checking in all chnages, including todays play with gnu-as

gnu-asm/hello1/hello.s

@@ -0,0 +1,93 @@
+# hello.s
+#
+# Ask for the user's name, then print:
+# Hello <name>
+# five times.
+
+.section .rodata
+
+prompt:
+    .ascii "What is your name? "
+prompt_end:
+
+hello:
+    .ascii "Hello "
+hello_end:
+
+newline:
+    .byte 10                   # ASCII newline: '\n'
+
+
+.section .bss
+
+    .align 16
+name_buf:
+    .skip 64                   # Reserve 64 bytes for the name
+
+
+.section .text
+
+    .global _start
+
+_start:
+    # write(STDOUT, prompt, prompt_length)
+    mov $1, %rax               # syscall 1: write
+    mov $1, %rdi               # file descriptor 1: stdout
+    lea prompt(%rip), %rsi     # address of prompt
+    mov $(prompt_end - prompt), %rdx
+    syscall
+
+    # read(STDIN, name_buf, 63)
+    xor %rax, %rax             # syscall 0: read
+    xor %rdi, %rdi             # file descriptor 0: stdin
+    lea name_buf(%rip), %rsi
+    mov $63, %rdx
+    syscall
+
+    # RAX contains the number of bytes read.
+    # Exit if read returned zero or an error.
+    test %rax, %rax
+    jle exit
+
+    # Save the length of the name in R12.
+    mov %rax, %r12
+
+    # Remove the trailing newline entered by the user.
+    lea name_buf(%rip), %rbx
+    cmpb $10, -1(%rbx,%r12)
+    jne repeat_setup
+    dec %r12
+
+repeat_setup:
+    mov $5, %r13               # Loop counter
+
+repeat_loop:
+    # Write "Hello "
+    mov $1, %rax
+    mov $1, %rdi
+    lea hello(%rip), %rsi
+    mov $(hello_end - hello), %rdx
+    syscall
+
+    # Write the user's name
+    mov $1, %rax
+    mov $1, %rdi
+    lea name_buf(%rip), %rsi
+    mov %r12, %rdx
+    syscall
+
+    # Write newline
+    mov $1, %rax
+    mov $1, %rdi
+    lea newline(%rip), %rsi
+    mov $1, %rdx
+    syscall
+
+    dec %r13
+    jne repeat_loop
+
+exit:
+    # exit(0)
+    mov $60, %rax              # syscall 60: exit
+    xor %rdi, %rdi             # exit status 0
+    syscall