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vmx.S
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vmx.S
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/*
* ksm - a really simple and fast x64 hypervisor
* Copyright (C) 2016, 2017 Ahmed Samy <[email protected]>
*
* Assembly stuff for GCC (AT&T aka GAS) only. See vmx.asm for MASM.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#ifndef __ASSEMBLY__
#error __ASSEMBLY__ is not defined...
#endif
#include "compiler.h"
#ifdef __linux__
/* Arguments */
#define REG_A1 %rdi
#define REG_A2 %rsi
#define REG_A3 %rdx
#define REG_A4 %rcx
/* Volatile registers (caller-saved) */
#define REG_V1 %rdx
#define REG_V2 %rcx
#define REG_V3 %rax
#define REG_V4 %r8
#define REG_V5 %r9
#define REG_V6 %r10
#define REG_V7 %r11
#define REG_V8 %rdi
#define REG_V9 %rsi
#else
/* Arguments */
#define REG_A1 %rcx
#define REG_A2 %rdx
#define REG_A3 %r8
#define REG_A4 %r9
/* Volatile registers (caller-saved) */
#define REG_V1 %rax
#define REG_V2 %rcx
#define REG_V3 %rdx
#define REG_V4 %r8
#define REG_V5 %r9
#define REG_V6 %r10
#define REG_V7 %r11
#endif
.macro PUSH_REGS
pushq %r15
pushq %r14
pushq %r13
pushq %r12
pushq %r11
pushq %r10
pushq %r9
pushq %r8
pushq %rdi
pushq %rsi
pushq %rbp
subq $8, %rsp /* placeholder */
pushq %rbx
pushq %rdx
pushq %rcx
pushq %rax
.endm
.macro POP_REGS
popq %rax
popq %rcx
popq %rdx
popq %rbx
addq $8, %rsp
popq %rbp
popq %rsi
popq %rdi
popq %r8
popq %r9
popq %r10
popq %r11
popq %r12
popq %r13
popq %r14
popq %r15
.endm
#define KFRAME_RPL -0x66
#define KFRAME_CSR -0x64
#define KFRAME_V1 -0x60
#define KFRAME_V2 -0x58
#define KFRAME_V3 -0x50
#define KFRAME_V4 -0x48
#define KFRAME_V5 -0x40
#define KFRAME_V6 -0x38
#define KFRAME_V7 -0x30
#define KFRAME_V8 -0x28
#define KFRAME_V9 -0x20
#define KFRAME_XMM0 -0x10
#define KFRAME_XMM1 0x00
#define KFRAME_XMM2 0x10
#define KFRAME_XMM3 0x20
#define KFRAME_XMM4 0x30
#define KFRAME_XMM5 0x40
#define KFRAME_SS 0x108
#define KFRAME_RSP 0x100
#define KFRAME_FLGS 0x0F8
#define KFRAME_CS 0x0F0
#define KFRAME_EC 0x0E0
#define KFRAME_IP 0x0E8
.macro TRAP_SAVE_GPR
pushq %rbp
subq $0x158, %rsp
leaq 0x80(%rsp), %rbp
movq REG_V1, KFRAME_V1(%rbp)
movq REG_V2, KFRAME_V2(%rbp)
movq REG_V3, KFRAME_V3(%rbp)
movq REG_V4, KFRAME_V4(%rbp)
movq REG_V5, KFRAME_V5(%rbp)
movq REG_V6, KFRAME_V6(%rbp)
movq REG_V7, KFRAME_V7(%rbp)
#ifdef REG_V8
movq REG_V8, KFRAME_V8(%rbp)
#endif
#ifdef REG_V9
movq REG_V9, KFRAME_V9(%rbp)
#endif
.endm
.macro TRAP_REST_GPR
#ifdef REG_V9
movq KFRAME_V9(%rbp), REG_V9
#endif
#ifdef REG_V8
movq KFRAME_V8(%rbp), REG_V8
#endif
movq KFRAME_V7(%rbp), REG_V7
movq KFRAME_V6(%rbp), REG_V6
movq KFRAME_V5(%rbp), REG_V5
movq KFRAME_V4(%rbp), REG_V4
movq KFRAME_V3(%rbp), REG_V3
movq KFRAME_V2(%rbp), REG_V2
movq KFRAME_V1(%rbp), REG_V1
movq %rbp, %rsp
movq 0xD8(%rbp), %rbp
addq $0xE8, %rsp
.endm
.macro TRAP_SAVE_XMM
#ifndef __linux__
stmxcsr KFRAME_CSR(%rbp)
ldmxcsr %gs:0x180
movaps %xmm0, KFRAME_XMM0(%rbp)
movaps %xmm1, KFRAME_XMM1(%rbp)
movaps %xmm2, KFRAME_XMM2(%rbp)
movaps %xmm3, KFRAME_XMM3(%rbp)
movaps %xmm4, KFRAME_XMM4(%rbp)
movaps %xmm5, KFRAME_XMM5(%rbp)
#endif
.endm
.macro TRAP_REST_XMM
#ifndef __linux__
ldmxcsr KFRAME_CSR(%rbp)
movaps KFRAME_XMM0(%rbp), %xmm0
movaps KFRAME_XMM1(%rbp), %xmm1
movaps KFRAME_XMM2(%rbp), %xmm2
movaps KFRAME_XMM3(%rbp), %xmm3
movaps KFRAME_XMM4(%rbp), %xmm4
movaps KFRAME_XMM5(%rbp), %xmm5
#endif
.endm
.macro TRAP_ENTER
TRAP_SAVE_GPR
movw KFRAME_CS(%rbp), %ax
andb $1, %al
movb %al, KFRAME_RPL(%rbp)
jz 1f
swapgs
1:
cld
TRAP_SAVE_XMM
.endm
.macro TRAP_EXIT
testb $1, KFRAME_RPL(%rbp)
jz 1f
TRAP_REST_XMM
TRAP_REST_GPR
swapgs
iretq
1:
TRAP_REST_XMM
TRAP_REST_GPR
iretq
.endm
.macro irq_entry symbol:req handler:req no_error_code:req
.globl \symbol
\symbol:
.if \no_error_code
subq $8, %rsp
.endif
TRAP_ENTER
movq KFRAME_CS(%rbp), REG_A1
movq KFRAME_IP(%rbp), REG_A2
subq $0x20, %rsp
call \handler
addq $0x20, %rsp
TRAP_EXIT
.endm
.text
/* EPT violations */
irq_entry __ept_violation __ept_handle_violation 1
.globl __vmx_vminit
__vmx_vminit:
pushfq
PUSH_REGS
/* parameter one is pass-through (vcpu). */
movq %rsp, REG_A2
movabs $do_resume, REG_A3
subq $0x20, %rsp
call vcpu_run
addq $0x20, %rsp
/* If we get here, we failed */
POP_REGS
popfq
movl ERR_DENIED, %eax
ret
do_resume:
/* Succeeded */
POP_REGS
popfq
xorl %eax, %eax
ret
.globl __vmx_entrypoint
__vmx_entrypoint:
/*
* Host entry point (aka VMX root mode).
* Note: all interrupts are disabled at this point.
*
* Save all guest general purpose registers, then let the C handler do
* the rest.
*
* This is how the stack looks like after PUSH_REGS:
* +0 = %rax
* +8 = %rcx
* +16 = %rdx
* +24 = %rbx
* +32 = %rsp (garbage, overwritten with real value in
* vcpu_handle_exit())
* +40 = %rbp
* +48 = %rsi
* +56 = %rdi
* +64 = %r8
* +72 = %r9
* +80 = %r10
* +88 = %r11
* +96 = %r12
* +104 = %r13
* +112 = %r14
* +120 = %r15
* +128 = vcpu (set in vcpu_create())
*
* Note: we pass vcpu->stack -8 to HOST_RSP, this is because
* at this specific area, it's set to the vcpu pointer. So basically,
* a pop here (before PUSH_REGS) will pop vcpu pointer, but the
* registers in this specific context are guest registers, we need
* their values as-is untouched, we may also modify them later on
* depending on the event (e.g. cpuid, etc.)
*/
PUSH_REGS
movq %rsp, REG_A1
subq $0x20, %rsp
call vcpu_handle_exit
addq $0x20, %rsp
testb %al, %al
jz 1f
POP_REGS
vmresume
/* Something went wrong during re-entry to guest... */
jmp 2f
1:
/* See exit.c (vcpu_do_exit) */
POP_REGS
vmxoff
jna 2f
/* Give them their stack pointer */
movq %rdx, %rsp
/* and their rflags (adjusted to indicate successful vmcall) */
pushq %rax
popfq
/*
* rcx contains return address, which is guest's rip + instr_len (aka
* VMCALL length)
*/
pushq %rcx
ret
2:
/* Either vmresume or vmxoff failure... */
nop
pushfq
PUSH_REGS
movq %rsp, REG_A1
subq $0x20, %rsp
call vcpu_handle_fail
addq $0x20, %rsp
3: /* shouldn't come here, but incase it does, hlt forever: */
hlt
jmp 3b