macOS Elementary problem with a simple assembly program

[Cromulent]

I'm trying to write a simple assembly program to open and read a file. I have the following code (sorry the forum has mucked up my formatting somewhat):

SECTION .data
	path  db 'test.txt'          ; open the file "test.txt"
	flags db 0x0000           ; set flags to O_RDONLY as defined in sys/fcntl.h
	mode  db 0x0		 ; set mode to NULL
	read_size db 0xFF	 ; set the size to read in bytes to 255

SECTION .text
	global start
	
start:
	enter 0,0			 ; enter the process
	pusha				 ; not sure about this
	push dword mode		 ; push path onto the stack
	push dword flags	         ; push flags onto the stack
	push dword path		 ; push mode onto the stack
	mov eax, 0x5		 ; call open() as defined in sys/syscall.h
	push dword eax		 ; push eax onto the stack
	int 0x80			 ; make the kernel call
	mov edx, eax		 ; store the return value from open in edx
	add esp, byte 16	         ; align the stack
	mov eax, 0x3		 ; call read() as defined in sys/syscall.h
	push dword eax		 ; push eax onto the stack
	int 0x80			 ; make the kernel call
	add esp, byte 16           ; align the stack again
	push dword read_size    ; push read_size onto the stack
	push dword edx            ; push edx onto the stack
	mov eax, 0x1		 ; call exit procedure
	int 0x80			 ; make the kernel call

After the mov eax, 0x3 and push dword eax calls I am missing the place to store the input that is read from the file and the file descriptor. The file descriptor is stored in edx currently but from what I have read I should use edx to store the things read from the file. Where should I store the file descriptor in this case? Can I just use any of the general purpose registers? My code assembles and executes without core dumping which is generally a good sign but as it does not do anything at the moment I can't really test it.

Any help is appreciated.

Edit: Aha, just read about esi and edi. They seem to be what I am looking for.