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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, ...

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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 ...
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How to telnet to a security camera

I have a C63S vstarcam camera and its RTSP servers keep crashing. I'm certain that if I can log into the camera I can at least restart the RTSP server or reboot the camera. The only open ports on the ...
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1answer
55 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, ...
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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, [...
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1answer
98 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 ...
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1answer
78 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 ...
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1answer
97 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 ...
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1answer
38 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 ...
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1answer
154 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. ...
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1answer
64 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 ...
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0answers
54 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 ...
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1answer
75 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 ...
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1answer
195 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
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1answer
142 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 ...
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2answers
137 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 ...
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2answers
106 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 ...
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1answer
211 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@@...
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1answer
214 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, ...
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1answer
74 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 ...
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0answers
210 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 ...
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1answer
57 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 ...
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1answer
43 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 ...
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2answers
439 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 ...
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1answer
1k 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 ...
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2answers
81 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 ...
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1answer
374 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 ...
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1answer
176 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 #...
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2answers
272 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 ...
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1answer
45 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, ...
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2answers
270 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?
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1answer
258 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 ...
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1answer
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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 ...
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2answers
35 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.
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1answer
253 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 ...
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2answers
190 views

Arm ldr diffrent between # and =

In ARM assembly, what is the difference between ldr r4, =0x44454433 and ldr r4, #0x44454433 ?
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1answer
235 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. ...
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2answers
161 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, ...
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1answer
106 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 ...
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3answers
2k 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 ...
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3answers
1k 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 ?
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1answer
212 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....
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1answer
295 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. ...
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0answers
567 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) ...
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1answer
176 views

How to change a string in a arm 32bit lsb executable binary using radare2?

I have a arm 32bit lsb executable which prints "hello world" to the screen. How do I change the string to "Good bye" using radare2. I believe this will teach me the basics of RE and radare2. Thank ...
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2answers
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How can i start the RE process in radare2?(make changes to the registers) [closed]

I'm an absolute newbie to reverse engineering. I have a 32bit lsb arm binary which I would like to reverse engineer using radare2. How should I begin ?
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1answer
235 views

Hex-Rays function signature does not match demangled name

From the demangled name, I know that a function takes an std::string const& as a parameter but when generating psuedo-c code with Hex-Rays' decompiler it autodetects the parameters as (int a1, int ...
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1answer
98 views

ARM function start points look strange sometimes in IDA Pro

I am a little bit confused with this strange issue with ARM firmware. My original firmware file has no symbols, so I need to find them by myself trough the internet. But here I have a certain function ...
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1answer
1k views

Entry point for STM32 firmware

I'm trying to disassemble a firmware for a DIY project, open hardware but closed firmware. My question is how to initialize the disassembler properly (Hopper Disassembler). The values I try to figure ...
2
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1answer
88 views

ARM system crashes after changing stack address

-- Edit with latest update on the problem, it is not solved yet :( -- While playing with an ARM embedded Linux system (Version 3.8.13), out of curiosity, I created a small "debug" kernel module. ...
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2answers
1k views

ARM64 syscalls table

I wonder if there some syscall table for Linux ARM64 architecture? I found syscall table for Linux ARM32 and many other architectures, but the problem still exists. Does anyone know where can I find ...