Re: [rfc] Remove SyscallNum.shjava and maintain syscallList manually for different architectures

[Yao Qi <qiyaoltc at cn dot ibm dot com>]

On Wed, Sep 06, 2006 at 11:36:12AM +0200, Mark Wielaard wrote:
> 
> Do you mean the -e <expr> option? (
> My version of ftrace has -o <x> being redirect output to <x>.
Do you mean strace here? :)
There is no option for frace now.

> > In the current setup one plausible approach would be to have multiple
> > Syscall objects with the same number but different names.  Then,
> > SyscallEventInfo would have an accessor to return the corresponding
> > Syscall -- which would be the "decoded" one.  Finally, Syscall would
> > have an equals() method that would compare both the name and the
> > number.
> 
> Yes, that seems the right approach.

syscalls with different names but the same number could only be found
on x86, and I could not find the similar case on other platforms.

Actually, I start to rewrite Syscall.java, SyscallEventInfo.java and
Linux<ISA>.java.  I am not sure I am on a right way, so any advice is
appreciated.

1) Write a new method getSyscall() in SyscallEventInfo to return a
Syscall object from a *certain* syscallList.

2) Build syscallList in every Linux<ISA>.java.
syscallList varies from ISA, so I place syscallList from Syscall.java
to Linux<ISA>.java
On i386, there are 2 syscall numbers for a group of "subcalls", so I
set up 3 syscallLists, 

   a) syscallList for common syscalls(1 syscall num, 1 syscall name), 
   b) socketSubCallList for socket subcalls group.(indexed by first
argument)
   c) ipcSubCallList for ipc subcalls group.(indexed by first argument)

3) In SyscallEventInfo.getSyscall(),  get syscall number and first
argument, and return the Syscall object in one of the three
syscallLists.

Any comments on this?  Thanks!
If I am on a right track, I will continue to do it.
> 
> > The only oddity then would be what to do in the case where an unknown
> > number is passed to syscallByNum.  But ... I wonder if this should
> > simply throw an exception.
> 
> Not an exception. Sometimes new system calls are introduced. It should
> just return a Syscall object for number xyz with as name "unknown-xyz"
> so as to be unique.
Emm, I think you are right, Mark.
A RuntimeException is thrown out in my code, :)

-- 
Yao Qi