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/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  * Copyright (c) 2007 The FreeBSD Foundation
    5  * All rights reserved.
    6  *
    7  * Portions of this software were developed by A. Joseph Koshy under
    8  * sponsorship from the FreeBSD Foundation and Google, Inc.
    9  *
   10  * Redistribution and use in source and binary forms, with or without
   11  * modification, are permitted provided that the following conditions
   12  * are met:
   13  * 1. Redistributions of source code must retain the above copyright
   14  *    notice, this list of conditions and the following disclaimer.
   15  * 2. Redistributions in binary form must reproduce the above copyright
   16  *    notice, this list of conditions and the following disclaimer in the
   17  *    documentation and/or other materials provided with the distribution.
   18  * 4. Neither the name of the University nor the names of its contributors
   19  *    may be used to endorse or promote products derived from this software
   20  *    without specific prior written permission.
   21  *
   22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   32  * SUCH DAMAGE.
   33  *
   34  * $FreeBSD: releng/7.4/sys/i386/i386/exception.s 193634 2009-06-07 10:00:35Z fabient $
   35  */
   36 
   37 #include "opt_apic.h"
   38 #include "opt_kdtrace.h"
   39 #include "opt_hwpmc_hooks.h"
   40 #include "opt_npx.h"
   41 
   42 #include <machine/asmacros.h>
   43 #include <machine/psl.h>
   44 #include <machine/trap.h>
   45 
   46 #include "assym.s"
   47 
   48 #define SEL_RPL_MASK    0x0003
   49 #define GSEL_KPL        0x0020  /* GSEL(GCODE_SEL, SEL_KPL) */
   50 
   51 
   52 #ifdef KDTRACE_HOOKS
   53         .bss
   54         .globl  dtrace_invop_jump_addr
   55         .align  4
   56         .type   dtrace_invop_jump_addr, @object
   57         .size   dtrace_invop_jump_addr, 4
   58 dtrace_invop_jump_addr:
   59         .zero   4
   60         .globl  dtrace_invop_calltrap_addr
   61         .align  4
   62         .type   dtrace_invop_calltrap_addr, @object
   63         .size   dtrace_invop_calltrap_addr, 4
   64 dtrace_invop_calltrap_addr:
   65         .zero   8
   66 #endif
   67         .text
   68 #ifdef HWPMC_HOOKS
   69         ENTRY(start_exceptions)
   70 #endif
   71 /*****************************************************************************/
   72 /* Trap handling                                                             */
   73 /*****************************************************************************/
   74 /*
   75  * Trap and fault vector routines.
   76  *
   77  * Most traps are 'trap gates', SDT_SYS386TGT.  A trap gate pushes state on
   78  * the stack that mostly looks like an interrupt, but does not disable 
   79  * interrupts.  A few of the traps we are use are interrupt gates, 
   80  * SDT_SYS386IGT, which are nearly the same thing except interrupts are
   81  * disabled on entry.
   82  *
   83  * The cpu will push a certain amount of state onto the kernel stack for
   84  * the current process.  The amount of state depends on the type of trap 
   85  * and whether the trap crossed rings or not.  See i386/include/frame.h.  
   86  * At the very least the current EFLAGS (status register, which includes 
   87  * the interrupt disable state prior to the trap), the code segment register,
   88  * and the return instruction pointer are pushed by the cpu.  The cpu 
   89  * will also push an 'error' code for certain traps.  We push a dummy 
   90  * error code for those traps where the cpu doesn't in order to maintain 
   91  * a consistent frame.  We also push a contrived 'trap number'.
   92  *
   93  * The cpu does not push the general registers, we must do that, and we 
   94  * must restore them prior to calling 'iret'.  The cpu adjusts the %cs and
   95  * %ss segment registers, but does not mess with %ds, %es, or %fs.  Thus we
   96  * must load them with appropriate values for supervisor mode operation.
   97  */
   98 
   99 MCOUNT_LABEL(user)
  100 MCOUNT_LABEL(btrap)
  101 
  102 #define TRAP(a)         pushl $(a) ; jmp alltraps
  103 
  104 IDTVEC(div)
  105         pushl $0; TRAP(T_DIVIDE)
  106 IDTVEC(dbg)
  107         pushl $0; TRAP(T_TRCTRAP)
  108 IDTVEC(nmi)
  109         pushl $0; TRAP(T_NMI)
  110 IDTVEC(bpt)
  111         pushl $0; TRAP(T_BPTFLT)
  112 IDTVEC(ofl)
  113         pushl $0; TRAP(T_OFLOW)
  114 IDTVEC(bnd)
  115         pushl $0; TRAP(T_BOUND)
  116 #ifndef KDTRACE_HOOKS
  117 IDTVEC(ill)
  118         pushl $0; TRAP(T_PRIVINFLT)
  119 #endif
  120 IDTVEC(dna)
  121         pushl $0; TRAP(T_DNA)
  122 IDTVEC(fpusegm)
  123         pushl $0; TRAP(T_FPOPFLT)
  124 IDTVEC(tss)
  125         TRAP(T_TSSFLT)
  126 IDTVEC(missing)
  127         TRAP(T_SEGNPFLT)
  128 IDTVEC(stk)
  129         TRAP(T_STKFLT)
  130 IDTVEC(prot)
  131         TRAP(T_PROTFLT)
  132 IDTVEC(page)
  133         TRAP(T_PAGEFLT)
  134 IDTVEC(mchk)
  135         pushl $0; TRAP(T_MCHK)
  136 IDTVEC(rsvd)
  137         pushl $0; TRAP(T_RESERVED)
  138 IDTVEC(fpu)
  139         pushl $0; TRAP(T_ARITHTRAP)
  140 IDTVEC(align)
  141         TRAP(T_ALIGNFLT)
  142 IDTVEC(xmm)
  143         pushl $0; TRAP(T_XMMFLT)
  144 
  145         /*
  146          * alltraps entry point.  Interrupts are enabled if this was a trap
  147          * gate (TGT), else disabled if this was an interrupt gate (IGT).
  148          * Note that int0x80_syscall is a trap gate.   Interrupt gates are
  149          * used by page faults, non-maskable interrupts, debug and breakpoint
  150          * exceptions.
  151          */
  152 
  153         SUPERALIGN_TEXT
  154         .globl  alltraps
  155         .type   alltraps,@function
  156 alltraps:
  157         pushal
  158         pushl   %ds
  159         pushl   %es
  160         pushl   %fs
  161 alltraps_with_regs_pushed:
  162         SET_KERNEL_SREGS
  163         FAKE_MCOUNT(TF_EIP(%esp))
  164 calltrap:
  165         pushl   %esp
  166         call    trap
  167         add     $4, %esp
  168         
  169         /*
  170          * Return via doreti to handle ASTs.
  171          */
  172         MEXITCOUNT
  173         jmp     doreti
  174 
  175 /*
  176  * Privileged instruction fault.
  177  */
  178 #ifdef KDTRACE_HOOKS
  179         SUPERALIGN_TEXT
  180 IDTVEC(ill)
  181         /* Check if there is no DTrace hook registered. */
  182         cmpl    $0,dtrace_invop_jump_addr
  183         je      norm_ill
  184 
  185         /* Check if this is a user fault. */
  186         cmpl    $GSEL_KPL, 4(%esp)      /* Check the code segment. */
  187               
  188         /* If so, just handle it as a normal trap. */
  189         jne     norm_ill
  190               
  191         /*
  192          * This is a kernel instruction fault that might have been caused
  193          * by a DTrace provider.
  194          */
  195         pushal                          /* Push all registers onto the stack. */
  196 
  197         /*
  198          * Set our jump address for the jump back in the event that
  199          * the exception wasn't caused by DTrace at all.
  200          */
  201         movl    $norm_ill, dtrace_invop_calltrap_addr
  202 
  203         /* Jump to the code hooked in by DTrace. */
  204         jmpl    *dtrace_invop_jump_addr
  205 
  206         /*
  207          * Process the instruction fault in the normal way.
  208          */
  209 norm_ill:
  210         pushl $0
  211         TRAP(T_PRIVINFLT)
  212 #endif
  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         subl    $4,%esp                 /* skip over tf_trapno */
  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    $12,%esp
  273         /* cut from syscall */
  274 
  275         /*
  276          * Return via doreti to handle ASTs.
  277          */
  278         MEXITCOUNT
  279         jmp     doreti
  280 
  281 
  282 /*
  283  * To efficiently implement classification of trap and interrupt handlers
  284  * for profiling, there must be only trap handlers between the labels btrap
  285  * and bintr, and only interrupt handlers between the labels bintr and
  286  * eintr.  This is implemented (partly) by including files that contain
  287  * some of the handlers.  Before including the files, set up a normal asm
  288  * environment so that the included files doen't need to know that they are
  289  * included.
  290  */
  291 
  292         .data
  293         .p2align 4
  294         .text
  295         SUPERALIGN_TEXT
  296 MCOUNT_LABEL(bintr)
  297 
  298 #include <i386/isa/atpic_vector.s>
  299 
  300 #ifdef DEV_APIC
  301         .data
  302         .p2align 4
  303         .text
  304         SUPERALIGN_TEXT
  305 
  306 #include <i386/i386/apic_vector.s>
  307 #endif
  308 
  309         .data
  310         .p2align 4
  311         .text
  312         SUPERALIGN_TEXT
  313 #include <i386/i386/vm86bios.s>
  314 
  315         .text
  316 MCOUNT_LABEL(eintr)
  317 
  318 /*
  319  * void doreti(struct trapframe)
  320  *
  321  * Handle return from interrupts, traps and syscalls.
  322  */
  323         .text
  324         SUPERALIGN_TEXT
  325         .type   doreti,@function
  326 doreti:
  327         FAKE_MCOUNT($bintr)             /* init "from" bintr -> doreti */
  328 doreti_next:
  329         /*
  330          * Check if ASTs can be handled now.  ASTs cannot be safely
  331          * processed when returning from an NMI.
  332          */
  333         cmpb    $T_NMI,TF_TRAPNO(%esp)
  334 #ifdef HWPMC_HOOKS
  335         je      doreti_nmi
  336 #else
  337         je      doreti_exit
  338 #endif
  339         /*
  340          * PSL_VM must be checked first since segment registers only
  341          * have an RPL in non-VM86 mode.
  342          */
  343         testl   $PSL_VM,TF_EFLAGS(%esp) /* are we in vm86 mode? */
  344         jz      doreti_notvm86
  345         movl    PCPU(CURPCB),%ecx
  346         testl   $PCB_VM86CALL,PCB_FLAGS(%ecx)   /* are we in a vm86 call? */
  347         jz      doreti_ast              /* can handle ASTS now if not */
  348         jmp     doreti_exit
  349 
  350 doreti_notvm86:
  351         testb   $SEL_RPL_MASK,TF_CS(%esp) /* are we returning to user mode? */
  352         jz      doreti_exit             /* can't handle ASTs now if not */
  353 
  354 doreti_ast:
  355         /*
  356          * Check for ASTs atomically with returning.  Disabling CPU
  357          * interrupts provides sufficient locking even in the SMP case,
  358          * since we will be informed of any new ASTs by an IPI.
  359          */
  360         cli
  361         movl    PCPU(CURTHREAD),%eax
  362         testl   $TDF_ASTPENDING | TDF_NEEDRESCHED,TD_FLAGS(%eax)
  363         je      doreti_exit
  364         sti
  365         pushl   %esp                    /* pass a pointer to the trapframe */
  366         call    ast
  367         add     $4,%esp
  368         jmp     doreti_ast
  369 
  370         /*
  371          * doreti_exit: pop registers, iret.
  372          *
  373          *      The segment register pop is a special case, since it may
  374          *      fault if (for example) a sigreturn specifies bad segment
  375          *      registers.  The fault is handled in trap.c.
  376          */
  377 doreti_exit:
  378         MEXITCOUNT
  379 
  380         .globl  doreti_popl_fs
  381 doreti_popl_fs:
  382         popl    %fs
  383         .globl  doreti_popl_es
  384 doreti_popl_es:
  385         popl    %es
  386         .globl  doreti_popl_ds
  387 doreti_popl_ds:
  388         popl    %ds
  389         popal
  390         addl    $8,%esp
  391         .globl  doreti_iret
  392 doreti_iret:
  393         iret
  394 
  395         /*
  396          * doreti_iret_fault and friends.  Alternative return code for
  397          * the case where we get a fault in the doreti_exit code
  398          * above.  trap() (i386/i386/trap.c) catches this specific
  399          * case, sends the process a signal and continues in the
  400          * corresponding place in the code below.
  401          */
  402         ALIGN_TEXT
  403         .globl  doreti_iret_fault
  404 doreti_iret_fault:
  405         subl    $8,%esp
  406         pushal
  407         pushl   %ds
  408         .globl  doreti_popl_ds_fault
  409 doreti_popl_ds_fault:
  410         pushl   %es
  411         .globl  doreti_popl_es_fault
  412 doreti_popl_es_fault:
  413         pushl   %fs
  414         .globl  doreti_popl_fs_fault
  415 doreti_popl_fs_fault:
  416         movl    $0,TF_ERR(%esp) /* XXX should be the error code */
  417         movl    $T_PROTFLT,TF_TRAPNO(%esp)
  418         jmp     alltraps_with_regs_pushed
  419 #ifdef HWPMC_HOOKS
  420 doreti_nmi:
  421         /*
  422          * Since we are returning from an NMI, check if the current trap
  423          * was from user mode and if so whether the current thread
  424          * needs a user call chain capture.
  425          */
  426         testb   $SEL_RPL_MASK,TF_CS(%esp)
  427         jz      doreti_exit
  428         movl    PCPU(CURTHREAD),%eax    /* curthread present? */
  429         orl     %eax,%eax
  430         jz      doreti_exit
  431         testl   $TDP_CALLCHAIN,TD_PFLAGS(%eax) /* flagged for capture? */
  432         jz      doreti_exit
  433         /*
  434          * Take the processor out of NMI mode by executing a fake "iret".
  435          */
  436         pushfl
  437         pushl   %cs
  438         pushl   $outofnmi
  439         iret
  440 outofnmi:
  441         /*
  442          * Call the callchain capture hook after turning interrupts back on.
  443          */
  444         movl    pmc_hook,%ecx
  445         orl     %ecx,%ecx
  446         jz      doreti_exit
  447         pushl   %esp                    /* frame pointer */
  448         pushl   $PMC_FN_USER_CALLCHAIN  /* command */
  449         movl    PCPU(CURTHREAD),%eax
  450         pushl   %eax                    /* curthread */
  451         sti
  452         call    *%ecx
  453         addl    $12,%esp
  454         jmp     doreti_ast
  455         ENTRY(end_exceptions)
  456 #endif

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