Re: [PATCH] tests/qtest: Make qtest_get_arch() cleverer

[Fabiano Rosas <farosas@suse.de>]

Peter Maydell <peter.maydell@linaro.org> writes:

> The qtest_get_arch() function tries to determine the architecture
> under test by extracting it from the binary name as provided in
> QTEST_QEMU_BINARY.  The current logic finds the last '-' in the
> string and assumes everything beyond it is the architecture name.
> Although we also look for the substring "-system-", the only effect
> this check has is that we will exit with an error if it is not
> present.
>
> Because the logic at the moment is very simplistic, although
> it is possible to provide more complex commands than a bare
> QEMU binary path, such as:
>   QTEST_QEMU_BINARY='rr record ./qemu-system-x86_64'
> it is not possible to provide extra arguments to QEMU, such as:
>   QTEST_QEMU_BINARY='./qemu-system-x86_64 -d trace:foo'
>
> Because the "-system-" check and the "find the architecture" check
> are not the same, the latter example will pass the "we found
> -system-" check and not notice that the "architecture name" it has
> found starts further on in the string; so rather than printing an
> error it will return "d trace:foo" to the test.
>
> Improve the "find the architecture name" logic to look for the
> rightmost occurrence of the substring "-system-" in
> QTEST_QEMU_BINARY, and take the architecture name as starting there
> and continuing until the first whitespace character or the end of the
> string.
>
> Because we now need to potentially modify the environment variable
> string to terminate the architecture name if it is not the last part
> of the string, we make a copy of it which we cache in a static
> variable.  This lets us avoid having to modify all the callers to get
> them to take ownership of the returned string.
>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
> I wanted to be able to pass trace arguments to a QEMU to help
> debug a failing test; in the past I've done this by writing
> a little wrapper shell script with the right shaped name, but
> we can do better than that.
>

There's QTEST_TRACE which can inject any command line option if you give
it a tracepoint name as first string:

QTEST_TRACE="cpu_reset -d guest_errors"

Maybe we should just rename it to QTEST_QEMU_ARGS.