问题
I am wondering if there is any difference between the MIPS syscall and trap instructions. I can't find anything involving this, so I am not sure if there is a difference. Traps seem to just be a conditional syscall, but some clarifying can be helpful.
回答1:
The SYSCALL and TRAP instructions both trigger exceptions, but the resulting exception is of a different type (SystemCall versus Trap), and the operating system will likely handle them differently.
回答2:
A Trap is an exception switches to kernel mode by invoking a kernel sub-routine (any system call). Usually trap creates any kind of control transfer to operating system. Where as SYSCALL is synchronous and planned user process to kernel mode.
来源：https://stackoverflow.com/questions/14004766/difference-between-syscall-and-traps