Homebrew Question Can anyone show me how to use syscall 0x6A & 0x6B in a C++ project?

[CosmoCortney]

Hello,

the title says all...
I need some examples on how to read/write data from/into memory using syscalls svcReadDebugProcessMemory and svcWriteDebugProcessMemory.
I'm very uncertain about how to implement everything in my C++ project and how to use the parameters.
(this is related to an older thread of mine when I was planning on making decent code types for cheats).

X0=buffer*, X1=debug_handle, X2=src_addr, X3=size

• what size should X0 (dereferenced value) be? Same as X3?
• how do I set a debug_handle?
• should the size value represent the number of bytes or bits? Is it restricted to sizes like 1, 2, 4, 8 bytes or can it be anything even higher than 16 bytes?

So an example on how to read or write a 1-byte value, a 4-byte would be really helpful (a program that does nothing more than that + which files to include).

thanks

 

[The Real Jdbye]

Hello,

the title says all...
I need some examples on how to read/write data from/into memory using syscalls svcReadDebugProcessMemory and svcWriteDebugProcessMemory.
I'm very uncertain about how to implement everything in my C++ project and how to use the parameters.
(this is related to an older thread of mine when I was planning on making decent code types for cheats).

X0=buffer*, X1=debug_handle, X2=src_addr, X3=size

• what size should X0 (dereferenced value) be? Same as X3?
• how do I set a debug_handle?
• should the size value represent the number of bytes or bits? Is it restricted to sizes like 1, 2, 4, 8 bytes or can it be anything even higher than 16 bytes?

So an example on how to read or write a 1-byte value, a 4-byte would be really helpful (a program that does nothing more than that + which files to include).

thanks

0 and 3 look fairly standard, meaning the buffer should be at least as large as the size (because the size is the number of bytes to be read into the buffer), but depending on how you're using it you may sometimes want a bigger buffer. It's probably in bytes, as I've never seen memory being read bit by bit.

As for debug_handle, I'm not sure about that one. The way it works on PC is that you have to attach to a process (using another API function) to get a handle to use, I guess it would work the same way on Switch?
I looked it up and it looks like svcDebugActiveProcess might be what you want: https://switchbrew.org/wiki/SVC - it takes a pid and returns a debug_handle. And then when you are done, svcBreakDebugProcess seems like it would detach the debugger, though the naming is odd so I might be wrong.
There are also some related functions in pm: https://switchbrew.org/wiki/Process_Manager_services

 

[CosmoCortney]

Thanks! Yea, I know such debug_handles from the Windows API. Using/obtaining them on the Switch is new territory tho.
The Process Manager Services page looks promising. Do you know any project on Git that uses sys calls 0x6A and 0x6B and builds up a handle? Maybe that'll be good enough as an example for me