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/9.0/sys/i386/i386/exception.s 211924 2010-08-28 08:03:29Z rpaulo $
   35  */
   36 
   37 #include "opt_apic.h"
   38 #include "opt_hwpmc_hooks.h"
   39 #include "opt_kdtrace.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 #ifdef KDTRACE_HOOKS
   52         .bss
   53         .globl  dtrace_invop_jump_addr
   54         .align  4
   55         .type   dtrace_invop_jump_addr, @object
   56         .size   dtrace_invop_jump_addr, 4
   57 dtrace_invop_jump_addr:
   58         .zero   4
   59         .globl  dtrace_invop_calltrap_addr
   60         .align  4
   61         .type   dtrace_invop_calltrap_addr, @object
   62         .size   dtrace_invop_calltrap_addr, 4
   63 dtrace_invop_calltrap_addr:
   64         .zero   8
   65 #endif
   66         .text
   67 #ifdef HWPMC_HOOKS
   68         ENTRY(start_exceptions)
   69 #endif
   70 /*****************************************************************************/
   71 /* Trap handling                                                             */
   72 /*****************************************************************************/
   73 /*
   74  * Trap and fault vector routines.
   75  *
   76  * Most traps are 'trap gates', SDT_SYS386TGT.  A trap gate pushes state on
   77  * the stack that mostly looks like an interrupt, but does not disable 
   78  * interrupts.  A few of the traps we are use are interrupt gates, 
   79  * SDT_SYS386IGT, which are nearly the same thing except interrupts are
   80  * disabled on entry.
   81  *
   82  * The cpu will push a certain amount of state onto the kernel stack for
   83  * the current process.  The amount of state depends on the type of trap 
   84  * and whether the trap crossed rings or not.  See i386/include/frame.h.  
   85  * At the very least the current EFLAGS (status register, which includes 
   86  * the interrupt disable state prior to the trap), the code segment register,
   87  * and the return instruction pointer are pushed by the cpu.  The cpu 
   88  * will also push an 'error' code for certain traps.  We push a dummy 
   89  * error code for those traps where the cpu doesn't in order to maintain 
   90  * a consistent frame.  We also push a contrived 'trap number'.
   91  *
   92  * The cpu does not push the general registers, we must do that, and we 
   93  * must restore them prior to calling 'iret'.  The cpu adjusts the %cs and
   94  * %ss segment registers, but does not mess with %ds, %es, or %fs.  Thus we
   95  * must load them with appropriate values for supervisor mode operation.
   96  */
   97 
   98 MCOUNT_LABEL(user)
   99 MCOUNT_LABEL(btrap)
  100 
  101 #define TRAP(a)         pushl $(a) ; jmp alltraps
  102 
  103 IDTVEC(div)
  104         pushl $0; TRAP(T_DIVIDE)
  105 IDTVEC(dbg)
  106         pushl $0; TRAP(T_TRCTRAP)
  107 IDTVEC(nmi)
  108         pushl $0; TRAP(T_NMI)
  109 IDTVEC(bpt)
  110         pushl $0; TRAP(T_BPTFLT)
  111 IDTVEC(dtrace_ret)
  112         pushl $0; TRAP(T_DTRACE_RET)
  113 IDTVEC(ofl)
  114         pushl $0; TRAP(T_OFLOW)
  115 IDTVEC(bnd)
  116         pushl $0; TRAP(T_BOUND)
  117 #ifndef KDTRACE_HOOKS
  118 IDTVEC(ill)
  119         pushl $0; TRAP(T_PRIVINFLT)
  120 #endif
  121 IDTVEC(dna)
  122         pushl $0; TRAP(T_DNA)
  123 IDTVEC(fpusegm)
  124         pushl $0; TRAP(T_FPOPFLT)
  125 IDTVEC(tss)
  126         TRAP(T_TSSFLT)
  127 IDTVEC(missing)
  128         TRAP(T_SEGNPFLT)
  129 IDTVEC(stk)
  130         TRAP(T_STKFLT)
  131 IDTVEC(prot)
  132         TRAP(T_PROTFLT)
  133 IDTVEC(page)
  134         TRAP(T_PAGEFLT)
  135 IDTVEC(mchk)
  136         pushl $0; TRAP(T_MCHK)
  137 IDTVEC(rsvd)
  138         pushl $0; TRAP(T_RESERVED)
  139 IDTVEC(fpu)
  140         pushl $0; TRAP(T_ARITHTRAP)
  141 IDTVEC(align)
  142         TRAP(T_ALIGNFLT)
  143 IDTVEC(xmm)
  144         pushl $0; TRAP(T_XMMFLT)
  145 
  146         /*
  147          * alltraps entry point.  Interrupts are enabled if this was a trap
  148          * gate (TGT), else disabled if this was an interrupt gate (IGT).
  149          * Note that int0x80_syscall is a trap gate.   Interrupt gates are
  150          * used by page faults, non-maskable interrupts, debug and breakpoint
  151          * exceptions.
  152          */
  153 
  154         SUPERALIGN_TEXT
  155         .globl  alltraps
  156         .type   alltraps,@function
  157 alltraps:
  158         pushal
  159         pushl   %ds
  160         pushl   %es
  161         pushl   %fs
  162 alltraps_with_regs_pushed:
  163         SET_KERNEL_SREGS
  164         cld
  165         FAKE_MCOUNT(TF_EIP(%esp))
  166 calltrap:
  167         pushl   %esp
  168         call    trap
  169         add     $4, %esp
  170         
  171         /*
  172          * Return via doreti to handle ASTs.
  173          */
  174         MEXITCOUNT
  175         jmp     doreti
  176 
  177 /*
  178  * Privileged instruction fault.
  179  */
  180 #ifdef KDTRACE_HOOKS
  181         SUPERALIGN_TEXT
  182 IDTVEC(ill)
  183         /* Check if there is no DTrace hook registered. */
  184         cmpl    $0,dtrace_invop_jump_addr
  185         je      norm_ill
  186 
  187         /* Check if this is a user fault. */
  188         cmpl    $GSEL_KPL, 4(%esp)      /* Check the code segment. */
  189               
  190         /* If so, just handle it as a normal trap. */
  191         jne     norm_ill
  192               
  193         /*
  194          * This is a kernel instruction fault that might have been caused
  195          * by a DTrace provider.
  196          */
  197         pushal                          /* Push all registers onto the stack. */
  198 
  199         /*
  200          * Set our jump address for the jump back in the event that
  201          * the exception wasn't caused by DTrace at all.
  202          */
  203         movl    $norm_ill, dtrace_invop_calltrap_addr
  204 
  205         /* Jump to the code hooked in by DTrace. */
  206         jmpl    *dtrace_invop_jump_addr
  207 
  208         /*
  209          * Process the instruction fault in the normal way.
  210          */
  211 norm_ill:
  212         pushl $0
  213         TRAP(T_PRIVINFLT)
  214 #endif
  215 
  216 /*
  217  * SYSCALL CALL GATE (old entry point for a.out binaries)
  218  *
  219  * The intersegment call has been set up to specify one dummy parameter.
  220  *
  221  * This leaves a place to put eflags so that the call frame can be
  222  * converted to a trap frame. Note that the eflags is (semi-)bogusly
  223  * pushed into (what will be) tf_err and then copied later into the
  224  * final spot. It has to be done this way because esp can't be just
  225  * temporarily altered for the pushfl - an interrupt might come in
  226  * and clobber the saved cs/eip.
  227  */
  228         SUPERALIGN_TEXT
  229 IDTVEC(lcall_syscall)
  230         pushfl                          /* save eflags */
  231         popl    8(%esp)                 /* shuffle into tf_eflags */
  232         pushl   $7                      /* sizeof "lcall 7,0" */
  233         subl    $4,%esp                 /* skip over tf_trapno */
  234         pushal
  235         pushl   %ds
  236         pushl   %es
  237         pushl   %fs
  238         SET_KERNEL_SREGS
  239         cld
  240         FAKE_MCOUNT(TF_EIP(%esp))
  241         pushl   %esp
  242         call    syscall
  243         add     $4, %esp
  244         MEXITCOUNT
  245         jmp     doreti
  246 
  247 /*
  248  * Call gate entry for FreeBSD ELF and Linux/NetBSD syscall (int 0x80)
  249  *
  250  * Even though the name says 'int0x80', this is actually a TGT (trap gate)
  251  * rather then an IGT (interrupt gate).  Thus interrupts are enabled on
  252  * entry just as they are for a normal syscall.
  253  */
  254         SUPERALIGN_TEXT
  255 IDTVEC(int0x80_syscall)
  256         pushl   $2                      /* sizeof "int 0x80" */
  257         subl    $4,%esp                 /* skip over tf_trapno */
  258         pushal
  259         pushl   %ds
  260         pushl   %es
  261         pushl   %fs
  262         SET_KERNEL_SREGS
  263         cld
  264         FAKE_MCOUNT(TF_EIP(%esp))
  265         pushl   %esp
  266         call    syscall
  267         add     $4, %esp
  268         MEXITCOUNT
  269         jmp     doreti
  270 
  271 ENTRY(fork_trampoline)
  272         pushl   %esp                    /* trapframe pointer */
  273         pushl   %ebx                    /* arg1 */
  274         pushl   %esi                    /* function */
  275         call    fork_exit
  276         addl    $12,%esp
  277         /* cut from syscall */
  278 
  279         /*
  280          * Return via doreti to handle ASTs.
  281          */
  282         MEXITCOUNT
  283         jmp     doreti
  284 
  285 
  286 /*
  287  * To efficiently implement classification of trap and interrupt handlers
  288  * for profiling, there must be only trap handlers between the labels btrap
  289  * and bintr, and only interrupt handlers between the labels bintr and
  290  * eintr.  This is implemented (partly) by including files that contain
  291  * some of the handlers.  Before including the files, set up a normal asm
  292  * environment so that the included files doen't need to know that they are
  293  * included.
  294  */
  295 
  296         .data
  297         .p2align 4
  298         .text
  299         SUPERALIGN_TEXT
  300 MCOUNT_LABEL(bintr)
  301 
  302 #include <i386/i386/atpic_vector.s>
  303 
  304 #ifdef DEV_APIC
  305         .data
  306         .p2align 4
  307         .text
  308         SUPERALIGN_TEXT
  309 
  310 #include <i386/i386/apic_vector.s>
  311 #endif
  312 
  313         .data
  314         .p2align 4
  315         .text
  316         SUPERALIGN_TEXT
  317 #include <i386/i386/vm86bios.s>
  318 
  319         .text
  320 MCOUNT_LABEL(eintr)
  321 
  322 /*
  323  * void doreti(struct trapframe)
  324  *
  325  * Handle return from interrupts, traps and syscalls.
  326  */
  327         .text
  328         SUPERALIGN_TEXT
  329         .type   doreti,@function
  330 doreti:
  331         FAKE_MCOUNT($bintr)             /* init "from" bintr -> doreti */
  332 doreti_next:
  333         /*
  334          * Check if ASTs can be handled now.  ASTs cannot be safely
  335          * processed when returning from an NMI.
  336          */
  337         cmpb    $T_NMI,TF_TRAPNO(%esp)
  338 #ifdef HWPMC_HOOKS
  339         je      doreti_nmi
  340 #else
  341         je      doreti_exit
  342 #endif
  343         /*
  344          * PSL_VM must be checked first since segment registers only
  345          * have an RPL in non-VM86 mode.
  346          */
  347         testl   $PSL_VM,TF_EFLAGS(%esp) /* are we in vm86 mode? */
  348         jz      doreti_notvm86
  349         movl    PCPU(CURPCB),%ecx
  350         testl   $PCB_VM86CALL,PCB_FLAGS(%ecx)   /* are we in a vm86 call? */
  351         jz      doreti_ast              /* can handle ASTS now if not */
  352         jmp     doreti_exit
  353 
  354 doreti_notvm86:
  355         testb   $SEL_RPL_MASK,TF_CS(%esp) /* are we returning to user mode? */
  356         jz      doreti_exit             /* can't handle ASTs now if not */
  357 
  358 doreti_ast:
  359         /*
  360          * Check for ASTs atomically with returning.  Disabling CPU
  361          * interrupts provides sufficient locking even in the SMP case,
  362          * since we will be informed of any new ASTs by an IPI.
  363          */
  364         cli
  365         movl    PCPU(CURTHREAD),%eax
  366         testl   $TDF_ASTPENDING | TDF_NEEDRESCHED,TD_FLAGS(%eax)
  367         je      doreti_exit
  368         sti
  369         pushl   %esp                    /* pass a pointer to the trapframe */
  370         call    ast
  371         add     $4,%esp
  372         jmp     doreti_ast
  373 
  374         /*
  375          * doreti_exit: pop registers, iret.
  376          *
  377          *      The segment register pop is a special case, since it may
  378          *      fault if (for example) a sigreturn specifies bad segment
  379          *      registers.  The fault is handled in trap.c.
  380          */
  381 doreti_exit:
  382         MEXITCOUNT
  383 
  384         .globl  doreti_popl_fs
  385 doreti_popl_fs:
  386         popl    %fs
  387         .globl  doreti_popl_es
  388 doreti_popl_es:
  389         popl    %es
  390         .globl  doreti_popl_ds
  391 doreti_popl_ds:
  392         popl    %ds
  393         popal
  394         addl    $8,%esp
  395         .globl  doreti_iret
  396 doreti_iret:
  397         iret
  398 
  399         /*
  400          * doreti_iret_fault and friends.  Alternative return code for
  401          * the case where we get a fault in the doreti_exit code
  402          * above.  trap() (i386/i386/trap.c) catches this specific
  403          * case, sends the process a signal and continues in the
  404          * corresponding place in the code below.
  405          */
  406         ALIGN_TEXT
  407         .globl  doreti_iret_fault
  408 doreti_iret_fault:
  409         subl    $8,%esp
  410         pushal
  411         pushl   %ds
  412         .globl  doreti_popl_ds_fault
  413 doreti_popl_ds_fault:
  414         pushl   %es
  415         .globl  doreti_popl_es_fault
  416 doreti_popl_es_fault:
  417         pushl   %fs
  418         .globl  doreti_popl_fs_fault
  419 doreti_popl_fs_fault:
  420         movl    $0,TF_ERR(%esp) /* XXX should be the error code */
  421         movl    $T_PROTFLT,TF_TRAPNO(%esp)
  422         jmp     alltraps_with_regs_pushed
  423 #ifdef HWPMC_HOOKS
  424 doreti_nmi:
  425         /*
  426          * Since we are returning from an NMI, check if the current trap
  427          * was from user mode and if so whether the current thread
  428          * needs a user call chain capture.
  429          */
  430         testb   $SEL_RPL_MASK,TF_CS(%esp)
  431         jz      doreti_exit
  432         movl    PCPU(CURTHREAD),%eax    /* curthread present? */
  433         orl     %eax,%eax
  434         jz      doreti_exit
  435         testl   $TDP_CALLCHAIN,TD_PFLAGS(%eax) /* flagged for capture? */
  436         jz      doreti_exit
  437         /*
  438          * Take the processor out of NMI mode by executing a fake "iret".
  439          */
  440         pushfl
  441         pushl   %cs
  442         pushl   $outofnmi
  443         iret
  444 outofnmi:
  445         /*
  446          * Call the callchain capture hook after turning interrupts back on.
  447          */
  448         movl    pmc_hook,%ecx
  449         orl     %ecx,%ecx
  450         jz      doreti_exit
  451         pushl   %esp                    /* frame pointer */
  452         pushl   $PMC_FN_USER_CALLCHAIN  /* command */
  453         movl    PCPU(CURTHREAD),%eax
  454         pushl   %eax                    /* curthread */
  455         sti
  456         call    *%ecx
  457         addl    $12,%esp
  458         jmp     doreti_ast
  459         ENTRY(end_exceptions)
  460 #endif

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