.\" $NetBSD: ddb.4,v 1.26 1998/05/26 05:09:10 msaitoh Exp $ .\" .\" Copyright (c) 1997, 1998 The NetBSD Foundation, Inc. .\" All rights reserved. .\" .\" This code is derived from software contributed to The NetBSD Foundation .\" by Luke Mewburn .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. All advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" This product includes software developed by the NetBSD .\" Foundation, Inc. and its contributors. .\" 4. Neither the name of The NetBSD Foundation nor the names of its .\" contributors may be used to endorse or promote products derived .\" from this software without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS .\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED .\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR .\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS .\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR .\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF .\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS .\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN .\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE .\" POSSIBILITY OF SUCH DAMAGE. .\" .\" --- .\" This manual page was derived from a -man.old document which bore .\" the following copyright message: .\" --- .\" .\" Mach Operating System .\" Copyright (c) 1991,1990 Carnegie Mellon University .\" All Rights Reserved. .\" .\" Permission to use, copy, modify and distribute this software and its .\" documentation is hereby granted, provided that both the copyright .\" notice and this permission notice appear in all copies of the .\" software, derivative works or modified versions, and any portions .\" thereof, and that both notices appear in supporting documentation. .\" .\" CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" .\" CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR .\" ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. .\" .\" Carnegie Mellon requests users of this software to return to .\" .\" Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU .\" School of Computer Science .\" Carnegie Mellon University .\" Pittsburgh PA 15213-3890 .\" .\" any improvements or extensions that they make and grant Carnegie Mellon .\" the rights to redistribute these changes. .\" .Dd November 17, 1997 .Dt DDB 4 .Os NetBSD .Sh NAME .Nm ddb .Nd in-kernel debugger .Sh SYNOPSIS .Cd options DDB .Pp To enable history editing: .Cd options DDB_HISTORY_SIZE=integer .Pp To disable entering .Nm upon kernel panic: .Cd options DDB_ONPANIC=0 .Sh DESCRIPTION .Nm is the in-kernel debugger. It may be entered at any time via a special key sequence, and optionally may be invoked when the kernel panics. .Sh ENTERING THE DEBUGGER Unless .Dv DDB_ONPANIC is set to 0, .Nm will be activated whenever the kernel would otherwise panic. .Pp .Nm may also be activated from the console. In general, sending a break on a serial console will activate .Nm "" . There are also key sequences for each port that will activate .Nm from the keyboard: .Bl -tag -offset indent -width "mvme68k" .It alpha -- on PC style keyboards. .It amiga -- .It hp300 - .It i386 -- .It mac68k -, or the Interrupt switch. .It mvme68k Abort switch on CPU card. .It pmax on .Tn LK-201 rcons console. .br on serial console. .It sparc -A, or -A on a .Tn Sun keyboard. .br on serial console. .It sun3 -A, or -A on a .Tn Sun keyboard. .br on serial console. .It sun3x -A, or -A on a .Tn Sun keyboard. .br on serial console. .It x68k Interrupt switch on the body. .El .Pp In addition, .Nm may be explicitly activated by the debugging code in the kernel if .Cm DDB is configured. .Sh COMMAND SYNTAX .Pp The general command syntax is: .Bd -ragged -offset indent .Ic command Ns Op Cm / Ns Ar modifier .Ar address .Op Cm , Ns Ar count .Ed .Pp The current memory location being edited is referred to as .Ar dot , and the next location is .Ar next . They are displayed as hexadecimal numbers. .Pp Commands that examine and/or modify memory update .Ar dot to the address of the last line examined or the last location modified, and set .Ar next to the next location to be examined or modified. Other commands don't change .Ar dot , and set .Ar next to be the same as .Ar dot . .Pp A blank line repeats the previous command from the address .Ar next with a .Cm count of 1 and no modifiers. Specifying .Cm address sets .Em dot to the address. If .Cm address is omitted, .Em dot is used. A missing .Cm count is taken to be 1 for printing commands, and infinity for stack traces. .Pp .Nm has a .Xr more 1 -like functionality; if a number of lines in a command's output exceeds the number defined in the .Va lines variable, then .Nm displays .Dq "--db more--" and waits for a response, which may be one of: .Bl -tag -offset indent -width "" .It one more line. .It one more page. .It Ic q abort the current command, and return to the command input mode. .El .Pp If .Nm history editing is enabled (by defining the .D1 Cd options DDB_HISTORY_SIZE=num kernel option), then a history of the last .Cm num commands is kept. The history can be manipulated with the following key sequences: .Bl -tag -offset indent -width "-P" .It -P retrieve previous command in history (if any). .It -N retrieve next command in history (if any). .El .Sh COMMANDS .Nm supports the following commands: .Bl -tag -width 5n .It Xo .Ic examine Ns Op Cm / Ns Ar modifier .Ar address Ns Op Cm , Ns Ar count .Xc Display the address locations according to the format in .Ar modifier . Multiple modifier formats display multiple locations. If .Ar modifier isn't specified, the modifier from the last use of .Ic examine is used. .Pp The valid format characters for .Ar modifier are: .Bl -tag -offset indent -width 2n .It Cm b examine bytes (8 bits). .It Cm h examine half-words (16 bits). .It Cm l examine long-words (32 bits). .It Cm a print the location being examined. .It Cm A print the location with a line number if possible. .It Cm x display in unsigned hex. .It Cm z display in signed hex. .It Cm o display in unsigned octal. .It Cm d display in signed decimal. .It Cm u display in unsigned decimal. .It Cm r display in current radix, signed. .It Cm c display low 8 bits as a character. Non-printing characters as displayed as an octal escape code (e.g., .Sq \e000 ) . .It Cm s display the NUL terminated string at the location. Non-printing characters are displayed as octal escapes. .It Cm m display in unsigned hex with a character dump at the end of each line. The location is displayed as hex at the beginning of each line. .It Cm i display as a machine instruction. .It Cm I display as a machine instruction, with possible alternative formats depending upon the machine: .Bl -tag -offset indent -width "sparc" .It alpha print register operands .It m68k use Motorola syntax .It pc532 print instruction bytes in hex .It vax don't assume that each external label is a procedure entry mask .El .El .It Xo .Ic x Ns Op Cm / Ns Ar modifier .Ar address Ns Op Cm , Ns Ar count .Xc A synonym for .Ic examine . .It Ic xf Examine forward. .Ic xf re-executes the most recent .Ic execute command with the same parameters except that .Ar address is set to .Ar next . .It Ic xb Examine backward. .Ic xb re-executes the most recent .Ic execute command with the same parameters, except that .Ar address is set to the last start address minus its size. .It Xo .Ic print Ns Op Cm /axzodurc .Ar address Op Ar address ... .Xc Print addresses .Ar address according to the modifier character, as per .Ic examine . Valid modifiers are: .Cm /a , .Cm /x , .Cm /z , .Cm /o , .Cm /d , .Cm /u , .Cm /r , and .Cm /c (as per .Ic examine ) . If no modifier is specified, the most recent one specified is used. .Ar address may be a string, and is printed .Dq as-is . For example: .Bd -literal -offset indent print/x "eax = " $eax "\enecx = " $ecx "\en" .Ed .Pp will produce: .Bd -literal -offset indent eax = xxxxxx ecx = yyyyyy .Ed .It Xo .Ic write Ns Op Cm /bhl .Ar address .Ar expression Op Ar expression ... .Xc Write the .Ar expression Ns s at succeeding locations. The unit size is specified with a modifier character, as per .Ic examine . Valid modifiers are: .Cm /b , .Cm /h , and .Cm /l . If no modifier is specified, .Cm /l is used. .Pp Warning: since there is no delimiter between .Ar expression Ns s , strange things may occur. It's best to enclose each .Ar expression in parentheses. .It Xo .Ic set .Cm $ Ns Ar variable .Op Cm = .Ar expression .Xc Set the named variable or register to the value of .Ar expression . Valid variable names are described in .Sx VARIABLES . .It Xo .Cm break Ns Op Cm /u .Ar address Ns Op Cm , Ns Ar count .Xc Set a breakpoint at .Ar address . If .Ar count is supplied, continues .Pq Ar count Ns -1 times before stopping at the breakpoint. If the breakpoint is set, a breakpoint number is printed with .Sq # . This number can be used to .Ic delete the breakpoint, or to add conditions to it. .Pp If .Cm /u is specified, set a breakpoint at a user-space address. Without .Cm /u , .Ar address is considered to be in the kernel-space, and an address in the wrong space will be rejected, and an error message will be emitted. This modifier may only be used if it is supported by machine dependent routines. .Pp Warning: if a user text is shadowed by a normal user-space debugger, user-space breakpoints may not work correctly. Setting a breakpoint at the low-level code paths may also cause strange behavior. .It Xo .Ic delete .Ar "address" | .Cm # Ns Ar number .Xc Delete a breakpoint. The target breakpoint may be specified by .Ar address , as per .Ic break , or by the breakpoint number returned by .Ic break if it's prefixed with .Sq Cm # . .It Xo .Ic step Ns Op Cm /p .Op Cm , Ns Ar count .Xc Single-step .Ar count times. If .Cm /p is specified, print each instruction at each step. Otherwise, only print the last instruction. .Pp Warning: depending on the machine type, it may not be possible to single-step through some low-level code paths or user-space code. On machines with software-emulated single-stepping (e.g., pmax), stepping through code executed by interrupt handlers will probably do the wrong thing. .It Ic continue Ns Op Cm /c Continue execution until a breakpoint or watchpoint. If .Cm /c is specified, count instructions while executing. Some machines (e.g., pmax) also count loads and stores. .Pp Warning: when counting, the debugger is really silently single-stepping. This means that single-stepping on low-level may cause strange behavior. .It Ic until Ns Op Cm /p Stop at the next call or return instruction. If .Cm /p is specified, print the call nesting depth and the cumulative instruction count at each call or return. Otherwise, only print when the matching return is hit. .It Ic next Ns Op Cm /p Stop at the matching return instruction. If .Cm /p is specified, print the call nesting depth and the cumulative instruction count at each call or return. Otherwise, only print when the matching return is hit. .It Ic match Ns Op Cm /p A synonym for .Ic next . .It Xo .Cm trace Ns Op Cm /u .Sm off .Op Ar frame-address .Op Cm , Ar count .Sm on .Xc Stack trace from .Ar frame-address . If .Cm /u is specified, trace user-space, otherwise trace kernel-space. .Ar count is the number of frames to be traced. If .Ar count is omitted, all frames are printed. .Pp Warning: user-space stack trace is valid only if the machine dependent code supports it. .It Xo .Cm trace/t .Sm off .Op Ar pid .Op Cm , Ar count .Sm on .Xc Stack trace by .Dq thread (process, on .Nx ) rather than by stack frame address. Note that .Ar pid is interpreted using the current radix, whilst .Ic ps displays pids in decimal; prefix .Ar pid with .Sq 0t to force it to be interpreted as decimal. .Pp Warning: trace by pid is valid only if the machine dependent code supports it. .It Xo .Ic search Ns Op Cm /bhl .Ar address .Ar value .Op Ar mask .Op Cm , Ns Ar count .Xc Search memory from .Ar address for .Ar value . The unit size is specified with a modifier character, as per .Ic examine . Valid modifiers are: .Cm /b , .Cm /h , and .Cm /l . If no modifier is specified, .Cm /l is used. .Pp This command might fail in interesting ways if it doesn't find .Ar value . This is because .Nm doesn't always recover from touching bad memory. The optional .Ar count limits the search. .It Ic reboot Op Ar flags Reboot, using the optionally supplied boot .Ar flags . .Pp Note: Limitations of the command line interface preclude specification of a boot string. .It Xo .Sm off .Ic "show\ all\ procs" .Op Cm /a .Op Cm /n .Op Cm /w .Sm on .Xc Display all process information. Valid modifiers: .Bl -tag -width 3n .It Cm /n show process information in a .Xr ps 1 style format (this is the default). Information printed includes: process ID, parent process ID, process group, UID, process status, process flags, process command name, and process wait channel message. .It Cm /a show the kernel virtual addresses of each process' proc structure, u-are, and vmspace structure. The vmspace address is also the address of the process' vm_map structure, and can be used in the .Ic "show map" command. .It Cm /w show each process' PID, command, system call emulation, wait channel address, and wait channel message. .El .It Xo .Sm off .Ic ps .Op Cm /a .Op Cm /n .Op Cm /w .Sm on .Xc A synonym for .Ic "show all procs" . .It Ic "show registers" Ns Op Cm /u Display the register set. If .Cm /u is specified, display user registers instead of kernel registers or the currently save one. .Pp Warning: support for .Cm /u is machine dependent. If not supported, incorrect information will be displayed. .It Xo .Ic "show map" Ns Op Cm /f .Ar address .Xc Print the vm_map at .Ar address . If .Cm /f is specified the complete map is printed. .It Xo .Ic "show object" Ns Op Cm /f .Ar address .Xc Print the vm_object at .Ar address . If .Cm /f is specified the complete object is printed. .It Ic "show watches" Display all watchpoints. .It Xo .Ic watch .Sm off .Ar address .Op Cm , Ar size .Sm on .Xc Set a watchpoint for a region. Execution stops when an attempt to modify the region occurs. .Ar size defaults to 4. .Pp If you specify a wrong space address, the request is rejected with an error message. .Pp Warning: attempts to watch wired kernel memory may cause an unrecoverable error in some systems such as i386. Watchpoints on user addresses work the best. .El .Sh MACHINE-SPECIFIC COMMANDS The "glue" code that hooks .Nm into the .Nx kernel for any given port can also add machine specific commands to the .Nm command parser. All of these commands are preceded by the command word .Em machine to indicate that they are part of the machine-specific command set (e.g. .Ic "machine reboot" ). Some of these commands are: .Ss ALPHA .Bl -tag -width "intrchain" .It Ic halt Call the PROM monitor to halt the CPU. .It Ic reboot Call the PROM monitor to reboot the CPU. .El .Ss ARM32 .Bl -tag -width "intrchain" .It Ic vmstat Equivalent to .Xr vmstat 8 output with "-s" option (statistics). .It Ic vnode Print out a description of a vnode. .It Ic intrchain Print the list of IRQ handlers. .It Ic panic Print the current "panic" string. .It Ic frame Given a trap frame address, print out the trap frame. .El .Ss MIPS .Bl -tag -width "intrchain" .It Ic halt Call the PROM monitor to halt the CPU. .It Ic tlb Print out the Translation Lookaside Buffer (TLB). .It Ic trapdump Print out the Trap Log. Only works in .Nx kernels compiled with .Dv DEBUG option. .El .Ss SPARC .Bl -tag -width "intrchain" .It Ic prom Exit to the Sun PROM monitor. .El .Ss SUN3 and SUN3X .Bl -tag -width "intrchain" .It Ic abort Drop into monitor via abort (allows continue). .It Ic halt Exit to Sun PROM monitor as in .Xr halt 8 . .It Ic reboot Reboot the machine as in .Xr reboot 8 . .It Ic pgmap Given an address, print the address, segment map, page map, and Page Table Entry (PTE). .El .Sh VARIABLES .Nm accesses registers and variables as .Cm $ Ns Ar name . Register names are as per the .Ic "show registers" command. Some variables are suffixed with numbers, and may have a modifier following a colon immediately after the variable name. For example, register variables may have a .Sq u modifier to indicate user register (e.g., .Li "$eax:u" ) . .Pp Built-in variables currently supported are: .Bl -tag -offset indent -width "maxwidth" .It Va lines The number of lines. This is used by the .Ic more feature. .It Va maxoff Addresses are printed as .Li 'symbol'+offset unless .Li offset is greater than .Va maxoff . .It Va maxwidth The width of the displayed line. .It Va onpanic If non-zero (the default), .Nm will be invoked when the kernel panics. If the kernel configuration option .D1 Cd options DDB_ONPANIC=0 is used, .Va onpanic will be initialised to off. .It Va radix Input and output radix. .It Va tabstops Tab stop width. .It Va work Ns Sy xx Temporary work variable. .Sq Sy xx is between 0 and 31. .El .Pp All built-in variables are accessible via .Xr sysctl 3 . .Sh EXPRESSIONS Almost all expression operators in C are supported, except .Sq ~ , .Sq ^ , and unary .Sq & . Special rules in .Nm are: .Bl -tag -offset indent -width "identifier" .It Ar identifier name of a symbol. It is translated to the address (or value) of it. .Sq . and .Sq : can be used in the identifier. If supported by an object format dependent routine, .Sm off .Xo .Oo Ar filename : Oc .Ar function .Oo : Ar "line number" Oc , .Xc .Xo .Oo Ar filename : Oc .Ar variable , .Xc and .Xo .Ar filename .Oo : Ar "line number" Oc , .Xc .Sm on can be accepted as a symbol. The symbol may be prefixed with .Ar "symbol_table_name" Ns :: (e.g., .Li emulator::mach_msg_trap ) to specify other than kernel symbols. .It Ar number number. Radix is determined by the first two characters: .Sq 0x - hex, .Sq 0o - octal, .Sq 0t - decimal, otherwise follow current radix. .It Cm . .Ar dot .It Cm + .Ar next .It Cm .. address of the start of the last line examined. Unlike .Ar dot or .Ar next , this is only changed by the .Ic examine or .Ic write commands. .It Cm , last address explicitly specified. .It Cm $ Ns Ar name register name or variable. It is translated to the value of it. It may be followed by a .Sq : and modifiers as described above. .It Cm a multiple of right-hand side. .It Cm * Ns Ar expr expression indirection. It may be followed by a .Sq : and modifiers as described above. .El .Sh HISTORY The .Nm kernel debugger was written as part of the MACH project at Carnegie-Mellon University. .Sh SEE ALSO .Xr options 4 , .Xr sysctl 8