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    SubjectRe: [PATCH v2 09/13] ARM: Disable jprobe selftests in thumb kernels
    On 11/07/13 12:26, Jon Medhurst (Tixy) wrote:
    > On Tue, 2013-10-15 at 17:04 -0400, David Long wrote:
    >> From: "David A. Long" <dave.long@linaro.org>
    >>
    >> jprobe kernel selftests are not supported for thumb kernels. Conditionally
    >> disable them in the kernel kprobes-test module.
    >
    > I don't think it's fair to say they aren't supported, it's just that the
    > implementation of jprobes and/or symbol lookup has bugs on Thumb kernels
    > which the test code is finding, see
    > http://lists.infradead.org/pipermail/linux-arm-kernel/2011-August/063026.html
    >
    > Note, the current code works OK if the function being probed is in a
    > loadable module (which is why I didn't spot the problem when doing the
    > original Thumb kprobes work).
    >
    > Now I admit that having the tests always bombing out because of this
    > hinders testing of kprobes, but simply disabling the test is just
    > burying this long standing problem even more. So what do people think
    > about something like the change below, to let other tests get run but
    > make the overall test still fail...?
    >
    > --- a/arch/arm/kernel/kprobes-test.c
    > +++ b/arch/arm/kernel/kprobes-test.c
    > @@ -221,6 +221,7 @@ static int pre_handler_called;
    > static int post_handler_called;
    > static int jprobe_func_called;
    > static int kretprobe_handler_called;
    > +static int tests_failed;
    >
    > #define FUNC_ARG1 0x12345678
    > #define FUNC_ARG2 0xabcdef
    > @@ -457,6 +458,13 @@ static int run_api_tests(long (*func)(long, long))
    >
    > pr_info(" jprobe\n");
    > ret = test_jprobe(func);
    > +#if defined(CONFIG_THUMB2_KERNEL) && !defined(MODULE)
    > + if (ret == -EINVAL) {
    > + pr_err("FAIL: Known longtime bug with jprobe on Thumb kernels");
    > + tests_failed = ret;
    > + ret = 0;
    > + }
    > +#endif
    > if (ret < 0)
    > return ret;
    >
    > @@ -1667,6 +1675,8 @@ static int __init run_all_tests(void)
    >
    > out:
    > if (ret == 0)
    > + ret = tests_failed;
    > + if (ret == 0)
    > pr_info("Finished kprobe tests OK\n");
    > else
    > pr_err("kprobe tests failed\n");
    >
    >
    >
    >


    Thanks for clarifying the problem Tixy. I agree we should try and allow
    the tests to run for these more typical use cases where they do actually
    work. I have tested your patch and I will use it in place of mine
    unless there are strong objections.

    -dl



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