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KVM: x86: Access to LDT/GDT that wraparound is incorrect

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When access to descriptor in LDT/GDT wraparound outside long-mode, the address
of the descriptor should be truncated to 32-bit.  Citing Intel SDM 2.1.1.1
"Global and Local Descriptor Tables in IA-32e Mode": "GDTR and LDTR registers
are expanded to 64-bits wide in both IA-32e sub-modes (64-bit mode and
compatibility mode)."

So in other cases, we need to truncate. Creating new function to return a
pointer to descriptor table to avoid too much code duplication.

Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
[Wrap 64-bit check with #ifdef CONFIG_X86_64, to avoid a "right shift count
 >= width of type" warning and consequent undefined behavior. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Nadav Amit 2014-12-25 02:52:23 +02:00 committed by Paolo Bonzini
parent e2cefa746e
commit edccda7ca7
1 changed files with 43 additions and 22 deletions
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65
arch/x86/kvm/emulate.c
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@ -1444,28 +1444,8 @@ static void get_descriptor_table_ptr(struct x86_emulate_ctxt *ctxt,
ops->get_gdt(ctxt, dt);
}
/* allowed just for 8 bytes segments */
static int read_segment_descriptor(struct x86_emulate_ctxt *ctxt,
u16 selector, struct desc_struct *desc,
ulong *desc_addr_p)
{
struct desc_ptr dt;
u16 index = selector >> 3;
ulong addr;
get_descriptor_table_ptr(ctxt, selector, &dt);
if (dt.size < index * 8 + 7)
return emulate_gp(ctxt, selector & 0xfffc);
*desc_addr_p = addr = dt.address + index * 8;
return ctxt->ops->read_std(ctxt, addr, desc, sizeof *desc,
&ctxt->exception);
}
/* allowed just for 8 bytes segments */
static int write_segment_descriptor(struct x86_emulate_ctxt *ctxt,
u16 selector, struct desc_struct *desc)
static int get_descriptor_ptr(struct x86_emulate_ctxt *ctxt,
u16 selector, ulong *desc_addr_p)
{
struct desc_ptr dt;
u16 index = selector >> 3;
@ -1477,6 +1457,47 @@ static int write_segment_descriptor(struct x86_emulate_ctxt *ctxt,
return emulate_gp(ctxt, selector & 0xfffc);
addr = dt.address + index * 8;
#ifdef CONFIG_X86_64
if (addr >> 32 != 0) {
u64 efer = 0;
ctxt->ops->get_msr(ctxt, MSR_EFER, &efer);
if (!(efer & EFER_LMA))
addr &= (u32)-1;
}
#endif
*desc_addr_p = addr;
return X86EMUL_CONTINUE;
}
/* allowed just for 8 bytes segments */
static int read_segment_descriptor(struct x86_emulate_ctxt *ctxt,
u16 selector, struct desc_struct *desc,
ulong *desc_addr_p)
{
int rc;
rc = get_descriptor_ptr(ctxt, selector, desc_addr_p);
if (rc != X86EMUL_CONTINUE)
return rc;
return ctxt->ops->read_std(ctxt, *desc_addr_p, desc, sizeof(*desc),
&ctxt->exception);
}
/* allowed just for 8 bytes segments */
static int write_segment_descriptor(struct x86_emulate_ctxt *ctxt,
u16 selector, struct desc_struct *desc)
{
int rc;
ulong addr;
rc = get_descriptor_ptr(ctxt, selector, &addr);
if (rc != X86EMUL_CONTINUE)
return rc;
return ctxt->ops->write_std(ctxt, addr, desc, sizeof *desc,
&ctxt->exception);
}