How To Find The Value In A Register Gdb
This is going to exist a small sit-in or 'tip' to analyze registers and memory via gdb when debugging a program. These commands are pretty much useful when debugging a program. It has its own use cases.
Examine registers:
$info registers is the control which can exist used to come across current register values at the moment from gdb prompt. Below command can be used as a brusque cut to view registers:
(gdb) i r
rax 0x1 1
rbx 0x7fff955a9df0 140735699131888
rcx 0xffffffffffffffff -1
rdx 0x7fff955a9e70 140735699132016
rsi 0x7fff955a9df0 140735699131888
rdi 0x16 22
rbp 0x7fff955a9e70 0x7fff955a9e70
rsp 0x7fff955a9dc0 0x7fff955a9dc0
r8 0x7fff955a9dd0 140735699131856
r9 0x1 1
r10 0x7fff955a9ef0 140735699132144
r11 0x293 659
r12 0x7fff955a9ef0 140735699132144
r13 0x0 0
r14 0x1 1
r15 0x0 0
rip 0x37e78da373 0x37e78da373
eflags 0x293 [ CF AF SF IF ]
cs 0x33 51
ss 0x2b 43
ds 0x0 0
es 0x0 0
fs 0x0 0
gs 0x0 0
Register information can exist fetched individually . For ex: "Stack pointer" and "Education pointer" information can be fetched past:
(gdb) i r $sp
sp: 0x7fff955a9dc0
(gdb) i r $rip
rip 0x37e78da373 0x37e78da373
(gdb)
Examining retention :
This is pretty much useful when debugging a plan:
"x" is the command which can exist used for the same purpose.. The general format of 'x' command every bit shown hither.
(gdb) help x Examine retentiveness: x/FMT ADDRESS.
ADDRESS is an expression for the memory accost to examine.
FMT is a repeat count followed past a format letter and a size alphabetic character.
Format letters are o(octal), x(hex), d(decimal), u(unsigned decimal),
t(binary), f(float), a(address), i(instruction), c(char) and s(string).
Size letters are b(byte), h(halfword), w(word), g(giant, 8 bytes).
The specified number of objects of the specified size are printed
co-ordinate to the format.
Defaults for format and size letters are those previously used.
The default count is 1. The default address is the post-obit the last thing printed
with this control or "impress".
(gdb)
In short :
Formats:
o – octal
d – decimal
10 – hexadecimal
u – unsigned integer
s – string
t – binary
Units:
b – byte
h – half
westward – word
thousand – double discussion
Instance use of 'x' command:
"three" words of memory 'higher up' stack pointer tin be displayed by:
Just why I used "above" hither? 'Ans': It is homework/assignment for you 🙂
(gdb) x/3xw $sp
0x7fff955a9dc0: 0x00000000 0x00000000 0x0041ecb1
(gdb)
"two" machine instructions from 0x37e78da373/eip
(gdb) x/2i 0x37e78da373
=> 0x37e78da373 : mov (%rsp),%rdi
0x37e78da377 : mov %rax,%rdx
(gdb)
To display a string yous can apply: ' I selected a random accost', so it may non give a human-readable example string as output.
(gdb) x/due south 0x0041ecb1
0x41ecb1: "A\211\307è—Ÿ\001"
(gdb)
I hope this helps.
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How To Find The Value In A Register Gdb,
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