Use a u16 instead of a u32 to track the dirty/valid status of GPRs in the
emulator. Unlike struct kvm_vcpu_arch, x86_emulate_ctxt tracks only the
"true" GPRs, i.e. doesn't include RIP in its array, and so only needs to
track 16 registers.
Note, maxing out at 16 GPRs is a fundamental property of x86-64 and will
not change barring a massive architecture update. Legacy x86 ModRM and
SIB encodings use 3 bits for GPRs, i.e. support 8 registers. x86-64 uses
a single bit in the REX prefix for each possible reference type to double
the number of supported GPRs to 16 registers (4 bits).
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <
20220526210817.
3428868-5-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
if (WARN_ON_ONCE(nr >= NR_EMULATOR_GPRS))
nr &= NR_EMULATOR_GPRS - 1;
+ BUILD_BUG_ON(sizeof(ctxt->regs_dirty) * BITS_PER_BYTE < NR_EMULATOR_GPRS);
+ BUILD_BUG_ON(sizeof(ctxt->regs_valid) * BITS_PER_BYTE < NR_EMULATOR_GPRS);
+
ctxt->regs_valid |= 1 << nr;
ctxt->regs_dirty |= 1 << nr;
return &ctxt->_regs[nr];
u8 lock_prefix;
u8 rep_prefix;
/* bitmaps of registers in _regs[] that can be read */
- u32 regs_valid;
+ u16 regs_valid;
/* bitmaps of registers in _regs[] that have been written */
- u32 regs_dirty;
+ u16 regs_dirty;
/* modrm */
u8 modrm;
u8 modrm_mod;