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I have an object file of a C program which prints hello world, just for the question. I am trying to understand using readelf utility or gdb or hexedit(I can't figure which tool is a correct one) where in the file does the code of function "main" starts.

I know using readelf that symbol _start & main occurs and the address where it is mapped in a virtual memory. Moreover, I also know what the size of .text section and the of coruse where entry point specified, i.e the address which the same of text section.

The question is - Where in the file does the code of function "main" starts? I tought that is the entry point and the offset of the text section but how I understand it the sections data, bss, rodata should be ran before main and it appears after section text in readelf.

Also I tought we should sum the size all the lines till main in symbol table, but I am not sure at all if it is correct.

Additional question which follow up this one is if I want to replace main function with NOP instrcutres or plant one ret instruction in my object file. how can I know the offset where I can do it using hexedit.

I have a file that I am searching for specific ascii characters.

I ran the following code after getting the text from a file:

var t = text.IndexOf((char)128);

Hexedit shows I have characters of HEX 80 which is ascii character 128, but t ends up with a value of -1.

Is there another way I should be searching for this character?

(See Updates at end of this post)

For $reasons, I need to codesign an old Director projector that we can no longer re-publish (no access to original source code or to Director).

I'm doing this because when run without being signed, the app now opens a Finder window with a prompt saying "Where is..." asking for a file that's one of the embedded projector resources.

But... If I cd into the Projector.app contents (it's not really called that, but you get the idea) and find the projector binary inside Contents/MacOS/ and run this binary from terminal, the app launches and runs fine, once it's decompressed the (presumably) attached archive at the end of the binary...

I would like to use a linux shell (bash, zsh, etc.) to insert a set of known bytes into a file at a certain position. Similar questions have been asked, but they modify in-place the bytes of a file. These questions don't address inserting new bytes at particular positions.

For example, if my file has a sequence of bytes like \x32\x33\x35 I might want to insert \x34 at position 2 so that this byte sequence in the file becomes \x32\x33\x34\x35.

I need to modify a byte in a binary file at a certain offset.

Example:

• Input file: A.bin
• Output file: B.bin

I need to read a byte at the offset 0x40c from A.bin, clear to 0 least significant 2 bits of this byte, and then write file B.bin equal to A.bin, but with the calculated byte at offset 0x40c.

• I can use bash and standard commands like printf and dd.
• I can easily write a byte into a binary file, but I don't know how to read it.

I have a JPEG that is un-openable in any program:

Opening in Ubuntu Image Viewer yields:

Passing the photo through convert yields similar results:

I have some .exe file (say some.exe) that writes to the standard output binary data. I have no sources of this program. I need to run some.exe from my C++/Qt application and read standard output of the process I created. When I'm trying to do this with QProcess::readAll someone replaces byte \n (0x0d) to \r\n (0x0a 0x0d).

Here is a code:

So I have this .fx file with HLSL code. The next step is to compile using 2MGFX.exe and this is where things go crazy. I can't run it on my computer at all.

So then I tried fxc.exe - installing this alone was a little too hard - but it generates a header. So I started following along with this post. I started trying to remove the headers byte-by-byte with HexEdit, again to no avail. What further bothers me is that there might also be extra footers, not just headers. No matter what I do, my project absolutely refuses to load my .mgfxo file.

I'm getting pretty fed-up with this process. Are there any other tools or methods I can employ? How about loading the file myself and feeding into the CPU myself?

I am working on understanding some ground concepts in embedded Systems. My question is similar to understand hexedit of an elf . In order to burn compiler output to ROM, the .out file is converted to HEX (say intel-hex). I wonder how the following informations are preserved in HEX format:

1. Section header
2. Symbol tables, debug symbols, linker symbols etc.
3. Elf header.
4. If these are preserved in HEX file, how they can be read from hex file?
5. A bit out question but how the microcontroller on boot knows where .data .bss etc. exists in HEX and to be coppied to RAM?