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freebsd-dev/sys/amd64/vmm/vmm_instruction_emul.c
John Baldwin 00f3efe1bd Add support for FreeBSD/i386 guests under bhyve. 
- Similar to the hack for bootinfo32.c in userboot, define
  _MACHINE_ELF_WANT_32BIT in the load_elf32 file handlers in userboot.
  This allows userboot to load 32-bit kernels and modules.
- Copy the SMAP generation code out of bootinfo64.c and into its own
  file so it can be shared with bootinfo32.c to pass an SMAP to the i386
  kernel.
- Use uint32_t instead of u_long when aligning module metadata in
  bootinfo32.c in userboot, as otherwise the metadata used 64-bit
  alignment which corrupted the layout.
- Populate the basemem and extmem members of the bootinfo struct passed
  to 32-bit kernels.
- Fix the 32-bit stack in userboot to start at the top of the stack
  instead of the bottom so that there is room to grow before the
  kernel switches to its own stack.
- Push a fake return address onto the 32-bit stack in addition to the
  arguments normally passed to exec() in the loader.  This return
  address is needed to convince recover_bootinfo() in the 32-bit
  locore code that it is being invoked from a "new" boot block.
- Add a routine to libvmmapi to setup a 32-bit flat mode register state
  including a GDT and TSS that is able to start the i386 kernel and
  update bhyveload to use it when booting an i386 kernel.
- Use the guest register state to determine the CPU's current instruction
  mode (32-bit vs 64-bit) and paging mode (flat, 32-bit, PAE, or long
  mode) in the instruction emulation code.  Update the gla2gpa() routine
  used when fetching instructions to handle flat mode, 32-bit paging, and
  PAE paging in addition to long mode paging.  Don't look for a REX
  prefix when the CPU is in 32-bit mode, and use the detected mode to
  enable the existing 32-bit mode code when decoding the mod r/m byte.

Reviewed by:	grehan, neel
MFC after:	1 month
2014-02-05 04:39:03 +00:00

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/*-
* Copyright (c) 2012 Sandvine, Inc.
* Copyright (c) 2012 NetApp, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $FreeBSD$
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#ifdef _KERNEL
#include <sys/param.h>
#include <sys/pcpu.h>
#include <sys/systm.h>
#include <vm/vm.h>
#include <vm/pmap.h>
#include <machine/vmparam.h>
#include <machine/vmm.h>
#else /* !_KERNEL */
#include <sys/types.h>
#include <sys/errno.h>
#include <machine/vmm.h>
#include <vmmapi.h>
#endif /* _KERNEL */
/* struct vie_op.op_type */
enum {
VIE_OP_TYPE_NONE = 0,
VIE_OP_TYPE_MOV,
VIE_OP_TYPE_MOVZX,
VIE_OP_TYPE_AND,
VIE_OP_TYPE_OR,
VIE_OP_TYPE_TWO_BYTE,
VIE_OP_TYPE_LAST
};
/* struct vie_op.op_flags */
#define VIE_OP_F_IMM (1 << 0) /* immediate operand present */
#define VIE_OP_F_IMM8 (1 << 1) /* 8-bit immediate operand */
static const struct vie_op two_byte_opcodes[256] = {
[0xB6] = {
.op_byte = 0xB6,
.op_type = VIE_OP_TYPE_MOVZX,
},
};
static const struct vie_op one_byte_opcodes[256] = {
[0x0F] = {
.op_byte = 0x0F,
.op_type = VIE_OP_TYPE_TWO_BYTE
},
[0x88] = {
.op_byte = 0x88,
.op_type = VIE_OP_TYPE_MOV,
},
[0x89] = {
.op_byte = 0x89,
.op_type = VIE_OP_TYPE_MOV,
},
[0x8A] = {
.op_byte = 0x8A,
.op_type = VIE_OP_TYPE_MOV,
},
[0x8B] = {
.op_byte = 0x8B,
.op_type = VIE_OP_TYPE_MOV,
},
[0xC7] = {
.op_byte = 0xC7,
.op_type = VIE_OP_TYPE_MOV,
.op_flags = VIE_OP_F_IMM,
},
[0x23] = {
.op_byte = 0x23,
.op_type = VIE_OP_TYPE_AND,
},
[0x81] = {
/* XXX Group 1 extended opcode - not just AND */
.op_byte = 0x81,
.op_type = VIE_OP_TYPE_AND,
.op_flags = VIE_OP_F_IMM,
},
[0x83] = {
/* XXX Group 1 extended opcode - not just OR */
.op_byte = 0x83,
.op_type = VIE_OP_TYPE_OR,
.op_flags = VIE_OP_F_IMM8,
},
};
/* struct vie.mod */
#define VIE_MOD_INDIRECT 0
#define VIE_MOD_INDIRECT_DISP8 1
#define VIE_MOD_INDIRECT_DISP32 2
#define VIE_MOD_DIRECT 3
/* struct vie.rm */
#define VIE_RM_SIB 4
#define VIE_RM_DISP32 5
#define GB (1024 * 1024 * 1024)
static enum vm_reg_name gpr_map[16] = {
VM_REG_GUEST_RAX,
VM_REG_GUEST_RCX,
VM_REG_GUEST_RDX,
VM_REG_GUEST_RBX,
VM_REG_GUEST_RSP,
VM_REG_GUEST_RBP,
VM_REG_GUEST_RSI,
VM_REG_GUEST_RDI,
VM_REG_GUEST_R8,
VM_REG_GUEST_R9,
VM_REG_GUEST_R10,
VM_REG_GUEST_R11,
VM_REG_GUEST_R12,
VM_REG_GUEST_R13,
VM_REG_GUEST_R14,
VM_REG_GUEST_R15
};
static uint64_t size2mask[] = {
[1] = 0xff,
[2] = 0xffff,
[4] = 0xffffffff,
[8] = 0xffffffffffffffff,
};
static int
vie_read_register(void *vm, int vcpuid, enum vm_reg_name reg, uint64_t *rval)
{
int error;
error = vm_get_register(vm, vcpuid, reg, rval);
return (error);
}
static int
vie_read_bytereg(void *vm, int vcpuid, struct vie *vie, uint8_t *rval)
{
uint64_t val;
int error, rshift;
enum vm_reg_name reg;
rshift = 0;
reg = gpr_map[vie->reg];
/*
* 64-bit mode imposes limitations on accessing legacy byte registers.
*
* The legacy high-byte registers cannot be addressed if the REX
* prefix is present. In this case the values 4, 5, 6 and 7 of the
* 'ModRM:reg' field address %spl, %bpl, %sil and %dil respectively.
*
* If the REX prefix is not present then the values 4, 5, 6 and 7
* of the 'ModRM:reg' field address the legacy high-byte registers,
* %ah, %ch, %dh and %bh respectively.
*/
if (!vie->rex_present) {
if (vie->reg & 0x4) {
/*
* Obtain the value of %ah by reading %rax and shifting
* right by 8 bits (same for %bh, %ch and %dh).
*/
rshift = 8;
reg = gpr_map[vie->reg & 0x3];
}
}
error = vm_get_register(vm, vcpuid, reg, &val);
*rval = val >> rshift;
return (error);
}
static int
vie_update_register(void *vm, int vcpuid, enum vm_reg_name reg,
uint64_t val, int size)
{
int error;
uint64_t origval;
switch (size) {
case 1:
case 2:
error = vie_read_register(vm, vcpuid, reg, &origval);
if (error)
return (error);
val &= size2mask[size];
val |= origval & ~size2mask[size];
break;
case 4:
val &= 0xffffffffUL;
break;
case 8:
break;
default:
return (EINVAL);
}
error = vm_set_register(vm, vcpuid, reg, val);
return (error);
}
/*
* The following simplifying assumptions are made during emulation:
*
* - guest is in 64-bit mode
* - default address size is 64-bits
* - default operand size is 32-bits
*
* - operand size override is not supported
*
* - address size override is not supported
*/
static int
emulate_mov(void *vm, int vcpuid, uint64_t gpa, struct vie *vie,
mem_region_read_t memread, mem_region_write_t memwrite, void *arg)
{
int error, size;
enum vm_reg_name reg;
uint8_t byte;
uint64_t val;
size = 4;
error = EINVAL;
switch (vie->op.op_byte) {
case 0x88:
/*
* MOV byte from reg (ModRM:reg) to mem (ModRM:r/m)
* 88/r: mov r/m8, r8
* REX + 88/r: mov r/m8, r8 (%ah, %ch, %dh, %bh not available)
*/
size = 1;
error = vie_read_bytereg(vm, vcpuid, vie, &byte);
if (error == 0)
error = memwrite(vm, vcpuid, gpa, byte, size, arg);
break;
case 0x89:
/*
* MOV from reg (ModRM:reg) to mem (ModRM:r/m)
* 89/r: mov r/m32, r32
* REX.W + 89/r mov r/m64, r64
*/
if (vie->rex_w)
size = 8;
reg = gpr_map[vie->reg];
error = vie_read_register(vm, vcpuid, reg, &val);
if (error == 0) {
val &= size2mask[size];
error = memwrite(vm, vcpuid, gpa, val, size, arg);
}
break;
case 0x8A:
case 0x8B:
/*
* MOV from mem (ModRM:r/m) to reg (ModRM:reg)
* 8A/r: mov r/m8, r8
* REX + 8A/r: mov r/m8, r8
* 8B/r: mov r32, r/m32
* REX.W 8B/r: mov r64, r/m64
*/
if (vie->op.op_byte == 0x8A)
size = 1;
else if (vie->rex_w)
size = 8;
error = memread(vm, vcpuid, gpa, &val, size, arg);
if (error == 0) {
reg = gpr_map[vie->reg];
error = vie_update_register(vm, vcpuid, reg, val, size);
}
break;
case 0xC7:
/*
* MOV from imm32 to mem (ModRM:r/m)
* C7/0 mov r/m32, imm32
* REX.W + C7/0 mov r/m64, imm32 (sign-extended to 64-bits)
*/
val = vie->immediate; /* already sign-extended */
if (vie->rex_w)
size = 8;
if (size != 8)
val &= size2mask[size];
error = memwrite(vm, vcpuid, gpa, val, size, arg);
break;
default:
break;
}
return (error);
}
/*
* The following simplifying assumptions are made during emulation:
*
* - guest is in 64-bit mode
* - default address size is 64-bits
* - default operand size is 32-bits
*
* - operand size override is not supported
*
* - address size override is not supported
*/
static int
emulate_movzx(void *vm, int vcpuid, uint64_t gpa, struct vie *vie,
mem_region_read_t memread, mem_region_write_t memwrite,
void *arg)
{
int error, size;
enum vm_reg_name reg;
uint64_t val;
size = 4;
error = EINVAL;
switch (vie->op.op_byte) {
case 0xB6:
/*
* MOV and zero extend byte from mem (ModRM:r/m) to
* reg (ModRM:reg).
*
* 0F B6/r movzx r/m8, r32
* REX.W + 0F B6/r movzx r/m8, r64
*/
/* get the first operand */
error = memread(vm, vcpuid, gpa, &val, 1, arg);
if (error)
break;
/* get the second operand */
reg = gpr_map[vie->reg];
if (vie->rex_w)
size = 8;
/* write the result */
error = vie_update_register(vm, vcpuid, reg, val, size);
break;
default:
break;
}
return (error);
}
static int
emulate_and(void *vm, int vcpuid, uint64_t gpa, struct vie *vie,
mem_region_read_t memread, mem_region_write_t memwrite, void *arg)
{
int error, size;
enum vm_reg_name reg;
uint64_t val1, val2;
size = 4;
error = EINVAL;
switch (vie->op.op_byte) {
case 0x23:
/*
* AND reg (ModRM:reg) and mem (ModRM:r/m) and store the
* result in reg.
*
* 23/r and r32, r/m32
* REX.W + 23/r and r64, r/m64
*/
if (vie->rex_w)
size = 8;
/* get the first operand */
reg = gpr_map[vie->reg];
error = vie_read_register(vm, vcpuid, reg, &val1);
if (error)
break;
/* get the second operand */
error = memread(vm, vcpuid, gpa, &val2, size, arg);
if (error)
break;
/* perform the operation and write the result */
val1 &= val2;
error = vie_update_register(vm, vcpuid, reg, val1, size);
break;
case 0x81:
/*
* AND mem (ModRM:r/m) with immediate and store the
* result in mem.
*
* 81/ and r/m32, imm32
* REX.W + 81/ and r/m64, imm32 sign-extended to 64
*
* Currently, only the AND operation of the 0x81 opcode
* is implemented (ModRM:reg = b100).
*/
if ((vie->reg & 7) != 4)
break;
if (vie->rex_w)
size = 8;
/* get the first operand */
error = memread(vm, vcpuid, gpa, &val1, size, arg);
if (error)
break;
/*
* perform the operation with the pre-fetched immediate
* operand and write the result
*/
val1 &= vie->immediate;
error = memwrite(vm, vcpuid, gpa, val1, size, arg);
break;
default:
break;
}
return (error);
}
static int
emulate_or(void *vm, int vcpuid, uint64_t gpa, struct vie *vie,
mem_region_read_t memread, mem_region_write_t memwrite, void *arg)
{
int error, size;
uint64_t val1;
size = 4;
error = EINVAL;
switch (vie->op.op_byte) {
case 0x83:
/*
* OR mem (ModRM:r/m) with immediate and store the
* result in mem.
*
* 83/ OR r/m32, imm8 sign-extended to 32
* REX.W + 83/ OR r/m64, imm8 sign-extended to 64
*
* Currently, only the OR operation of the 0x83 opcode
* is implemented (ModRM:reg = b001).
*/
if ((vie->reg & 7) != 1)
break;
if (vie->rex_w)
size = 8;
/* get the first operand */
error = memread(vm, vcpuid, gpa, &val1, size, arg);
if (error)
break;
/*
* perform the operation with the pre-fetched immediate
* operand and write the result
*/
val1 |= vie->immediate;
error = memwrite(vm, vcpuid, gpa, val1, size, arg);
break;
default:
break;
}
return (error);
}
int
vmm_emulate_instruction(void *vm, int vcpuid, uint64_t gpa, struct vie *vie,
mem_region_read_t memread, mem_region_write_t memwrite,
void *memarg)
{
int error;
if (!vie->decoded)
return (EINVAL);
switch (vie->op.op_type) {
case VIE_OP_TYPE_MOV:
error = emulate_mov(vm, vcpuid, gpa, vie,
memread, memwrite, memarg);
break;
case VIE_OP_TYPE_MOVZX:
error = emulate_movzx(vm, vcpuid, gpa, vie,
memread, memwrite, memarg);
break;
case VIE_OP_TYPE_AND:
error = emulate_and(vm, vcpuid, gpa, vie,
memread, memwrite, memarg);
break;
case VIE_OP_TYPE_OR:
error = emulate_or(vm, vcpuid, gpa, vie,
memread, memwrite, memarg);
break;
default:
error = EINVAL;
break;
}
return (error);
}
#ifdef _KERNEL
void
vie_init(struct vie *vie)
{
bzero(vie, sizeof(struct vie));
vie->base_register = VM_REG_LAST;
vie->index_register = VM_REG_LAST;
}
static int
gla2gpa(struct vm *vm, uint64_t gla, uint64_t ptpphys,
uint64_t *gpa, enum vie_paging_mode paging_mode)
{
int nlevels, ptpshift, ptpindex;
uint64_t *ptpbase, pte, pgsize;
uint32_t *ptpbase32, pte32;
void *cookie;
if (paging_mode == PAGING_MODE_FLAT) {
*gpa = gla;
return (0);
}
if (paging_mode == PAGING_MODE_32) {
nlevels = 2;
while (--nlevels >= 0) {
/* Zero out the lower 12 bits. */
ptpphys &= ~0xfff;
ptpbase32 = vm_gpa_hold(vm, ptpphys, PAGE_SIZE,
VM_PROT_READ, &cookie);
if (ptpbase32 == NULL)
goto error;
ptpshift = PAGE_SHIFT + nlevels * 10;
ptpindex = (gla >> ptpshift) & 0x3FF;
pgsize = 1UL << ptpshift;
pte32 = ptpbase32[ptpindex];
vm_gpa_release(cookie);
if ((pte32 & PG_V) == 0)
goto error;
if (pte32 & PG_PS)
break;
ptpphys = pte32;
}
/* Zero out the lower 'ptpshift' bits */
pte32 >>= ptpshift; pte32 <<= ptpshift;
*gpa = pte32 | (gla & (pgsize - 1));
return (0);
}
if (paging_mode == PAGING_MODE_PAE) {
/* Zero out the lower 5 bits and the upper 12 bits */
ptpphys >>= 5; ptpphys <<= 17; ptpphys >>= 12;
ptpbase = vm_gpa_hold(vm, ptpphys, sizeof(*ptpbase) * 4,
VM_PROT_READ, &cookie);
if (ptpbase == NULL)
goto error;
ptpindex = (gla >> 30) & 0x3;
pte = ptpbase[ptpindex];
vm_gpa_release(cookie);
if ((pte & PG_V) == 0)
goto error;
ptpphys = pte;
nlevels = 2;
} else
nlevels = 4;
while (--nlevels >= 0) {
/* Zero out the lower 12 bits and the upper 12 bits */
ptpphys >>= 12; ptpphys <<= 24; ptpphys >>= 12;
ptpbase = vm_gpa_hold(vm, ptpphys, PAGE_SIZE, VM_PROT_READ,
&cookie);
if (ptpbase == NULL)
goto error;
ptpshift = PAGE_SHIFT + nlevels * 9;
ptpindex = (gla >> ptpshift) & 0x1FF;
pgsize = 1UL << ptpshift;
pte = ptpbase[ptpindex];
vm_gpa_release(cookie);
if ((pte & PG_V) == 0)
goto error;
if (pte & PG_PS) {
if (pgsize > 1 * GB)
goto error;
else
break;
}
ptpphys = pte;
}
/* Zero out the lower 'ptpshift' bits and the upper 12 bits */
pte >>= ptpshift; pte <<= (ptpshift + 12); pte >>= 12;
*gpa = pte | (gla & (pgsize - 1));
return (0);
error:
return (-1);
}
int
vmm_fetch_instruction(struct vm *vm, int cpuid, uint64_t rip, int inst_length,
uint64_t cr3, enum vie_paging_mode paging_mode,
struct vie *vie)
{
int n, err, prot;
uint64_t gpa, off;
void *hpa, *cookie;
/*
* XXX cache previously fetched instructions using 'rip' as the tag
*/
prot = VM_PROT_READ | VM_PROT_EXECUTE;
if (inst_length > VIE_INST_SIZE)
panic("vmm_fetch_instruction: invalid length %d", inst_length);
/* Copy the instruction into 'vie' */
while (vie->num_valid < inst_length) {
err = gla2gpa(vm, rip, cr3, &gpa, paging_mode);
if (err)
break;
off = gpa & PAGE_MASK;
n = min(inst_length - vie->num_valid, PAGE_SIZE - off);
if ((hpa = vm_gpa_hold(vm, gpa, n, prot, &cookie)) == NULL)
break;
bcopy(hpa, &vie->inst[vie->num_valid], n);
vm_gpa_release(cookie);
rip += n;
vie->num_valid += n;
}
if (vie->num_valid == inst_length)
return (0);
else
return (-1);
}
static int
vie_peek(struct vie *vie, uint8_t *x)
{
if (vie->num_processed < vie->num_valid) {
*x = vie->inst[vie->num_processed];
return (0);
} else
return (-1);
}
static void
vie_advance(struct vie *vie)
{
vie->num_processed++;
}
static int
decode_rex(struct vie *vie)
{
uint8_t x;
if (vie_peek(vie, &x))
return (-1);
if (x >= 0x40 && x <= 0x4F) {
vie->rex_present = 1;
vie->rex_w = x & 0x8 ? 1 : 0;
vie->rex_r = x & 0x4 ? 1 : 0;
vie->rex_x = x & 0x2 ? 1 : 0;
vie->rex_b = x & 0x1 ? 1 : 0;
vie_advance(vie);
}
return (0);
}
static int
decode_two_byte_opcode(struct vie *vie)
{
uint8_t x;
if (vie_peek(vie, &x))
return (-1);
vie->op = two_byte_opcodes[x];
if (vie->op.op_type == VIE_OP_TYPE_NONE)
return (-1);
vie_advance(vie);
return (0);
}
static int
decode_opcode(struct vie *vie)
{
uint8_t x;
if (vie_peek(vie, &x))
return (-1);
vie->op = one_byte_opcodes[x];
if (vie->op.op_type == VIE_OP_TYPE_NONE)
return (-1);
vie_advance(vie);
if (vie->op.op_type == VIE_OP_TYPE_TWO_BYTE)
return (decode_two_byte_opcode(vie));
return (0);
}
static int
decode_modrm(struct vie *vie, enum vie_cpu_mode cpu_mode)
{
uint8_t x;
if (vie_peek(vie, &x))
return (-1);
vie->mod = (x >> 6) & 0x3;
vie->rm = (x >> 0) & 0x7;
vie->reg = (x >> 3) & 0x7;
/*
* A direct addressing mode makes no sense in the context of an EPT
* fault. There has to be a memory access involved to cause the
* EPT fault.
*/
if (vie->mod == VIE_MOD_DIRECT)
return (-1);
if ((vie->mod == VIE_MOD_INDIRECT && vie->rm == VIE_RM_DISP32) ||
(vie->mod != VIE_MOD_DIRECT && vie->rm == VIE_RM_SIB)) {
/*
* Table 2-5: Special Cases of REX Encodings
*
* mod=0, r/m=5 is used in the compatibility mode to
* indicate a disp32 without a base register.
*
* mod!=3, r/m=4 is used in the compatibility mode to
* indicate that the SIB byte is present.
*
* The 'b' bit in the REX prefix is don't care in
* this case.
*/
} else {
vie->rm |= (vie->rex_b << 3);
}
vie->reg |= (vie->rex_r << 3);
/* SIB */
if (vie->mod != VIE_MOD_DIRECT && vie->rm == VIE_RM_SIB)
goto done;
vie->base_register = gpr_map[vie->rm];
switch (vie->mod) {
case VIE_MOD_INDIRECT_DISP8:
vie->disp_bytes = 1;
break;
case VIE_MOD_INDIRECT_DISP32:
vie->disp_bytes = 4;
break;
case VIE_MOD_INDIRECT:
if (vie->rm == VIE_RM_DISP32) {
vie->disp_bytes = 4;
/*
* Table 2-7. RIP-Relative Addressing
*
* In 64-bit mode mod=00 r/m=101 implies [rip] + disp32
* whereas in compatibility mode it just implies disp32.
*/
if (cpu_mode == CPU_MODE_64BIT)
vie->base_register = VM_REG_GUEST_RIP;
else
vie->base_register = VM_REG_LAST;
}
break;
}
done:
vie_advance(vie);
return (0);
}
static int
decode_sib(struct vie *vie)
{
uint8_t x;
/* Proceed only if SIB byte is present */
if (vie->mod == VIE_MOD_DIRECT || vie->rm != VIE_RM_SIB)
return (0);
if (vie_peek(vie, &x))
return (-1);
/* De-construct the SIB byte */
vie->ss = (x >> 6) & 0x3;
vie->index = (x >> 3) & 0x7;
vie->base = (x >> 0) & 0x7;
/* Apply the REX prefix modifiers */
vie->index |= vie->rex_x << 3;
vie->base |= vie->rex_b << 3;
switch (vie->mod) {
case VIE_MOD_INDIRECT_DISP8:
vie->disp_bytes = 1;
break;
case VIE_MOD_INDIRECT_DISP32:
vie->disp_bytes = 4;
break;
}
if (vie->mod == VIE_MOD_INDIRECT &&
(vie->base == 5 || vie->base == 13)) {
/*
* Special case when base register is unused if mod = 0
* and base = %rbp or %r13.
*
* Documented in:
* Table 2-3: 32-bit Addressing Forms with the SIB Byte
* Table 2-5: Special Cases of REX Encodings
*/
vie->disp_bytes = 4;
} else {
vie->base_register = gpr_map[vie->base];
}
/*
* All encodings of 'index' are valid except for %rsp (4).
*
* Documented in:
* Table 2-3: 32-bit Addressing Forms with the SIB Byte
* Table 2-5: Special Cases of REX Encodings
*/
if (vie->index != 4)
vie->index_register = gpr_map[vie->index];
/* 'scale' makes sense only in the context of an index register */
if (vie->index_register < VM_REG_LAST)
vie->scale = 1 << vie->ss;
vie_advance(vie);
return (0);
}
static int
decode_displacement(struct vie *vie)
{
int n, i;
uint8_t x;
union {
char buf[4];
int8_t signed8;
int32_t signed32;
} u;
if ((n = vie->disp_bytes) == 0)
return (0);
if (n != 1 && n != 4)
panic("decode_displacement: invalid disp_bytes %d", n);
for (i = 0; i < n; i++) {
if (vie_peek(vie, &x))
return (-1);
u.buf[i] = x;
vie_advance(vie);
}
if (n == 1)
vie->displacement = u.signed8; /* sign-extended */
else
vie->displacement = u.signed32; /* sign-extended */
return (0);
}
static int
decode_immediate(struct vie *vie)
{
int i, n;
uint8_t x;
union {
char buf[4];
int8_t signed8;
int32_t signed32;
} u;
/* Figure out immediate operand size (if any) */
if (vie->op.op_flags & VIE_OP_F_IMM)
vie->imm_bytes = 4;
else if (vie->op.op_flags & VIE_OP_F_IMM8)
vie->imm_bytes = 1;
if ((n = vie->imm_bytes) == 0)
return (0);
if (n != 1 && n != 4)
panic("decode_immediate: invalid imm_bytes %d", n);
for (i = 0; i < n; i++) {
if (vie_peek(vie, &x))
return (-1);
u.buf[i] = x;
vie_advance(vie);
}
if (n == 1)
vie->immediate = u.signed8; /* sign-extended */
else
vie->immediate = u.signed32; /* sign-extended */
return (0);
}
/*
* Verify that all the bytes in the instruction buffer were consumed.
*/
static int
verify_inst_length(struct vie *vie)
{
if (vie->num_processed == vie->num_valid)
return (0);
else
return (-1);
}
/*
* Verify that the 'guest linear address' provided as collateral of the nested
* page table fault matches with our instruction decoding.
*/
static int
verify_gla(struct vm *vm, int cpuid, uint64_t gla, struct vie *vie)
{
int error;
uint64_t base, idx;
/* Skip 'gla' verification */
if (gla == VIE_INVALID_GLA)
return (0);
base = 0;
if (vie->base_register != VM_REG_LAST) {
error = vm_get_register(vm, cpuid, vie->base_register, &base);
if (error) {
printf("verify_gla: error %d getting base reg %d\n",
error, vie->base_register);
return (-1);
}
/*
* RIP-relative addressing starts from the following
* instruction
*/
if (vie->base_register == VM_REG_GUEST_RIP)
base += vie->num_valid;
}
idx = 0;
if (vie->index_register != VM_REG_LAST) {
error = vm_get_register(vm, cpuid, vie->index_register, &idx);
if (error) {
printf("verify_gla: error %d getting index reg %d\n",
error, vie->index_register);
return (-1);
}
}
if (base + vie->scale * idx + vie->displacement != gla) {
printf("verify_gla mismatch: "
"base(0x%0lx), scale(%d), index(0x%0lx), "
"disp(0x%0lx), gla(0x%0lx)\n",
base, vie->scale, idx, vie->displacement, gla);
return (-1);
}
return (0);
}
int
vmm_decode_instruction(struct vm *vm, int cpuid, uint64_t gla,
enum vie_cpu_mode cpu_mode, struct vie *vie)
{
if (cpu_mode == CPU_MODE_64BIT) {
if (decode_rex(vie))
return (-1);
}
if (decode_opcode(vie))
return (-1);
if (decode_modrm(vie, cpu_mode))
return (-1);
if (decode_sib(vie))
return (-1);
if (decode_displacement(vie))
return (-1);
if (decode_immediate(vie))
return (-1);
if (verify_inst_length(vie))
return (-1);
if (verify_gla(vm, cpuid, gla, vie))
return (-1);
vie->decoded = 1; /* success */
return (0);
}
#endif /* _KERNEL */
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