diff options
| author | Nelson Elhage <nelhage@ksplice.com> | 2011-04-13 15:44:13 (GMT) |
|---|---|---|
| committer | Avi Kivity <avi@redhat.com> | 2011-05-11 11:57:09 (GMT) |
| commit | 0521e4c0bc73aa86152ee4e4bd03724c8a9e1d6b (patch) | |
| tree | 01e60574962d06155ebea802e0dd7832a893f474 | |
| parent | 49704f26586ca87fcab4fe9323fff8db41e78910 (diff) | |
| download | linux-0521e4c0bc73aa86152ee4e4bd03724c8a9e1d6b.tar.xz | |
KVM: x86 emulator: Handle wraparound in (cs_base + offset) when fetching insns
Currently, setting a large (i.e. negative) base address for %cs does not work on
a 64-bit host. The "JOS" teaching operating system, used by MIT and other
universities, relies on such segments while bootstrapping its way to full
virtual memory management.
Signed-off-by: Nelson Elhage <nelhage@ksplice.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
| -rw-r--r-- | arch/x86/kvm/emulate.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index cb2efa4..4c5ff22 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -637,9 +637,12 @@ static int do_fetch_insn_byte(struct x86_emulate_ctxt *ctxt, int size, cur_size; if (eip == fc->end) { + unsigned long linear = eip + ctxt->cs_base; + if (ctxt->mode != X86EMUL_MODE_PROT64) + linear &= (u32)-1; cur_size = fc->end - fc->start; size = min(15UL - cur_size, PAGE_SIZE - offset_in_page(eip)); - rc = ops->fetch(ctxt->cs_base + eip, fc->data + cur_size, + rc = ops->fetch(linear, fc->data + cur_size, size, ctxt->vcpu, &ctxt->exception); if (rc != X86EMUL_CONTINUE) return rc; |