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1.1 root 1:
2:
3: db Command db
4:
5:
6:
7:
8: Assembler-level symbolic debugger
9:
10: ddbb [-ccddeeffoorrtt] [_m_a_p_f_i_l_e] [_d_a_t_a_f_i_l_e]
11:
12: db is an assembly language-level debugger. It allows you to run
13: object files and executable programs under trace control (see
14: ppttrraaccee), run programs with embedded breakpoints, and dump and
15: patch files in a variety of forms. You can use it to debug as-
16: sembly-language programs that have been assembled by aass, the Mark
17: Williams assembler, as well as those that have been compiled with
18: the Mark Williams C compiler.
19:
20: ***** What is db? *****
21:
22: db is a symbolic debugger, which means that it works with the
23: symbol tables that the compiler builds into the object files it
24: generates. Because db is designed to work on the level of as-
25: sembly language, the user needs a working knowledge of the ap-
26: propriate assembly language and microprocessor architecture.
27:
28: ***** Invoking db *****
29:
30: To invoke db, type its name, plus the options you want (if any)
31: and the name of the files with which you will be working. map-
32: file is an object file that supplies a symbol table. datafile is
33: the executable program to be debugged. If both names are given,
34: the options default to -c. If only one name is given, it is the
35: program; in this case the options default to -o. If both names
36: are omitted, mapfile defaults to l.out and program defaults to
37: core. If possible, db accesses datafile with write permission.
38:
39: The following options to the db command specify the format of
40: program:
41:
42: -cc program is a core file produced by a user core dump. db
43: checks the name of the command that invoked the process that
44: produced the core, against the name of the mapfile, if given.
45: Pure segments are read from the mapfile.
46:
47: -dd program is a system dump. If only one file is mentioned, map-
48: file defaults to /coherent.
49:
50: -ee The next argument is an object file; db executes it as a child
51: process and passes it the rest of the command line.
52:
53: -ff Map program as a straight array of bytes (file).
54:
55: -oo program is an object file. If mapfile is given, it is another
56: object file that provides the symbol table.
57:
58: -rr Read file only, even though you can write into it. This is
59: used to give a file additional protection.
60:
61:
62:
63:
64: COHERENT Lexicon Page 1
65:
66:
67:
68:
69: db Command db
70:
71:
72:
73: -tt Perform input and output for db via /dev/tty. This permits
74: the debugging of processes whose standard input or output have
75: been redirected.
76:
77: ***** Commands and Addresses *****
78:
79: db executes commands that you give it from the standard input. A
80: command usually consists of an address, which tells db where in
81: the program to execute the command; and then the command name and
82: its options, if any.
83:
84: An address is represented by an expression, which can be built
85: out of one or more of the following elements:
86:
87: * The `.', which represents the current address. When an ad-
88: dress is entered, the current address is set to that location.
89: The current address can be advanced by typing <return>.
90:
91: * The name of a register. db recognizes the register names r0
92: through r7, sp, and pc for the PDP-11; r0 through r15 and pc
93: for the Z-8001 and Z-8002; and ax, ah, al, bx, bh, bl, cx, ch,
94: cl, dx, dh, dl, si, di, bp, sp, sp, pc, cs, ds, es, and ss for
95: the i8086. Typing the name of a register displays its con-
96: tents. The usual numeric base (octal on the PDP-11,
97: hexadecimal on all other machines) is always used for register
98: display and stack tracebacks, regardless of the current
99: default radix.
100:
101: * The symbols dd, ii, and uu, which represent location 0 in,
102: respectively, the data space, the instruction space, and the
103: u-area.
104:
105: * The names of global symbols and symbolic addresses can be used
106: in place of the addresses where they occur. This is useful
107: when setting a breakpoint at the beginning of a subroutine.
108:
109: * An integer constant, which can be used in the same manner as a
110: global symbol. The default is decimal; a leading 0 indicates
111: octal and 0x indicates hexadecimal.
112:
113: * The following binary operators can be used:
114: + Addition
115: - Subtraction
116: * Multiplication
117: / Integer division
118:
119: All arithmetic is done in longs.
120:
121: * The following unary operators can be used:
122: ~ Complementation
123: - Negation
124: * Indirection
125:
126: All operators are supported with their normal level of
127: precedence. Parentheses `()' can be used for binding.
128:
129:
130: COHERENT Lexicon Page 2
131:
132:
133:
134:
135: db Command db
136:
137:
138:
139:
140:
141: Every symbol refers to a segment: the data segment, the instruc-
142: tion segment, or the u-area. This segment, in turn, dictates the
143: format in which db displays by default what it finds at that ad-
144: dress. The format used by an expression is that of its leftmost
145: operand. The symbols dd, ii, and uu can name specific segments in
146: the absence of other symbols.
147:
148: ***** Display Commands *****
149:
150: The following commands merely display information about program.
151: The symbol `.' represents the address, which defaults to the cur-
152: rent display address if omitted. count defaults to one.
153:
154: _a_d_d_r_e_s_s[,_c_o_u_n_t]?[_f_o_r_m_a_t]
155: Display the format count times, starting at address. The
156: format string consists of one or more of the following
157: characters:
158:
159: ^ Reset display address to `.'
160: + Increment display address
161: - Decrement display address
162: bb Byte
163: cc cchhaarr; control and non-cchhaarrs escaped
164: CC Like `c' except `\0' not displayed
165: dd Decimal
166: ff ffllooaatt
167: FF ddoouubbllee
168: ii Machine instruction, disassembled
169: ll lloonngg
170: nn Output `\n'
171: OO octal
172: pp Symbolic address
173: ss String terminated by `\0', with escapes
174: SS String terminated by `\0', no escapes
175: uu uunnssiiggnneedd
176: WW word
177: xx Hexadecimal
178: YY time (as in i-node etc.)
179:
180: The format characters d, o, u, and x, which specify a numeric
181: base, can be followed by b, l, or w, which specify a datum size,
182: to describe a single datum for display. A format item may also
183: be preceded by a count that specifies how many times the item is
184: to be applied. Note that format defaults to the previously set
185: format for the segment (initially oo for data and u-area, and i
186: for instructions). Except where otherwise noted, db increments
187: the display address by the size of the datum displayed after each
188: format item.
189:
190: ***** Execution Commands *****
191:
192: In the following commands, address defaults to the address where
193: execution stopped, unless otherwise specified; count and expr
194:
195:
196: COHERENT Lexicon Page 3
197:
198:
199:
200:
201: db Command db
202:
203:
204:
205: default to 1. commands is an arbitrary string of db commands,
206: terminated by a newline. A newline may be included by preceding
207: it with a backslash `\'.
208:
209: [_a_d_d_r_e_s_s]=
210: Print address in octal. address defaults to `.'. The com-
211: mand = assigns values to locations in the traced process.
212: The size of the assigned value is determined from the last
213: display format used. You can set and display the registers
214: of the traced process, just like any other address in the
215: traced process.
216:
217: [_a_d_d_r_e_s_s[,_c_o_u_n_t]]=_v_a_l_u_e[,_v_a_l_u_e[,_v_a_l_u_e]...]
218: Patch the contents starting at address to the given value.
219: address defaults to `.'. Up to ten values can be listed.
220:
221: ? Print verbose version of last error message.
222:
223: [_a_d_d_r_e_s_s] :aa
224: Print address symbolically. address defaults to `.'.
225:
226: [_a_d_d_r_e_s_s]:bb[_c_o_m_m_a_n_d_s]
227: Set breakpoint at address; save commands to be executed when
228: breakpoint is encountered. commands defaults to
229: .:aa\nnii+.?ii\nn:xx.
230:
231: :bbrr [_c_o_m_m_a_n_d_s]
232: Set breakpoint at return from current routine. The defaults
233: are the same as for :bb, above.
234:
235: [_a_d_d_r_e_s_s] :cc
236: Continue execution from address.
237:
238: [_a_d_d_r_e_s_s] :dd[rr][ss]
239: Delete breakpoint at address. If optional r or s is
240: specified, delete return or single-step breakpoint. address
241: defaults to `.'.
242:
243: [_a_d_d_r_e_s_s]:ee[_c_o_m_m_a_n_d_l_i_n_e]
244: Begin traced execution of the object file at address
245: (default, entry point). The commandline is parsed and
246: passed to the traced process. argv[0] must be typed
247: directly after :e if supplied. For example, :e3 foo bar baz
248: sets argv[0] to 3, argv[1] to foo, argv[2] to bar, and
249: argv[3] to baz. Quotation marks, apostrophes, and redirec-
250: tion are parsed as by sh, but special characters `?*[]' and
251: shell punctuation `(){}|;' are not. For complete shell com-
252: mand line parsing use the -e option.
253:
254: :ff Print type of fault which caused core dump or stopped the
255: traced process.
256:
257: :mm Display segmentation map.
258:
259:
260:
261:
262: COHERENT Lexicon Page 4
263:
264:
265:
266:
267: db Command db
268:
269:
270:
271: [_e_x_p_r] :nn
272: Set default numeric display base to expr: 88, 1100, and 1166 in-
273: dicate, respectively, octal, decimal, and hexadecimal.
274:
275: :pp Display breakpoints.
276:
277: [_e_x_p_r] :qq
278: If expr is nonzero, quit the current level of command input
279: (see :x). expr defaults to 1. End of file is equivalent to
280: :q.
281:
282: :rr Display registers.
283:
284: [_a_d_d_r_e_s_s],[_c_o_u_n_t]:ss[cc][_c_o_m_m_a_n_d_s]
285: Single-step execution starting at address, for count steps,
286: executing commands at each step. commands defaults to
287: ii+.?ii.
288:
289: After a single-step command, <rreettuurrnn> is equivalent to
290: .,11:ss[cc]. If the optional c is present, db turns off
291: single-stepping at a subroutine call and turns it back on
292: upon return.
293:
294: [_d_e_p_t_h] :tt
295: Print a call traceback to depth levels. If depth is 0
296: (default), unwind the whole stack.
297:
298: [_e_x_p_r] :xx
299: If expr is nonzero, read and execute commands from the stan-
300: dard input up to end of file or :q. expr defaults to 1.
301:
302: ***** See Also *****
303:
304: commands, core, l.out.h, od, ptrace()
305:
306:
307:
308:
309:
310:
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312:
313:
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325:
326:
327:
328: COHERENT Lexicon Page 5
329:
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