Messages in this thread | | | From | (Eric W. Biederman) | Subject | Re: [Fastboot] [PATCH] x86_64: Reload CS when startup_64 is used. | Date | Tue, 22 Aug 2006 03:25:55 -0600 |
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"Magnus Damm" <magnus.damm@gmail.com> writes:
> Hi Eric, > > On 8/22/06, Eric W. Biederman <ebiederm@xmission.com> 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@xmission.com> > > 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?
I guess I'm not opposed to a patch but I have some serious reservations about a solution that limits my address to 32bits in 64bit mode, and appears to break the gdt used for entering the 32bit kernel.
I'm up way to late tonight. I just wanted to resolve the situation when it was clear what was going on.
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