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/i386/i386/swtch.s

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    1 /*-
    2  * Copyright (c) 1990 The Regents of the University of California.
    3  * All rights reserved.
    4  *
    5  * This code is derived from software contributed to Berkeley by
    6  * William Jolitz.
    7  *
    8  * Redistribution and use in source and binary forms, with or without
    9  * modification, are permitted provided that the following conditions
   10  * are met:
   11  * 1. Redistributions of source code must retain the above copyright
   12  *    notice, this list of conditions and the following 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  * 4. Neither the name of the University nor the names of its contributors
   17  *    may be used to endorse or promote products derived from this software
   18  *    without specific prior written permission.
   19  *
   20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   30  * SUCH DAMAGE.
   31  *
   32  * $FreeBSD: releng/6.2/sys/i386/i386/swtch.s 145034 2005-04-13 22:57:17Z peter $
   33  */
   34 
   35 #include "opt_npx.h"
   36 
   37 #include <machine/asmacros.h>
   38 
   39 #include "assym.s"
   40 
   41 /*****************************************************************************/
   42 /* Scheduling                                                                */
   43 /*****************************************************************************/
   44 
   45         .text
   46 
   47 /*
   48  * cpu_throw()
   49  *
   50  * This is the second half of cpu_switch(). It is used when the current
   51  * thread is either a dummy or slated to die, and we no longer care
   52  * about its state.  This is only a slight optimization and is probably
   53  * not worth it anymore.  Note that we need to clear the pm_active bits so
   54  * we do need the old proc if it still exists.
   55  * 0(%esp) = ret
   56  * 4(%esp) = oldtd
   57  * 8(%esp) = newtd
   58  */
   59 ENTRY(cpu_throw)
   60         movl    PCPU(CPUID), %esi
   61         movl    4(%esp),%ecx                    /* Old thread */
   62         testl   %ecx,%ecx                       /* no thread? */
   63         jz      1f
   64         /* release bit from old pm_active */
   65         movl    PCPU(CURPMAP), %ebx
   66 #ifdef SMP
   67         lock
   68 #endif
   69         btrl    %esi, PM_ACTIVE(%ebx)           /* clear old */
   70 1:
   71         movl    8(%esp),%ecx                    /* New thread */
   72         movl    TD_PCB(%ecx),%edx
   73         movl    PCB_CR3(%edx),%eax
   74         movl    %eax,%cr3                       /* new address space */
   75         /* set bit in new pm_active */
   76         movl    TD_PROC(%ecx),%eax
   77         movl    P_VMSPACE(%eax), %ebx
   78         addl    $VM_PMAP, %ebx
   79         movl    %ebx, PCPU(CURPMAP)
   80 #ifdef SMP
   81         lock
   82 #endif
   83         btsl    %esi, PM_ACTIVE(%ebx)           /* set new */
   84         jmp     sw1
   85 
   86 /*
   87  * cpu_switch(old, new)
   88  *
   89  * Save the current thread state, then select the next thread to run
   90  * and load its state.
   91  * 0(%esp) = ret
   92  * 4(%esp) = oldtd
   93  * 8(%esp) = newtd
   94  */
   95 ENTRY(cpu_switch)
   96 
   97         /* Switch to new thread.  First, save context. */
   98         movl    4(%esp),%ecx
   99 
  100 #ifdef INVARIANTS
  101         testl   %ecx,%ecx                       /* no thread? */
  102         jz      badsw2                          /* no, panic */
  103 #endif
  104 
  105         movl    TD_PCB(%ecx),%edx
  106 
  107         movl    (%esp),%eax                     /* Hardware registers */
  108         movl    %eax,PCB_EIP(%edx)
  109         movl    %ebx,PCB_EBX(%edx)
  110         movl    %esp,PCB_ESP(%edx)
  111         movl    %ebp,PCB_EBP(%edx)
  112         movl    %esi,PCB_ESI(%edx)
  113         movl    %edi,PCB_EDI(%edx)
  114         movl    %gs,PCB_GS(%edx)
  115         pushfl                                  /* PSL */
  116         popl    PCB_PSL(%edx)
  117         /* Check to see if we need to call a switchout function. */
  118         movl    PCB_SWITCHOUT(%edx),%eax
  119         cmpl    $0, %eax
  120         je      1f
  121         call    *%eax
  122 1:
  123         /* Test if debug registers should be saved. */
  124         testl   $PCB_DBREGS,PCB_FLAGS(%edx)
  125         jz      1f                              /* no, skip over */
  126         movl    %dr7,%eax                       /* yes, do the save */
  127         movl    %eax,PCB_DR7(%edx)
  128         andl    $0x0000fc00, %eax               /* disable all watchpoints */
  129         movl    %eax,%dr7
  130         movl    %dr6,%eax
  131         movl    %eax,PCB_DR6(%edx)
  132         movl    %dr3,%eax
  133         movl    %eax,PCB_DR3(%edx)
  134         movl    %dr2,%eax
  135         movl    %eax,PCB_DR2(%edx)
  136         movl    %dr1,%eax
  137         movl    %eax,PCB_DR1(%edx)
  138         movl    %dr0,%eax
  139         movl    %eax,PCB_DR0(%edx)
  140 1:
  141 
  142 #ifdef DEV_NPX
  143         /* have we used fp, and need a save? */
  144         cmpl    %ecx,PCPU(FPCURTHREAD)
  145         jne     1f
  146         addl    $PCB_SAVEFPU,%edx               /* h/w bugs make saving complicated */
  147         pushl   %edx
  148         call    npxsave                         /* do it in a big C function */
  149         popl    %eax
  150 1:
  151 #endif
  152 
  153         /* Save is done.  Now fire up new thread. Leave old vmspace. */
  154         movl    %ecx,%edi
  155         movl    8(%esp),%ecx                    /* New thread */
  156 #ifdef INVARIANTS
  157         testl   %ecx,%ecx                       /* no thread? */
  158         jz      badsw3                          /* no, panic */
  159 #endif
  160         movl    TD_PCB(%ecx),%edx
  161         movl    PCPU(CPUID), %esi
  162 
  163         /* switch address space */
  164         movl    PCB_CR3(%edx),%eax
  165 #ifdef PAE
  166         cmpl    %eax,IdlePDPT                   /* Kernel address space? */
  167 #else
  168         cmpl    %eax,IdlePTD                    /* Kernel address space? */
  169 #endif
  170         je      sw1
  171         movl    %cr3,%ebx                       /* The same address space? */
  172         cmpl    %ebx,%eax
  173         je      sw1
  174         movl    %eax,%cr3                       /* new address space */
  175 
  176         /* Release bit from old pmap->pm_active */
  177         movl    PCPU(CURPMAP), %ebx
  178 #ifdef SMP
  179         lock
  180 #endif
  181         btrl    %esi, PM_ACTIVE(%ebx)           /* clear old */
  182 
  183         /* Set bit in new pmap->pm_active */
  184         movl    TD_PROC(%ecx),%eax              /* newproc */
  185         movl    P_VMSPACE(%eax), %ebx
  186         addl    $VM_PMAP, %ebx
  187         movl    %ebx, PCPU(CURPMAP)
  188 #ifdef SMP
  189         lock
  190 #endif
  191         btsl    %esi, PM_ACTIVE(%ebx)           /* set new */
  192 
  193 sw1:
  194         /*
  195          * At this point, we've switched address spaces and are ready
  196          * to load up the rest of the next context.
  197          */
  198         cmpl    $0, PCB_EXT(%edx)               /* has pcb extension? */
  199         je      1f                              /* If not, use the default */
  200         btsl    %esi, private_tss               /* mark use of private tss */
  201         movl    PCB_EXT(%edx), %edi             /* new tss descriptor */
  202         jmp     2f                              /* Load it up */
  203 
  204 1:      /*
  205          * Use the common default TSS instead of our own.
  206          * Set our stack pointer into the TSS, it's set to just
  207          * below the PCB.  In C, common_tss.tss_esp0 = &pcb - 16;
  208          */
  209         leal    -16(%edx), %ebx                 /* leave space for vm86 */
  210         movl    %ebx, PCPU(COMMON_TSS) + TSS_ESP0
  211 
  212         /*
  213          * Test this CPU's  bit in the bitmap to see if this
  214          * CPU was using a private TSS.
  215          */
  216         btrl    %esi, private_tss               /* Already using the common? */
  217         jae     3f                              /* if so, skip reloading */
  218         PCPU_ADDR(COMMON_TSSD, %edi)
  219 2:
  220         /* Move correct tss descriptor into GDT slot, then reload tr. */
  221         movl    PCPU(TSS_GDT), %ebx             /* entry in GDT */
  222         movl    0(%edi), %eax
  223         movl    4(%edi), %esi
  224         movl    %eax, 0(%ebx)
  225         movl    %esi, 4(%ebx)
  226         movl    $GPROC0_SEL*8, %esi             /* GSEL(entry, SEL_KPL) */
  227         ltr     %si
  228 3:
  229 
  230         /* Copy the %fs and %gs selectors into this pcpu gdt */
  231         leal    PCB_FSD(%edx), %esi
  232         movl    PCPU(FSGS_GDT), %edi
  233         movl    0(%esi), %eax           /* %fs selector */
  234         movl    4(%esi), %ebx
  235         movl    %eax, 0(%edi)
  236         movl    %ebx, 4(%edi)
  237         movl    8(%esi), %eax           /* %gs selector, comes straight after */
  238         movl    12(%esi), %ebx
  239         movl    %eax, 8(%edi)
  240         movl    %ebx, 12(%edi)
  241 
  242         /* Restore context. */
  243         movl    PCB_EBX(%edx),%ebx
  244         movl    PCB_ESP(%edx),%esp
  245         movl    PCB_EBP(%edx),%ebp
  246         movl    PCB_ESI(%edx),%esi
  247         movl    PCB_EDI(%edx),%edi
  248         movl    PCB_EIP(%edx),%eax
  249         movl    %eax,(%esp)
  250         pushl   PCB_PSL(%edx)
  251         popfl
  252 
  253         movl    %edx, PCPU(CURPCB)
  254         movl    %ecx, PCPU(CURTHREAD)           /* into next thread */
  255 
  256         /*
  257          * Determine the LDT to use and load it if is the default one and
  258          * that is not the current one.
  259          */
  260         movl    TD_PROC(%ecx),%eax
  261         cmpl    $0,P_MD+MD_LDT(%eax)
  262         jnz     1f
  263         movl    _default_ldt,%eax
  264         cmpl    PCPU(CURRENTLDT),%eax
  265         je      2f
  266         lldt    _default_ldt
  267         movl    %eax,PCPU(CURRENTLDT)
  268         jmp     2f
  269 1:
  270         /* Load the LDT when it is not the default one. */
  271         pushl   %edx                            /* Preserve pointer to pcb. */
  272         addl    $P_MD,%eax                      /* Pointer to mdproc is arg. */
  273         pushl   %eax
  274         call    set_user_ldt
  275         addl    $4,%esp
  276         popl    %edx
  277 2:
  278 
  279         /* This must be done after loading the user LDT. */
  280         .globl  cpu_switch_load_gs
  281 cpu_switch_load_gs:
  282         movl    PCB_GS(%edx),%gs
  283 
  284         /* Test if debug registers should be restored. */
  285         testl   $PCB_DBREGS,PCB_FLAGS(%edx)
  286         jz      1f
  287 
  288         /*
  289          * Restore debug registers.  The special code for dr7 is to
  290          * preserve the current values of its reserved bits.
  291          */
  292         movl    PCB_DR6(%edx),%eax
  293         movl    %eax,%dr6
  294         movl    PCB_DR3(%edx),%eax
  295         movl    %eax,%dr3
  296         movl    PCB_DR2(%edx),%eax
  297         movl    %eax,%dr2
  298         movl    PCB_DR1(%edx),%eax
  299         movl    %eax,%dr1
  300         movl    PCB_DR0(%edx),%eax
  301         movl    %eax,%dr0
  302         movl    %dr7,%eax
  303         andl    $0x0000fc00,%eax
  304         movl    PCB_DR7(%edx),%ecx
  305         andl    $~0x0000fc00,%ecx
  306         orl     %ecx,%eax
  307         movl    %eax,%dr7
  308 1:
  309         ret
  310 
  311 #ifdef INVARIANTS
  312 badsw1:
  313         pushal
  314         pushl   $sw0_1
  315         call    panic
  316 sw0_1:  .asciz  "cpu_throw: no newthread supplied"
  317 
  318 badsw2:
  319         pushal
  320         pushl   $sw0_2
  321         call    panic
  322 sw0_2:  .asciz  "cpu_switch: no curthread supplied"
  323 
  324 badsw3:
  325         pushal
  326         pushl   $sw0_3
  327         call    panic
  328 sw0_3:  .asciz  "cpu_switch: no newthread supplied"
  329 #endif
  330 
  331 /*
  332  * savectx(pcb)
  333  * Update pcb, saving current processor state.
  334  */
  335 ENTRY(savectx)
  336         /* Fetch PCB. */
  337         movl    4(%esp),%ecx
  338 
  339         /* Save caller's return address.  Child won't execute this routine. */
  340         movl    (%esp),%eax
  341         movl    %eax,PCB_EIP(%ecx)
  342 
  343         movl    %cr3,%eax
  344         movl    %eax,PCB_CR3(%ecx)
  345 
  346         movl    %ebx,PCB_EBX(%ecx)
  347         movl    %esp,PCB_ESP(%ecx)
  348         movl    %ebp,PCB_EBP(%ecx)
  349         movl    %esi,PCB_ESI(%ecx)
  350         movl    %edi,PCB_EDI(%ecx)
  351         movl    %gs,PCB_GS(%ecx)
  352         pushfl
  353         popl    PCB_PSL(%ecx)
  354 
  355 #ifdef DEV_NPX
  356         /*
  357          * If fpcurthread == NULL, then the npx h/w state is irrelevant and the
  358          * state had better already be in the pcb.  This is true for forks
  359          * but not for dumps (the old book-keeping with FP flags in the pcb
  360          * always lost for dumps because the dump pcb has 0 flags).
  361          *
  362          * If fpcurthread != NULL, then we have to save the npx h/w state to
  363          * fpcurthread's pcb and copy it to the requested pcb, or save to the
  364          * requested pcb and reload.  Copying is easier because we would
  365          * have to handle h/w bugs for reloading.  We used to lose the
  366          * parent's npx state for forks by forgetting to reload.
  367          */
  368         pushfl
  369         cli
  370         movl    PCPU(FPCURTHREAD),%eax
  371         testl   %eax,%eax
  372         je      1f
  373 
  374         pushl   %ecx
  375         movl    TD_PCB(%eax),%eax
  376         leal    PCB_SAVEFPU(%eax),%eax
  377         pushl   %eax
  378         pushl   %eax
  379         call    npxsave
  380         addl    $4,%esp
  381         popl    %eax
  382         popl    %ecx
  383 
  384         pushl   $PCB_SAVEFPU_SIZE
  385         leal    PCB_SAVEFPU(%ecx),%ecx
  386         pushl   %ecx
  387         pushl   %eax
  388         call    bcopy
  389         addl    $12,%esp
  390 1:
  391         popfl
  392 #endif  /* DEV_NPX */
  393 
  394         ret

Cache object: ec6c0ffb72ae922f8ada14dbd587a296


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