User-level applications use as integer registers for passing the sequence %rdi, %rsi, %rdx, %rcx, %r8 and %r9. The kernel interface uses %rdi, %rsi, %rdx, %r10, %r8 and %r9.
A system-call is done via the syscall instruction. The kernel destroys registers %rcx and %r11.
The number of the syscall has to be passed in register %rax.
System-calls are limited to six arguments, no argument is passed directly on the stack.
Returning from the syscall, register %rax contains the result of the system-call. A value in the range between -4095 and -1 indicates an error, it is -errno.
Only values of class INTEGER or class MEMORY are passed to the kernel.
2、调用指令不同
For a 32bit kernel, SYSENTER/SYSEXIT are the only compatible pair [between AMD and Intel CPUs]
For a 64bit kernel in Long mode only… SYSCALL/SYSRET are the only compatible pair [between AMD and Intel CPUs]
