From: Paul Durrant <Paul.Durrant@citrix.com>
To: 'Petre Pircalabu' <ppircalabu@bitdefender.com>,
"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>
Cc: Kevin Tian <kevin.tian@intel.com>,
"sstabellini@kernel.org" <sstabellini@kernel.org>,
Wei Liu <wei.liu2@citrix.com>,
"jun.nakajima@intel.com" <jun.nakajima@intel.com>,
"rcojocaru@bitdefender.com" <rcojocaru@bitdefender.com>,
Andrew Cooper <Andrew.Cooper3@citrix.com>,
"Tim (Xen.org)" <tim@xen.org>,
George Dunlap <George.Dunlap@citrix.com>,
"tamas@tklengyel.com" <tamas@tklengyel.com>,
"jbeulich@suse.com" <jbeulich@suse.com>,
Ian Jackson <Ian.Jackson@citrix.com>
Subject: Re: [PATCH v12 1/4] x86emul: New return code for unimplemented instruction
Date: Thu, 21 Sep 2017 08:53:13 +0000 [thread overview]
Message-ID: <a58519000334488db8a5f6c7cf23e4dc@AMSPEX02CL03.citrite.net> (raw)
In-Reply-To: <1505970726-5671-2-git-send-email-ppircalabu@bitdefender.com>
> -----Original Message-----
> From: Petre Pircalabu [mailto:ppircalabu@bitdefender.com]
> Sent: 21 September 2017 06:12
> To: xen-devel@lists.xen.org
> Cc: Ian Jackson <Ian.Jackson@citrix.com>; Wei Liu <wei.liu2@citrix.com>;
> Andrew Cooper <Andrew.Cooper3@citrix.com>; George Dunlap
> <George.Dunlap@citrix.com>; jbeulich@suse.com; konrad.wilk@oracle.com;
> sstabellini@kernel.org; Tim (Xen.org) <tim@xen.org>; Paul Durrant
> <Paul.Durrant@citrix.com>; rcojocaru@bitdefender.com;
> tamas@tklengyel.com; jun.nakajima@intel.com; Kevin Tian
> <kevin.tian@intel.com>; Petre Pircalabu <ppircalabu@bitdefender.com>
> Subject: [PATCH v12 1/4] x86emul: New return code for unimplemented
> instruction
>
> Enforce the distinction between an instruction not implemented by the
> emulator and the failure to emulate that instruction by defining a new
> return code, X86EMUL_UNIMPLEMENTED.
>
> This value should only be returned by the core emulator only if it fails to
> properly decode the current instruction's opcode, and not by any of other
> functions, such as the x86_emulate_ops or the hvm_io_ops callbacks.
>
> e.g. hvm_process_io_intercept should not return
> X86EMUL_UNIMPLEMENTED.
> The return value of this function depends on either the return code of
> one of the hvm_io_ops handlers (read/write) or the value returned by
> hvm_copy_guest_from_phys / hvm_copy_to_guest_phys.
>
> Similary, none of this functions should return X86EMUL_UNIMPLEMENTED.
> - hvm_io_intercept
> - hvmemul_do_io
> - hvm_send_buffered_ioreq
> - hvm_send_ioreq
> - hvm_broadcast_ioreq
> - hvmemul_do_io_buffer
> - hvmemul_validate
>
> Signed-off-by: Petre Pircalabu <ppircalabu@bitdefender.com>
>
> ---
> Changed since v10:
> * Added asserts to make sure the return code cannot be
> X86EMUL_UNIMPLEMENTED.
> * Add new return code (X86EMUL_UNRECOGNIZED) to be used when
> trying
> to emulate an instruction with an invalid opcode.
>
> Changed since v11:
> * Fixed double negative in the patch description.
> * Move assertion into the switch and use ASSERT_UNREACHABLE() when
> applicable.
> * Changed the description of X86EMUL_UNIMPLEMENTED /
> X86EMUL_UNRECOGNIZED
> to reflect the differences between those 2 return codes.
> * Changed the returned value to X86EMUL_UNRECOGNIZED in the
> following cases:
> X86EMUL_OPC(0x0f, 0x73): /* Group 14 */
> X86EMUL_OPC_66(0x0f, 0x73):
> X86EMUL_OPC_VEX_66(0x0f, 0x73):
> - All valid opcodes are defined, so it should return
> X86EMUL_UNRECOGNIZED if mod R/M bits are not matched.
>
> X86EMUL_OPC(0x0f, 0xc7) /* Group 9 */
> - For register type instructions all possible opcodes are
> defined, so it should return X86EMUL_UNRECOGNIZED if
> mod R/M bits are not matched.
>
> X86EMUL_OPC_VEX(0x0f38, 0xf3): /* Group 17 */
> - All valid opcodes are defined, so it should return
> X86EMUL_UNRECOGNIZED if mod R/M bits are not matched.
>
> X86EMUL_OPC_XOP(09, 0x01): /* XOP Grp1 */
> X86EMUL_OPC_XOP(09, 0x02): /* XOP Grp2 */
> - All valid opcodes are defined, so it should return
> X86EMUL_UNRECOGNIZED if mod R/M bits are not matched.
>
> X86EMUL_OPC(0x0f, 0x01): /* Grp7 */
> - Not all valid opcodes are defined so it should return
> X86EMUL_UNIMPLEMENTED if mod R/M bits are not matched.
> (e.g. XGETBV)
>
> X86EMUL_OPC_66(0x0f, 0x78):
> - All valid opcodes are defined, so it should return
> X86EMUL_UNRECOGNIZED if mod R/M bits are not matched.
>
> X86EMUL_OPC(0x0f, 0xae):
> X86EMUL_OPC_66(0x0f, 0xae): /* Grp15 */
> - Not all valid opcodes are defined so it should return
> X86EMUL_UNIMPLEMENTED if mod R/M bits are not matched.
> (e.g. FXSAVE/FXRSTOR )
> ---
> xen/arch/x86/hvm/emulate.c | 12 ++++++++
> xen/arch/x86/hvm/hvm.c | 1 +
> xen/arch/x86/hvm/io.c | 1 +
> xen/arch/x86/hvm/vmx/realmode.c | 2 +-
> xen/arch/x86/mm/shadow/multi.c | 2 +-
> xen/arch/x86/x86_emulate/x86_emulate.c | 52 ++++++++++++++++++++--
> ------------
> xen/arch/x86/x86_emulate/x86_emulate.h | 13 +++++++++
> 7 files changed, 60 insertions(+), 23 deletions(-)
>
> diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
> index cc874ce..385fe1e 100644
> --- a/xen/arch/x86/hvm/emulate.c
> +++ b/xen/arch/x86/hvm/emulate.c
> @@ -284,10 +284,15 @@ static int hvmemul_do_io(
> }
> break;
> }
> + case X86EMUL_UNIMPLEMENTED:
> + ASSERT_UNREACHABLE();
> + /* Fall-through */
Kind of surprised you need the fall-through if you assert the code is unreachable... but analysis tools can be a bit temperamental so ok.
> default:
> BUG();
> }
>
> + ASSERT(rc != X86EMUL_UNIMPLEMENTED);
> +
Isn't this assertion redundant given the ASSERT_UNREACHABLE() above?
Paul
> if ( rc != X86EMUL_OKAY )
> return rc;
>
> @@ -313,6 +318,9 @@ static int hvmemul_do_io_buffer(
>
> rc = hvmemul_do_io(is_mmio, addr, reps, size, dir, df, 0,
> (uintptr_t)buffer);
> +
> + ASSERT(rc != X86EMUL_UNIMPLEMENTED);
> +
> if ( rc == X86EMUL_UNHANDLEABLE && dir == IOREQ_READ )
> memset(buffer, 0xff, size);
>
> @@ -405,6 +413,8 @@ static int hvmemul_do_io_addr(
> rc = hvmemul_do_io(is_mmio, addr, &count, size, dir, df, 1,
> ram_gpa);
>
> + ASSERT(rc != X86EMUL_UNIMPLEMENTED);
> +
> if ( rc == X86EMUL_OKAY )
> v->arch.hvm_vcpu.hvm_io.mmio_retry = (count < *reps);
>
> @@ -2045,6 +2055,7 @@ int hvm_emulate_one_mmio(unsigned long mfn,
> unsigned long gla)
> switch ( rc )
> {
> case X86EMUL_UNHANDLEABLE:
> + case X86EMUL_UNIMPLEMENTED:
> hvm_dump_emulation_state(XENLOG_G_WARNING, "MMCFG",
> &ctxt);
> break;
> case X86EMUL_EXCEPTION:
> @@ -2102,6 +2113,7 @@ void hvm_emulate_one_vm_event(enum
> emul_kind kind, unsigned int trapnr,
> * consistent with X86EMUL_RETRY.
> */
> return;
> + case X86EMUL_UNIMPLEMENTED:
> case X86EMUL_UNHANDLEABLE:
> hvm_dump_emulation_state(XENLOG_G_DEBUG, "Mem event", &ctx);
> hvm_inject_hw_exception(trapnr, errcode);
> diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
> index 93394c1..43ff5aa 100644
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -3723,6 +3723,7 @@ void hvm_ud_intercept(struct cpu_user_regs
> *regs)
> switch ( hvm_emulate_one(&ctxt) )
> {
> case X86EMUL_UNHANDLEABLE:
> + case X86EMUL_UNIMPLEMENTED:
> hvm_inject_hw_exception(TRAP_invalid_op, X86_EVENT_NO_EC);
> break;
> case X86EMUL_EXCEPTION:
> diff --git a/xen/arch/x86/hvm/io.c b/xen/arch/x86/hvm/io.c
> index bf41954..984db21 100644
> --- a/xen/arch/x86/hvm/io.c
> +++ b/xen/arch/x86/hvm/io.c
> @@ -96,6 +96,7 @@ bool hvm_emulate_one_insn(hvm_emulate_validate_t
> *validate, const char *descr)
> switch ( rc )
> {
> case X86EMUL_UNHANDLEABLE:
> + case X86EMUL_UNIMPLEMENTED:
> hvm_dump_emulation_state(XENLOG_G_WARNING, descr, &ctxt);
> return false;
>
> diff --git a/xen/arch/x86/hvm/vmx/realmode.c
> b/xen/arch/x86/hvm/vmx/realmode.c
> index 12d43ad..cf48139 100644
> --- a/xen/arch/x86/hvm/vmx/realmode.c
> +++ b/xen/arch/x86/hvm/vmx/realmode.c
> @@ -106,7 +106,7 @@ void vmx_realmode_emulate_one(struct
> hvm_emulate_ctxt *hvmemul_ctxt)
> if ( hvm_vcpu_io_need_completion(vio) || vio->mmio_retry )
> vio->io_completion = HVMIO_realmode_completion;
>
> - if ( rc == X86EMUL_UNHANDLEABLE )
> + if ( rc == X86EMUL_UNHANDLEABLE || rc == X86EMUL_UNIMPLEMENTED
> )
> {
> gdprintk(XENLOG_ERR, "Failed to emulate insn.\n");
> goto fail;
> diff --git a/xen/arch/x86/mm/shadow/multi.c
> b/xen/arch/x86/mm/shadow/multi.c
> index 8d4f244..2557e21 100644
> --- a/xen/arch/x86/mm/shadow/multi.c
> +++ b/xen/arch/x86/mm/shadow/multi.c
> @@ -3488,7 +3488,7 @@ static int sh_page_fault(struct vcpu *v,
> * would be a good unshadow hint. If we *do* decide to unshadow-on-
> fault
> * then it must be 'failable': we cannot require the unshadow to succeed.
> */
> - if ( r == X86EMUL_UNHANDLEABLE )
> + if ( r == X86EMUL_UNHANDLEABLE || r == X86EMUL_UNIMPLEMENTED )
> {
> perfc_incr(shadow_fault_emulate_failed);
> #if SHADOW_OPTIMIZATIONS & SHOPT_FAST_EMULATION
> diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c
> b/xen/arch/x86/x86_emulate/x86_emulate.c
> index c1e2300..f334de9 100644
> --- a/xen/arch/x86/x86_emulate/x86_emulate.c
> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c
> @@ -848,7 +848,8 @@ do{ asm volatile ( \
> stub.func); \
> generate_exception_if(res_.fields.trapnr == EXC_UD, EXC_UD); \
> domain_crash(current->domain); \
> - goto cannot_emulate; \
> + rc = X86EMUL_UNHANDLEABLE; \
> + goto done; \
> } \
> } while (0)
> #else
> @@ -2585,7 +2586,7 @@ x86_decode(
> d = twobyte_table[0x3a].desc;
> break;
> default:
> - rc = X86EMUL_UNHANDLEABLE;
> + rc = X86EMUL_UNRECOGNIZED;
> goto done;
> }
> }
> @@ -2599,7 +2600,7 @@ x86_decode(
> }
> else
> {
> - rc = X86EMUL_UNHANDLEABLE;
> + rc = X86EMUL_UNRECOGNIZED;
> goto done;
> }
>
> @@ -2879,7 +2880,7 @@ x86_decode(
>
> default:
> ASSERT_UNREACHABLE();
> - return X86EMUL_UNHANDLEABLE;
> + return X86EMUL_UNIMPLEMENTED;
> }
>
> if ( ea.type == OP_MEM )
> @@ -4191,7 +4192,7 @@ x86_emulate(
> break;
> case 4: /* fldenv - TODO */
> state->fpu_ctrl = true;
> - goto cannot_emulate;
> + goto unimplemented_insn;
> case 5: /* fldcw m2byte */
> state->fpu_ctrl = true;
> if ( (rc = ops->read(ea.mem.seg, ea.mem.off, &src.val,
> @@ -4202,7 +4203,7 @@ x86_emulate(
> break;
> case 6: /* fnstenv - TODO */
> state->fpu_ctrl = true;
> - goto cannot_emulate;
> + goto unimplemented_insn;
> case 7: /* fnstcw m2byte */
> state->fpu_ctrl = true;
> emulate_fpu_insn_memdst("fnstcw", dst.val);
> @@ -4438,7 +4439,7 @@ x86_emulate(
> case 4: /* frstor - TODO */
> case 6: /* fnsave - TODO */
> state->fpu_ctrl = true;
> - goto cannot_emulate;
> + goto unimplemented_insn;
> case 7: /* fnstsw m2byte */
> state->fpu_ctrl = true;
> emulate_fpu_insn_memdst("fnstsw", dst.val);
> @@ -5197,7 +5198,7 @@ x86_emulate(
> #undef _GRP7
>
> default:
> - goto cannot_emulate;
> + goto unimplemented_insn;
> }
> break;
> }
> @@ -6195,7 +6196,7 @@ x86_emulate(
> /* vpsll{w,d} $imm8,{x,y}mm,{x,y}mm */
> break;
> default:
> - goto cannot_emulate;
> + goto unimplemented_insn;
> }
> simd_0f_shift_imm:
> generate_exception_if(ea.type != OP_REG, EXC_UD);
> @@ -6243,7 +6244,8 @@ x86_emulate(
> case 6: /* psllq $imm8,mm */
> goto simd_0f_shift_imm;
> }
> - goto cannot_emulate;
> + rc = X86EMUL_UNRECOGNIZED;
> + goto done;
>
> case X86EMUL_OPC_66(0x0f, 0x73):
> case X86EMUL_OPC_VEX_66(0x0f, 0x73):
> @@ -6259,7 +6261,8 @@ x86_emulate(
> /* vpslldq $imm8,{x,y}mm,{x,y}mm */
> goto simd_0f_shift_imm;
> }
> - goto cannot_emulate;
> + rc = X86EMUL_UNRECOGNIZED;
> + goto done;
>
> case X86EMUL_OPC(0x0f, 0x77): /* emms */
> case X86EMUL_OPC_VEX(0x0f, 0x77): /* vzero{all,upper} */
> @@ -6323,7 +6326,8 @@ x86_emulate(
> case 0: /* extrq $imm8,$imm8,xmm */
> break;
> default:
> - goto cannot_emulate;
> + rc = X86EMUL_UNRECOGNIZED;
> + goto done;
> }
> /* fall through */
> case X86EMUL_OPC_F2(0x0f, 0x78): /* insertq $imm8,$imm8,xmm,xmm
> */
> @@ -6518,7 +6522,7 @@ x86_emulate(
> goto done;
> break;
> default:
> - goto cannot_emulate;
> + goto unimplemented_insn;
> }
> break;
>
> @@ -6534,7 +6538,8 @@ x86_emulate(
> vcpu_must_have(avx);
> goto stmxcsr;
> }
> - goto cannot_emulate;
> + rc = X86EMUL_UNRECOGNIZED;
> + goto done;
>
> case X86EMUL_OPC_F3(0x0f, 0xae): /* Grp15 */
> fail_if(modrm_mod != 3);
> @@ -6777,7 +6782,8 @@ x86_emulate(
> switch ( modrm_reg & 7 )
> {
> default:
> - goto cannot_emulate;
> + rc = X86EMUL_UNRECOGNIZED;
> + goto done;
>
> #ifdef HAVE_GAS_RDRAND
> case 6: /* rdrand */
> @@ -7359,7 +7365,8 @@ x86_emulate(
> host_and_vcpu_must_have(bmi1);
> break;
> default:
> - goto cannot_emulate;
> + rc = X86EMUL_UNRECOGNIZED;
> + goto done;
> }
>
> generate_exception_if(vex.l, EXC_UD);
> @@ -7670,7 +7677,8 @@ x86_emulate(
> host_and_vcpu_must_have(tbm);
> break;
> default:
> - goto cannot_emulate;
> + rc = X86EMUL_UNRECOGNIZED;
> + goto done;
> }
>
> xop_09_rm_rv:
> @@ -7704,7 +7712,8 @@ x86_emulate(
> host_and_vcpu_must_have(tbm);
> goto xop_09_rm_rv;
> }
> - goto cannot_emulate;
> + rc = X86EMUL_UNRECOGNIZED;
> + goto done;
>
> case X86EMUL_OPC_XOP(0a, 0x10): /* bextr imm,r/m,r */
> {
> @@ -7736,8 +7745,8 @@ x86_emulate(
> }
>
> default:
> - cannot_emulate:
> - rc = X86EMUL_UNHANDLEABLE;
> + unimplemented_insn:
> + rc = X86EMUL_UNIMPLEMENTED;
> goto done;
> }
>
> @@ -7789,7 +7798,8 @@ x86_emulate(
> if ( (d & DstMask) != DstMem )
> {
> ASSERT_UNREACHABLE();
> - goto cannot_emulate;
> + rc = X86EMUL_UNHANDLEABLE;
> + goto done;
> }
> break;
> }
> diff --git a/xen/arch/x86/x86_emulate/x86_emulate.h
> b/xen/arch/x86/x86_emulate/x86_emulate.h
> index 4ddf111..1fb74c0 100644
> --- a/xen/arch/x86/x86_emulate/x86_emulate.h
> +++ b/xen/arch/x86/x86_emulate/x86_emulate.h
> @@ -133,6 +133,19 @@ struct x86_emul_fpu_aux {
> * Undefined behavior when used anywhere else.
> */
> #define X86EMUL_DONE 4
> + /*
> + * Current instruction is not implemented by the emulator.
> + * This value should only be returned by the core emulator when a valid
> + * opcode is found but the execution logic for that instruction is missing.
> + * It should NOT be returned by any of the x86_emulate_ops callbacks.
> + */
> +#define X86EMUL_UNIMPLEMENTED 5
> + /*
> + * The current instruction's opcode is not valid.
> + * If this error code is returned by a function, an #UD trap should be
> + * raised by the final consumer of it.
> + */
> +#define X86EMUL_UNRECOGNIZED X86EMUL_UNIMPLEMENTED
>
> /* FPU sub-types which may be requested via ->get_fpu(). */
> enum x86_emulate_fpu_type {
> --
> 2.7.4
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next prev parent reply other threads:[~2017-09-21 8:53 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-21 5:12 [PATCH v12 0/4] Notify monitor when emulating an unimplemented instruction Petre Pircalabu
2017-09-21 5:12 ` [PATCH v12 1/4] x86emul: New return code for " Petre Pircalabu
2017-09-21 8:53 ` Paul Durrant [this message]
2017-09-23 18:56 ` Petre Ovidiu PIRCALABU
2017-09-25 7:54 ` Paul Durrant
2017-09-21 12:42 ` Jan Beulich
2017-09-25 9:16 ` Petre Ovidiu PIRCALABU
2017-09-25 10:36 ` Jan Beulich
2017-09-22 9:10 ` Jan Beulich
2017-09-21 5:12 ` [PATCH v12 2/4] x86emul: Add return code information to error messages Petre Pircalabu
2017-09-21 5:12 ` [PATCH v12 3/4] x86/monitor: Notify monitor if an emulation fails Petre Pircalabu
2017-09-21 5:12 ` [PATCH v12 4/4] x86emul: Raise #UD when emulating an unrecognized instruction Petre Pircalabu
2017-09-21 8:57 ` Paul Durrant
2017-09-21 12:44 ` Jan Beulich
2017-09-25 6:22 ` Petre Ovidiu PIRCALABU
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