Check CPUID instruction in Stage0 #VC handler #4921
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andrisaar
reviewed
Mar 20, 2024
stage0_bin/src/asm/boot.s
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| @@ -43,7 +43,10 @@ gp_handler: | |||
| vc_handler: | |||
| pop %ebx # get the error code | |||
| cmp $0x72, %ebx # is this about CPUID? | |||
| jne 2f # if not, skip ahead | |||
| jne 2f # if not, skip ahead and crash | |||
| pop %ebx # get the instruction pointer | |||
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This pops the EIP value off the stack, I think that'll break the IRET later (where should it return to?).
What you'd really want to do is effectively ((%esp)) (first dereference ESP to get the value of EIP, then dereference EIP) but I'm pretty sure you can't do it like that.
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Ah yes, good point.
andrisaar
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Mar 20, 2024
waywardgeek
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Mar 21, 2024
We want to make sure that the instruction pointer in a #VC exception really pointed to a CPUID instruction since it is the only #VC exception type we support. Ref b/330197837
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We want to make sure that the instruction pointer in a #VC exception really pointed to a CPUID instruction since it is the only #VC exception type we support.
Ref b/330197837