Questions tagged [arm]
A family of instruction set architectures based on a RISC architecture developed by British company ARM Holdings. Heavily used in embedded devices such as mobile phones, tablets, set-top boxes, ...
4
votes
1answer
50 views
In Ghidra what do I need to set so disassembler is in Thumb mode instead of ARM
In IDA I would press Alt+G and set the T register to 1 to first the code to be Thumb, but in Ghidra am not not sure how to force it.
The context is I have some functions pointed to by a data ...
0
votes
0answers
18 views
Can't use J-Link with ADuC7126 evaluation board
I'm new to embedded, and would like your help.
Using uVision/Keil I successfully flashed my ADuC7126 Evaluation Board using the micro-USB.
I tried to use a mIDAS-Link JTAG (recognized as J-Link) ...
0
votes
1answer
62 views
How to split ARM code/data from binary in Inmarsat Isatphone Pro?
I'm analyzing the 3 binaries for updating firmware to the Inmarsat Isatphone Pro phone. Additionally, I'm following the Groundworks Technologies paper, and attempting to recreate their work as a ...
0
votes
0answers
30 views
Find offset in binary file
I have arm binary file that I can open with Ida, I want to find out the address of some bytes.
When I load the binary with Ida there is Image base address that the binary lodded and the offset of the ...
0
votes
1answer
37 views
Finding function at offset loaded with ADRP/ADD
I have this assembly:
ADRP X8, #off_FFFFFFF006F1E960@PAGE
ADD X8, X8, #off_FFFFFFF006F1E960@PAGEOFF
LDR X0, [X8] ; qword_FFFFFFF0077F08A8
LDR X8, [X0]
...
4
votes
1answer
113 views
Reverse engineering a compression algorithm to decompress ASCII text (LZ-variant?)
Reposted from StackOverflow as is.
I'm trying to decompress a very long text block from an ARMv5t powered Gameboy Advance ROM, which was compressed using some kind of custom LZ-esque compression ...
1
vote
1answer
46 views
How is thumb branch calculated
I have the instruction which is:
5ff1aed4 bl sub_5ff171d0
which assembles to:
FCF77CF9
This appears to mean that the program is branching backwards, However I can't seem to find ...
0
votes
0answers
36 views
Dumping flash from a running Cortex-M
I have a working device with a STM32F405ZGT6 in it. I want to dump the software it runs.
As far as I can tell, there's no external flash on the device, so it must be running off of the internal flash....
0
votes
1answer
121 views
Firmware reverse engineering
this question is a follow-up from this previous post: Flash dump binwalk blank, low entropy
I need to reverse engineer a firmware from a very secure device. I was able to reverse engineer the PCB ...
2
votes
1answer
64 views
Process Immediately Killed
I'm trying to reverse an ARM executable. It's for an embedded system, but I don't have any details about the normally targeted environment.
Here's what file shows: ELF 32-bit LSB executable, ARM, ...
1
vote
0answers
62 views
Help understanding ARM Assembly example code - loops, set flags and code mnemonics
This is the example code:
_start:
LDR r0, =n
LDR r0, [r0]
LDR r1, =array1
MOV r2, #0
LDR r4, =array2
loop:
LDR r3, [r1], #4
CMP r3, #58
BGT a_point
CMP r3, #47
BLT a_point
SUB r3, r3, #0x30
STR r3, [...
-1
votes
1answer
293 views
how should i change an instruction to NOP in IDA?
I am new with IDA assembler and i used to work with hopper app.
the problem is i can't change instruction in IDA from something like CBNZ to NOP.
is there any button to do this? i can't find anything ...
0
votes
1answer
93 views
Confused about a firmware binary
I'm trying to reverse engineer an ARM Thumb2 firmware binary, and I've come across a few oddities. Parts of the file when treated as RGB binary data form perfect images, which seems unusual for a ...
2
votes
1answer
197 views
Find function in a stripped dynamic ELF library
Im currently reverse engineering an android app and this app calls a function named "getUserInfo" in an ARM 32bit ELF library called "libcms.so" via the Java Native Interface.
My Problem is: The ...
3
votes
1answer
47 views
Enumerating (name, addresses) in PLT of an ELF file without elf.h
I want to show users imported symbols of a given ELF file like this(#1) in a disassembler project.(Android app)
1d21a: f7fa e8e8 blx 173ec ; __android_log_print@plt ...
Currently, I can only show ...
5
votes
1answer
228 views
How does API call work on Android (NDK)?
In windows platform, an application usually references its IAT(Import Access Table) to get the address of the APIs it wants, then call it. Then some mechanisms are done as demonstrated here nicely.
...
1
vote
1answer
69 views
Bp on memory access in arm deb
I'm using idapro for arm native debugging (with androidseever) . I'd like to check when a memory data is read by code (what instruction and where). Hardware bp is not possible. How can i do? How to ...
2
votes
0answers
62 views
Understanding ESIL
I cross-compiled a simple program with the aarch-linux-gnu-gcc compiler for ARM. So the machine is "ARM aarch64". I want to understand a single instruction and it's realization in ESIL. The opcode of ...
2
votes
1answer
81 views
How are ARMv7 assembly opcodes and operands stored in bytes?
I've been trying to analyze an ARM binary but cannot figure out how the operators and operands are stored in the bytes of a program.
For example, by looking at the disassembly listing of an ARMv7 ...
3
votes
1answer
220 views
Need help understanding XOR cipher
I am trying to modify a save file for a game. I think it is using an XOR cipher to encrypt it. Looking though the disassembly I think I found the function that decrypts it. I ran the assembly ...
2
votes
1answer
194 views
ELF - The start address of .got section is different from the entry point address of the GOT(global offset table)
I used readelf to read the information of the ELF file. I found the address of .got section in the section header is different from the GOT entry point address read from the dynamic section. Is the ...
1
vote
2answers
159 views
Reverse engineer a ARM-v7a function
Currently I am trying to reverse engineer the following armeabi-v7a function:
I already wrote the following Java code:
static double getFunc(double param0, double param1, double param2, double ...
4
votes
2answers
118 views
Disassemble ELF - PC is set to 0?
I tried to disassemble a ELF file which is a shared object file executed on armv7a (Android). I saw a strange block. It seems that the PC, program counter register, is set to 0. Did I miss something ...
1
vote
1answer
288 views
Finding RegisterNatives function calls in JNI_OnLoad's assembly code
My goal is to see what a native method m does. It doesn't have a direct counterpart in the so file, but I've found the JNI_OnLoad function's ARM assembly code. It starts with
AAAAAAAA <JNI_OnLoad@@...
0
votes
1answer
313 views
How to Modify this Branch in ARM64?
I try to modify the branch of this disassembly in a binary:
SUB SP, SP, #0x60
STP X26, X25, [SP,#0x50+var_40]
STP X24, X23, [SP,#0x50+var_30]
STP X22, ...
1
vote
1answer
90 views
Could someone explain how this ARM instructions works compared to the actual Objective-C code?
I'm trying to understands how it works by decompiling my own Objective-C code. Here's the decompiled instruction:
var_8= -8
var_4= -4
SUB SP, SP, #8
MOVS R2, #1
STR ...
1
vote
0answers
274 views
Patching an ipa (iPhone app) using Hopper Disassembler
I have learned in the past to patch some iOS apps to bypass jailbreak detection. Today, I decided to change the UI elements in the Spotify app on iOS Platform (ios 11). I downloaded a .ipa file of ...
-1
votes
1answer
68 views
Which ARM command is influencing the SP position?
I do static analysis of ARM assembly code (I can't debug it).
When I look on argument that in SP+0x<SomeOffset> I can find what I'm looking for, but if I look a few lines further down I see ...
1
vote
1answer
52 views
Why would an ELF SHT_REL section contain relocations outside the section its sh_info refers to?
I have a .so from an Android JNI/NDK application. Here are two of its sections:
[Nr] Name Type Addr Off Size ES Flg Lk Inf Al
[10] .rel.plt REL ...
2
votes
2answers
591 views
How can I make sense of an Android NDK library?
So I'm currently trying to understand how an Android app interprets the data sent from a Bluetooth-enabled scale.
Understanding the Java code was relatively easy. The code was obfuscated but I found ...
7
votes
1answer
2k views
Why is this ARM binary throwing an 'Illegal instruction' error and quitting?
Issue
I'm hoping someone can help me determine why this binary won't execute.
It is a closed-source, stripped ARM binary. That said, it is freely downloadable on the internet so there is a link to ...
4
votes
2answers
86 views
ARM Thumb2 register usage
I am reversing ARM Thumb2 code.
I am looking for a table that shows which registers are used to pass arguments to functions, and which registers must be saved after the function ends.
By the way, if ...
11
votes
1answer
452 views
How to write [sp+local_variable] in radare2
Hello I'm playing with my native android library, everything was going smoothly till now. I have problem with opcodes, i don't know how to tell radare2 to write str opcode with specifc registry, and ...
0
votes
1answer
223 views
how to understand branch arm instruction
I have this instruction F6F700B8 I know that it b #-0xA000 but how I can understand from F6F700B8 that is b #-0xA000 ? .
When I tried to translate it on http://armconverter.com/hextoarm/ I get B.W #...
6
votes
2answers
323 views
Best Way to Identify Statically Linked Functions in Firmware
I have a piece of firmware that I pulled off an NXP LPC17XX series chip. Through reviewing the processor manual, I was able to identify the entry point of the code and disassemble the code without any ...
0
votes
1answer
46 views
Ldr arm thumb2 must be multiple of 4?
I saw here http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0489c/CIHDGFEG.html that on arm thumb2 ldr must be multiple of 4.
I run on arm thumb 2 and want run this instruction ldr r0, ...
-1
votes
2answers
326 views
translate arm instructions to hex
I looking for simple tool(not site) to translate arm instruction to hex like http://armconverter.com/.
Without linker , I want put 1 instruction , and want get the hex .
Do you know one please?
1
vote
1answer
329 views
Determining endianness of PE files (Windows on ARM?)
For ELF files, there is a field near the start of the ELF header that indicates the endianness of the file:e_ident[EI_DATA]. If an application wants to extract data from the header of a given ELF ...
0
votes
1answer
123 views
Arm function save registers r0 and r1
I see arm 32 bits assembly code.
Usually each function do push { r4-r9,lr} ( save 6 registers on stack ). And in the end of function pop them .
I see function that save push {r0,r1,r4-r9,lr} but ...
-1
votes
2answers
39 views
Edit arm thumb2 intelhex file
I have intelhex file to arm 32 bits thumb 2.
I want edit this file add/ change instructions.
Looking for easy and free tool (prefer gui windows tool ) to do it please.
0
votes
1answer
285 views
How ida choose arm Thumb/Thumb2
I load binary file to ida and choose arm cpu.
How can I see if ida choose on arm/arm Thumb2 / arm Thumb? and how can I change it?
Bytes translate is depend witch arm is it(arm/arm Thumb2 / arm ...
3
votes
2answers
219 views
Arm ldr diffrent between # and =
In ARM assembly, what is the difference between
ldr r4, =0x44454433
and
ldr r4, #0x44454433 ?
0
votes
1answer
288 views
Patching branch on assembly code
I compile this code
1. #include <stdio.h>
2. void F(int a, int b)
3. {
4. int c= a+b;
5. int d= a*b;
6. }
7. void printAll()
8. {
9. printf("test1");
10. printf("test2");
11. ...
0
votes
2answers
236 views
explain c compile code
I compile c code to arm with this site https://godbolt.org/
int F(int a, int b)
{
int c=0;
for(int i=0;i<=10;i++)
{
c+=a+b;
}
return c;
}
the result was
F(int, ...
0
votes
1answer
110 views
Newbie here: hidden values in assembly? [closed]
So i'm new to the whole reverse engineering thing with only experience in C#. So I wanted to try and change the framerate of applications (eg. this unity game) at an assembly level on iOS ( I have an ...
0
votes
3answers
3k views
What is an immediate value?
I just read this post.
What does mean an "immediate value" ? Is there any string/ascii there?
How can I find this value on the binary file?
I have the same code and when I search on 0x28 address I ...
2
votes
3answers
2k views
How does the ldr instruction work on ARM?
ldr r0, #0x28
What does thw ldr instruction ? Does it load a string from some offset?
How can I find the string/value that is actually loaded ?
1
vote
1answer
262 views
Undefined instruction in Go binary compiled for ARM
I'm reverse engineering an ARM binary written in Go, and the following code sequence occurs fairly often (from runtime.cgoIsGoPointer):
BL runtime.panicindex
DCD 0xF7FABCFD
or, from runtime....
1
vote
1answer
322 views
Binary encryption
I'd like to ask your help to understand the algorithm used to encrypt these hex/bin firmware (for an ARM-Cortex M4 microcontroller).
In the tar file above you can find different firmware versions.
...
2
votes
0answers
678 views
Arm hex firmware reverse
it has been a couple of months that I'm working on the firmware produced by a company that makes (not licensed) gamepad console adapters.
One of my goal was to understand how they bypassed (hacked) ...
