Re: [Fastboot] [PATCH] x86_64: Reload CS when startup_64 is used.

From: Magnus Damm
Date: Tue Aug 22 2006 - 04:50:59 EST

Hi Eric,

On 8/22/06, Eric W. Biederman <ebiederm@xxxxxxxxxxxx> wrote:

In long mode the %cs is largely a relic. However there are a few cases
like lret where it matters that we have a valid value. Without this
patch it is possible to enter the kernel in startup_64 without setting
%cs to a valid value. With this patch we don't care what %cs value
we enter the kernel with, so long as the cs shadow register indicates
it is a privileged code segment.

Thanks to Magnus Damm for finding this problem and posting the
first workable patch. I have moved the jump to set %cs down a
few instructions so we don't need to take an extra jump. Which
keeps the code simpler.

Signed-of-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>

While at it, could you please fix up the purgatory code in kexec-tools
to include this fix so we can boot older versions of the kernel too?


/ magnus
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