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/8.1/sys/i386/i386/swtch.s 199583 2009-11-20 15:27:52Z jhb $
   33  */
   34 
   35 #include "opt_npx.h"
   36 #include "opt_sched.h"
   37 
   38 #include <machine/asmacros.h>
   39 
   40 #include "assym.s"
   41 
   42 #if defined(SMP) && defined(SCHED_ULE)
   43 #define SETOP           xchgl
   44 #define BLOCK_SPIN(reg)                                                 \
   45                 movl            $blocked_lock,%eax ;                    \
   46         100: ;                                                          \
   47                 lock ;                                                  \
   48                 cmpxchgl        %eax,TD_LOCK(reg) ;                     \
   49                 jne             101f ;                                  \
   50                 pause ;                                                 \
   51                 jmp             100b ;                                  \
   52         101:
   53 #else
   54 #define SETOP           movl
   55 #define BLOCK_SPIN(reg)
   56 #endif
   57 
   58 /*****************************************************************************/
   59 /* Scheduling                                                                */
   60 /*****************************************************************************/
   61 
   62         .text
   63 
   64 /*
   65  * cpu_throw()
   66  *
   67  * This is the second half of cpu_switch(). It is used when the current
   68  * thread is either a dummy or slated to die, and we no longer care
   69  * about its state.  This is only a slight optimization and is probably
   70  * not worth it anymore.  Note that we need to clear the pm_active bits so
   71  * we do need the old proc if it still exists.
   72  * 0(%esp) = ret
   73  * 4(%esp) = oldtd
   74  * 8(%esp) = newtd
   75  */
   76 ENTRY(cpu_throw)
   77         movl    PCPU(CPUID), %esi
   78         movl    4(%esp),%ecx                    /* Old thread */
   79         testl   %ecx,%ecx                       /* no thread? */
   80         jz      1f
   81         /* release bit from old pm_active */
   82         movl    PCPU(CURPMAP), %ebx
   83 #ifdef SMP
   84         lock
   85 #endif
   86         btrl    %esi, PM_ACTIVE(%ebx)           /* clear old */
   87 1:
   88         movl    8(%esp),%ecx                    /* New thread */
   89         movl    TD_PCB(%ecx),%edx
   90         movl    PCB_CR3(%edx),%eax
   91         LOAD_CR3(%eax)
   92         /* set bit in new pm_active */
   93         movl    TD_PROC(%ecx),%eax
   94         movl    P_VMSPACE(%eax), %ebx
   95         addl    $VM_PMAP, %ebx
   96         movl    %ebx, PCPU(CURPMAP)
   97 #ifdef SMP
   98         lock
   99 #endif
  100         btsl    %esi, PM_ACTIVE(%ebx)           /* set new */
  101         jmp     sw1
  102 END(cpu_throw)
  103 
  104 /*
  105  * cpu_switch(old, new)
  106  *
  107  * Save the current thread state, then select the next thread to run
  108  * and load its state.
  109  * 0(%esp) = ret
  110  * 4(%esp) = oldtd
  111  * 8(%esp) = newtd
  112  * 12(%esp) = newlock
  113  */
  114 ENTRY(cpu_switch)
  115 
  116         /* Switch to new thread.  First, save context. */
  117         movl    4(%esp),%ecx
  118 
  119 #ifdef INVARIANTS
  120         testl   %ecx,%ecx                       /* no thread? */
  121         jz      badsw2                          /* no, panic */
  122 #endif
  123 
  124         movl    TD_PCB(%ecx),%edx
  125 
  126         movl    (%esp),%eax                     /* Hardware registers */
  127         movl    %eax,PCB_EIP(%edx)
  128         movl    %ebx,PCB_EBX(%edx)
  129         movl    %esp,PCB_ESP(%edx)
  130         movl    %ebp,PCB_EBP(%edx)
  131         movl    %esi,PCB_ESI(%edx)
  132         movl    %edi,PCB_EDI(%edx)
  133         mov     %gs,PCB_GS(%edx)
  134         pushfl                                  /* PSL */
  135         popl    PCB_PSL(%edx)
  136         /* Test if debug registers should be saved. */
  137         testl   $PCB_DBREGS,PCB_FLAGS(%edx)
  138         jz      1f                              /* no, skip over */
  139         movl    %dr7,%eax                       /* yes, do the save */
  140         movl    %eax,PCB_DR7(%edx)
  141         andl    $0x0000fc00, %eax               /* disable all watchpoints */
  142         movl    %eax,%dr7
  143         movl    %dr6,%eax
  144         movl    %eax,PCB_DR6(%edx)
  145         movl    %dr3,%eax
  146         movl    %eax,PCB_DR3(%edx)
  147         movl    %dr2,%eax
  148         movl    %eax,PCB_DR2(%edx)
  149         movl    %dr1,%eax
  150         movl    %eax,PCB_DR1(%edx)
  151         movl    %dr0,%eax
  152         movl    %eax,PCB_DR0(%edx)
  153 1:
  154 
  155 #ifdef DEV_NPX
  156         /* have we used fp, and need a save? */
  157         cmpl    %ecx,PCPU(FPCURTHREAD)
  158         jne     1f
  159         addl    $PCB_SAVEFPU,%edx               /* h/w bugs make saving complicated */
  160         pushl   %edx
  161         call    npxsave                         /* do it in a big C function */
  162         popl    %eax
  163 1:
  164 #endif
  165 
  166         /* Save is done.  Now fire up new thread. Leave old vmspace. */
  167         movl    4(%esp),%edi
  168         movl    8(%esp),%ecx                    /* New thread */
  169         movl    12(%esp),%esi                   /* New lock */
  170 #ifdef INVARIANTS
  171         testl   %ecx,%ecx                       /* no thread? */
  172         jz      badsw3                          /* no, panic */
  173 #endif
  174         movl    TD_PCB(%ecx),%edx
  175 
  176         /* switch address space */
  177         movl    PCB_CR3(%edx),%eax
  178 #ifdef PAE
  179         cmpl    %eax,IdlePDPT                   /* Kernel address space? */
  180 #else
  181         cmpl    %eax,IdlePTD                    /* Kernel address space? */
  182 #endif
  183         je      sw0
  184         READ_CR3(%ebx)                          /* The same address space? */
  185         cmpl    %ebx,%eax
  186         je      sw0
  187         LOAD_CR3(%eax)                          /* new address space */
  188         movl    %esi,%eax
  189         movl    PCPU(CPUID),%esi
  190         SETOP   %eax,TD_LOCK(%edi)              /* Switchout td_lock */
  191 
  192         /* Release bit from old pmap->pm_active */
  193         movl    PCPU(CURPMAP), %ebx
  194 #ifdef SMP
  195         lock
  196 #endif
  197         btrl    %esi, PM_ACTIVE(%ebx)           /* clear old */
  198 
  199         /* Set bit in new pmap->pm_active */
  200         movl    TD_PROC(%ecx),%eax              /* newproc */
  201         movl    P_VMSPACE(%eax), %ebx
  202         addl    $VM_PMAP, %ebx
  203         movl    %ebx, PCPU(CURPMAP)
  204 #ifdef SMP
  205         lock
  206 #endif
  207         btsl    %esi, PM_ACTIVE(%ebx)           /* set new */
  208         jmp     sw1
  209 
  210 sw0:
  211         SETOP   %esi,TD_LOCK(%edi)              /* Switchout td_lock */
  212 sw1:
  213         BLOCK_SPIN(%ecx)
  214 #ifdef XEN
  215         pushl   %eax
  216         pushl   %ecx
  217         pushl   %edx
  218         call    xen_handle_thread_switch
  219         popl    %edx
  220         popl    %ecx
  221         popl    %eax
  222         /*
  223          * XXX set IOPL
  224          */
  225 #else           
  226         /*
  227          * At this point, we've switched address spaces and are ready
  228          * to load up the rest of the next context.
  229          */
  230         cmpl    $0, PCB_EXT(%edx)               /* has pcb extension? */
  231         je      1f                              /* If not, use the default */
  232         movl    $1, PCPU(PRIVATE_TSS)           /* mark use of private tss */
  233         movl    PCB_EXT(%edx), %edi             /* new tss descriptor */
  234         jmp     2f                              /* Load it up */
  235 
  236 1:      /*
  237          * Use the common default TSS instead of our own.
  238          * Set our stack pointer into the TSS, it's set to just
  239          * below the PCB.  In C, common_tss.tss_esp0 = &pcb - 16;
  240          */
  241         leal    -16(%edx), %ebx                 /* leave space for vm86 */
  242         movl    %ebx, PCPU(COMMON_TSS) + TSS_ESP0
  243 
  244         /*
  245          * Test this CPU's  bit in the bitmap to see if this
  246          * CPU was using a private TSS.
  247          */
  248         cmpl    $0, PCPU(PRIVATE_TSS)           /* Already using the common? */
  249         je      3f                              /* if so, skip reloading */
  250         movl    $0, PCPU(PRIVATE_TSS)
  251         PCPU_ADDR(COMMON_TSSD, %edi)
  252 2:
  253         /* Move correct tss descriptor into GDT slot, then reload tr. */
  254         movl    PCPU(TSS_GDT), %ebx             /* entry in GDT */
  255         movl    0(%edi), %eax
  256         movl    4(%edi), %esi
  257         movl    %eax, 0(%ebx)
  258         movl    %esi, 4(%ebx)
  259         movl    $GPROC0_SEL*8, %esi             /* GSEL(GPROC0_SEL, SEL_KPL) */
  260         ltr     %si
  261 3:
  262 
  263         /* Copy the %fs and %gs selectors into this pcpu gdt */
  264         leal    PCB_FSD(%edx), %esi
  265         movl    PCPU(FSGS_GDT), %edi
  266         movl    0(%esi), %eax           /* %fs selector */
  267         movl    4(%esi), %ebx
  268         movl    %eax, 0(%edi)
  269         movl    %ebx, 4(%edi)
  270         movl    8(%esi), %eax           /* %gs selector, comes straight after */
  271         movl    12(%esi), %ebx
  272         movl    %eax, 8(%edi)
  273         movl    %ebx, 12(%edi)
  274 #endif
  275         /* Restore context. */
  276         movl    PCB_EBX(%edx),%ebx
  277         movl    PCB_ESP(%edx),%esp
  278         movl    PCB_EBP(%edx),%ebp
  279         movl    PCB_ESI(%edx),%esi
  280         movl    PCB_EDI(%edx),%edi
  281         movl    PCB_EIP(%edx),%eax
  282         movl    %eax,(%esp)
  283         pushl   PCB_PSL(%edx)
  284         popfl
  285 
  286         movl    %edx, PCPU(CURPCB)
  287         movl    TD_TID(%ecx),%eax
  288         movl    %ecx, PCPU(CURTHREAD)           /* into next thread */
  289 
  290         /*
  291          * Determine the LDT to use and load it if is the default one and
  292          * that is not the current one.
  293          */
  294         movl    TD_PROC(%ecx),%eax
  295         cmpl    $0,P_MD+MD_LDT(%eax)
  296         jnz     1f
  297         movl    _default_ldt,%eax
  298         cmpl    PCPU(CURRENTLDT),%eax
  299         je      2f
  300         LLDT(_default_ldt)
  301         movl    %eax,PCPU(CURRENTLDT)
  302         jmp     2f
  303 1:
  304         /* Load the LDT when it is not the default one. */
  305         pushl   %edx                            /* Preserve pointer to pcb. */
  306         addl    $P_MD,%eax                      /* Pointer to mdproc is arg. */
  307         pushl   %eax
  308         call    set_user_ldt
  309         addl    $4,%esp
  310         popl    %edx
  311 2:
  312 
  313         /* This must be done after loading the user LDT. */
  314         .globl  cpu_switch_load_gs
  315 cpu_switch_load_gs:
  316         mov     PCB_GS(%edx),%gs
  317 
  318         /* Test if debug registers should be restored. */
  319         testl   $PCB_DBREGS,PCB_FLAGS(%edx)
  320         jz      1f
  321 
  322         /*
  323          * Restore debug registers.  The special code for dr7 is to
  324          * preserve the current values of its reserved bits.
  325          */
  326         movl    PCB_DR6(%edx),%eax
  327         movl    %eax,%dr6
  328         movl    PCB_DR3(%edx),%eax
  329         movl    %eax,%dr3
  330         movl    PCB_DR2(%edx),%eax
  331         movl    %eax,%dr2
  332         movl    PCB_DR1(%edx),%eax
  333         movl    %eax,%dr1
  334         movl    PCB_DR0(%edx),%eax
  335         movl    %eax,%dr0
  336         movl    %dr7,%eax
  337         andl    $0x0000fc00,%eax
  338         movl    PCB_DR7(%edx),%ecx
  339         andl    $~0x0000fc00,%ecx
  340         orl     %ecx,%eax
  341         movl    %eax,%dr7
  342 1:
  343         ret
  344 
  345 #ifdef INVARIANTS
  346 badsw1:
  347         pushal
  348         pushl   $sw0_1
  349         call    panic
  350 sw0_1:  .asciz  "cpu_throw: no newthread supplied"
  351 
  352 badsw2:
  353         pushal
  354         pushl   $sw0_2
  355         call    panic
  356 sw0_2:  .asciz  "cpu_switch: no curthread supplied"
  357 
  358 badsw3:
  359         pushal
  360         pushl   $sw0_3
  361         call    panic
  362 sw0_3:  .asciz  "cpu_switch: no newthread supplied"
  363 #endif
  364 END(cpu_switch)
  365 
  366 /*
  367  * savectx(pcb)
  368  * Update pcb, saving current processor state.
  369  */
  370 ENTRY(savectx)
  371         /* Fetch PCB. */
  372         movl    4(%esp),%ecx
  373 
  374         /* Save caller's return address.  Child won't execute this routine. */
  375         movl    (%esp),%eax
  376         movl    %eax,PCB_EIP(%ecx)
  377 
  378         movl    %cr3,%eax
  379         movl    %eax,PCB_CR3(%ecx)
  380 
  381         movl    %ebx,PCB_EBX(%ecx)
  382         movl    %esp,PCB_ESP(%ecx)
  383         movl    %ebp,PCB_EBP(%ecx)
  384         movl    %esi,PCB_ESI(%ecx)
  385         movl    %edi,PCB_EDI(%ecx)
  386         mov     %gs,PCB_GS(%ecx)
  387         pushfl
  388         popl    PCB_PSL(%ecx)
  389 
  390 #ifdef DEV_NPX
  391         /*
  392          * If fpcurthread == NULL, then the npx h/w state is irrelevant and the
  393          * state had better already be in the pcb.  This is true for forks
  394          * but not for dumps (the old book-keeping with FP flags in the pcb
  395          * always lost for dumps because the dump pcb has 0 flags).
  396          *
  397          * If fpcurthread != NULL, then we have to save the npx h/w state to
  398          * fpcurthread's pcb and copy it to the requested pcb, or save to the
  399          * requested pcb and reload.  Copying is easier because we would
  400          * have to handle h/w bugs for reloading.  We used to lose the
  401          * parent's npx state for forks by forgetting to reload.
  402          */
  403         pushfl
  404         CLI
  405         movl    PCPU(FPCURTHREAD),%eax
  406         testl   %eax,%eax
  407         je      1f
  408 
  409         pushl   %ecx
  410         movl    TD_PCB(%eax),%eax
  411         leal    PCB_SAVEFPU(%eax),%eax
  412         pushl   %eax
  413         pushl   %eax
  414         call    npxsave
  415         addl    $4,%esp
  416         popl    %eax
  417         popl    %ecx
  418 
  419         pushl   $PCB_SAVEFPU_SIZE
  420         leal    PCB_SAVEFPU(%ecx),%ecx
  421         pushl   %ecx
  422         pushl   %eax
  423         call    bcopy
  424         addl    $12,%esp
  425 1:
  426         popfl
  427 #endif  /* DEV_NPX */
  428 
  429         ret
  430 END(savectx)

Cache object: 43424ba38b3ed71a7b57d44a19e914fe


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