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SubjectRe: [PATCH v3 2/9] kprobes: Add a test case for stacktrace from kretprobe handler
On Thu, 21 Oct 2021 09:54:32 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:

> Add a test case for stacktrace from kretprobe handler and
> nested kretprobe handlers.
>
> This test checks both of stack trace inside kretprobe handler
> and stack trace from pt_regs. Those stack trace must include
> actual function return address instead of kretprobe trampoline.
> The nested kretprobe stacktrace test checks whether the unwinder
> can correctly unwind the call frame on the stack which has been
> modified by the kretprobe.
>
> Since the stacktrace on kretprobe is correctly fixed only on x86,
> this introduces a meta kconfig ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
> which tells user that the stacktrace on kretprobe is correct or not.
>
> The test results will be shown like below;
>
> TAP version 14
> 1..1
> # Subtest: kprobes_test
> 1..6
> ok 1 - test_kprobe
> ok 2 - test_kprobes
> ok 3 - test_kretprobe
> ok 4 - test_kretprobes
> ok 5 - test_stacktrace_on_kretprobe
> ok 6 - test_stacktrace_on_nested_kretprobe
> # kprobes_test: pass:6 fail:0 skip:0 total:6
> # Totals: pass:6 fail:0 skip:0 total:6
> ok 1 - kprobes_test

So my allmodconfig test failed on this:

ERROR: modpost: "stack_trace_save_regs" [kernel/test_kprobes.ko] undefined!


> + /*
> + * Test stacktrace from pt_regs at the return address. Thus the stack
> + * trace must start from the target return address.
> + */
> + ret = stack_trace_save_regs(regs, stack_buf, STACK_BUF_SIZE, 0);
> + KUNIT_EXPECT_NE(current_test, ret, 0);
> + KUNIT_EXPECT_EQ(current_test, stack_buf[0], target_return_address[1]);
> +
> + return 0;
> +}

It appears that that "stack_trace_save_regs" is not exported. And this code
can be compiled as a module.

I'm going to continue testing my code, as I have over 40 patches that need
to go into next. I'll just rebase removing this commit only (hopefully
nothing else breaks), and if everything then passes, I'll push to next.

-- Steve

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