The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/amd64/amd64/cpu_switch.S

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    1 /*-
    2  * Copyright (c) 2003 Peter Wemm.
    3  * Copyright (c) 1990 The Regents of the University of California.
    4  * All rights reserved.
    5  *
    6  * This code is derived from software contributed to Berkeley by
    7  * William Jolitz.
    8  *
    9  * Redistribution and use in source and binary forms, with or without
   10  * modification, are permitted provided that the following conditions
   11  * are met:
   12  * 1. Redistributions of source code must retain the above copyright
   13  *    notice, this list of conditions and the following disclaimer.
   14  * 2. Redistributions in binary form must reproduce the above copyright
   15  *    notice, this list of conditions and the following disclaimer in the
   16  *    documentation and/or other materials provided with the distribution.
   17  * 4. Neither the name of the University nor the names of its contributors
   18  *    may be used to endorse or promote products derived from this software
   19  *    without specific prior written permission.
   20  *
   21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   31  * SUCH DAMAGE.
   32  *
   33  * $FreeBSD: releng/6.1/sys/amd64/amd64/cpu_switch.S 158179 2006-04-30 16:44:43Z cvs2svn $
   34  */
   35 
   36 #include <machine/asmacros.h>
   37 #include <machine/specialreg.h>
   38 
   39 #include "assym.s"
   40 
   41 /*****************************************************************************/
   42 /* Scheduling                                                                */
   43 /*****************************************************************************/
   44 
   45         .text
   46 
   47 #ifdef SMP
   48 #define LK      lock ;
   49 #else
   50 #define LK
   51 #endif
   52 
   53 /*
   54  * cpu_throw()
   55  *
   56  * This is the second half of cpu_switch(). It is used when the current
   57  * thread is either a dummy or slated to die, and we no longer care
   58  * about its state.  This is only a slight optimization and is probably
   59  * not worth it anymore.  Note that we need to clear the pm_active bits so
   60  * we do need the old proc if it still exists.
   61  * %rdi = oldtd
   62  * %rsi = newtd
   63  */
   64 ENTRY(cpu_throw)
   65         movl    PCPU(CPUID), %eax
   66         testq   %rdi,%rdi                       /* no thread? */
   67         jz      1f
   68         /* release bit from old pm_active */
   69         movq    TD_PROC(%rdi), %rdx             /* oldtd->td_proc */
   70         movq    P_VMSPACE(%rdx), %rdx           /* proc->p_vmspace */
   71         LK btrl %eax, VM_PMAP+PM_ACTIVE(%rdx)   /* clear old */
   72 1:
   73         movq    TD_PCB(%rsi),%rdx               /* newtd->td_proc */
   74         movq    PCB_CR3(%rdx),%rdx
   75         movq    %rdx,%cr3                       /* new address space */
   76         /* set bit in new pm_active */
   77         movq    TD_PROC(%rsi),%rdx
   78         movq    P_VMSPACE(%rdx), %rdx
   79         LK btsl %eax, VM_PMAP+PM_ACTIVE(%rdx)   /* set new */
   80         jmp     sw1
   81 
   82 /*
   83  * cpu_switch(old, new)
   84  *
   85  * Save the current thread state, then select the next thread to run
   86  * and load its state.
   87  * %rdi = oldtd
   88  * %rsi = newtd
   89  */
   90 ENTRY(cpu_switch)
   91         /* Switch to new thread.  First, save context. */
   92         movq    TD_PCB(%rdi),%r8
   93 
   94         movq    (%rsp),%rax                     /* Hardware registers */
   95         movq    %rax,PCB_RIP(%r8)
   96         movq    %rbx,PCB_RBX(%r8)
   97         movq    %rsp,PCB_RSP(%r8)
   98         movq    %rbp,PCB_RBP(%r8)
   99         movq    %r12,PCB_R12(%r8)
  100         movq    %r13,PCB_R13(%r8)
  101         movq    %r14,PCB_R14(%r8)
  102         movq    %r15,PCB_R15(%r8)
  103 
  104         testl   $PCB_32BIT,PCB_FLAGS(%r8)
  105         jz      1f                              /* no, skip over */
  106 
  107         /* Save segment selector numbers */
  108         movl    %ds,PCB_DS(%r8)
  109         movl    %es,PCB_ES(%r8)
  110         movl    %fs,PCB_FS(%r8)
  111         movl    %gs,PCB_GS(%r8)
  112 1:
  113         /* Test if debug registers should be saved. */
  114         testl   $PCB_DBREGS,PCB_FLAGS(%r8)
  115         jz      1f                              /* no, skip over */
  116         movq    %dr7,%rax                       /* yes, do the save */
  117         movq    %rax,PCB_DR7(%r8)
  118         andq    $0x0000fc00, %rax               /* disable all watchpoints */
  119         movq    %rax,%dr7
  120         movq    %dr6,%rax
  121         movq    %rax,PCB_DR6(%r8)
  122         movq    %dr3,%rax
  123         movq    %rax,PCB_DR3(%r8)
  124         movq    %dr2,%rax
  125         movq    %rax,PCB_DR2(%r8)
  126         movq    %dr1,%rax
  127         movq    %rax,PCB_DR1(%r8)
  128         movq    %dr0,%rax
  129         movq    %rax,PCB_DR0(%r8)
  130 1:
  131 
  132         /* have we used fp, and need a save? */
  133         cmpq    %rdi,PCPU(FPCURTHREAD)
  134         jne     1f
  135         addq    $PCB_SAVEFPU,%r8
  136         clts
  137         fxsave  (%r8)
  138         smsw    %ax
  139         orb     $CR0_TS,%al
  140         lmsw    %ax
  141         xorq    %rax,%rax
  142         movq    %rax,PCPU(FPCURTHREAD)
  143 1:
  144 
  145         /* Save is done.  Now fire up new thread. Leave old vmspace. */
  146         movq    TD_PCB(%rsi),%r8
  147 
  148         /* switch address space */
  149         movq    PCB_CR3(%r8),%rdx
  150         movq    %cr3,%rax
  151         cmpq    %rdx,%rax                       /* Same address space? */
  152         je      sw1
  153         movq    %rdx,%cr3                       /* new address space */
  154 
  155         movl    PCPU(CPUID), %eax
  156         /* Release bit from old pmap->pm_active */
  157         movq    TD_PROC(%rdi), %rdx             /* oldproc */
  158         movq    P_VMSPACE(%rdx), %rdx
  159         LK btrl %eax, VM_PMAP+PM_ACTIVE(%rdx)   /* clear old */
  160 
  161         /* Set bit in new pmap->pm_active */
  162         movq    TD_PROC(%rsi),%rdx              /* newproc */
  163         movq    P_VMSPACE(%rdx), %rdx
  164         LK btsl %eax, VM_PMAP+PM_ACTIVE(%rdx)   /* set new */
  165 
  166 sw1:
  167         /*
  168          * At this point, we've switched address spaces and are ready
  169          * to load up the rest of the next context.
  170          */
  171         movq    TD_PCB(%rsi),%r8
  172 
  173         testl   $PCB_32BIT,PCB_FLAGS(%r8)
  174         jz      1f                              /* no, skip over */
  175 
  176         /* Restore segment selector numbers */
  177         movl    PCB_DS(%r8),%ds
  178         movl    PCB_ES(%r8),%es
  179         movl    PCB_FS(%r8),%fs
  180 
  181         /* Restore userland %gs while preserving kernel gsbase */
  182         movl    $MSR_GSBASE,%ecx
  183         rdmsr
  184         movl    PCB_GS(%r8),%gs
  185         wrmsr
  186         jmp     2f
  187 1:
  188 
  189         /* Restore userland %fs */
  190         movl    $MSR_FSBASE,%ecx
  191         movl    PCB_FSBASE(%r8),%eax
  192         movl    PCB_FSBASE+4(%r8),%edx
  193         wrmsr
  194 
  195         /* Restore userland %gs */
  196         movl    $MSR_KGSBASE,%ecx
  197         movl    PCB_GSBASE(%r8),%eax
  198         movl    PCB_GSBASE+4(%r8),%edx
  199         wrmsr
  200 2:
  201 
  202         /* Update the TSS_RSP0 pointer for the next interrupt */
  203         movq    PCPU(TSSP), %rax
  204         addq    $COMMON_TSS_RSP0, %rax
  205         leaq    -16(%r8), %rbx
  206         movq    %rbx, (%rax)
  207         movq    %rbx, PCPU(RSP0)
  208 
  209         /* Restore context. */
  210         movq    PCB_RBX(%r8),%rbx
  211         movq    PCB_RSP(%r8),%rsp
  212         movq    PCB_RBP(%r8),%rbp
  213         movq    PCB_R12(%r8),%r12
  214         movq    PCB_R13(%r8),%r13
  215         movq    PCB_R14(%r8),%r14
  216         movq    PCB_R15(%r8),%r15
  217         movq    PCB_RIP(%r8),%rax
  218         movq    %rax,(%rsp)
  219 
  220         movq    %r8, PCPU(CURPCB)
  221         movq    %rsi, PCPU(CURTHREAD)           /* into next thread */
  222 
  223         /* Test if debug registers should be restored. */
  224         testl   $PCB_DBREGS,PCB_FLAGS(%r8)
  225         jz      1f
  226         movq    PCB_DR6(%r8),%rax
  227         movq    %rax,%dr6
  228         movq    PCB_DR3(%r8),%rax
  229         movq    %rax,%dr3
  230         movq    PCB_DR2(%r8),%rax
  231         movq    %rax,%dr2
  232         movq    PCB_DR1(%r8),%rax
  233         movq    %rax,%dr1
  234         movq    PCB_DR0(%r8),%rax
  235         movq    %rax,%dr0
  236         /* But preserve reserved bits in %dr7 */
  237         movq    %dr7,%rax
  238         andq    $0x0000fc00,%rax
  239         movq    PCB_DR7(%r8),%rcx
  240         andq    $~0x0000fc00,%rcx
  241         orq     %rcx,%rax
  242         movq    %rax,%dr7
  243 1:
  244         ret
  245 
  246 /*
  247  * savectx(pcb)
  248  * Update pcb, saving current processor state.
  249  */
  250 ENTRY(savectx)
  251         /* Fetch PCB. */
  252         movq    %rdi,%rcx
  253 
  254         /* Save caller's return address. */
  255         movq    (%rsp),%rax
  256         movq    %rax,PCB_RIP(%rcx)
  257 
  258         movq    %cr3,%rax
  259         movq    %rax,PCB_CR3(%rcx)
  260 
  261         movq    %rbx,PCB_RBX(%rcx)
  262         movq    %rsp,PCB_RSP(%rcx)
  263         movq    %rbp,PCB_RBP(%rcx)
  264         movq    %r12,PCB_R12(%rcx)
  265         movq    %r13,PCB_R13(%rcx)
  266         movq    %r14,PCB_R14(%rcx)
  267         movq    %r15,PCB_R15(%rcx)
  268 
  269         /*
  270          * If fpcurthread == NULL, then the fpu h/w state is irrelevant and the
  271          * state had better already be in the pcb.  This is true for forks
  272          * but not for dumps (the old book-keeping with FP flags in the pcb
  273          * always lost for dumps because the dump pcb has 0 flags).
  274          *
  275          * If fpcurthread != NULL, then we have to save the fpu h/w state to
  276          * fpcurthread's pcb and copy it to the requested pcb, or save to the
  277          * requested pcb and reload.  Copying is easier because we would
  278          * have to handle h/w bugs for reloading.  We used to lose the
  279          * parent's fpu state for forks by forgetting to reload.
  280          */
  281         pushfq
  282         cli
  283         movq    PCPU(FPCURTHREAD),%rax
  284         testq   %rax,%rax
  285         je      1f
  286 
  287         movq    TD_PCB(%rax),%rdi
  288         leaq    PCB_SAVEFPU(%rdi),%rdi
  289         clts
  290         fxsave  (%rdi)
  291         smsw    %ax
  292         orb     $CR0_TS,%al
  293         lmsw    %ax
  294 
  295         movq    $PCB_SAVEFPU_SIZE,%rdx  /* arg 3 */
  296         leaq    PCB_SAVEFPU(%rcx),%rsi  /* arg 2 */
  297         /* arg 1 (%rdi) already loaded */
  298         call    bcopy
  299 1:
  300         popfq
  301 
  302         ret

Cache object: 3516dcd37c622985b930d944978bf626


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