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

[Lirong Yuan]

On Tue, Jul 21, 2020 at 1:29 PM Lirong Yuan <yuanzi@google.com> wrote:
>
> On Tue, Jul 21, 2020 at 12:50 PM Alex Bennée <alex.bennee@linaro.org> wrote:
> >
> >
> > 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
>
> Hmm I installed binutils-multiarch but it still did not work. The
> error messages are the same as the previous ones.

Turns out that it can be fixed by installing gdb-multiarch and
rerunning configure.

I submitted a new patch, and here is the link to patchwork. :)
20200730193932.3654677-1-yuanzi@google.com/">http://patchwork.ozlabs.org/project/qemu-devel/patch/20200730193932.3654677-1-yuanzi@google.com/