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Re: Single-stepping with interrupts enabled.
- From: Richard J Moore <richardj_moore at uk dot ibm dot com>
- To: fche at redhat dot com (Frank Ch. Eigler)
- Cc: systemtap at sources dot redhat dot com
- Date: Mon, 27 Feb 2006 14:03:58 +0000
- Subject: Re: Single-stepping with interrupts enabled.
- Sensitivity:
You can't do without post-handlers. SystemTap might not use them explicitly
but post-handling of the single-step (in kprobes) is required whether or
not a user handler is registered. For example for correcting the outcome of
an instructions execution (certain adjustments may have to be made - E49,
etc..); for handling exceptions from the single-stepped instruction
correctly; for giving the correct 'logical' view at a higher level of a
trace event following the generation of a recoverable page-fault on
single-step; for correcting IF manipulating instructions where the state of
the interrupt flag is not actually as the probed program logically thinks
it is; for correcting the TRAP Flag for the same reasons as IF.
There must be more.
- -
Richard J Moore
IBM Advanced Linux Response Team - Linux Technology Centre
MOBEX: 264807; Mobile (+44) (0)7739-875237
Office: (+44) (0)1962-817072
fche@redhat.com
(Frank Ch.
Eigler) To
Sent by: Richard J Moore/UK/IBM@IBMGB
fche@redhat.com cc
systemtap@sources.redhat.com
bcc
27/02/2006
13:51 Subject
Re: Single-stepping with interrupts
enabled.
richardj_moore wrote:
> [...] The problem is down to the need to save state over the
> single-step, so that pre- and post-processing either side of the
> single-step can be correctly associated with each other. [...]
How much of this would be simplified if we did away with support for
post_handlers (which we don't use in systemtap)?
- FChE