Date: Wed, 13 Jul 2016 08:24:37 +0800 From: Julian Elischer <julian@freebsd.org> To: Mark Johnston <markj@FreeBSD.org> Cc: freebsd-dtrace@freebsd.org, freebsd-current <freebsd-current@freebsd.org> Subject: Re: dtrace and kernel modules Message-ID: <c82dfb9d-2942-9e1d-2984-f0c4173a90ce@freebsd.org> In-Reply-To: <20160712171404.GB71220@wkstn-mjohnston.west.isilon.com> References: <d99a41d6-fe55-fb09-4466-c1d8082a40d6@freebsd.org> <20160712171404.GB71220@wkstn-mjohnston.west.isilon.com>
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On 13/07/2016 1:14 AM, Mark Johnston wrote:
> On Thu, Jul 07, 2016 at 12:51:52PM +0800, Julian Elischer wrote:
>> I'm specifically interested in the case of kernel modules that
>> instantiate new syscalls.
>>
>> How much support do we have for that? In the one example in our
>> sources of a kld with a syscall (kgssapi.ko) dtrace seems to find
>> regular function entrypoints but not the syscall.
>>
>>
>> root@porridge:/usr/src # dtrace -n ":kgssapi::entry {}"
>> dtrace: description ':kgssapi::entry ' matched 138 probes
>> ^C
>>
>> root@porridge:/usr/src # dtrace -n "syscall:kgssapi::entry {}"
>> dtrace: invalid probe specifier syscall:kgssapi::entry {}: probe
>> description syscall:kgssapi::entry does not match any probes
>> root@porridge:/usr/src #
>>
>>
>> Do we have plans to support dynamic syscall support?
> I don't know of any plans to add support. It would be fairly
> straightforward to dynamically create syscall probes using a hook or
> eventhandler in syscall_register(), but getting argument type info would
> be more difficult. Right now, argument types are specified by code
> generated by makesyscalls.sh using the types in syscalls.master. I'm not
> sure how one might obtain these types for dynamically-registered
> syscalls.
>
yes that is the tricky part for sure.
for now function calls is probably enough because every syscall ends
up calling a function somewhere :-)
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