Messages in this thread | | | Date | Tue, 17 May 2022 21:21:57 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH v2] arch/x86: Check validity of EBDA pointer in mpparse.c |
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On Mon, May 16, 2022 at 11:43:48AM +0200, Vit Kabele wrote: > And the valid upper bound of the EBDA pointer is also different > for these two use-cases. (The mpparse.c usage is interested in EBDA > pointer only if it ends 1KiB before the end of low memory, while the > ebda.c accepts even the values in the last KiB below 640KiB).
And I still don't know why this difference in the upper bounds is really relevant and why you can't simply use the code in reserve_bios_regions() after carving it out in a helper?
The latter considers ebda_start valid when it is between BIOS_START_MIN and bios_start, after having sanitized that bios_start to 640K if "out of bounds".
Why can't default_find_smp_config() simply scan the last KiB below 640KiB twice for the sake of simpler code?
I.e., there needs to be a single get_bios_ebda() - the current one can be renamed to __get_bios_ebda() - and that get_bios_ebda() should give either a sane EBDA address or 0 if the checks don't pass. And all code should use that.
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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