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24.13 GDB/MI Data Manipulation

This section describes the GDB/MI commands that manipulate data: examine memory and registers, evaluate expressions, etc.

The -data-disassemble Command

Synopsis

 
 -data-disassemble
    [ -s start-addr -e end-addr ]
  | [ -f filename -l linenum [ -n lines ] ]
  -- mode

Where:

start-addr

is the beginning address (or $pc)

end-addr

is the end address

filename

is the name of the file to disassemble

linenum

is the line number to disassemble around

lines

is the number of disassembly lines to be produced. If it is -1, the whole function will be disassembled, in case no end-addr is specified. If end-addr is specified as a non-zero value, and lines is lower than the number of disassembly lines between start-addr and end-addr, only lines lines are displayed; if lines is higher than the number of lines between start-addr and end-addr, only the lines up to end-addr are displayed.

mode

is either 0 (meaning only disassembly) or 1 (meaning mixed source and disassembly).

Result

The output for each instruction is composed of four fields:

Note that whatever included in the instruction field, is not manipulated directly by GDB/MI, i.e., it is not possible to adjust its format.

No value for GDBN Command

There's no direct mapping from this command to the CLI.

Example

Disassemble from the current value of $pc to $pc + 20:

 
(gdb)
-data-disassemble -s $pc -e "$pc + 20" -- 0
^done,
asm_insns=[
{address="0x000107c0",func-name="main",offset="4",
inst="mov  2, %o0"},
{address="0x000107c4",func-name="main",offset="8",
inst="sethi  %hi(0x11800), %o2"},
{address="0x000107c8",func-name="main",offset="12",
inst="or  %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"},
{address="0x000107cc",func-name="main",offset="16",
inst="sethi  %hi(0x11800), %o2"},
{address="0x000107d0",func-name="main",offset="20",
inst="or  %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"}]
(gdb)

Disassemble the whole main function. Line 32 is part of main.

 
-data-disassemble -f basics.c -l 32 -- 0
^done,asm_insns=[
{address="0x000107bc",func-name="main",offset="0",
inst="save  %sp, -112, %sp"},
{address="0x000107c0",func-name="main",offset="4",
inst="mov   2, %o0"},
{address="0x000107c4",func-name="main",offset="8",
inst="sethi %hi(0x11800), %o2"},
[…]
{address="0x0001081c",func-name="main",offset="96",inst="ret "},
{address="0x00010820",func-name="main",offset="100",inst="restore "}]
(gdb)

Disassemble 3 instructions from the start of main:

 
(gdb)
-data-disassemble -f basics.c -l 32 -n 3 -- 0
^done,asm_insns=[
{address="0x000107bc",func-name="main",offset="0",
inst="save  %sp, -112, %sp"},
{address="0x000107c0",func-name="main",offset="4",
inst="mov  2, %o0"},
{address="0x000107c4",func-name="main",offset="8",
inst="sethi  %hi(0x11800), %o2"}]
(gdb)

Disassemble 3 instructions from the start of main in mixed mode:

 
(gdb)
-data-disassemble -f basics.c -l 32 -n 3 -- 1
^done,asm_insns=[
src_and_asm_line={line="31",
file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
  testsuite/gdb.mi/basics.c",line_asm_insn=[
{address="0x000107bc",func-name="main",offset="0",
inst="save  %sp, -112, %sp"}]},
src_and_asm_line={line="32",
file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
  testsuite/gdb.mi/basics.c",line_asm_insn=[
{address="0x000107c0",func-name="main",offset="4",
inst="mov  2, %o0"},
{address="0x000107c4",func-name="main",offset="8",
inst="sethi  %hi(0x11800), %o2"}]}]
(gdb)

The -data-evaluate-expression Command

Synopsis

 
 -data-evaluate-expression expr

Evaluate expr as an expression. The expression could contain an inferior function call. The function call will execute synchronously. If the expression contains spaces, it must be enclosed in double quotes.

No value for GDBN Command

The corresponding No value for GDBN commands are ‘print’, ‘output’, and ‘call’. In gdbtk only, there's a corresponding ‘gdb_eval’ command.

Example

In the following example, the numbers that precede the commands are the tokens described in GDB/MI Command Syntax. Notice how GDB/MI returns the same tokens in its output.

 
211-data-evaluate-expression A
211^done,value="1"
(gdb)
311-data-evaluate-expression &A
311^done,value="0xefffeb7c"
(gdb)
411-data-evaluate-expression A+3
411^done,value="4"
(gdb)
511-data-evaluate-expression "A + 3"
511^done,value="4"
(gdb)

The -data-list-changed-registers Command

Synopsis

 
 -data-list-changed-registers

Display a list of the registers that have changed.

No value for GDBN Command

No value for GDBN doesn't have a direct analog for this command; gdbtk has the corresponding command ‘gdb_changed_register_list’.

Example

On a PPC MBX board:

 
(gdb)
-exec-continue
^running

(gdb)
*stopped,reason="breakpoint-hit",bkptno="1",frame={func="main",
args=[],file="try.c",fullname="/home/foo/bar/try.c",line="5"}
(gdb)
-data-list-changed-registers
^done,changed-registers=["0","1","2","4","5","6","7","8","9",
"10","11","13","14","15","16","17","18","19","20","21","22","23",
"24","25","26","27","28","30","31","64","65","66","67","69"]
(gdb)

The -data-list-register-names Command

Synopsis

 
 -data-list-register-names [ ( regno )+ ]

Show a list of register names for the current target. If no arguments are given, it shows a list of the names of all the registers. If integer numbers are given as arguments, it will print a list of the names of the registers corresponding to the arguments. To ensure consistency between a register name and its number, the output list may include empty register names.

No value for GDBN Command

No value for GDBN does not have a command which corresponds to ‘-data-list-register-names’. In gdbtk there is a corresponding command ‘gdb_regnames’.

Example

For the PPC MBX board:

 
(gdb)
-data-list-register-names
^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
"r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
"r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
"r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
"f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
"f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
"", "pc","ps","cr","lr","ctr","xer"]
(gdb)
-data-list-register-names 1 2 3
^done,register-names=["r1","r2","r3"]
(gdb)

The -data-list-register-values Command

Synopsis

 
 -data-list-register-values fmt [ ( regno )*]

Display the registers' contents. fmt is the format according to which the registers' contents are to be returned, followed by an optional list of numbers specifying the registers to display. A missing list of numbers indicates that the contents of all the registers must be returned.

Allowed formats for fmt are:

x

Hexadecimal

o

Octal

t

Binary

d

Decimal

r

Raw

N

Natural

No value for GDBN Command

The corresponding No value for GDBN commands are ‘info reg’, ‘info all-reg’, and (in gdbtk) ‘gdb_fetch_registers’.

Example

For a PPC MBX board (note: line breaks are for readability only, they don't appear in the actual output):

 
(gdb)
-data-list-register-values r 64 65
^done,register-values=[{number="64",value="0xfe00a300"},
{number="65",value="0x00029002"}]
(gdb)
-data-list-register-values x
^done,register-values=[{number="0",value="0xfe0043c8"},
{number="1",value="0x3fff88"},{number="2",value="0xfffffffe"},
{number="3",value="0x0"},{number="4",value="0xa"},
{number="5",value="0x3fff68"},{number="6",value="0x3fff58"},
{number="7",value="0xfe011e98"},{number="8",value="0x2"},
{number="9",value="0xfa202820"},{number="10",value="0xfa202808"},
{number="11",value="0x1"},{number="12",value="0x0"},
{number="13",value="0x4544"},{number="14",value="0xffdfffff"},
{number="15",value="0xffffffff"},{number="16",value="0xfffffeff"},
{number="17",value="0xefffffed"},{number="18",value="0xfffffffe"},
{number="19",value="0xffffffff"},{number="20",value="0xffffffff"},
{number="21",value="0xffffffff"},{number="22",value="0xfffffff7"},
{number="23",value="0xffffffff"},{number="24",value="0xffffffff"},
{number="25",value="0xffffffff"},{number="26",value="0xfffffffb"},
{number="27",value="0xffffffff"},{number="28",value="0xf7bfffff"},
{number="29",value="0x0"},{number="30",value="0xfe010000"},
{number="31",value="0x0"},{number="32",value="0x0"},
{number="33",value="0x0"},{number="34",value="0x0"},
{number="35",value="0x0"},{number="36",value="0x0"},
{number="37",value="0x0"},{number="38",value="0x0"},
{number="39",value="0x0"},{number="40",value="0x0"},
{number="41",value="0x0"},{number="42",value="0x0"},
{number="43",value="0x0"},{number="44",value="0x0"},
{number="45",value="0x0"},{number="46",value="0x0"},
{number="47",value="0x0"},{number="48",value="0x0"},
{number="49",value="0x0"},{number="50",value="0x0"},
{number="51",value="0x0"},{number="52",value="0x0"},
{number="53",value="0x0"},{number="54",value="0x0"},
{number="55",value="0x0"},{number="56",value="0x0"},
{number="57",value="0x0"},{number="58",value="0x0"},
{number="59",value="0x0"},{number="60",value="0x0"},
{number="61",value="0x0"},{number="62",value="0x0"},
{number="63",value="0x0"},{number="64",value="0xfe00a300"},
{number="65",value="0x29002"},{number="66",value="0x202f04b5"},
{number="67",value="0xfe0043b0"},{number="68",value="0xfe00b3e4"},
{number="69",value="0x20002b03"}]
(gdb)

The -data-read-memory Command

Synopsis

 
 -data-read-memory [ -o byte-offset ]
   address word-format word-size
   nr-rows nr-cols [ aschar ]

where:

address

An expression specifying the address of the first memory word to be read. Complex expressions containing embedded white space should be quoted using the C convention.

word-format

The format to be used to print the memory words. The notation is the same as for No value for GDBN's print command (see section Output Formats).

word-size

The size of each memory word in bytes.

nr-rows

The number of rows in the output table.

nr-cols

The number of columns in the output table.

aschar

If present, indicates that each row should include an ASCII dump. The value of aschar is used as a padding character when a byte is not a member of the printable ASCII character set (printable ASCII characters are those whose code is between 32 and 126, inclusively).

byte-offset

An offset to add to the address before fetching memory.

This command displays memory contents as a table of nr-rows by nr-cols words, each word being word-size bytes. In total, nr-rows * nr-cols * word-size bytes are read (returned as ‘total-bytes’). Should less than the requested number of bytes be returned by the target, the missing words are identified using ‘N/A’. The number of bytes read from the target is returned in ‘nr-bytes’ and the starting address used to read memory in ‘addr’.

The address of the next/previous row or page is available in ‘next-row’ and ‘prev-row’, ‘next-page’ and ‘prev-page’.

No value for GDBN Command

The corresponding No value for GDBN command is ‘x’. gdbtk has ‘gdb_get_mem’ memory read command.

Example

Read six bytes of memory starting at bytes+6 but then offset by -6 bytes. Format as three rows of two columns. One byte per word. Display each word in hex.

 
(gdb)
9-data-read-memory -o -6 -- bytes+6 x 1 3 2
9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
prev-page="0x0000138a",memory=[
{addr="0x00001390",data=["0x00","0x01"]},
{addr="0x00001392",data=["0x02","0x03"]},
{addr="0x00001394",data=["0x04","0x05"]}]
(gdb)

Read two bytes of memory starting at address shorts + 64 and display as a single word formatted in decimal.

 
(gdb)
5-data-read-memory shorts+64 d 2 1 1
5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
next-row="0x00001512",prev-row="0x0000150e",
next-page="0x00001512",prev-page="0x0000150e",memory=[
{addr="0x00001510",data=["128"]}]
(gdb)

Read thirty two bytes of memory starting at bytes+16 and format as eight rows of four columns. Include a string encoding with ‘x’ used as the non-printable character.

 
(gdb)
4-data-read-memory bytes+16 x 1 8 4 x
4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
next-row="0x000013c0",prev-row="0x0000139c",
next-page="0x000013c0",prev-page="0x00001380",memory=[
{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"},
{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"},
{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"},
{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"},
{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"},
{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"},
{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"},
{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"}]
(gdb)

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