objdump.txt

00105b24 <syscall_handler>:
  105b24:       55                      push   %ebp
  105b25:       89 e5                   mov    %esp,%ebp
  105b27:       51                      push   %ecx
  105b28:       52                      push   %edx
  105b29:       50                      push   %eax
  105b2a:       83 e4 f0                and    $0xfffffff0,%esp
  105b2d:       83 ec 40                sub    $0x40,%esp
  105b30:       8d 45 04                lea    0x4(%ebp),%eax
  105b33:       89 44 24 2c             mov    %eax,0x2c(%esp)
  105b37:       8b 44 24 2c             mov    0x2c(%esp),%eax
  105b3b:       8b 00                   mov    (%eax),%eax
  105b3d:       c7 44 24 32 00 00 00    movl   $0x0,0x32(%esp)
  105b44:       00 
  105b45:       c7 44 24 36 00 00 00    movl   $0x0,0x36(%esp)
  105b4c:       00 
  105b4d:       c7 44 24 3a 00 00 00    movl   $0x0,0x3a(%esp)
  105b54:       00 
  105b55:       66 c7 44 24 3e 00 00    movw   $0x0,0x3e(%esp)
  105b5c:       c6 44 24 32 03          movb   $0x3,0x32(%esp)
  105b61:       83 ec 08                sub    $0x8,%esp
  105b64:       50                      push   %eax
  105b65:       68 e4 fc 10 00          push   $0x10fce4
  105b6a:       83 ec 10                sub    $0x10,%esp
  105b6d:       89 e0                   mov    %esp,%eax
  105b6f:       8b 54 24 52             mov    0x52(%esp),%edx
  105b73:       89 10                   mov    %edx,(%eax)
  105b75:       8b 54 24 56             mov    0x56(%esp),%edx
  105b79:       89 50 04                mov    %edx,0x4(%eax)
  105b7c:       8b 54 24 5a             mov    0x5a(%esp),%edx
  105b80:       89 50 08                mov    %edx,0x8(%eax)
  105b83:       0f b7 54 24 5e          movzwl 0x5e(%esp),%edx
  105b88:       66 89 50 0c             mov    %dx,0xc(%eax)
  105b8c:       fc                      cld    
  105b8d:       e8 55 d6 ff ff          call   1031e7 <vga_printf>
  105b92:       83 c4 20                add    $0x20,%esp
  105b95:       90                      nop
  105b96:       8d 65 f4                lea    -0xc(%ebp),%esp
  105b99:       58                      pop    %eax
  105b9a:       5a                      pop    %edx
  105b9b:       59                      pop    %ecx
  105b9c:       5d                      pop    %ebp
  105b9d:       cf                      iret   

syscall.c

typedef struct __attribute__((packed)) int_frame {
  // used for syscalls
  uint32_t eax;
  uint32_t code;

  uint32_t eip;
  uint32_t cs;
  uint32_t eflags;
  uint32_t sp;
  uint32_t ss;
} int_frame;

#define INTERRUPT                                                              \
  __attribute__((target("general-regs-only"))) __attribute__((interrupt))
  
  
INTERRUPT static void syscall_handler(int_frame *frame) {
  DEBUG_MSG("INT 0x80 (syscall) called with eax %u", frame->eax);
}