Messages in this thread | | | Date | Tue, 9 Apr 2024 13:05:48 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH] kaslr: x86: fixes log message nokaslr |
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On Mon, Apr 01, 2024 at 07:38:17AM +0200, Mahmoud Younes wrote: > I don't think this gets printed after executing dmesg. This gets > printed to console if earlyprintks are captured to the console and the > kernel is configured with printing low level debug info. that is not > the default behavior and requires manipulating the kernel > configuration and command line to get this message. Specifically, > enabling DEBUG_LL and EARLY_PRINTK and adding "earlyprintk=ttyS0" or > whatever console in use. the message is just not visible in dmesg even > though it would exist in kernel log buffer, just the console wouldn't > be initialized at that moment.
If it is in the log buffer, it should come out at some point.
> this is not visible when booting a real hardware.
I don't think so - otherwise earlyprintk is broken.
> Since I am new to the kernel code base, I would appreciate some > guidance on how to move forward. Thank you!
Since those very early params are a handful and need special treatment, I'd prefer if they're handled explicitly as every arch does its own thing.
So print_unknown_bootoptions() is perhaps not the best place as it is arch-agnostic.
For this particular one:
void choose_random_location(unsigned long input, unsigned long input_size, unsigned long *output, unsigned long output_size, unsigned long *virt_addr) { unsigned long random_addr, min_addr;
if (cmdline_find_option_bool("nokaslr")) { warn("KASLR disabled: 'nokaslr' on cmdline."); return; }
boot_params_ptr->hdr.loadflags |= KASLR_FLAG;
So your dummy stub could look at the loader flags and at least warn when there's a mismatch.
And it should have a big fat comment explaining why this stub is there.
I guess that would be a good compromise between overengineering this for no good reason and not doing anything at all and confusing users.
Thx.
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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