Messages in this thread | | | Date | Wed, 26 Apr 2006 11:46:07 -0400 | From | Jeff Dike <> | Subject | Re: [uml-devel] [RFC] PATCH 3/4 - Time virtualization : PTRACE_SYSCALL_MASK |
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On Wed, Apr 26, 2006 at 05:47:54PM +0200, Blaisorblade wrote: > If we can do without MASK_STRICT_VERIFY, that works fully, and > anyway it's simpler - however, say, when running strace -e read,tee > (sys_tee will soon be added, it seems) this call would fail, while it > would be desirable to have it work as strace -e read. > > MASK_STRICT_VERIFY isn't necessarily the best solution, but if > userspace must search the maximum allowed syscall by multiple > attempts, we've still a bad API. > > Probably, a better option (_instead_ of MASK_STRICT_VERIFY) would be > to return somewhere an "extended error code" saying which is the > last allowed syscall or (better) which is the first syscall which > failed. I.e. if there is strace -e read,splice,tee and nor splice nor > tee are supported, then this value would be __NR_splice and strace (or > any app) could then decide what to do.
Why not just zero out the bits that the kernel knows about? Then, if we return -EINVAL, the process just looks at the remaining bits that are set to see what system calls the kernel didn't know about.
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