Messages in this thread | | | Date | Thu, 7 Jun 2007 14:08:20 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [patch 7/8] fdmap v2 - implement sys_socket2 |
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On Thu, 7 Jun 2007, Eric Dumazet wrote: > > This is a nice idea, but 32/64 compat code is going to hate it :)
It should be fairly simple for 32/64-bit compat code too.
The compat code should just call the compat system call
> syscall_indirect() would be writen in assembly for each arch, since there is > no generic syscall table. Thats really a lot of work, especially if we want to > mess with signal mask, umask ...
No no no. That would be horribly idiotic.
The thing should be 99% generic code, ie we would have
syscall_indirect(..) { long retval;
.. set up signals/flags .. retval = arch_syscall_indirect(syscall, args); .. unsetup signals/flags .. return retval; }
compat_syscall_indirect(..) { int retval;
.. set up signals/flags .. retval = compat_arch_syscall_indirect(syscall, args); .. unsetup signals/flags .. return retval; }
and the *only* thing that each architecture would need to do is that (trivial) arch_syscall_indirect() thing (and the compat version, if applicable). And those literally should be generally pretty damn trivial.
The only _subtle_ issue is any system call that actually uses "pt_regs". So we'd have to disallow exec/fork/vfork/clone/. They take magic pt_regs pointers etc. On x86, for example, the following system calls should *not* be things you can do this with:
asmlinkage int sys_fork(struct pt_regs regs) asmlinkage int sys_clone(struct pt_regs regs) asmlinkage int sys_vfork(struct pt_regs regs) asmlinkage int sys_execve(struct pt_regs regs) asmlinkage int sys_vm86old(struct pt_regs regs) asmlinkage int sys_vm86(struct pt_regs regs) asmlinkage long sys_iopl(unsigned long unused)
because those either take pt_regs, or make pt_regs out of their arguments (that "unused" is used to do:
volatile struct pt_regs * regs = (struct pt_regs *) &unused;
so there is *some* care needed, but other than taking care of this, the implementation on x86 should really be totally trivial.
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