Process command line in Linux 64 bit

[AlexFr]

I have problems accessing the process command line from Linux 64 bit Assembly program. To reproduce this with minimal code, I made this 32-bit program which prints first 5 characters of the program name:

.section .text

.globl _start
_start:
 movl  %esp, %ebp
  
 movl $4, %eax        # write
 movl $1, %ebx        # stdout
 movl 4(%ebp), %ecx   # program name address (argv[0])
 movl $5, %edx        # hard-coded length
 int  $0x80

 movl $1, %eax
 movl $0, %ebx
 int  $0x80

This program is working. When I translate it to 64 bit and run in Linux 64, it doesn't print anything:

.section .text

.globl _start
_start:
 movq  %rsp, %rbp
  
 movq $4, %rax
 movq $1, %rbx
 movq 8(%rbp), %rcx       # program name address ?
 movq $5, %rdx
 int  $0x80

 movq $1, %rax
 movq $0, %rbx
 int  $0x80

Where is my mistake?