Survey of Systems Providing Process or Object Migration Imperial College Research Report DoC 94/10
Mark Nuttall
To my interest:
1. Condor
Provide a special version of the C library which performs system calls remotely.
Either execute a request locally by mimicking the normal stubs or
package it into a message which is sent to the shadow process.
The shadow process executes the system call on the initiating machine, packages the results, and sends them back to the stub.
"System Calls" and "C Library Routines" appear to be very similar from the programmer's perspecitive, however, they are distincted.
If one wants to link the altered write() and printf() routines with existing code, keeping the names the same will be crucial.
Changing printf() would be easy, however, how can one get the kernel to transfer data to the disk without calling write()? We cannot call write() from within a routine called write() ---- that would be recursion.
The solution is a little known routine called syscall()
Since every UNIX system call is associated with a number defined by a macro in , one can replace an invocation of a system call with a call to the syscall routine. In this case, the first argument is the system call number, and the remaining arguments are just the normal arguments to the system call.
阅读(1367) | 评论(0) | 转发(0) |
