Debugging with an assemble program with GDB - gdb

Question

Here is my question:
I wrote a piece of code of assemble. It could read a file, transform the content to the uppercase and print the outputs in a newfile.
I complie and link the assemble code with:
as -gstabs read-files.s -o read-files.o
ld read-files.o -o read-files
And a test like "./read-files input-file output-file" works well.
But what if I want to debug this piece of code with gdb? I tried, but:
when I set the breakpoint and args of target code in gdb with:
(gdb) b *_start+1
(gdb) run test-file TEST-FILE
It will end with a segmentfault immediately.
Can I really debug this code like what I just stated aboved? Thanks
And the assemble code is here:
.section .data
.equ SYS_OPEN, 5
.equ SYS_WRITE, 4
.equ SYS_READ, 3
.equ SYS_CLOSE, 6
.equ SYS_EXIT, 1
.equ O_RDONLY, 0
.equ O_CREAT_WRONLY_TRUNC, 03101
.equ STDIN, 0
.equ STDOUT, 1
.equ STDERR, 2
.equ LINUX_SYSCALL, 0x80
.equ END_OF_FILE, 0
.equ NUMBER_ARGUMENTS, 2
.section .bss
.equ BUFFER_SIZE, 500
.lcomm BUFFER_DATA, BUFFER_SIZE
.section .text
.equ ST_SIZE_RESERVE, 8
.equ ST_FD_IN, -4
.equ ST_FD_OUT, -8
.equ ST_ARGC, 0
.equ ST_ARGV_0, 4
.equ ST_ARGV_1, 8
.equ ST_ARGV_2, 12
.globl _start
_start:
movl %esp, %ebp
subl $ST_SIZE_RESERVE, %esp
open_files:
open_fd_in:
movl $SYS_OPEN, %eax
movl ST_ARGV_1(%ebp), %ebx
movl $O_RDONLY, %ecx
movl $0666, %edx
int $LINUX_SYSCALL
store_fd_in:
movl %eax, ST_FD_IN(%ebp)
open_fd_out:
movl $SYS_OPEN, %eax
movl ST_ARGV_2(%ebp), %ebx
movl $O_CREAT_WRONLY_TRUNC, %ecx
movl $0666, %edx
int $LINUX_SYSCALL
store_fd_out:
movl %eax, ST_FD_OUT(%ebp)
read_loop_begin:
movl $SYS_READ, %eax
movl ST_FD_IN(%ebp), %ebx
movl $BUFFER_DATA, %ecx
movl $BUFFER_SIZE, %edx
int $LINUX_SYSCALL
cmpl $END_OF_FILE, %eax
jle end_loop
continue_read_loop:
pushl $BUFFER_DATA
pushl %eax
call convert_to_upper
popl %eax
addl $4, %esp
movl %eax, %edx
movl $SYS_WRITE, %eax
movl ST_FD_OUT(%ebp), %ebx
movl $BUFFER_DATA, %ecx
int $LINUX_SYSCALL
jmp read_loop_begin
end_loop:
movl $SYS_CLOSE, %eax
movl ST_FD_OUT(%ebp), %ebx
int $LINUX_SYSCALL
movl $SYS_CLOSE, %eax
movl ST_FD_IN(%ebp), %ebx
int $LINUX_SYSCALL
movl $SYS_EXIT, %eax
movl $0, %ebx
int $LINUX_SYSCALL
.equ LOWERCASE_A, 'a'
.equ LOWERCASE_Z, 'z'
.equ UPPER_CONVERSION, 'A' - 'a'
.equ ST_BUFFER_LEN, 8
.equ ST_BUFFER, 12
convert_to_upper:
pushl %ebp
movl %esp, %ebp
movl ST_BUFFER(%ebp), %eax
movl ST_BUFFER_LEN(%ebp), %ebx
movl $0, %edi
cmpl $0, %ebx
je end_convert_loop
convert_loop:
movb (%eax, %edi, 1), %cl
cmpb $LOWERCASE_A, %cl
jl next_byte
cmpb $LOWERCASE_Z, %cl
jg next_byte
addb $UPPER_CONVERSION, %cl
movb %cl, (%eax, %edi, 1)
next_byte:
incl %edi
cmpl %edi, %ebx
jne convert_loop
end_convert_loop:
movl %ebp, %esp
popl %ebp
ret