Messages in this thread | | | Date | Sat, 2 Apr 2016 22:47:52 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH v5 3/9] x86/head: Move early exception panic code into early_fixup_exception |
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On Sat, Apr 02, 2016 at 01:13:37PM -0700, Andy Lutomirski wrote: > Given that I this isn't really a regression with my patches (it > probably never worked much better on 32-bit and the regs never would > have shown at all on 64-bit),
You're right. That thing calls printk *and* early_printk, WTF:
#ifdef CONFIG_EARLY_PRINTK
call early_printk ...
call dump_stack
...
call __print_symbol
those last two call printk. Great.
> I propose a different approach: make > printk work earlier. Something like: > > if (early) { > early_printk(args); > } > > or early_vprintk or whatever. > > If the cost of a branch mattered, this could be alternative-patched > out later on, but that seems silly. I also bet that a more sensible > fallback could be created in which printk would try to use an early > console if there's no real console.
So how about this:
printk() does
vprintk_func = this_cpu_read(printk_func);
and that's
DEFINE_PER_CPU(printk_func_t, printk_func) = vprintk_default
I guess we can make that function be early_printk-something and once printk is initialized, we overwrite it with vprintk_default.
Elegant and no need for if branches and alternatives.
Hmmm.
-- Regards/Gruss, Boris.
ECO tip #101: Trim your mails when you reply.
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