On Thu, Mar 11, 2010 at 06:15:07PM -0500, Jung-uk Kim wrote: > On Thursday 11 March 2010 04:55 pm, Marcel Moolenaar wrote: > > On Mar 11, 2010, at 1:24 PM, Jung-uk Kim wrote: > > > While I was debugging syscalls, I found a very useful field in > > > struct thread, td_errno. It seems it was added for dtrace but it > > > is only populated on amd64 and i386. Is the attached patch > > > acceptable for maintainers of other platforms? > > > > Isn't it better to do it in cpu_set_syscall_retval()? > > That way you catch all cases, plus you can save the > > translated error as well... > > I just took amd64/i386 as an example and I was not sure whether it was > meant to store translated error or not. Does anyone with DTrace > internal knowledge answer the question?
I do not know that much about DTrace, but it seems that setting td_errno in cpu_set_syscall_retval() is too late. Dtrace has a probe after the syscall return, and it is called right before cpu_set_syscall_retval() can be reasonably called. The probe only issued for syscall that goes into sysent.
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