thanks,
> Lirong


-- 
Alex Bennée