From: "K.Prasad" <prasad@linux.vnet.ibm.com>
To: "Frank Ch. Eigler" <fche@redhat.com>
Cc: Prerna Saxena <prerna@linux.vnet.ibm.com>,
systemtap@sourceware.org,
Roland McGrath <roland@redhat.com>
Subject: Re: [RFC] Systemtap translator support for hw breakpoints on x86
Date: Sat, 09 Jan 2010 01:41:00 -0000 [thread overview]
Message-ID: <20100109014051.GB5975@in.ibm.com> (raw)
In-Reply-To: <y0miqbcpqqf.fsf@fche.csb>
On Fri, Jan 08, 2010 at 10:21:12AM -0500, Frank Ch. Eigler wrote:
> Prerna Saxena <prerna@linux.vnet.ibm.com> writes:
<snipped>
>
> > [...] For now, I had designed the probes to error out if a user
> > defined a length that was not supported by architecture (eg a length
> > 3 on x86, as this supports lengths like 1,2,4 bytes only) [...]
>
> My concern with the above was not the script language interface or
> mappings, but only the cleanliness / simplicity of the generated code.
> If the translator neglects to filter out unsupported lengths, and the
> generated code propagates the value 3, will the kernel's registration
> function check and reject such requests at run time? If so, then
> there is no need for the generated code to contain preemptive checks /
> filters / error messages. Just let it listen to the result code from
> the kernel's registration function.
>
> As to having the translator filter for parameters expected to be
> valid, that is fine, but those checks need not show up redundantly in
> generated C code.
>
The hw-breakpoint API for registration returns success only after a
successful sanity check for alignment, breakpoint length (supported or
not), improper addresses (user vs kernel-space) among a few others.
So unless the translator wants to show more meaningful error messages
that states the exact cause (given that the bkpt API will return -EINVAL
in all of these cases), it can rely upon the kernel's registration
function.
Thanks,
K.Prasad
next prev parent reply other threads:[~2010-01-09 1:41 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-07 8:35 [RFC] Systemtap translator support for hardware breakpoints on Prerna Saxena
2010-01-07 18:01 ` Frank Ch. Eigler
2010-01-07 21:57 ` Roland McGrath
2010-01-07 22:39 ` Roland McGrath
2010-01-07 22:45 ` Frank Ch. Eigler
2010-01-08 5:01 ` Ananth N Mavinakayanahalli
2010-01-08 10:24 ` Roland McGrath
2010-01-09 1:29 ` K.Prasad
2010-01-09 1:56 ` Roland McGrath
2010-01-08 14:35 ` [RFC] Systemtap translator support for hw breakpoints on x86 Prerna Saxena
2010-01-08 15:21 ` Frank Ch. Eigler
2010-01-09 1:41 ` K.Prasad [this message]
2010-01-25 19:00 ` [RFC V2] Systemtap translator support for kernel hardware breakpoints Prerna Saxena
2010-01-26 21:16 ` Frank Ch. Eigler
2010-01-27 15:55 ` Prerna Saxena
2010-01-27 17:12 ` Frank Ch. Eigler
2010-01-28 9:59 ` Prerna Saxena
2010-01-29 9:15 ` Prerna Saxena
2010-01-07 23:15 ` [RFC] Systemtap translator support for hardware breakpoints on Roland McGrath
2010-01-08 1:03 ` Frank Ch. Eigler
2010-01-08 1:28 ` Roland McGrath
2010-01-08 1:19 ` Roland McGrath
2010-01-08 1:53 ` Roland McGrath
2010-01-08 16:08 ` Prerna Saxena
2010-01-08 18:52 ` Roland McGrath
2010-01-09 0:54 ` K.Prasad
2010-01-09 1:07 ` Roland McGrath
2010-01-09 1:11 ` K.Prasad
2010-01-09 1:45 ` Roland McGrath
2010-01-09 2:46 ` K.Prasad
2010-01-10 21:37 ` Roland McGrath
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