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Re: Probe on function entry rather than the end of the prolog (s390x only)
- From: fche at redhat dot com (Frank Ch. Eigler)
- To: David Wilder <dwilder at us dot ibm dot com>
- Cc: systemtap at sources dot redhat dot com
- Date: 31 Jan 2007 21:20:19 -0500
- Subject: Re: Probe on function entry rather than the end of the prolog (s390x only)
- References: <45C1497B.3010408@us.ibm.com>
David Wilder <dwilder@us.ibm.com> writes:
> [...] However; the debug information to identify all the arguments
> at the function entry point looks to be correct. [...]
Indeed, for more modern compilers it often seems to be. In order to
tolerate older compilers or less lucky cases, the prologue code is
probably still necessary to be kept around. It would be activated iff
debugging info for the function entry address is imperfect.
This could be implemented with a dwarf_derived_probe extension that
stores a group of possible addresses for the probe (probably just 2,
but this generalizes to more because of fuzzy prologues). If a
problem occurs during resolution of the embedded $target variables,
the other addresses would be tried.
Would someone like to try to come up with a patch for this?
- FChE