Expressions
Expressions are mathematical representations of 64-bit numerical values. These are handled anywhere RNum API is used, the api takes a string that can contain multiple math operations with different numeric bases and operations and computes the resulting value.
They can be displayed in different formats, be compared or used with all commands accepting numeric arguments. Expressions can use traditional arithmetic operations, as well as binary and boolean ones.
To evaluate mathematical expressions prepend them with command ?:
[0xb7f9d810]> ?vi 0x8048000
134512640
[0xv7f9d810]> ?vi 0x8048000+34
134512674
[0xb7f9d810]> ?vi 0x8048000+0x34
134512692
[0xb7f9d810]> ? 1+2+3-4*3
hex 0xfffffffffffffffa
octal 01777777777777777777772
unit 17179869184.0G
segment fffff000:0ffa
int64 -6
string "\xfa\xff\xff\xff\xff\xff\xff\xff"
binary 0b1111111111111111111111111111111111111111111111111111111111111010
fvalue: -6.0
float: nanf
double: nan
trits 0t11112220022122120101211020120210210211201
Supported arithmetic operations are:
+ addition
- subtraction
* multiplication
/ division
% modulus
& binary and
| binary or
^ binary xor
>> shift right
<< shift left
For example, using the ?vi command we the the integer (base10) value resulting it from evaluating the given math expression
[0x00000000]> ?vi 1+2+3
6
To use of binary OR should quote the whole command to avoid executing the | pipe:
[0x00000000]> "? 1 | 2"
hex 0x3
octal 03
unit 3
segment 0000:0003
int32 3
string "\x03"
binary 0b00000011
fvalue: 2.0
float: 0.000000f
double: 0.000000
trits 0t10
Note that on modern r2 versions you can use the single quote at the begining of the command to avoid evaluating the rest of the expression:
'? 1 | 2 is the equivalent to "? 1 | 2"
Numbers can be displayed in several formats:
0x033 : hexadecimal can be displayed
3334 : decimal
sym.fo : resolve flag offset
10K : KBytes 10*1024
10M : MBytes 10*1024*1024
You can also use variables and seek positions to build complex expressions.
Use the ?$? command to list all the available commands or read the refcard chapter of this book.
$$ here (the current virtual seek)
$l opcode length
$s file size
$j jump address (e.g. jmp 0x10, jz 0x10 => 0x10)
$f jump fail address (e.g. jz 0x10 => next instruction)
$m opcode memory reference (e.g. mov eax,[0x10] => 0x10)
$b block size
Some more examples:
[0x4A13B8C0]> ? $m + $l
140293837812900 0x7f98b45df4a4 03771426427372244 130658.0G 8b45d000:04a4 140293837812900 10100100 140293837812900.0 -0.000000
Disassembling the very next instruction after the current one
[0x4A13B8C0]> pd 1 @ +$l
0x4A13B8C2 call 0x4a13c000