EK-TM4C123GXL: My variables are not initialized in RAM?

Hello, I'm having trouble with something I'm writing in my TM4C123GX Launch Pad. I'm inexperienced with microcontrollers so I'm playing around with it using assembly. My problem is, I tried writing a program with a startup file provided in one of the TivaWare examples (startup_rvmdk.S), and it works fine except for that the variable I initialized (PM5_MASK) is blank. I tried asking this question somewhere else and was told it was the bootloader. Having little experience with microcontrollers, I'm very lost to where to even begin to figure out why my variable is 0 in RAM let alone understand how to use a bootloader. When I debug with the simulator and look at the value that should contain the value of the variable, it's always 0 unless I set it myself. What is the cause of this problem and how can I fix it? Here is my code below. I'm usaing Keil uVision. Thank you in advance!

main.s

	;Include constants I define to main
	INCLUDE my_Constants.s
	;Include variables I define to main
	IMPORT PB5_MASK

	AREA |.text|, CODE, READONLY
	THUMB
	EXPORT __main
	ENTRY
	
	;This  subroutine initializes GPIO
GPIO_Init	PROC
	...
	;write "high" to data register for port F pin 1 to turn on red LED. GPIODATA
	LDR r0, =AHB_PORTB
	LDR r1,[r0,#GPIODATAPB5]
	LDR r2, =PB5_MASK	;get RAM address of PB5 mask (pointer)
	LDR r3,[r2]	;get the value of PB5 mask
	ORR r3, r3, #0xF0
	STR r3,[r2]
	
	ORR r1, r1, r3	;Set PB5 to 'high'
	STR r1,[r0,#GPIODATAPB5]
	;LDR r1,[r0,#GPIODATAPB5]

	...
	BX LR
	
	ENDP
	
	
	;This subroutine initialies SysTick
SysTick_Init	PROC
	...
	ENDP
		
		
	
__main
	
	;call GPIO_Init subroutine and return
	BL GPIO_Init
	
	;call SysTick_Init subroutine and return
	BL SysTick_Init
	
stop 
	B stop	;While(1)
	
	END

my_Constants.s

	AREA My_Constants, CODE, READONLY
	THUMB
		
	;defining addresses here for practice

	;general base addresses
SYS_CONTROL	EQU 0x400FE000
...
	
	;offsets
GPIOHBCTL 	EQU 0x06C
...
	
	END

startup_rvmdk.s

;includes constants I define to startup file
		INCLUDE my_Constants.s
		;Include variables I define to startup file
		IMPORT PB5_MASK

        AREA    STACK, NOINIT, READWRITE, ALIGN=3
StackMem
        SPACE   Stack
__initial_sp

;******************************************************************************
;
; Allocate space for the heap.
;
;******************************************************************************
        AREA    HEAP, NOINIT, READWRITE, ALIGN=3
__heap_base
HeapMem
        SPACE   Heap
__heap_limit

;******************************************************************************
;
; Indicate that the code in this file preserves 8-byte alignment of the stack.
;
;******************************************************************************
        PRESERVE8

;******************************************************************************
;
; Place code into the reset code section.
;
;******************************************************************************
        AREA    RESET, CODE, READONLY
        THUMB

;******************************************************************************
;
; The vector table.
;
;******************************************************************************
        EXPORT  __Vectors
__Vectors
        DCD     StackMem + Stack            ; Top of Stack
        DCD     Reset_Handler               ; Reset Handler
        DCD     NmiSR                       ; NMI Handler
        DCD     FaultISR                    ; Hard Fault Handler
        ...                        ; Reserved
        DCD     IntDefaultHandler           ; The PendSV handler
        DCD     SysTick_Handler           	; The SysTick handler
        ...
;******************************************************************************
;
; This is the code that gets called when the processor first starts execution
; following a reset event.
;
;******************************************************************************
        EXPORT  Reset_Handler
Reset_Handler
        ;
        ; Enable the floating-point unit.  This must be done here to handle the
        ; case where main() uses floating-point and the function prologue saves
        ; floating-point registers (which will fault if floating-point is not
        ; enabled).  Any configuration of the floating-point unit using
        ; DriverLib APIs must be done here prior to the floating-point unit
        ; being enabled.
        ;
        ; Note that this does not use DriverLib since it might not be included
        ; in this project.
        ;
        MOVW    R0, #0xED88
        MOVT    R0, #0xE000
        LDR     R1, [R0]
        ORR     R1, #0x00F00000
        STR     R1, [R0]

        ;
        ; Call the C library enty point that handles startup.  This will copy
        ; the .data section initializers from flash to SRAM and zero fill the
        ; .bss section.
        ;
        IMPORT  __main
        B       __main

...
;I added the SysTick_Handler here. This toggle GPIODATA so the LED blinks
SysTick_Handler	PROC
	
	EXPORT SysTick_Handler
		
	;write "high" to data register for port F pin 1 to turn on red LED. GPIODATA
	LDR r0, =AHB_PORTB
	LDR r1, =PB5_MASK ;Get RAM address of PB5 mask value
	LDR r2,[r1] ;Grab value of PB5 mask
	EOR r2, r2, #0xF0	;Toggle mas to toggle PB5
	STR r2,[r1]	;Store the toggled mask to properly toggle next time
	STR r2,[r0,#GPIODATAPB5]
	;LDR r2,[r0,#GPIODATAPB5]

	;return to __main
	BX LR
	
	ENDP

...
        END