The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/i386/xen/exception.s

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    1 /*-
    2  * Copyright (c) 1989, 1990 William F. Jolitz.
    3  * Copyright (c) 1990 The Regents of the University of California.
    4  * All rights reserved.
    5  *
    6  * Redistribution and use in source and binary forms, with or without
    7  * modification, are permitted provided that the following conditions
    8  * are met:
    9  * 1. Redistributions of source code must retain the above copyright
   10  *    notice, this list of conditions and the following disclaimer.
   11  * 2. Redistributions in binary form must reproduce the above copyright
   12  *    notice, this list of conditions and the following disclaimer in the
   13  *    documentation and/or other materials provided with the distribution.
   14  * 4. Neither the name of the University nor the names of its contributors
   15  *    may be used to endorse or promote products derived from this software
   16  *    without specific prior written permission.
   17  *
   18  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   19  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   20  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   21  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   22  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   23  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   24  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   25  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   26  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   27  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   28  * SUCH DAMAGE.
   29  *
   30  * $FreeBSD: stable/9/sys/i386/xen/exception.s 199852 2009-11-27 01:02:17Z attilio $
   31  */
   32 
   33 #include "opt_apic.h"
   34 #include "opt_npx.h"
   35 
   36 #include <machine/asmacros.h>
   37 #include <machine/psl.h>
   38 #include <machine/trap.h>
   39 
   40 #include "assym.s"
   41 
   42 #define SEL_RPL_MASK    0x0002
   43 #define __HYPERVISOR_iret       23
   44         
   45 /* Offsets into shared_info_t. */
   46 
   47 #define evtchn_upcall_pending /* 0 */
   48 #define evtchn_upcall_mask       1
   49 
   50 #define sizeof_vcpu_shift       6
   51 
   52                 
   53 #ifdef SMP
   54 #define GET_VCPU_INFO(reg)      movl PCPU(CPUID),reg                    ; \
   55                                 shl  $sizeof_vcpu_shift,reg             ; \
   56                                 addl HYPERVISOR_shared_info,reg
   57 #else
   58 #define GET_VCPU_INFO(reg)      movl HYPERVISOR_shared_info,reg
   59 #endif
   60 
   61 #define __DISABLE_INTERRUPTS(reg)       movb $1,evtchn_upcall_mask(reg)
   62 #define __ENABLE_INTERRUPTS(reg)        movb $0,evtchn_upcall_mask(reg)
   63 #define DISABLE_INTERRUPTS(reg) GET_VCPU_INFO(reg)                      ; \
   64                                 __DISABLE_INTERRUPTS(reg)
   65 #define ENABLE_INTERRUPTS(reg)  GET_VCPU_INFO(reg)                      ; \
   66                                 __ENABLE_INTERRUPTS(reg)
   67 #define __TEST_PENDING(reg)     testb $0xFF,evtchn_upcall_pending(reg)
   68 
   69 #define POPA \
   70         popl %edi; \
   71         popl %esi; \
   72         popl %ebp; \
   73         popl %ebx; \
   74         popl %ebx; \
   75         popl %edx; \
   76         popl %ecx; \
   77         popl %eax;
   78 
   79         .text
   80 
   81 /*****************************************************************************/
   82 /* Trap handling                                                             */
   83 /*****************************************************************************/
   84 /*
   85  * Trap and fault vector routines.
   86  *
   87  * Most traps are 'trap gates', SDT_SYS386TGT.  A trap gate pushes state on
   88  * the stack that mostly looks like an interrupt, but does not disable 
   89  * interrupts.  A few of the traps we are use are interrupt gates, 
   90  * SDT_SYS386IGT, which are nearly the same thing except interrupts are
   91  * disabled on entry.
   92  *
   93  * The cpu will push a certain amount of state onto the kernel stack for
   94  * the current process.  The amount of state depends on the type of trap 
   95  * and whether the trap crossed rings or not.  See i386/include/frame.h.  
   96  * At the very least the current EFLAGS (status register, which includes 
   97  * the interrupt disable state prior to the trap), the code segment register,
   98  * and the return instruction pointer are pushed by the cpu.  The cpu 
   99  * will also push an 'error' code for certain traps.  We push a dummy 
  100  * error code for those traps where the cpu doesn't in order to maintain 
  101  * a consistent frame.  We also push a contrived 'trap number'.
  102  *
  103  * The cpu does not push the general registers, we must do that, and we 
  104  * must restore them prior to calling 'iret'.  The cpu adjusts the %cs and
  105  * %ss segment registers, but does not mess with %ds, %es, or %fs.  Thus we
  106  * must load them with appropriate values for supervisor mode operation.
  107  */
  108 
  109 MCOUNT_LABEL(user)
  110 MCOUNT_LABEL(btrap)
  111 
  112 #define TRAP(a)         pushl $(a) ; jmp alltraps
  113 
  114 IDTVEC(div)
  115         pushl $0; TRAP(T_DIVIDE)
  116 IDTVEC(dbg)
  117         pushl $0; TRAP(T_TRCTRAP)
  118 IDTVEC(nmi)
  119         pushl $0; TRAP(T_NMI)
  120 IDTVEC(bpt)
  121         pushl $0; TRAP(T_BPTFLT)
  122 IDTVEC(ofl)
  123         pushl $0; TRAP(T_OFLOW)
  124 IDTVEC(bnd)
  125         pushl $0; TRAP(T_BOUND)
  126 IDTVEC(ill)
  127         pushl $0; TRAP(T_PRIVINFLT)
  128 IDTVEC(dna)
  129         pushl $0; TRAP(T_DNA)
  130 IDTVEC(fpusegm)
  131         pushl $0; TRAP(T_FPOPFLT)
  132 IDTVEC(tss)
  133         TRAP(T_TSSFLT)
  134 IDTVEC(missing)
  135         TRAP(T_SEGNPFLT)
  136 IDTVEC(stk)
  137         TRAP(T_STKFLT)
  138 IDTVEC(prot)
  139         TRAP(T_PROTFLT)
  140 IDTVEC(page)
  141         TRAP(T_PAGEFLT)
  142 IDTVEC(mchk)
  143         pushl $0; TRAP(T_MCHK)
  144 IDTVEC(rsvd)
  145         pushl $0; TRAP(T_RESERVED)
  146 IDTVEC(fpu)
  147         pushl $0; TRAP(T_ARITHTRAP)
  148 IDTVEC(align)
  149         TRAP(T_ALIGNFLT)
  150 IDTVEC(xmm)
  151         pushl $0; TRAP(T_XMMFLT)
  152 
  153 IDTVEC(hypervisor_callback)
  154         pushl $0; 
  155         pushl $0; 
  156         pushal
  157         pushl   %ds
  158         pushl   %es
  159         pushl   %fs
  160 upcall_with_regs_pushed:
  161         SET_KERNEL_SREGS
  162         FAKE_MCOUNT(TF_EIP(%esp))
  163 call_evtchn_upcall:
  164         movl    TF_EIP(%esp),%eax
  165         cmpl    $scrit,%eax
  166         jb      10f
  167         cmpl    $ecrit,%eax
  168         jb      critical_region_fixup
  169         
  170 10:     pushl   %esp
  171         call    evtchn_do_upcall
  172         addl    $4,%esp
  173 
  174         /*
  175          * Return via doreti to handle ASTs.
  176          */
  177         MEXITCOUNT
  178         jmp     doreti
  179 
  180         
  181 hypervisor_callback_pending:
  182         DISABLE_INTERRUPTS(%esi)                                /*      cli */  
  183         jmp     10b
  184         /*
  185          * alltraps entry point.  Interrupts are enabled if this was a trap
  186          * gate (TGT), else disabled if this was an interrupt gate (IGT).
  187          * Note that int0x80_syscall is a trap gate.  Only page faults
  188          * use an interrupt gate.
  189          */
  190         SUPERALIGN_TEXT
  191         .globl  alltraps
  192         .type   alltraps,@function
  193 alltraps:
  194         pushal
  195         pushl   %ds
  196         pushl   %es
  197         pushl   %fs
  198 
  199 alltraps_with_regs_pushed:
  200         SET_KERNEL_SREGS
  201         FAKE_MCOUNT(TF_EIP(%esp))
  202 
  203 calltrap:
  204         push    %esp
  205         call    trap
  206         add     $4, %esp
  207 
  208         /*
  209          * Return via doreti to handle ASTs.
  210          */
  211         MEXITCOUNT
  212         jmp     doreti
  213 
  214 /*
  215  * SYSCALL CALL GATE (old entry point for a.out binaries)
  216  *
  217  * The intersegment call has been set up to specify one dummy parameter.
  218  *
  219  * This leaves a place to put eflags so that the call frame can be
  220  * converted to a trap frame. Note that the eflags is (semi-)bogusly
  221  * pushed into (what will be) tf_err and then copied later into the
  222  * final spot. It has to be done this way because esp can't be just
  223  * temporarily altered for the pushfl - an interrupt might come in
  224  * and clobber the saved cs/eip.
  225  */
  226         SUPERALIGN_TEXT
  227 IDTVEC(lcall_syscall)
  228         pushfl                          /* save eflags */
  229         popl    8(%esp)                 /* shuffle into tf_eflags */
  230         pushl   $7                      /* sizeof "lcall 7,0" */
  231         subl    $4,%esp                 /* skip over tf_trapno */
  232         pushal
  233         pushl   %ds
  234         pushl   %es
  235         pushl   %fs
  236         SET_KERNEL_SREGS
  237         FAKE_MCOUNT(TF_EIP(%esp))
  238         pushl   %esp
  239         call    syscall
  240         add     $4, %esp
  241         MEXITCOUNT
  242         jmp     doreti
  243 
  244 /*
  245  * Call gate entry for FreeBSD ELF and Linux/NetBSD syscall (int 0x80)
  246  *
  247  * Even though the name says 'int0x80', this is actually a TGT (trap gate)
  248  * rather then an IGT (interrupt gate).  Thus interrupts are enabled on
  249  * entry just as they are for a normal syscall.
  250  */
  251         SUPERALIGN_TEXT
  252 IDTVEC(int0x80_syscall)
  253         pushl   $2                      /* sizeof "int 0x80" */
  254         pushl   $0xBEEF                 /* for debug */
  255         pushal
  256         pushl   %ds
  257         pushl   %es
  258         pushl   %fs
  259         SET_KERNEL_SREGS
  260         FAKE_MCOUNT(TF_EIP(%esp))
  261         pushl   %esp
  262         call    syscall
  263         add     $4, %esp
  264         MEXITCOUNT
  265         jmp     doreti
  266 
  267 ENTRY(fork_trampoline)
  268         pushl   %esp                    /* trapframe pointer */
  269         pushl   %ebx                    /* arg1 */
  270         pushl   %esi                    /* function */
  271         call    fork_exit
  272         addl    $12,%esp
  273         /* cut from syscall */
  274 
  275         /*
  276          * Return via doreti to handle ASTs.
  277          */
  278         MEXITCOUNT
  279         jmp     doreti
  280 
  281 
  282 /*
  283  * To efficiently implement classification of trap and interrupt handlers
  284  * for profiling, there must be only trap handlers between the labels btrap
  285  * and bintr, and only interrupt handlers between the labels bintr and
  286  * eintr.  This is implemented (partly) by including files that contain
  287  * some of the handlers.  Before including the files, set up a normal asm
  288  * environment so that the included files doen't need to know that they are
  289  * included.
  290  */
  291 
  292         .data
  293         .p2align 4
  294         .text
  295         SUPERALIGN_TEXT
  296 MCOUNT_LABEL(bintr)
  297 
  298 #ifdef DEV_APIC
  299         .data
  300         .p2align 4
  301         .text
  302         SUPERALIGN_TEXT
  303 
  304 #include <i386/i386/apic_vector.s>
  305 #endif
  306 
  307         .data
  308         .p2align 4
  309         .text
  310         SUPERALIGN_TEXT
  311 #include <i386/i386/vm86bios.s>
  312 
  313         .text
  314 MCOUNT_LABEL(eintr)
  315 
  316 /*
  317  * void doreti(struct trapframe)
  318  *
  319  * Handle return from interrupts, traps and syscalls.
  320  */
  321         .text
  322         SUPERALIGN_TEXT
  323         .type   doreti,@function
  324 doreti:
  325         FAKE_MCOUNT($bintr)             /* init "from" bintr -> doreti */
  326 doreti_next:
  327 #ifdef notyet
  328         /*
  329          * Check if ASTs can be handled now.  PSL_VM must be checked first
  330          * since segment registers only have an RPL in non-VM86 mode.
  331          */
  332         testl   $PSL_VM,TF_EFLAGS(%esp) /* are we in vm86 mode? */
  333         jz      doreti_notvm86
  334         movl    PCPU(CURPCB),%ecx
  335         testl   $PCB_VM86CALL,PCB_FLAGS(%ecx)   /* are we in a vm86 call? */
  336         jz      doreti_ast              /* can handle ASTS now if not */
  337         jmp     doreti_exit
  338 
  339 doreti_notvm86:
  340 #endif
  341         testb   $SEL_RPL_MASK,TF_CS(%esp) /* are we returning to user mode? */
  342         jz      doreti_exit             /* can't handle ASTs now if not */
  343 
  344 doreti_ast:
  345         /*
  346          * Check for ASTs atomically with returning.  Disabling CPU
  347          * interrupts provides sufficient locking even in the SMP case,
  348          * since we will be informed of any new ASTs by an IPI.
  349          */
  350         DISABLE_INTERRUPTS(%esi)                                /*      cli */
  351         movl    PCPU(CURTHREAD),%eax
  352         testl   $TDF_ASTPENDING | TDF_NEEDRESCHED,TD_FLAGS(%eax)
  353         je      doreti_exit
  354         ENABLE_INTERRUPTS(%esi) /* sti */
  355         pushl   %esp                    /* pass a pointer to the trapframe */
  356         call    ast
  357         add     $4,%esp
  358         jmp     doreti_ast
  359 
  360         /*
  361          * doreti_exit: pop registers, iret.
  362          *
  363          *      The segment register pop is a special case, since it may
  364          *      fault if (for example) a sigreturn specifies bad segment
  365          *      registers.  The fault is handled in trap.c.
  366          */
  367 doreti_exit:
  368         ENABLE_INTERRUPTS(%esi) # reenable event callbacks (sti)
  369 
  370         .globl  scrit
  371 scrit:
  372         __TEST_PENDING(%esi)
  373         jnz     hypervisor_callback_pending     /* More to go  */
  374 
  375         MEXITCOUNT
  376 
  377         .globl  doreti_popl_fs
  378 doreti_popl_fs:
  379         popl    %fs
  380         .globl  doreti_popl_es
  381 doreti_popl_es:
  382         popl    %es
  383         .globl  doreti_popl_ds
  384 doreti_popl_ds:
  385         popl    %ds
  386 
  387         /*
  388          * This is important: as nothing is atomic over here (we can get
  389          * interrupted any time), we use the critical_region_fixup() in
  390          * order to figure out where out stack is. Therefore, do NOT use
  391          * 'popal' here without fixing up the table!
  392          */
  393         POPA
  394         addl    $8,%esp
  395         .globl  doreti_iret
  396 doreti_iret:
  397         jmp     hypercall_page + (__HYPERVISOR_iret * 32)
  398         .globl  ecrit
  399 ecrit:
  400         /*
  401          * doreti_iret_fault and friends.  Alternative return code for
  402          * the case where we get a fault in the doreti_exit code
  403          * above.  trap() (i386/i386/trap.c) catches this specific
  404          * case, sends the process a signal and continues in the
  405          * corresponding place in the code below.
  406          */
  407         ALIGN_TEXT
  408         .globl  doreti_iret_fault
  409 doreti_iret_fault:
  410         subl    $8,%esp
  411         pushal
  412         pushl   %ds
  413         .globl  doreti_popl_ds_fault
  414 doreti_popl_ds_fault:
  415         pushl   %es
  416         .globl  doreti_popl_es_fault
  417 doreti_popl_es_fault:
  418         pushl   %fs
  419         .globl  doreti_popl_fs_fault
  420 doreti_popl_fs_fault:
  421         movl    $0,TF_ERR(%esp) /* XXX should be the error code */
  422         movl    $T_PROTFLT,TF_TRAPNO(%esp)
  423         jmp     alltraps_with_regs_pushed
  424 
  425         /*
  426 # [How we do the fixup]. We want to merge the current stack frame with the
  427 # just-interrupted frame. How we do this depends on where in the critical
  428 # region the interrupted handler was executing, and so how many saved
  429 # registers are in each frame. We do this quickly using the lookup table
  430 # 'critical_fixup_table'. For each byte offset in the critical region, it
  431 # provides the number of bytes which have already been popped from the
  432 # interrupted stack frame.
  433 */
  434 
  435 .globl critical_region_fixup
  436 critical_region_fixup:
  437         addl $critical_fixup_table-scrit,%eax
  438         movzbl (%eax),%eax    # %eax contains num bytes popped
  439         movl  %esp,%esi
  440         add  %eax,%esi        # %esi points at end of src region
  441         movl  %esp,%edi
  442         add  $0x40,%edi       # %edi points at end of dst region
  443         movl  %eax,%ecx
  444         shr  $2,%ecx          # convert bytes to words
  445         je   16f              # skip loop if nothing to copy
  446 15:     subl $4,%esi          # pre-decrementing copy loop
  447         subl $4,%edi
  448         movl (%esi),%eax
  449         movl %eax,(%edi)
  450         loop 15b
  451 16:     movl %edi,%esp        # final %edi is top of merged stack
  452         jmp  hypervisor_callback_pending
  453 
  454 
  455 critical_fixup_table:        
  456 .byte   0x0,0x0,0x0                     #testb  $0x1,(%esi)
  457 .byte   0x0,0x0,0x0,0x0,0x0,0x0         #jne    ea 
  458 .byte   0x0,0x0                         #pop    %fs
  459 .byte   0x04                            #pop    %es
  460 .byte   0x08                            #pop    %ds
  461 .byte   0x0c                            #pop    %edi
  462 .byte   0x10                            #pop    %esi
  463 .byte   0x14                            #pop    %ebp
  464 .byte   0x18                            #pop    %ebx
  465 .byte   0x1c                            #pop    %ebx
  466 .byte   0x20                            #pop    %edx
  467 .byte   0x24                            #pop    %ecx
  468 .byte   0x28                            #pop    %eax
  469 .byte   0x2c,0x2c,0x2c                  #add    $0x8,%esp
  470 #if 0
  471         .byte   0x34                            #iret   
  472 #endif
  473 .byte   0x34,0x34,0x34,0x34,0x34        #HYPERVISOR_iret 
  474         
  475         
  476 /* # Hypervisor uses this for application faults while it executes.*/
  477 ENTRY(failsafe_callback)
  478         pushal
  479         call xen_failsafe_handler
  480 /*#     call install_safe_pf_handler */
  481         movl 28(%esp),%ebx
  482 1:      movl %ebx,%ds
  483         movl 32(%esp),%ebx
  484 2:      movl %ebx,%es
  485         movl 36(%esp),%ebx
  486 3:      movl %ebx,%fs
  487         movl 40(%esp),%ebx
  488 4:      movl %ebx,%gs
  489 /*#        call install_normal_pf_handler */
  490         popal
  491         addl $12,%esp
  492         iret
  493 
  494 

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