Re: [PATCH 4.19 41/48] x86/unwind/orc: Prevent unwinding before ORC initialization

Pavel Machek
2020-05-13T21:52:14Z

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Hi!

> From: Josh Poimboeuf <jpoimboe@redhat.com>
>
> commit 98d0c8ebf77e0ba7c54a9ae05ea588f0e9e3f46e upstream.
>
> If the unwinder is called before the ORC data has been initialized,
> orc_find() returns NULL, and it tries to fall back to using frame
> pointers. This can cause some unexpected warnings during boot.
>
> Move the 'orc_init' check from orc_find() to __unwind_init(), so that it
> doesn't even try to unwind from an uninitialized state.

> @@ -563,6 +560,9 @@ EXPORT_SYMBOL_GPL(unwind_next_frame);
> void __unwind_start(struct unwind_state *state, struct task_struct *task,
> struct pt_regs *regs, unsigned long *first_frame)
> {
> + if (!orc_init)
> + goto done;
> +
> memset(state, 0, sizeof(*state));
> state->task = task;
>

As this returns the *state to the caller, should the "goto done" move
below the memset? Otherwise we are returning partialy-initialized
struct, which is ... weird.

Best regards,
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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