Arm64 Syscalls

Common Arm64 Syscalls

1. read (syscall number 63)

   • Description: Reads data from a file descriptor.

   • Arguments:

     • x0: File descriptor.

     • x1: Buffer to store the read data.

     • x2: Number of bytes to read.

   • Return Value: Number of bytes read or a negative error code.

   .global _start .section .bss buffer: .skip 100 .section .text _start: mov x8, #63 // Syscall number for read mov x0, #0 // File descriptor (stdin) ldr x1, =buffer // Pointer to the buffer mov x2, #100 // Number of bytes to read svc #0 // Invoke the syscall mov x8, #93 // Syscall number for exit mov x0, #0 // Exit code 0 svc #0 // Invoke the syscall

2. write (syscall number 64)

   • Description: Writes data to a file descriptor.

   • Arguments:

     • x0: File descriptor.

     • x1: Buffer containing the data to write.

     • x2: Number of bytes to write.

   • Return Value: Number of bytes written or a negative error code.

   .global _start .section .data msg: .asciz "Hello, World!\n" .section .text _start: mov x8, #64 // Syscall number for write mov x0, #1 // File descriptor (stdout) ldr x1, =msg // Pointer to the message mov x2, #14 // Length of the message svc #0 // Invoke the syscall mov x8, #93 // Syscall number for exit mov x0, #0 // Exit code 0 svc #0 // Invoke the syscall

3. open (syscall number 56)

   • Description: Opens a file.

   • Arguments:

     • x0: Path to the file.

     • x1: Flags.

     • x2: Mode (optional, used when creating a file).

   • Return Value: File descriptor or a negative error code.

   .global _start .section .data path: .asciz "/path/to/file" .section .text _start: mov x8, #56 // Syscall number for open ldr x0, =path // Path to the file mov x1, #0 // Flags (O_RDONLY) mov x2, #0 // Mode (not used) svc #0 // Invoke the syscall mov x8, #93 // Syscall number for exit mov x0, #0 // Exit code 0 svc #0 // Invoke the syscall

4. close (syscall number 57)

   • Description: Closes a file descriptor.

   • Arguments:

     • x0: File descriptor.

   • Return Value: 0 on success or a negative error code.

   .global _start .section .text _start: mov x8, #57 // Syscall number for close mov x0, #3 // File descriptor svc #0 // Invoke the syscall mov x8, #93 // Syscall number for exit mov x0, #0 // Exit code 0 svc #0 // Invoke the syscall

5. exit (syscall number 93)

   • Description: Terminates the calling process.

   • Arguments:

     • x0: Exit status.

   • Return Value: Does not return.

   .global _start .section .text _start: mov x8, #93 // Syscall number for exit mov x0, #0 // Exit code 0 svc #0 // Invoke the syscall

These examples demonstrate how to use the Arm64 syscall convention to perform basic operations such as reading, writing, opening, closing files, and exiting a program. For a complete list of syscalls, refer to the Linux kernel documentation.