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  * 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  * $FreeBSD$
   31  */
   32 
   33 #include "opt_apic.h"
   34 #include "opt_kdtrace.h"
   35 #include "opt_npx.h"
   36 
   37 #include <machine/asmacros.h>
   38 #include <machine/psl.h>
   39 #include <machine/trap.h>
   40 
   41 #include "assym.s"
   42 
   43 #define SEL_RPL_MASK    0x0003
   44 #define GSEL_KPL        0x0020  /* GSEL(GCODE_SEL, SEL_KPL) */
   45 
   46 
   47 #ifdef KDTRACE_HOOKS
   48         .bss
   49         .globl  dtrace_invop_jump_addr
   50         .align  4
   51         .type   dtrace_invop_jump_addr, @object
   52         .size   dtrace_invop_jump_addr, 4
   53 dtrace_invop_jump_addr:
   54         .zero   4
   55         .globl  dtrace_invop_calltrap_addr
   56         .align  4
   57         .type   dtrace_invop_calltrap_addr, @object
   58         .size   dtrace_invop_calltrap_addr, 4
   59 dtrace_invop_calltrap_addr:
   60         .zero   8
   61 #endif
   62         .text
   63 
   64 /*****************************************************************************/
   65 /* Trap handling                                                             */
   66 /*****************************************************************************/
   67 /*
   68  * Trap and fault vector routines.
   69  *
   70  * Most traps are 'trap gates', SDT_SYS386TGT.  A trap gate pushes state on
   71  * the stack that mostly looks like an interrupt, but does not disable 
   72  * interrupts.  A few of the traps we are use are interrupt gates, 
   73  * SDT_SYS386IGT, which are nearly the same thing except interrupts are
   74  * disabled on entry.
   75  *
   76  * The cpu will push a certain amount of state onto the kernel stack for
   77  * the current process.  The amount of state depends on the type of trap 
   78  * and whether the trap crossed rings or not.  See i386/include/frame.h.  
   79  * At the very least the current EFLAGS (status register, which includes 
   80  * the interrupt disable state prior to the trap), the code segment register,
   81  * and the return instruction pointer are pushed by the cpu.  The cpu 
   82  * will also push an 'error' code for certain traps.  We push a dummy 
   83  * error code for those traps where the cpu doesn't in order to maintain 
   84  * a consistent frame.  We also push a contrived 'trap number'.
   85  *
   86  * The cpu does not push the general registers, we must do that, and we 
   87  * must restore them prior to calling 'iret'.  The cpu adjusts the %cs and
   88  * %ss segment registers, but does not mess with %ds, %es, or %fs.  Thus we
   89  * must load them with appropriate values for supervisor mode operation.
   90  */
   91 
   92 MCOUNT_LABEL(user)
   93 MCOUNT_LABEL(btrap)
   94 
   95 #define TRAP(a)         pushl $(a) ; jmp alltraps
   96 
   97 IDTVEC(div)
   98         pushl $0; TRAP(T_DIVIDE)
   99 IDTVEC(dbg)
  100         pushl $0; TRAP(T_TRCTRAP)
  101 IDTVEC(nmi)
  102         pushl $0; TRAP(T_NMI)
  103 IDTVEC(bpt)
  104         pushl $0; TRAP(T_BPTFLT)
  105 IDTVEC(ofl)
  106         pushl $0; TRAP(T_OFLOW)
  107 IDTVEC(bnd)
  108         pushl $0; TRAP(T_BOUND)
  109 #ifndef KDTRACE_HOOKS
  110 IDTVEC(ill)
  111         pushl $0; TRAP(T_PRIVINFLT)
  112 #endif
  113 IDTVEC(dna)
  114         pushl $0; TRAP(T_DNA)
  115 IDTVEC(fpusegm)
  116         pushl $0; TRAP(T_FPOPFLT)
  117 IDTVEC(tss)
  118         TRAP(T_TSSFLT)
  119 IDTVEC(missing)
  120         TRAP(T_SEGNPFLT)
  121 IDTVEC(stk)
  122         TRAP(T_STKFLT)
  123 IDTVEC(prot)
  124         TRAP(T_PROTFLT)
  125 IDTVEC(page)
  126         TRAP(T_PAGEFLT)
  127 IDTVEC(mchk)
  128         pushl $0; TRAP(T_MCHK)
  129 IDTVEC(rsvd)
  130         pushl $0; TRAP(T_RESERVED)
  131 IDTVEC(fpu)
  132         pushl $0; TRAP(T_ARITHTRAP)
  133 IDTVEC(align)
  134         TRAP(T_ALIGNFLT)
  135 IDTVEC(xmm)
  136         pushl $0; TRAP(T_XMMFLT)
  137 
  138         /*
  139          * alltraps entry point.  Interrupts are enabled if this was a trap
  140          * gate (TGT), else disabled if this was an interrupt gate (IGT).
  141          * Note that int0x80_syscall is a trap gate.   Interrupt gates are
  142          * used by page faults, non-maskable interrupts, debug and breakpoint
  143          * exceptions.
  144          */
  145 
  146         SUPERALIGN_TEXT
  147         .globl  alltraps
  148         .type   alltraps,@function
  149 alltraps:
  150         pushal
  151         pushl   %ds
  152         pushl   %es
  153         pushl   %fs
  154 alltraps_with_regs_pushed:
  155         SET_KERNEL_SREGS
  156         FAKE_MCOUNT(TF_EIP(%esp))
  157 calltrap:
  158         pushl   %esp
  159         call    trap
  160         add     $4, %esp
  161         
  162         /*
  163          * Return via doreti to handle ASTs.
  164          */
  165         MEXITCOUNT
  166         jmp     doreti
  167 
  168 /*
  169  * Privileged instruction fault.
  170  */
  171 #ifdef KDTRACE_HOOKS
  172         SUPERALIGN_TEXT
  173 IDTVEC(ill)
  174         /* Check if there is no DTrace hook registered. */
  175         cmpl    $0,dtrace_invop_jump_addr
  176         je      norm_ill
  177 
  178         /* Check if this is a user fault. */
  179         cmpl    $GSEL_KPL, 4(%esp)      /* Check the code segment. */
  180               
  181         /* If so, just handle it as a normal trap. */
  182         jne     norm_ill
  183               
  184         /*
  185          * This is a kernel instruction fault that might have been caused
  186          * by a DTrace provider.
  187          */
  188         pushal                          /* Push all registers onto the stack. */
  189 
  190         /*
  191          * Set our jump address for the jump back in the event that
  192          * the exception wasn't caused by DTrace at all.
  193          */
  194         movl    $norm_ill, dtrace_invop_calltrap_addr
  195 
  196         /* Jump to the code hooked in by DTrace. */
  197         jmpl    *dtrace_invop_jump_addr
  198 
  199         /*
  200          * Process the instruction fault in the normal way.
  201          */
  202 norm_ill:
  203         pushl $0
  204         TRAP(T_PRIVINFLT)
  205 #endif
  206 
  207 /*
  208  * SYSCALL CALL GATE (old entry point for a.out binaries)
  209  *
  210  * The intersegment call has been set up to specify one dummy parameter.
  211  *
  212  * This leaves a place to put eflags so that the call frame can be
  213  * converted to a trap frame. Note that the eflags is (semi-)bogusly
  214  * pushed into (what will be) tf_err and then copied later into the
  215  * final spot. It has to be done this way because esp can't be just
  216  * temporarily altered for the pushfl - an interrupt might come in
  217  * and clobber the saved cs/eip.
  218  */
  219         SUPERALIGN_TEXT
  220 IDTVEC(lcall_syscall)
  221         pushfl                          /* save eflags */
  222         popl    8(%esp)                 /* shuffle into tf_eflags */
  223         pushl   $7                      /* sizeof "lcall 7,0" */
  224         subl    $4,%esp                 /* skip over tf_trapno */
  225         pushal
  226         pushl   %ds
  227         pushl   %es
  228         pushl   %fs
  229         SET_KERNEL_SREGS
  230         FAKE_MCOUNT(TF_EIP(%esp))
  231         pushl   %esp
  232         call    syscall
  233         add     $4, %esp
  234         MEXITCOUNT
  235         jmp     doreti
  236 
  237 /*
  238  * Call gate entry for FreeBSD ELF and Linux/NetBSD syscall (int 0x80)
  239  *
  240  * Even though the name says 'int0x80', this is actually a TGT (trap gate)
  241  * rather then an IGT (interrupt gate).  Thus interrupts are enabled on
  242  * entry just as they are for a normal syscall.
  243  */
  244         SUPERALIGN_TEXT
  245 IDTVEC(int0x80_syscall)
  246         pushl   $2                      /* sizeof "int 0x80" */
  247         subl    $4,%esp                 /* skip over tf_trapno */
  248         pushal
  249         pushl   %ds
  250         pushl   %es
  251         pushl   %fs
  252         SET_KERNEL_SREGS
  253         FAKE_MCOUNT(TF_EIP(%esp))
  254         pushl   %esp
  255         call    syscall
  256         add     $4, %esp
  257         MEXITCOUNT
  258         jmp     doreti
  259 
  260 ENTRY(fork_trampoline)
  261         pushl   %esp                    /* trapframe pointer */
  262         pushl   %ebx                    /* arg1 */
  263         pushl   %esi                    /* function */
  264         call    fork_exit
  265         addl    $12,%esp
  266         /* cut from syscall */
  267 
  268         /*
  269          * Return via doreti to handle ASTs.
  270          */
  271         MEXITCOUNT
  272         jmp     doreti
  273 
  274 
  275 /*
  276  * To efficiently implement classification of trap and interrupt handlers
  277  * for profiling, there must be only trap handlers between the labels btrap
  278  * and bintr, and only interrupt handlers between the labels bintr and
  279  * eintr.  This is implemented (partly) by including files that contain
  280  * some of the handlers.  Before including the files, set up a normal asm
  281  * environment so that the included files doen't need to know that they are
  282  * included.
  283  */
  284 
  285         .data
  286         .p2align 4
  287         .text
  288         SUPERALIGN_TEXT
  289 MCOUNT_LABEL(bintr)
  290 
  291 #include <i386/isa/atpic_vector.s>
  292 
  293 #ifdef DEV_APIC
  294         .data
  295         .p2align 4
  296         .text
  297         SUPERALIGN_TEXT
  298 
  299 #include <i386/i386/apic_vector.s>
  300 #endif
  301 
  302         .data
  303         .p2align 4
  304         .text
  305         SUPERALIGN_TEXT
  306 #include <i386/i386/vm86bios.s>
  307 
  308         .text
  309 MCOUNT_LABEL(eintr)
  310 
  311 /*
  312  * void doreti(struct trapframe)
  313  *
  314  * Handle return from interrupts, traps and syscalls.
  315  */
  316         .text
  317         SUPERALIGN_TEXT
  318         .type   doreti,@function
  319 doreti:
  320         FAKE_MCOUNT($bintr)             /* init "from" bintr -> doreti */
  321 doreti_next:
  322         /*
  323          * Check if ASTs can be handled now.  PSL_VM must be checked first
  324          * since segment registers only have an RPL in non-VM86 mode.
  325          */
  326         testl   $PSL_VM,TF_EFLAGS(%esp) /* are we in vm86 mode? */
  327         jz      doreti_notvm86
  328         movl    PCPU(CURPCB),%ecx
  329         testl   $PCB_VM86CALL,PCB_FLAGS(%ecx)   /* are we in a vm86 call? */
  330         jz      doreti_ast              /* can handle ASTS now if not */
  331         jmp     doreti_exit
  332 
  333 doreti_notvm86:
  334         testb   $SEL_RPL_MASK,TF_CS(%esp) /* are we returning to user mode? */
  335         jz      doreti_exit             /* can't handle ASTs now if not */
  336 
  337 doreti_ast:
  338         /*
  339          * Check for ASTs atomically with returning.  Disabling CPU
  340          * interrupts provides sufficient locking even in the SMP case,
  341          * since we will be informed of any new ASTs by an IPI.
  342          */
  343         cli
  344         movl    PCPU(CURTHREAD),%eax
  345         testl   $TDF_ASTPENDING | TDF_NEEDRESCHED,TD_FLAGS(%eax)
  346         je      doreti_exit
  347         sti
  348         pushl   %esp                    /* pass a pointer to the trapframe */
  349         call    ast
  350         add     $4,%esp
  351         jmp     doreti_ast
  352 
  353         /*
  354          * doreti_exit: pop registers, iret.
  355          *
  356          *      The segment register pop is a special case, since it may
  357          *      fault if (for example) a sigreturn specifies bad segment
  358          *      registers.  The fault is handled in trap.c.
  359          */
  360 doreti_exit:
  361         MEXITCOUNT
  362 
  363         .globl  doreti_popl_fs
  364 doreti_popl_fs:
  365         popl    %fs
  366         .globl  doreti_popl_es
  367 doreti_popl_es:
  368         popl    %es
  369         .globl  doreti_popl_ds
  370 doreti_popl_ds:
  371         popl    %ds
  372         popal
  373         addl    $8,%esp
  374         .globl  doreti_iret
  375 doreti_iret:
  376         iret
  377 
  378         /*
  379          * doreti_iret_fault and friends.  Alternative return code for
  380          * the case where we get a fault in the doreti_exit code
  381          * above.  trap() (i386/i386/trap.c) catches this specific
  382          * case, sends the process a signal and continues in the
  383          * corresponding place in the code below.
  384          */
  385         ALIGN_TEXT
  386         .globl  doreti_iret_fault
  387 doreti_iret_fault:
  388         subl    $8,%esp
  389         pushal
  390         pushl   %ds
  391         .globl  doreti_popl_ds_fault
  392 doreti_popl_ds_fault:
  393         pushl   %es
  394         .globl  doreti_popl_es_fault
  395 doreti_popl_es_fault:
  396         pushl   %fs
  397         .globl  doreti_popl_fs_fault
  398 doreti_popl_fs_fault:
  399         movl    $0,TF_ERR(%esp) /* XXX should be the error code */
  400         movl    $T_PROTFLT,TF_TRAPNO(%esp)
  401         jmp     alltraps_with_regs_pushed

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