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examine command in gdb?
Improve INSERT-per-second performance of SQLite?GDB: What to do when you type “list” to see the code in C, but it prints to you “No source file for address __________”GDB examine command, multiple units at target addressIos Debugging with GDB and No Symbols - Examine ObjectsGDB examine command confusionExamining strings using gdbget return address GDBGDB find command error “warning: Unable to access x bytes of target memory at y, halting search”What mechanism overwrites the return address of a stack frame, preventing certain buffer overflow exploits?Finding argv address in GDB
.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty height:90px;width:728px;box-sizing:border-box;
A number can also be prepended to the format of the examine command
to examine multiple units at the target address.
source: hacking the art of exploration
(gdb) x/2x $eip
0x8048384 <main+16>: 0x00fc45c7 0x83000000
(gdb) x/x $eip
0x8048384 <main+16>: 0x00fc45c7
I know that the second examine command returns the memory address that eip is currently locating. What about the first one which returns two memory address?
c gdb
asked Mar 8 at 7:16
Henok TesfayeHenok Tesfaye
757522
|
show 3 more comments
A number can also be prepended to the format of the examine command
to examine multiple units at the target address.
source: hacking the art of exploration
(gdb) x/2x $eip
0x8048384 <main+16>: 0x00fc45c7 0x83000000
(gdb) x/x $eip
0x8048384 <main+16>: 0x00fc45c7
I know that the second examine command returns the memory address that eip is currently locating. What about the first one which returns two memory address?
c gdb
asked Mar 8 at 7:16
Henok TesfayeHenok Tesfaye
757522
$eipcan be seen as a pointer variable. So in C terms,x/x $eipprints$eip[0]andx/2x $eipprints$eip[0]and$eip[1].
– Some programmer dude
Mar 8 at 7:19
OK, what does they indicate?
– Henok Tesfaye
Mar 8 at 7:21
Then let me ask you this: Do you know whatEIPis and what it's used for? What do you think that$eipis pointing at?
– Some programmer dude
Mar 8 at 7:24
Yes, EIP is a register inside the CPU, it is used to hold the memory address of instructions in our program which is currently executing. $eip is pointing to the address in the .text section of our program.
– Henok Tesfaye
Mar 8 at 7:27
My question is, there is only 1 $eip, so why it shows two memory address?
– Henok Tesfaye
Mar 8 at 7:31
|
show 3 more comments
A number can also be prepended to the format of the examine command
to examine multiple units at the target address.
source: hacking the art of exploration
(gdb) x/2x $eip
0x8048384 <main+16>: 0x00fc45c7 0x83000000
(gdb) x/x $eip
0x8048384 <main+16>: 0x00fc45c7
I know that the second examine command returns the memory address that eip is currently locating. What about the first one which returns two memory address?
c gdb
asked Mar 8 at 7:16
Henok TesfayeHenok Tesfaye
757522
A number can also be prepended to the format of the examine command
to examine multiple units at the target address.
source: hacking the art of exploration
(gdb) x/2x $eip
0x8048384 <main+16>: 0x00fc45c7 0x83000000
(gdb) x/x $eip
0x8048384 <main+16>: 0x00fc45c7
I know that the second examine command returns the memory address that eip is currently locating. What about the first one which returns two memory address?
c gdb
c gdb
asked Mar 8 at 7:16
Henok TesfayeHenok Tesfaye
757522
asked Mar 8 at 7:16
Henok TesfayeHenok Tesfaye
757522
asked Mar 8 at 7:16
Henok TesfayeHenok Tesfaye
757522
asked Mar 8 at 7:16
Henok TesfayeHenok Tesfaye
757522
asked Mar 8 at 7:16
Henok TesfayeHenok Tesfaye
757522
757522
$eipcan be seen as a pointer variable. So in C terms,x/x $eipprints$eip[0]andx/2x $eipprints$eip[0]and$eip[1].
– Some programmer dude
Mar 8 at 7:19
OK, what does they indicate?
– Henok Tesfaye
Mar 8 at 7:21
Then let me ask you this: Do you know whatEIPis and what it's used for? What do you think that$eipis pointing at?
– Some programmer dude
Mar 8 at 7:24
Yes, EIP is a register inside the CPU, it is used to hold the memory address of instructions in our program which is currently executing. $eip is pointing to the address in the .text section of our program.
– Henok Tesfaye
Mar 8 at 7:27
My question is, there is only 1 $eip, so why it shows two memory address?
– Henok Tesfaye
Mar 8 at 7:31
|
show 3 more comments
$eipcan be seen as a pointer variable. So in C terms,x/x $eipprints$eip[0]andx/2x $eipprints$eip[0]and$eip[1].
– Some programmer dude
Mar 8 at 7:19
OK, what does they indicate?
– Henok Tesfaye
Mar 8 at 7:21
Then let me ask you this: Do you know whatEIPis and what it's used for? What do you think that$eipis pointing at?
– Some programmer dude
Mar 8 at 7:24
Yes, EIP is a register inside the CPU, it is used to hold the memory address of instructions in our program which is currently executing. $eip is pointing to the address in the .text section of our program.
– Henok Tesfaye
Mar 8 at 7:27
My question is, there is only 1 $eip, so why it shows two memory address?
– Henok Tesfaye
Mar 8 at 7:31
$eip can be seen as a pointer variable. So in C terms, x/x $eip prints $eip[0] and x/2x $eip prints $eip[0] and $eip[1].– Some programmer dude
Mar 8 at 7:19
$eip can be seen as a pointer variable. So in C terms, x/x $eip prints $eip[0] and x/2x $eip prints $eip[0] and $eip[1].– Some programmer dude
Mar 8 at 7:19
OK, what does they indicate?
– Henok Tesfaye
Mar 8 at 7:21
OK, what does they indicate?
– Henok Tesfaye
Mar 8 at 7:21
Then let me ask you this: Do you know what
EIP is and what it's used for? What do you think that $eip is pointing at?– Some programmer dude
Mar 8 at 7:24
Then let me ask you this: Do you know what
EIP is and what it's used for? What do you think that $eip is pointing at?– Some programmer dude
Mar 8 at 7:24
Yes, EIP is a register inside the CPU, it is used to hold the memory address of instructions in our program which is currently executing. $eip is pointing to the address in the .text section of our program.
– Henok Tesfaye
Mar 8 at 7:27
Yes, EIP is a register inside the CPU, it is used to hold the memory address of instructions in our program which is currently executing. $eip is pointing to the address in the .text section of our program.
– Henok Tesfaye
Mar 8 at 7:27
My question is, there is only 1 $eip, so why it shows two memory address?
– Henok Tesfaye
Mar 8 at 7:31
My question is, there is only 1 $eip, so why it shows two memory address?
– Henok Tesfaye
Mar 8 at 7:31
|
show 3 more comments
1 Answer
1
active
oldest
votes
The examine command of gdb has the following syntax:
x/[n][f][u]
where n, f and u are optional and n is the length, f the format and u the unit size.
Possible formats are:
- s (null terminated string)
- i (machine code instruction)
- x (hexadecimal value)
If no unit size can be one of the following values:
- b (bytes)
- h (2 bytes)
- w (4 bytes)
- g (8 bytes)
where w is the default.
Therefore x/2x prints 2 hexadecimal values with a size of 4 bytes from your code segment.
answered Mar 8 at 7:23
kalehmannkalehmann
2,7631023
add a comment |
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1 Answer
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oldest
votes
The examine command of gdb has the following syntax:
x/[n][f][u]
where n, f and u are optional and n is the length, f the format and u the unit size.
Possible formats are:
- s (null terminated string)
- i (machine code instruction)
- x (hexadecimal value)
If no unit size can be one of the following values:
- b (bytes)
- h (2 bytes)
- w (4 bytes)
- g (8 bytes)
where w is the default.
Therefore x/2x prints 2 hexadecimal values with a size of 4 bytes from your code segment.
answered Mar 8 at 7:23
kalehmannkalehmann
2,7631023
add a comment |
The examine command of gdb has the following syntax:
x/[n][f][u]
where n, f and u are optional and n is the length, f the format and u the unit size.
Possible formats are:
- s (null terminated string)
- i (machine code instruction)
- x (hexadecimal value)
If no unit size can be one of the following values:
- b (bytes)
- h (2 bytes)
- w (4 bytes)
- g (8 bytes)
where w is the default.
Therefore x/2x prints 2 hexadecimal values with a size of 4 bytes from your code segment.
answered Mar 8 at 7:23
kalehmannkalehmann
2,7631023
add a comment |
The examine command of gdb has the following syntax:
x/[n][f][u]
where n, f and u are optional and n is the length, f the format and u the unit size.
Possible formats are:
- s (null terminated string)
- i (machine code instruction)
- x (hexadecimal value)
If no unit size can be one of the following values:
- b (bytes)
- h (2 bytes)
- w (4 bytes)
- g (8 bytes)
where w is the default.
Therefore x/2x prints 2 hexadecimal values with a size of 4 bytes from your code segment.
answered Mar 8 at 7:23
kalehmannkalehmann
2,7631023
The examine command of gdb has the following syntax:
x/[n][f][u]
where n, f and u are optional and n is the length, f the format and u the unit size.
Possible formats are:
- s (null terminated string)
- i (machine code instruction)
- x (hexadecimal value)
If no unit size can be one of the following values:
- b (bytes)
- h (2 bytes)
- w (4 bytes)
- g (8 bytes)
where w is the default.
Therefore x/2x prints 2 hexadecimal values with a size of 4 bytes from your code segment.
answered Mar 8 at 7:23
kalehmannkalehmann
2,7631023
edited Mar 8 at 7:29
answered Mar 8 at 7:23
kalehmannkalehmann
2,7631023
answered Mar 8 at 7:23
kalehmannkalehmann
2,7631023
answered Mar 8 at 7:23
kalehmannkalehmann
2,7631023
2,7631023
add a comment |
add a comment |
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$eipcan be seen as a pointer variable. So in C terms,x/x $eipprints$eip[0]andx/2x $eipprints$eip[0]and$eip[1].– Some programmer dude
Mar 8 at 7:19
OK, what does they indicate?
– Henok Tesfaye
Mar 8 at 7:21
Then let me ask you this: Do you know what
EIPis and what it's used for? What do you think that$eipis pointing at?– Some programmer dude
Mar 8 at 7:24
Yes, EIP is a register inside the CPU, it is used to hold the memory address of instructions in our program which is currently executing. $eip is pointing to the address in the .text section of our program.
– Henok Tesfaye
Mar 8 at 7:27
My question is, there is only 1 $eip, so why it shows two memory address?
– Henok Tesfaye
Mar 8 at 7:31