check_cs(0x2b): not a valid code segment (0x2b is a TSS)

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clementttttttttt
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check_cs(0x2b): not a valid code segment (0x2b is a TSS)

Post by clementttttttttt »

Why can't the interrupt handler iret with this? I thought you can far jump into TSSs.
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rdos
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Re: check_cs(0x2b): not a valid code segment (0x2b is a TSS)

Post by rdos »

clementttttttttt wrote:Why can't the interrupt handler iret with this? I thought you can far jump into TSSs.
Having a TSS in ring 3 seems a bit strange. I think you would normally have TSSes in kernel with ring = 0 as the privilege level (RPL field of selector). Also, what DPL does the TSS have?

Also, the processor changes the TSS type to busy and if you iret to an TSS I think NT flag must be set and the TSS must be busy. Normal task switching with TSS will use far jmps and TSS RPL & DPL set to 0.

Since it is an interrupt, if interrupts can happen in ring 0, then the TSS must have RPL of 0.
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