svm_support.S

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    1 /*-
    2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
    3  *
    4  * Copyright (c) 2013, Anish Gupta (akgupt3@gmail.com)
    5  * All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice unmodified, this list of conditions, and the following
   12  *    disclaimer.
   13  * 2. Redistributions in binary form must reproduce the above copyright
   14  *    notice, this list of conditions and the following disclaimer in the
   15  *    documentation and/or other materials provided with the distribution.
   16  *
   17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   18  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   19  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   20  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   21  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   22  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   27  *
   28  * $FreeBSD$
   29  */
   30 #include <machine/asmacros.h>
   31 
   32 #include "svm_assym.h"
   33 
   34 /*
   35  * Be friendly to DTrace FBT's prologue/epilogue pattern matching.
   36  *
   37  * They are also responsible for saving/restoring the host %rbp across VMRUN.
   38  */
   39 #define VENTER  push %rbp ; mov %rsp,%rbp
   40 #define VLEAVE  pop %rbp
   41 
   42 /*
   43  * svm_launch(uint64_t vmcb, struct svm_regctx *gctx, struct pcpu *pcpu)
   44  * %rdi: physical address of VMCB
   45  * %rsi: pointer to guest context
   46  * %rdx: pointer to the pcpu data
   47  */
   48 ENTRY(svm_launch)
   49         VENTER
   50 
   51         /* save pointer to the pcpu data */
   52         push %rdx
   53 
   54         /*
   55          * Host register state saved across a VMRUN.
   56          *
   57          * All "callee saved registers" except:
   58          * %rsp: because it is preserved by the processor across VMRUN.
   59          * %rbp: because it is saved/restored by the function prologue/epilogue.
   60          */
   61         push %rbx
   62         push %r12
   63         push %r13
   64         push %r14
   65         push %r15
   66 
   67         /* Save the physical address of the VMCB in %rax */
   68         movq %rdi, %rax
   69 
   70         push %rsi               /* push guest context pointer on the stack */
   71 
   72         /*
   73          * Restore guest state.
   74          */
   75         movq SCTX_R8(%rsi), %r8
   76         movq SCTX_R9(%rsi), %r9
   77         movq SCTX_R10(%rsi), %r10
   78         movq SCTX_R11(%rsi), %r11
   79         movq SCTX_R12(%rsi), %r12
   80         movq SCTX_R13(%rsi), %r13
   81         movq SCTX_R14(%rsi), %r14
   82         movq SCTX_R15(%rsi), %r15
   83         movq SCTX_RBP(%rsi), %rbp
   84         movq SCTX_RBX(%rsi), %rbx
   85         movq SCTX_RCX(%rsi), %rcx
   86         movq SCTX_RDX(%rsi), %rdx
   87         movq SCTX_RDI(%rsi), %rdi
   88         movq SCTX_RSI(%rsi), %rsi       /* %rsi must be restored last */
   89 
   90         vmload %rax
   91         vmrun %rax
   92         vmsave %rax
   93 
   94         pop %rax                /* pop guest context pointer from the stack */
   95 
   96         /*
   97          * Save guest state.
   98          */
   99         movq %r8, SCTX_R8(%rax)
  100         movq %r9, SCTX_R9(%rax)
  101         movq %r10, SCTX_R10(%rax)
  102         movq %r11, SCTX_R11(%rax)
  103         movq %r12, SCTX_R12(%rax)
  104         movq %r13, SCTX_R13(%rax)
  105         movq %r14, SCTX_R14(%rax)
  106         movq %r15, SCTX_R15(%rax)
  107         movq %rbp, SCTX_RBP(%rax)
  108         movq %rbx, SCTX_RBX(%rax)
  109         movq %rcx, SCTX_RCX(%rax)
  110         movq %rdx, SCTX_RDX(%rax)
  111         movq %rdi, SCTX_RDI(%rax)
  112         movq %rsi, SCTX_RSI(%rax)
  113 
  114         /*
  115          * To prevent malicious branch target predictions from
  116          * affecting the host, overwrite all entries in the RSB upon
  117          * exiting a guest.
  118          */
  119         mov $16, %ecx   /* 16 iterations, two calls per loop */
  120         mov %rsp, %rax
  121 0:      call 2f         /* create an RSB entry. */
  122 1:      pause
  123         call 1b         /* capture rogue speculation. */
  124 2:      call 2f         /* create an RSB entry. */
  125 1:      pause
  126         call 1b         /* capture rogue speculation. */
  127 2:      sub $1, %ecx
  128         jnz 0b
  129         mov %rax, %rsp
  130 
  131         /* Restore host state */
  132         pop %r15
  133         pop %r14
  134         pop %r13
  135         pop %r12
  136         pop %rbx
  137 
  138         /* Restore %GS.base to point to the host's pcpu data */
  139         pop %rdx
  140         mov %edx, %eax
  141         shr $32, %rdx
  142         mov $MSR_GSBASE, %rcx
  143         wrmsr
  144 
  145         /*
  146          * Clobber the remaining registers with guest contents so they
  147          * can't be misused.
  148          */
  149         xor %rbp, %rbp
  150         xor %rdi, %rdi
  151         xor %rsi, %rsi
  152         xor %r8, %r8
  153         xor %r9, %r9
  154         xor %r10, %r10
  155         xor %r11, %r11
  156 
  157         VLEAVE
  158         ret
  159 END(svm_launch)

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