[Qemu-devel] [Bug 629791] [NEW] sysret sets invalid ss

[dascandy]

Public bug reported:

I'm developing an OS. I use only sysret to enter user space. When an
interrupt occurred, it would GPF on iretq'ing from it. On investigating,
the cs on the stack is 0x2b (valid and correct). The ss on the stack is
0x20, which has a rpl of 0 which is incorrect. iretq checks that and
gpf's. Making the irq handler manually modify it to 0x23 fixes it
locally.

This happens on the non-kvm'ed qemu. I haven't tried the kvm'ed one.
Qemu version 0.12.5. I haven't tried with the current development
version either.

** Affects: qemu
     Importance: Undecided
         Status: New


** Tags: dpl ss sysret

-- 
sysret sets invalid ss
https://bugs.launchpad.net/bugs/629791
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Status in QEMU: New

Bug description:
I'm developing an OS. I use only sysret to enter user space. When an interrupt 
occurred, it would GPF on iretq'ing from it. On investigating, the cs on the 
stack is 0x2b (valid and correct). The ss on the stack is 0x20, which has a rpl 
of 0 which is incorrect. iretq checks that and gpf's. Making the irq handler 
manually modify it to 0x23 fixes it locally.

This happens on the non-kvm'ed qemu. I haven't tried the kvm'ed one. Qemu 
version 0.12.5. I haven't tried with the current development version either.