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KVM: x86: Shrink the usercopy region of the emulation context 

Shuffle a few operand structs to the end of struct x86_emulate_ctxt and
update the cache creation to whitelist only the region of the emulation
context that is expected to be copied to/from user memory, e.g. the
instruction operands, registers, and fetch/io/mem caches.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2020-02-18 15:29:50 -08:00 committed by Paolo Bonzini
parent 2f728d66e8
commit 06add254c7
2 changed files with 11 additions and 9 deletions
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8
arch/x86/kvm/kvm_emulate.h
View File

@ -334,9 +334,6 @@ struct x86_emulate_ctxt {
u8 intercept;
u8 op_bytes;
u8 ad_bytes;
struct operand src;
struct operand src2;
struct operand dst;
union {
int (*execute)(struct x86_emulate_ctxt *ctxt);
fastop_t fop;
@ -364,6 +361,11 @@ struct x86_emulate_ctxt {
u8 seg_override;
u64 d;
unsigned long _eip;
/* Here begins the usercopy section. */
struct operand src;
struct operand src2;
struct operand dst;
struct operand memop;
/* Fields above regs are cleared together. */
unsigned long _regs[NR_VCPU_REGS];

12
arch/x86/kvm/x86.c
View File

@ -235,13 +235,13 @@ static struct kmem_cache *x86_emulator_cache;
static struct kmem_cache *kvm_alloc_emulator_cache(void)
{
return kmem_cache_create_usercopy("x86_emulator",
sizeof(struct x86_emulate_ctxt),
unsigned int useroffset = offsetof(struct x86_emulate_ctxt, src);
unsigned int size = sizeof(struct x86_emulate_ctxt);
return kmem_cache_create_usercopy("x86_emulator", size,
__alignof__(struct x86_emulate_ctxt),
SLAB_ACCOUNT,
0,
sizeof(struct x86_emulate_ctxt),
NULL);
SLAB_ACCOUNT, useroffset,
size - useroffset, NULL);
}
static int emulator_fix_hypercall(struct x86_emulate_ctxt *ctxt);