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SubjectRe: EFI Boot Stub Early Console
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On Sun, 2012-03-18 at 08:10 -0400, Shea Levy wrote:
> Hi Matt,
>
> On 3/18/12 7:21 AM, Matt Fleming wrote:
> > I don't think you'll need to use the graphics protocols, you should
> > just be able to put something together using the 'output_string'
> > function from the EFI simple text output protocol, e.g. something like
> > this, https://lkml.org/lkml/2012/3/16/193
>
> From the UEFI 2.3.1 spec:
>
> > Prior to a call to ExitBootServices(), all of the fields of the EFI
> > System Table are valid. After an operating system has taken control of
> > the platform with a call to ExitBootServices(), only the Hdr,
> > FirmwareVendor, FirmwareRevision, RuntimeServices,
> > NumberOfTableEntries, and ConfigurationTable fields are valid.
>
> Doesn't this mean that ConOut can't be used for the earlyprintk, since
> any bootloader (including the bootstub) will call ExitBootServices()
> before any printk'ing actually happens?? Or am I misunderstanding the
> spec somehow? I suppose I could just try it and see what happens...

Oops. Good point, that isn't going to work.



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