x86 setup: make PM transition more paranoid; cleanup 32-bit entry

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Make the transition to protected mode more paranoid by having
back-to-back near jump (to synchronize the 386/486 prefetch queue) and
far jump (to set up the code segment.)

While we're at it, zero as many registers as practical (for future
expandability of the 32-bit entry interface) and enter 32-bit mode
with a valid stack.  Note that the 32-bit code cannot rely on this
stack, or we'll break all other existing users of the 32-bit
entrypoint, but it may make debugging hacks easier to write.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

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H. Peter Anvin 2008-01-30 13:33:01 +01:00 • committed by Ingo Molnar

parent 2a6648e65a

commit c4d9ba6da9

1 changed files with 32 additions and 12 deletions

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arch/x86/boot/pmjump.S

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