353705930f
Historical behavior of letting other CPUs merily go on is a default for time being. The new behavior can be switched on via kern.stop_scheduler_on_panic tunable and sysctl. Stopping of the CPUs has (at least) the following benefits: - more of the system state at panic time is preserved intact - threads and interrupts do not interfere with dumping of the system state Only one thread runs uninterrupted after panic if stop_scheduler_on_panic is set. That thread might call code that is also used in normal context and that code might use locks to prevent concurrent execution of certain parts. Those locks might be held by the stopped threads and would never be released. To work around this issue, it was decided that instead of explicit checks for panic context, we would rather put those checks inside the locking primitives. This change has substantial portions written and re-written by attilio and kib at various times. Other changes are heavily based on the ideas and patches submitted by jhb and mdf. bde has provided many insights into the details and history of the current code. The new behavior may cause problems for systems that use a USB keyboard for interfacing with system console. This is because of some unusual locking patterns in the ukbd code which have to be used because on one hand ukbd is below syscons, but on the other hand it has to interface with other usb code that uses regular mutexes/Giant for its concurrency protection. Dumping to USB-connected disks may also be affected. PR: amd64/139614 (at least) In cooperation with: attilio, jhb, kib, mdf Discussed with: arch@, bde Tested by: Eugene Grosbein <eugen@grosbein.net>, gnn, Steven Hartland <killing@multiplay.co.uk>, glebius, Andrew Boyer <aboyer@averesystems.com> (various versions of the patch) MFC after: 3 months (or never)
646 lines
14 KiB
C
646 lines
14 KiB
C
/*-
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* Copyright (c) 2004 The FreeBSD Project
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include "opt_kdb.h"
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#include "opt_stack.h"
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/kdb.h>
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#include <sys/kernel.h>
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#include <sys/malloc.h>
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#include <sys/pcpu.h>
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#include <sys/proc.h>
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#include <sys/sbuf.h>
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#include <sys/smp.h>
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#include <sys/stack.h>
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#include <sys/sysctl.h>
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#include <machine/kdb.h>
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#include <machine/pcb.h>
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#ifdef SMP
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#include <machine/smp.h>
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#endif
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int kdb_active = 0;
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static void *kdb_jmpbufp = NULL;
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struct kdb_dbbe *kdb_dbbe = NULL;
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static struct pcb kdb_pcb;
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struct pcb *kdb_thrctx = NULL;
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struct thread *kdb_thread = NULL;
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struct trapframe *kdb_frame = NULL;
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#ifdef BREAK_TO_DEBUGGER
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#define KDB_BREAK_TO_DEBUGGER 1
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#else
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#define KDB_BREAK_TO_DEBUGGER 0
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#endif
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#ifdef ALT_BREAK_TO_DEBUGGER
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#define KDB_ALT_BREAK_TO_DEBUGGER 1
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#else
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#define KDB_ALT_BREAK_TO_DEBUGGER 0
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#endif
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static int kdb_break_to_debugger = KDB_BREAK_TO_DEBUGGER;
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static int kdb_alt_break_to_debugger = KDB_ALT_BREAK_TO_DEBUGGER;
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KDB_BACKEND(null, NULL, NULL, NULL);
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SET_DECLARE(kdb_dbbe_set, struct kdb_dbbe);
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static int kdb_sysctl_available(SYSCTL_HANDLER_ARGS);
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static int kdb_sysctl_current(SYSCTL_HANDLER_ARGS);
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static int kdb_sysctl_enter(SYSCTL_HANDLER_ARGS);
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static int kdb_sysctl_panic(SYSCTL_HANDLER_ARGS);
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static int kdb_sysctl_trap(SYSCTL_HANDLER_ARGS);
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static int kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS);
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static SYSCTL_NODE(_debug, OID_AUTO, kdb, CTLFLAG_RW, NULL, "KDB nodes");
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SYSCTL_PROC(_debug_kdb, OID_AUTO, available, CTLTYPE_STRING | CTLFLAG_RD, NULL,
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0, kdb_sysctl_available, "A", "list of available KDB backends");
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SYSCTL_PROC(_debug_kdb, OID_AUTO, current, CTLTYPE_STRING | CTLFLAG_RW, NULL,
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0, kdb_sysctl_current, "A", "currently selected KDB backend");
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SYSCTL_PROC(_debug_kdb, OID_AUTO, enter,
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CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE, NULL, 0,
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kdb_sysctl_enter, "I", "set to enter the debugger");
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SYSCTL_PROC(_debug_kdb, OID_AUTO, panic,
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CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE, NULL, 0,
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kdb_sysctl_panic, "I", "set to panic the kernel");
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SYSCTL_PROC(_debug_kdb, OID_AUTO, trap,
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CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE, NULL, 0,
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kdb_sysctl_trap, "I", "set to cause a page fault via data access");
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SYSCTL_PROC(_debug_kdb, OID_AUTO, trap_code,
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CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE, NULL, 0,
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kdb_sysctl_trap_code, "I", "set to cause a page fault via code access");
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SYSCTL_INT(_debug_kdb, OID_AUTO, break_to_debugger,
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CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_TUN | CTLFLAG_SECURE,
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&kdb_break_to_debugger, 0, "Enable break to debugger");
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TUNABLE_INT("debug.kdb.break_to_debugger", &kdb_break_to_debugger);
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SYSCTL_INT(_debug_kdb, OID_AUTO, alt_break_to_debugger,
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CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_TUN | CTLFLAG_SECURE,
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&kdb_alt_break_to_debugger, 0, "Enable alternative break to debugger");
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TUNABLE_INT("debug.kdb.alt_break_to_debugger", &kdb_alt_break_to_debugger);
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/*
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* Flag to indicate to debuggers why the debugger was entered.
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*/
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const char * volatile kdb_why = KDB_WHY_UNSET;
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static int
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kdb_sysctl_available(SYSCTL_HANDLER_ARGS)
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{
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struct kdb_dbbe **iter;
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struct sbuf sbuf;
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int error;
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sbuf_new_for_sysctl(&sbuf, NULL, 64, req);
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SET_FOREACH(iter, kdb_dbbe_set) {
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if ((*iter)->dbbe_active == 0)
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sbuf_printf(&sbuf, "%s ", (*iter)->dbbe_name);
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}
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error = sbuf_finish(&sbuf);
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sbuf_delete(&sbuf);
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return (error);
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}
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static int
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kdb_sysctl_current(SYSCTL_HANDLER_ARGS)
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{
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char buf[16];
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int error;
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if (kdb_dbbe != NULL)
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strlcpy(buf, kdb_dbbe->dbbe_name, sizeof(buf));
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else
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*buf = '\0';
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error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
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if (error != 0 || req->newptr == NULL)
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return (error);
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if (kdb_active)
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return (EBUSY);
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return (kdb_dbbe_select(buf));
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}
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static int
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kdb_sysctl_enter(SYSCTL_HANDLER_ARGS)
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{
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int error, i;
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error = sysctl_wire_old_buffer(req, sizeof(int));
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if (error == 0) {
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i = 0;
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error = sysctl_handle_int(oidp, &i, 0, req);
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}
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if (error != 0 || req->newptr == NULL)
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return (error);
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if (kdb_active)
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return (EBUSY);
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kdb_enter(KDB_WHY_SYSCTL, "sysctl debug.kdb.enter");
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return (0);
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}
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static int
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kdb_sysctl_panic(SYSCTL_HANDLER_ARGS)
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{
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int error, i;
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error = sysctl_wire_old_buffer(req, sizeof(int));
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if (error == 0) {
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i = 0;
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error = sysctl_handle_int(oidp, &i, 0, req);
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}
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if (error != 0 || req->newptr == NULL)
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return (error);
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panic("kdb_sysctl_panic");
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return (0);
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}
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static int
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kdb_sysctl_trap(SYSCTL_HANDLER_ARGS)
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{
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int error, i;
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int *addr = (int *)0x10;
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error = sysctl_wire_old_buffer(req, sizeof(int));
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if (error == 0) {
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i = 0;
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error = sysctl_handle_int(oidp, &i, 0, req);
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}
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if (error != 0 || req->newptr == NULL)
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return (error);
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return (*addr);
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}
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static int
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kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS)
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{
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int error, i;
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void (*fp)(u_int, u_int, u_int) = (void *)0xdeadc0de;
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error = sysctl_wire_old_buffer(req, sizeof(int));
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if (error == 0) {
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i = 0;
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error = sysctl_handle_int(oidp, &i, 0, req);
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}
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if (error != 0 || req->newptr == NULL)
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return (error);
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(*fp)(0x11111111, 0x22222222, 0x33333333);
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return (0);
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}
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void
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kdb_panic(const char *msg)
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{
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printf("KDB: panic\n");
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panic("%s", msg);
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}
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void
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kdb_reboot(void)
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{
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printf("KDB: reboot requested\n");
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shutdown_nice(0);
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}
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/*
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* Solaris implements a new BREAK which is initiated by a character sequence
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* CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
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* Remote Console.
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*
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* Note that this function may be called from almost anywhere, with interrupts
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* disabled and with unknown locks held, so it must not access data other than
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* its arguments. Its up to the caller to ensure that the state variable is
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* consistent.
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*/
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#define KEY_CR 13 /* CR '\r' */
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#define KEY_TILDE 126 /* ~ */
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#define KEY_CRTLB 2 /* ^B */
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#define KEY_CRTLP 16 /* ^P */
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#define KEY_CRTLR 18 /* ^R */
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/* States of th KDB "alternate break sequence" detecting state machine. */
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enum {
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KDB_ALT_BREAK_SEEN_NONE,
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KDB_ALT_BREAK_SEEN_CR,
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KDB_ALT_BREAK_SEEN_CR_TILDE,
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};
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int
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kdb_break(void)
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{
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if (!kdb_break_to_debugger)
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return (0);
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kdb_enter(KDB_WHY_BREAK, "Break to debugger");
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return (KDB_REQ_DEBUGGER);
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}
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static int
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kdb_alt_break_state(int key, int *state)
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{
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int brk;
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/* All states transition to KDB_ALT_BREAK_SEEN_CR on a CR. */
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if (key == KEY_CR) {
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*state = KDB_ALT_BREAK_SEEN_CR;
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return (0);
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}
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brk = 0;
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switch (*state) {
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case KDB_ALT_BREAK_SEEN_CR:
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*state = KDB_ALT_BREAK_SEEN_NONE;
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if (key == KEY_TILDE)
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*state = KDB_ALT_BREAK_SEEN_CR_TILDE;
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break;
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case KDB_ALT_BREAK_SEEN_CR_TILDE:
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*state = KDB_ALT_BREAK_SEEN_NONE;
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if (key == KEY_CRTLB)
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brk = KDB_REQ_DEBUGGER;
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else if (key == KEY_CRTLP)
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brk = KDB_REQ_PANIC;
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else if (key == KEY_CRTLR)
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brk = KDB_REQ_REBOOT;
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break;
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case KDB_ALT_BREAK_SEEN_NONE:
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default:
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*state = KDB_ALT_BREAK_SEEN_NONE;
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break;
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}
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return (brk);
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}
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static int
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kdb_alt_break_internal(int key, int *state, int force_gdb)
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{
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int brk;
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if (!kdb_alt_break_to_debugger)
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return (0);
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brk = kdb_alt_break_state(key, state);
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switch (brk) {
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case KDB_REQ_DEBUGGER:
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if (force_gdb)
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kdb_dbbe_select("gdb");
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kdb_enter(KDB_WHY_BREAK, "Break to debugger");
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break;
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case KDB_REQ_PANIC:
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if (force_gdb)
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kdb_dbbe_select("gdb");
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kdb_panic("Panic sequence on console");
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break;
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case KDB_REQ_REBOOT:
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kdb_reboot();
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break;
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}
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return (0);
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}
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int
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kdb_alt_break(int key, int *state)
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{
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return (kdb_alt_break_internal(key, state, 0));
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}
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/*
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* This variation on kdb_alt_break() is used only by dcons, which has its own
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* configuration flag to force GDB use regardless of the global KDB
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* configuration.
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*/
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int
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kdb_alt_break_gdb(int key, int *state)
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{
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return (kdb_alt_break_internal(key, state, 1));
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}
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/*
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* Print a backtrace of the calling thread. The backtrace is generated by
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* the selected debugger, provided it supports backtraces. If no debugger
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* is selected or the current debugger does not support backtraces, this
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* function silently returns.
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*/
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void
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kdb_backtrace(void)
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{
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if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) {
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printf("KDB: stack backtrace:\n");
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kdb_dbbe->dbbe_trace();
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}
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#ifdef STACK
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else {
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struct stack st;
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printf("KDB: stack backtrace:\n");
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stack_save(&st);
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stack_print_ddb(&st);
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}
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#endif
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}
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/*
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* Set/change the current backend.
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*/
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int
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kdb_dbbe_select(const char *name)
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{
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struct kdb_dbbe *be, **iter;
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SET_FOREACH(iter, kdb_dbbe_set) {
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be = *iter;
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if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
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kdb_dbbe = be;
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return (0);
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}
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}
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return (EINVAL);
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}
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/*
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* Enter the currently selected debugger. If a message has been provided,
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* it is printed first. If the debugger does not support the enter method,
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* it is entered by using breakpoint(), which enters the debugger through
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* kdb_trap(). The 'why' argument will contain a more mechanically usable
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* string than 'msg', and is relied upon by DDB scripting to identify the
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* reason for entering the debugger so that the right script can be run.
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*/
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void
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kdb_enter(const char *why, const char *msg)
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{
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if (kdb_dbbe != NULL && kdb_active == 0) {
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if (msg != NULL)
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printf("KDB: enter: %s\n", msg);
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kdb_why = why;
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breakpoint();
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kdb_why = KDB_WHY_UNSET;
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}
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}
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/*
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* Initialize the kernel debugger interface.
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*/
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void
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kdb_init(void)
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{
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struct kdb_dbbe *be, **iter;
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int cur_pri, pri;
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kdb_active = 0;
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kdb_dbbe = NULL;
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cur_pri = -1;
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SET_FOREACH(iter, kdb_dbbe_set) {
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be = *iter;
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pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
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be->dbbe_active = (pri >= 0) ? 0 : -1;
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if (pri > cur_pri) {
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cur_pri = pri;
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kdb_dbbe = be;
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}
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}
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if (kdb_dbbe != NULL) {
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printf("KDB: debugger backends:");
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SET_FOREACH(iter, kdb_dbbe_set) {
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be = *iter;
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if (be->dbbe_active == 0)
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printf(" %s", be->dbbe_name);
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}
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printf("\n");
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printf("KDB: current backend: %s\n",
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kdb_dbbe->dbbe_name);
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}
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}
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/*
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* Handle contexts.
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*/
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void *
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kdb_jmpbuf(jmp_buf new)
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{
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void *old;
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old = kdb_jmpbufp;
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kdb_jmpbufp = new;
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return (old);
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}
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void
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kdb_reenter(void)
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{
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if (!kdb_active || kdb_jmpbufp == NULL)
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return;
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longjmp(kdb_jmpbufp, 1);
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/* NOTREACHED */
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}
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/*
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* Thread related support functions.
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*/
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struct pcb *
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kdb_thr_ctx(struct thread *thr)
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{
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#if defined(SMP) && defined(KDB_STOPPEDPCB)
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struct pcpu *pc;
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#endif
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|
|
|
if (thr == curthread)
|
|
return (&kdb_pcb);
|
|
|
|
#if defined(SMP) && defined(KDB_STOPPEDPCB)
|
|
STAILQ_FOREACH(pc, &cpuhead, pc_allcpu) {
|
|
if (pc->pc_curthread == thr &&
|
|
CPU_ISSET(pc->pc_cpuid, &stopped_cpus))
|
|
return (KDB_STOPPEDPCB(pc));
|
|
}
|
|
#endif
|
|
return (thr->td_pcb);
|
|
}
|
|
|
|
struct thread *
|
|
kdb_thr_first(void)
|
|
{
|
|
struct proc *p;
|
|
struct thread *thr;
|
|
|
|
p = LIST_FIRST(&allproc);
|
|
while (p != NULL) {
|
|
if (p->p_flag & P_INMEM) {
|
|
thr = FIRST_THREAD_IN_PROC(p);
|
|
if (thr != NULL)
|
|
return (thr);
|
|
}
|
|
p = LIST_NEXT(p, p_list);
|
|
}
|
|
return (NULL);
|
|
}
|
|
|
|
struct thread *
|
|
kdb_thr_from_pid(pid_t pid)
|
|
{
|
|
struct proc *p;
|
|
|
|
p = LIST_FIRST(&allproc);
|
|
while (p != NULL) {
|
|
if (p->p_flag & P_INMEM && p->p_pid == pid)
|
|
return (FIRST_THREAD_IN_PROC(p));
|
|
p = LIST_NEXT(p, p_list);
|
|
}
|
|
return (NULL);
|
|
}
|
|
|
|
struct thread *
|
|
kdb_thr_lookup(lwpid_t tid)
|
|
{
|
|
struct thread *thr;
|
|
|
|
thr = kdb_thr_first();
|
|
while (thr != NULL && thr->td_tid != tid)
|
|
thr = kdb_thr_next(thr);
|
|
return (thr);
|
|
}
|
|
|
|
struct thread *
|
|
kdb_thr_next(struct thread *thr)
|
|
{
|
|
struct proc *p;
|
|
|
|
p = thr->td_proc;
|
|
thr = TAILQ_NEXT(thr, td_plist);
|
|
do {
|
|
if (thr != NULL)
|
|
return (thr);
|
|
p = LIST_NEXT(p, p_list);
|
|
if (p != NULL && (p->p_flag & P_INMEM))
|
|
thr = FIRST_THREAD_IN_PROC(p);
|
|
} while (p != NULL);
|
|
return (NULL);
|
|
}
|
|
|
|
int
|
|
kdb_thr_select(struct thread *thr)
|
|
{
|
|
if (thr == NULL)
|
|
return (EINVAL);
|
|
kdb_thread = thr;
|
|
kdb_thrctx = kdb_thr_ctx(thr);
|
|
return (0);
|
|
}
|
|
|
|
/*
|
|
* Enter the debugger due to a trap.
|
|
*/
|
|
|
|
int
|
|
kdb_trap(int type, int code, struct trapframe *tf)
|
|
{
|
|
#ifdef SMP
|
|
cpuset_t other_cpus;
|
|
#endif
|
|
struct kdb_dbbe *be;
|
|
register_t intr;
|
|
int handled;
|
|
#ifdef SMP
|
|
int did_stop_cpus;
|
|
#endif
|
|
|
|
be = kdb_dbbe;
|
|
if (be == NULL || be->dbbe_trap == NULL)
|
|
return (0);
|
|
|
|
/* We reenter the debugger through kdb_reenter(). */
|
|
if (kdb_active)
|
|
return (0);
|
|
|
|
intr = intr_disable();
|
|
|
|
#ifdef SMP
|
|
if (!SCHEDULER_STOPPED()) {
|
|
other_cpus = all_cpus;
|
|
CPU_CLR(PCPU_GET(cpuid), &other_cpus);
|
|
stop_cpus_hard(other_cpus);
|
|
did_stop_cpus = 1;
|
|
} else
|
|
did_stop_cpus = 0;
|
|
#endif
|
|
|
|
kdb_active++;
|
|
|
|
kdb_frame = tf;
|
|
|
|
/* Let MD code do its thing first... */
|
|
kdb_cpu_trap(type, code);
|
|
|
|
makectx(tf, &kdb_pcb);
|
|
kdb_thr_select(curthread);
|
|
|
|
for (;;) {
|
|
handled = be->dbbe_trap(type, code);
|
|
if (be == kdb_dbbe)
|
|
break;
|
|
be = kdb_dbbe;
|
|
if (be == NULL || be->dbbe_trap == NULL)
|
|
break;
|
|
printf("Switching to %s back-end\n", be->dbbe_name);
|
|
}
|
|
|
|
kdb_active--;
|
|
|
|
#ifdef SMP
|
|
if (did_stop_cpus)
|
|
restart_cpus(stopped_cpus);
|
|
#endif
|
|
|
|
intr_restore(intr);
|
|
|
|
return (handled);
|
|
}
|